International Reviews of Immunology, Early Online:1–21, 2015Copyright C© Informa Healthcare USA, Inc.ISSN: 0883-0185 print / 1563-5244 onlineDOI: 10.3109/08830185.2015.1015719

REVIEW

Regulatory B Cells and Mechanisms

Hector Rincon-Arevalo1, Claudia C. Sanchez-Parra1, Diana Castano1,Lina Yassin,,1,2 and Gloria Vasquez,1

1Grupo de Inmunologıa Celular e Inmunogenetica, Instituto de Investigaciones Medicas,Facultad de Medicina, Universidad de Antioquia UdeA and; 2Grupo de Ciencias Basicas.Facultad de Medicina. Universidad CES. Medellın, Colombia

Regulatory B cells have gained prominence in their role as modulators of the immune responseagainst tumors, infectious diseases, and autoimmune diseases, such as systemic lupus erythe-matosus, rheumatoid arthritis, and multiple sclerosis, among others. The concept of regulatory Bcells has been strongly associated with interleukin (IL)-10 production; however, there is growingevidence that supports the existence of other regulatory mechanisms, such as the productionof transforming growth factor β (TGF-β), induced cell death of effector T cells, and the inductionof CD4+CD25−Foxp3+ regulatory T cells. The regulatory function of B cells has been associatedwith the presence and activation of molecules such as CD40, CD19, CD1d, and BCR. Alterations insignaling by any of these pathways leads to a marked defect in regulatory B cells and to increasedclinical symptoms and proinflammatory signs, both in murine models and in autoimmune dis-eases in humans. B cells mainly exert their regulatory effect through the inhibition of proliferationand production of proinflammatory mediators, such as TNF-α, IFN-γ , and IL-17 by CD4+ T cells. Abetter understanding of how regulatory B cells function will offer new perspectives with regardto the treatment of various human diseases.

Keywords: B10, IL-10, regulatory B cell, T cell, TGF-β

INTRODUCTION

B cells play diverse roles both in innate immunity, through the production of natu-ral antibodies directed to T–cell-independent antigens [1], and in adaptive immunity,through their differentiation into memory and plasma B cells, which produce high-affinity antibodies directed to T–cell-dependent antigens [2]. Besides participating inhumoral immune response, B cells play a main role in the modulation of effector T-cellresponse by antigen presentation, costimulation, and cytokine production [3].

In recent years, the existence of a B-cell subset with regulatory functions in the im-mune response to pathogens and autoantigens has been demonstrated. These regu-latory cells have become a target for the study of autoimmune and infectious diseasesas well as cancer in an attempt to generate and propose alternative therapies based onimmunomodulation [4].

Accepted 20 January 2015.Address correspondence to Lina M Yassin. Calle 70 No. 52-21. SIU. Laboratory 510. Medellın,Colombia. E-mail: yascatorce@yahoo.com

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

This review focuses on the mechanisms implicated in the regulatory function ofB cells as well as on the main pathways and molecules involved in this regulatoryprocess.

B CELLS AS IMMUNE RESPONSE REGULATORS

Several B-cell subsets have been described both in mice and humans. The most widelydescribed B-cell subpopulations in murines: Transitional 1 (T1) CD19+CD21−CD23−,2 (T2) CD19+CD21hiCD23+, marginal zone (MZ) CD19+CD21+CD23−/low, follicular(FO) CD19+CD21+/lowCD23+, B1a CD19+CD5+, and B1b CD19+CD5−CD11b+ (onlyin peritoneum) are included [4]. Some of these subsets correspond to immature stagesof B cells (T1 and T2), others have a T–cell-dependent response (FO), whereas stillothers have a T-independent response (MZ, B1a, and B1b). On the other hand, inhumans, the main reported B-cell subsets in peripheral blood correspond to tran-sitional (CD19+CD27−CD24hiCD38hi), mature (CD19+CD27−CD24+/lowCD38+/low),and memory (CD19+CD27+CD24hiCD38−/low) B cells [5].

The hypothesis of B cells as suppressors or regulators of the immune system wasoriginally proposed in the 1960s. The transfer of antibody-producing splenic cells (7S,with low hemolytic efficiency) from mice that had been previously immunized withsheep red blood cells (SRBCs) into non-immunized syngeneic mice inhibited the pro-duction of antibodies directed against SRBCs (19S, hemolytic antibody), comparedwith mice that did not receive splenocytes. It was proposed that the 7S antibodieshad a regulatory role in innate immune response, because 7S antibodies have lowerhemolytic efficiency compared with 19S antibodies, which could favor 7S to competefor the antigen-avoiding stimulation of the 19S-producing cells [6].

However, the first report that described B cells with regulatory capacity was in ex-perimental autoimmune encephalomyelitis (EAE), a mouse model of multiple sclero-sis. B–cell-deficient (μMT) C57BL/6 mice, induced to EAE by myelin oligodendrocyteglycoprotein (MOG) immunization, failed to control the disease, compared with thespontaneous remission observed in wild-type mice [7]. The regulatory function of Bcells was also demonstrated in the T-cell receptor α (TCRα−/−) autoimmune murinemodel of colitis (spontaneously develop the disease), in which B-cell deficiency cor-related with chronic inflammation and early onset of the disease [8].

Similar results suggesting the role of B cells in immune response regulation havebeen described in other murine models for autoimmune diseases, such as rheumatoidarthritis (RA) [9], autoimmune diabetes [10], and systemic lupus erythematosus (SLE)[11] as well as cancer [12] and other models of infectious diseases caused by bacteria,viruses, and parasites [13–16].

The concept of regulatory B cells was first used by Fillatreau et al. in 2002 to de-scribe IL–10-producing B cells capable of diminishing the clinical manifestations inEAE [17]. However, evidence supports the existence of additional regulatory mecha-nisms, besides IL-10 production, both in mice and humans, such as cell death induc-tion and transforming growth factor β (TGF-β) and immunoglobulin M (IgM) produc-tion, among others. Because regulation of the immune response by B cells is as yet ayoung field of study, their differentiation, activation, and function as regulatory B cellsremain poorly understood.

B–CELL-REGULATORY MECHANISMS

Different elements and effector pathways have been involved in immune responseregulation mediated by B cells; as explained below, such mechanisms have been de-scribed mainly in autoimmune disease models (Figure 1).

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

FIGURE 1. B–cell-regulatory mechanisms. (a) IL-10 production. The action of this cytokine inhibitsproliferation of CD4+ T cells and their differentiation into Th1 and Th17 profiles (proinflammatorycytokine producers). IL–10-producing B cells induce CD4+CD25− T-cell differentiation into IL–10-producing cells with a regulatory phenotype and inhibit TNF-α production by monocytes. (b) TGF-β production. B cells produce TGF-β, which induces CD4+ T cells to differentiate into an IL–10-producing regulatory profile (Tregs) and inhibits the TNF-α and cells producing the Th1 profile.(c) IgM production. IgM produced by B cells induces removal of apoptotic bodies, which leads toreduced proinflammatory mediators. (d) Cell–cell interaction. Signals from CD40, MHC-II, CD80,CD86, and PD-L1 by regulatory B cells induce CD4+ T cells to reduce proliferation and Th1 cytokineproduction. (e) Death ligands. The Fas-FasL interaction between B cells and T cells induces apopto-sis in proinflammatory CD4+ T cells. (f ) IgG4 production. IgG4 has a lower affinity for Fc receptorsand the C1q complex; therefore, it induces lower complement activation and reduces targets ofother immunoglobulins with greater inflammation-inducing capacity. This could be an alternativemechanism used by regulatory B cells. (g) IL-35 production. B cells produce IL-35, which inhibitsthe Th1 and Th17 profiles.

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

Interleukin-10The most widely studied and understood regulatory mechanism executed by B cellsis mediated by interleukin (IL)-10, which is one of the most relevant cytokines inregulating inflammation [18]. IL-10 has a variety of effects over almost every type ofhematopoietic cell, and its role relies mainly on the regulation of antigen presentingcells (APCc) and T cells [19]. The action of IL-10 on APC induces an inhibition of proin-flammatory cytokine production, such as tumor necrosis factor α (TNF-α) and IL-1β,and decreases the expression of major histocompatibility complex (MHC)-I, MHC-II (involved in antigen presentation), and costimulatory and adhesion molecules [20,21]. Moreover, IL-10 directly affects CD4+ T cells by inhibiting proliferation and pro-duction of Th1 and Th2 cytokines [22, 23].

B-cell regulatory capacity associated with IL-10 production was demonstrated inC57BL/6 mice with a selective defect in IL-10 production by B cells and induced toEAE, which did not reach remission, whereas wild-type mice resolved the diseasespontaneously [17]. In the model of collagen-induced arthritis (CIA), the adoptivetransfer of B cells from DBA/1 mice in remission stage prevented the developmentof the disease in collagen-immunized mice, whereas adoptive transfer of IL-10−/− Bcells did not present the protector effect [9].

These findings suggest the existence of an IL–10-producing B-cell subset with reg-ulatory capacity over autoimmune and inflammatory manifestations.

The study of the phenotype of IL–10-producing B cells has allowed the definitionof transitional-2 cells and B10 cells (Table 1). These two subsets have been studiedboth in mice and humans, with some differences in their regulatory functions. Aswill be discussed here, in murines, B-cell regulation seems to be IL–10-dependent,whereas the results in human cells show a partial dependence on this cytokine(Figure 2).

Transitional-2 B cellsIn the CIA model, IL–10-producing splenocytes were identified in response tolipopolysaccharide (LPS) or anti-IgM in vitro stimulation and presented a phenotypecorresponding to transitional-2 marginal zone precursor B cells (T2-MZP) (Table 1).When activated in vitro, these cells inhibited IFN-γ production by CD4+ T cells stim-ulated with anti-CD3. Adoptive transfer of T2-MZP cells from CIA mice in disease re-mission into type II collagen-immunized mice significantly reduced both the cellu-lar infiltrate and the cartilage damage. However, clinical remission was not achievedwhen these cells were transferred from IL-10−/− mice [24].

In the mouse model of adjuvant-induced arthritis (AIA), co-culture of T2-MZP Bcells with effector CD4+CD25− T cells induced the differentiation of T cells into aCD4+Foxp3+ regulatory phenotype producing IL-10. Adoptive transfer of T2-MZPfrom mice in remission into mice immunized with methylated serum bovine albuminreduced joint swelling and the proportion of CD4+IFN-γ + and IL-17+ T cells, and sig-nificantly increased the proportion of CD4+Foxp3+ T cells in these mice, whereas thetransfer of IL-10−/− T2-MZP B cells did not show this regulatory role over disease de-velopment [25, 26].

Similar results have been found in a lupus murine model. The transfer of T2 B cellsderived from MRL/lpr mice and stimulated in vitro with a CD40 agonist antibody re-duced signs of clinical disease (proteinuria and glomerular infiltration), the levels ofanti-dsDNA antibodies, and disease-associated deaths when transferred to MRL/lprmice. In contrast, when using an IL–10-blocking antibody, this regulation was not ob-served [4].

This and other evidence have shown the existence of a B-cell subset with transi-tional phenotype that has the capacity to regulate different autoimmune manifesta-

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Tab

le1

.Su

bp

opu

lati

ons

and

som

ech

arac

teri

stic

sof

regu

lato

ryB

cells

.

EFF

EC

TS

RE

PO

RT

ED

ON

:(R

EP

OR

TE

DC

YT

OK

INE

SP

RO

DU

CE

D)

Ph

enot

ype

Th1

(TN

F-α

,IF

N-γ

)Th

17(I

L-17

)Th

2(I

L-13

)M

onoc

ytes

(TN

F-α

)R

egu

lato

ryT-

cell

ind

uct

ion

(IL-

10)

IL-1

0+B

Cel

ls

Mu

rin

eB

10C

D19

+

CD

5+

CD

1dh

i

Inh

ibit

s[1

3,30

,32

,59,

76]

Inh

ibit

s[3

0,34

,59

]

Pro

mot

es[7

6]N

SP

rom

otes

[32,

74]

Incr

ease

d:h

CD

19Tg

[30,

31],

CD

22−/

−[3

1]N

orm

al:M

HC

-I/I

L−/−

[31,

33],

CD

21−/

−[3

1]D

ecre

ased

:CD

19−/

−[3

0,31

,33]

,MD

4[3

1,59

],C

D40

−/−

[33]

,Il-

21r−/

−

[33]

,Myd

88−/

− [31]

,M

uri

ne

T2-

MZ

PC

D19

+

CD

21+

CD

23+

IgM

+

CD

1dh

i

Inh

ibit

s[4

,24

–26]

Inh

ibit

s[2

5,26

]N

SN

SP

rom

otes

[4,

24–2

6]N

S

Hu

man

B10

CD

19+

CD

24h

i

CD

27+

Inh

ibit

s[3

8,39

]N

SN

SIn

hib

its

[38]

NS

Incr

ease

d:R

heu

mat

oid

Art

hri

tis

[38]

,SLE

[38]

,Sj

ogre

n’s

Syn

dro

me

[38]

Nor

mal

:Mu

ltip

leSc

lero

sis

[38]

,Eu

thyr

oid

Gra

ves’

dis

ease

[39]

Dec

reas

ed:N

ewly

dia

gnos

edG

rave

s’[3

9]H

um

anT

2C

D19

+

CD

24h

i

CD

38h

i

Inh

ibit

s[2

7,29

](D

efec

-ti

vein

SLE

pa-

tien

ts)

[27]

Inh

ibit

s(d

efec

-ti

vein

rheu

ma-

toid

arth

riti

sp

a-ti

ents

)[2

9]

NS

NS

Pro

mot

esIn

crea

sed

:SLE

[27]

Nor

mal

:Sjo

gren

’sSy

nd

rom

e[2

7],

Ost

eoar

thri

tis

[27]

Dec

reas

ed:A

ctiv

eR

heu

mat

oid

Art

hri

tis

[29]

aN

S:N

otst

ud

ied

orre

por

ted

.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

FIGURE 2. Subpopulations of IL–10-producing B cells. In murines, two IL–10-producingpopulations have been described: B10 cells (CD19+CD5+CD1dhi) and T2-MZP cells(CD19+CD21hiCD23+CD1dhi). In humans (as in murine models), transitional-2 B cells(CD19+CD24hiCD38hiCD1dhi) and human B10 cells (CD19+CD24hiCD27+CD1dhi) have beenidentified.

tions in mice. Regulation of proinflammatory cytokine production and proliferationof CD4+ T cells by B cells seems to be a mechanism mainly dependent on IL-10.

In humans, in parallel, the presence of IL–10-producing B cells with a transi-tional CD19+CD38hiCD24hi phenotype have been described in peripheral blood fromhealthy controls [27].

In vitro stimulation of these cells with an anti-CD40 antibody reduced prolifera-tion and TNF-α and IFN-γ production by pre-activated CD4+ T cells in a mechanismpartially dependent on IL-10, because the blockage of this cytokine in the co-culturesinduced modulation of these proinflammatory cytokines, but had no effect on T-cellproliferation [27, 28].

In SLE patients, it has been reported that T2 B cells are significantly increased com-pared with healthy controls and patients with other autoimmune diseases, such asSjogren’s syndrome and osteoarthritis. However, T2 cells from SLE patients were un-able to inhibit TNF-α and interferon gamma (IFN-γ ) production by activated CD4+

T cells, compared with T2 cells from healthy subjects or patients with other autoim-mune diseases. These findings were associated with a decreased IL-10 production byCD40-stimulated T2 cells from SLE patients [27].

A study in active RA patients showed a decreased frequency ofCD19+CD38hiCD24hi T2 cells in peripheral blood from these patients comparedwith healthy controls and RA patients with inactive disease. However, T2 B cells fromRA patients could regulate the production of the proinflammatory cytokines IFN-γand TNF-α by activated effector CD4+CD25− T cells and increased the frequencyof regulatory CD4+Foxp3+ T cells, comparable with healthy controls, in a processdependent on IL-10. Nevertheless, compared with healthy controls, T2 cells from RApatients could not block the polarization of T cells to a Th17 profile [29].

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

FIGURE 3. IL-10 production of C57BL/6 mouse spleen B cells after ex vivo stimulation with LPS,PMA, and ionomycin for 5 hours.

Compared with murines, results in humans suggest that B-cell regulation is notcompletely dependent on IL-10, and seems to require additional mechanisms thatremain unclear, which suggests that more studies are needed to understand regula-tory mechanisms executed by B cells in humans.

B10 cellsIn mice, B cells with a CD19+CD5+CD1dhi phenotype, known as B10 cells, have beencharacterized in the spleen and peritoneum as IL–10-producing cells in response toex vivo stimulation with LPS plus phorbol-12-myristate-13-acetate (PMA) and iono-mycin (L+PI) (Figure 3). Although a small percentage of B10 cells are IL-10 producers(0.5–1.5%), these cells can increase (5–6%) and acquire IL-10 production capacity invitro (B10pro cells) through CD40 stimulation by agonist antibodies or with the CD40ligand (CD40L) [30, 31].

In the EAE model, B10 cells stimulated with anti-CD40 and LPS reduced the pro-duction of IFN-γ and TNF-α by CD4+ T cells, compared with B10 from IL-10−/−

EAE-induced mice that did not induce the regulatory effect on T cells. However, itwas observed that generation of B cells with a regulatory phenotype was not IL–10-dependent, since the frequency of B10 cells in IL-10−/− mice did not differ from wild-type mice [32].

Similarly, in the murine model of colitis induced by oral administration of dex-tran sulphate sodium, adoptive transfer of B10 cells from wild-type mice reduced dis-ease severity, whereas this effect was not observed with the B10 cells from IL-10−/−

mice [33]. Moroever, in the CIA model, adoptive transfer of B10 cells into collagen II-immunized DBA/1 mice significantly decreased arthritis development and reducedthe frequency of Th17 T cells, whereas B10 cells from IL-10−/− mice did not inducedisease regulation [34].

In a viral brain infection model induced with murine cytomegalovirus, a significantincrease in the frequency of B cells with B10 phenotype was observed. Stimulation of

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

CD19+IL-10+ cells with anti-CD40, LPS, PMA, and ionomycin reduced the productionof TNF-α by microglial cells infected with murine cytomegalovirus, compared withCD19+IL-10− lymphocytes [35], suggesting that IL-10 production by B cells can inhibitthe efficient neuroimmune response.

B10 cells have also been proved to be involved in cancer. CD20−/− mice presentedsimilar frequencies of IL-10+ B cell compared with wild-type mice, suggesting thatthis molecule is not necessary for the maturation and function of IL–10-producingB cells. The transfer of B10 cells from CD20−/− mice into wild-type mice treatedwith anti-CD20 before tumoral cell inoculation induced an increase in tumor sizecompared with the effect observed with B10 cell transfer from CD20−/− IL-10−/−

mice [12], which suggests that IL-10 production by B cells can inhibit the anti-tumoralresponse needed for cancer cell elimination. Interestingly, it has been observed thatpatients with non-Hodgkin lymphoma and depletion of CD20+ cells by anti-CD20treatment could not induce a lasting response in a portion of the patients [36],possibly due to failure to eliminate this IL–10-producing B-cell subset that is resistantto depletion with rituximab [37].

The parallel of murine B10 cells in humans has been described in peripheral bloodwith a CD19+CD24hiCD27+ phenotype (“human B10”). These are IL–10-producingcells after a short ex vivo stimulation with TLR ligands and PMA-ionomycin. Addi-tionally, these B10 cells can differentiate into IL–10-producing cells (human B10pro)in response to in vitro CD40 stimulation, together with LPS or CpGs, compared withex vivo stimulation [38]. These B10 cells could also regulate because, in co-culturesof anti-CD3 activated CD4+ T cells or with LPS-activated monocytes, they reducedthe proportion of CD4+ T cells or monocytes producing of TNF-α. Interestingly, theregulation over monocytes was inhibited with a blocking antibody for IL-10, whereasregulation over T cells was not affected [38].

The frequency of IL–10-producing CD19+CD24hiCD27+ B10 cells was found in-creased in patients with RA, SLE, and Sjogren’s syndrome, compared with patientswith multiple sclerosis and healthy controls [38]. On the other hand, other autoim-mune diseases, such as Graves’ disease, reported a decrease in B cells with this phe-notype compared with healthy controls and patients that responded to methimazoletreatment (called “euthyroid”) [39].

Similar to murine transitional 2 B cells, murine B10 cells depend on IL-10 produc-tion to execute their regulatory functions. Likewise, in humans, regulation seems to beonly partially mediated by the production of this cytokine. Evidence suggests that B10cells are capable of reducing the clinical signs in several models of autoimmune dis-eases. Alterations in these cells could partially explain the alterations in the immuneresponse observed in autoimmune diseases.

Plasmablasts CD138+CD44+

In the EAE model, it was reported that plasmablasts CD138+CD44+ were an importantsource of IL-10 in the spleen and draining lymph nodes. These cells had an increase to40% in the latter phase of inflammation onset. In agreement with this, it was observedthat the absence of IL-10+ plasmablasts increased the clinical score of this experimen-tal disease [40]. Moreover, mice infected with virulent Salmonella typhimurium pre-sented an increased frequency of CD138+IL-10+ cells compared with mice withoutinfection [41]. These results suggest that B cells differentiated into plasmablasts canfunction as regulatory B cells through IL-10 secretion.

Tissue Growth Factor BetaTGF-β is a mutifunctional cytokine produced by mononuclear phagocytes and regu-latory T lymphocytes, among other cells, that has pleiotropic effects on different types

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

of cells. From the point of view of immunological regulation, this cytokine is importantfor the inhibition of CD4+ cell differentiation to a Th1 profile and is a necessary factorfor generating Th17 and regulatory T cells [42]. In the non-obese diabetic autoimmunemodel, B cells activated with LPS in vitro produced significantly higher levels of TGF-β,but no differences were observed for IL-10 production compared with non-stimulatedB cells. These TGF–β-producing cells inhibited Th1 responses directed against theinsulin-producing β-pancreatic cells. Adoptive transfer of these activated B cells in-hibited the development of diabetes in NOD mice, reducing the clinical signs and in-creasing the apoptosis of effector T cells compared with the transfer of non-activatedB cells [43]. Although no TGF–β-blockage experiments were performed in this study,regulation by B cells was associated with higher production of this cytokine [43].

B cells derived from hilar lymph nodes of C57BL/6 mice that developed local toler-ance to inhaled ovalbumin induced a significant increase in the proportion of Foxp3+

T cells derived from effector CD4+CD25− T cells previously stimulated with anti-CD3/anti-CD28. This differentiation from effector into regulatory T cells was inhibitedby a blocking anti-TGF-β antibody, whereas an anti-IL-10 antibody had no effect [44].A subsequent study described that the subset of CD19+CD5+ cells contained the Bcells that regulate through a TGFβ-dependent mechanism [45].

In addition to the previously described regulatory B-cell phenotypes, aCD19+CD25hi B-cell subset producing high levels of IL-10 [46] and TGF-β in re-sponse to TLR9 stimulation has been described in human peripheral blood [47].These B cells stimulated with CpG and CD40L in vitro induced a significant increasein Foxp3 expression in CD4+CD25hi regulatory T cells. Use of an antibody directedto TGF-β inhibited this regulatory response, whereas an anti-IL-10 antibody did notalter the induction of the regulatory phenotype observed in these cells [47].

Regulation mediated by TGF-β together with IL-10 production seems to be impor-tant in controlling diverse inflammatory manifestations. However, additional studiesare warranted to clarify whether there are one or several regulatory B-cell subsets,which could carry out their function through TGF-β, IL-10, or both cytokines.

Immunoglobulin M ProductionIgM promotes apoptotic cell removal, both in murines and humans, inducing theirphagocytosis and avoiding activation of proinflammatory signals through Fcγ R [48]and complement cascade activation [49]; this results in a decrease in the antigenicload and, therefore, in the inflammatory signals.

It was observed that C57BL/6 mice deficient in IgM secretion presented higher lev-els of plasma creatinine and renal injury explained by ischemia–reperfusion com-pared with wild-type mice. Meanwhile, the administration of polyclonal IgM to defi-cient mice reversed clinical symptoms, which was not observed with immunoglobulinG (IgG) administration or in untreated IgM-deficient mice [50].

Splenectomy in the deficient apolipoprotein (apoE−/−) atherosclerosis mousemodel removes MZ and B1a B-cell subsets, which are the main IgM-producing cells.ApoE−/− mice that received this intervention presented a significant increase in thesize of atherosclerotic plaques, macrophage infiltrates, and number of apoptotic cellsin the lesions. When B1a cells were transferred from wild-type to apoE−/− mice, dis-ease manifestations were reduced, compared to that with splenectomized and wild-type mice without treatment. However, transfer of B1a cells from sIgM−/− incapable ofsecreting IgM had no regulatory effect [51].

Transfer of autoreactive polyclonal IgM directed to nuclear antigens into lupus-likeFcγ rIIb−/− Tlr9−/− mice increased their survival and decreased the accumulation ofTh1 and Th17 CD4+ T cells in the spleen and in peripheral blood compared with un-treated mice or those treated with control IgM [52].

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

In humans, it has been observed that SLE patients with high anti-ds-DNA IgG andanti-cardiolipin IgM levels presented a significantly lower risk of developing kidneyinvolvement compared with patients with lower levels of these antibodies. Similarly,SLE patients with high levels of anti-phosphorylcholine IgM had a lower risk of suffer-ing cardiovascular disease compared with patients with lower levels of this antibody[53].

Production of natural IgM antibodies could contribute to efficient removal of au-toantigens, which is an important step toward controlling inflammation and prevent-ing autoimmune disease development. However, it is necessary to clarify which B-cellsubsets are in charge of this IgM production. It is possible that the production of IgMmay be one of the regulatory mechanisms implemented by regulating the B cells.

Cell Death InductionActivation-induced cell death and clonal deletion are some of the most widely ac-cepted mechanisms of peripheral tolerance, as well as a mechanism to regulate dura-tion and extent of the immune response. The main molecules involved in this responseare Fas and FasL [54]. FasL belongs to the family of TNF receptor proteins and inducesapoptosis in cells expressing the Fas receptor [54].

In CBA/Jk mice infected subcutaneously with Schistosoma mansoni, it was ob-served that B cells, especially the B1a subset, upregulated FasL expression, which wasassociated with an inefficient development of granulomas surrounding S. mansonieggs in the liver [55]. Adoptive transfer of B1a cells stimulated with antigens from S.mansoni eggs, which expressed higher levels of FasL compared with non-stimulatedB1a cells, induced a significant increase in the percentage of apoptotic CD4+ T cells,compared with the adoptive transfer of non-stimulated B cells [56]. Increase in FasLexpression in B cells has been observed previously in other conditions, such as Try-panosoma cruzi infection in BALB/c mice [57] and infection of mononuclear cells byEpstein–Barr virus [58]. Therefore, it is suggested that some pathogenic agents use theregulation mediated by B cells, specifically the induction of apoptosis of effector Tcells, as a mechanism to avoid adaptive immune responses through the disruptionof the protecting immune response.

In the NOD autoimmune diabetes mouse model, B cells previously activated invitro with LPS expressed higher levels of TGF-β and increased FasL expression com-pared with untreated B cells. Adoptive co-transfer of T and B cells from NOD mice intoimmunodeficient (Scid) NOD mice transferred the autoimmune diabetes, whereas co-transfer of T cells and B cells previously activated with LPS prevented disease devel-opment. The authors suggest that the observed regulatory effect could be explainedby the increased expression of FasL in activated B cells, which could correlate with theincreased percentage of apoptotic T cells observed in the presence of activated B cells[43].

The evidence suggests that apoptosis induction by B cells could lead to a reductionin the percentage of effector T cells. This mechanism could contribute to the controlof autoimmune manifestations and would affect the development of a protecting im-mune response against infections and cancer. However, it is necessary to clarify therole of cell-death inductor pathways in the regulation executed by B cells.

Cell Contact-Dependent MechanismsIn addition to regulation by IL-10, regulatory effects mediated by cellular interactionshave been described, mainly with T cells. Results demonstrate that the regulation of Tcells by B cells is not only dependent on IL-10, but also on molecules involved in cellcontact [29].

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

MHC molecules are involved in antigen presentation of intracellular (class I) or ex-tracellular (class II) antigens to T cells. In the EAE mouse model, adoptive transferof B cells from MHC-I/II−/− mice (deficient in MHC-I and II and CD1d) into B–cell-deficient Cd19−/− mice did not induce a reduction in the clinical symptoms of thedisease, compared with mice that received the adoptive transfer with B cells from wild-type animals. Further, B cells from MHC-II−/− mice did not induce a decrease in pro-liferation of activated CD4+ T cells, or in IFN-γ and IL-17 production when comparedwith wild type cells [59]. A lower percentage of B cells with a B10 phenotype has beenobserved in MHC-I/II−/− mice, after L+PI ex vivo stimulation compared with wild-type mice. Evidence suggest that antigen presentation by B cells is mandatory for reg-ulation executed by these cells on effector T lymphocytes and on autoimmune mani-festations [59].

CD80 and CD86 molecules belong to the B7 family; they are expressed on APCs,and are important in establishing the immunological synapse and in the activation ofadaptive immune response. B–cell-deficient (μMT) EAE mice partially reconstitutedwith bone marrow from wild-type mice significantly increased both Foxp3 and IL-10production in the spinal cord and entered into remission; these effects were not ob-served when the tissue was derived from a B7-deficient mouse restricted to B cells[60]. This suggests that B7 costimulatory molecules expressed on B cells are necessaryfor the establishment of central nervous system tolerance.

In humans, the culture of CD19+CD38hiCD24hi cells from healthy controls withanti-CD3/PI stimulated CD4+CD25− T cells inhibited IFN-γ and TNF-α production byT cells as well as T-cell proliferation. The use of blocking antibodies directed to CD80or CD86 partially reduced the regulatory effect of transitional B cells on inflammatorycytokine production, but had no effect on T-cell proliferation. Simultaneous blockadeof IL-10, CD80, and CD86 with antibodies induced a complete loss of the inhibitoryeffect [29], suggesting that regulation of clinical signs and proinflammatory cytokineproduction by B cells is dependent on contact with T cells through the participation ofAPCs, such as MHC-II and the costimulatory molecules CD80 and CD86. It is not yetknown whether there are costimulatory molecules from other families (besides CD40,described further) that are important for the regulatory function of B cells, and if theregulation executed by these cells on monocytes and macrophages depends on cellcontact.

PD-L1 is a member of the B7 family with a capacity for inhibiting T-cell activationby binding to PD-1. It recruits phosphatases toward its intracellular domain. Thesephosphatases dephosphorylate complexes involved in the transduction of signalingoriginating in TCR [61]. C57BL/6 μMT mice who received adoptive transfer of B cellsfrom C57BL/6 wild-type mice with EAE presented reduced clinical signs of the experi-mental disease compared with B-cell transfer from a Pd-l1−/− mouse [62]. It has beensuggested that this signaling pathway allows B cells to regulate autoreactive cells inmultiple autoimmune diseases; however, further study is warranted to confirm theseimplications in B cells with a regulatory phenotype.

Other MechanismsThe findings obtained to date in the study of regulatory B cells indicated that variousregulatory mechanisms are yet to be identified in the function of these cells. As shownfurther, evidence suggests the participation of other molecules in B–cell-induced reg-ulation.

IgG4 functionally differs from other IgGs due to its low affinity for Fcγ receptorsand C1q complex and, therefore, has a reduced capacity to activate the complementcascade and the proinflammatory response in innate immune cells [63]. Due to thesecharacteristics, it has been described as “anti-inflammatory IgG.” In fact, it has been

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

observed how administration of serum with IgG4 specifically directed to the acetyl-choline receptor (AChR) protects rhesus monkeys from developing myasthenia graviscompared to administration of serum with the AChR-specific antibody IgG1 [63]. Inanother study, IgG4-producing B cells from the peripheral blood of healthy individ-uals were confined to IL–10-producing B-cell phenotype [64]. When conducting im-munotherapy with bee venom, the phospholipase A-specific IgE/IgG4 ratio was signif-icantly increased in controls compared with venom-tolerant beekeepers [64]. Thesefindings suggest there could be an additional regulatory mechanism mediated byIL–10-producing B cells through IgG4 production.

IL-35, a member of the IL-12 family of heterodimeric cytokines, is produced byTregs and contributes to their suppressive activities. IL-35 deficiency restricted to Bcells (Bp35) in the EAE model induced an increased clinical score with higher IFN-γand IL-17 production compared with non-deficient mice [65]. This evidence suggestsIL-35 production by B cells as a potential regulatory mechanism executed by B cells.

MOLECULES INVOLVED IN THE ACTIVATION OF THE B-CELLREGULATORY FUNCTION

CD40CD40 is a membrane protein that belongs to the TNF receptor superfamily and is in-volved in a wide variety of immunological processes, such as isotype switching, mem-ory B-cell development, and germinal center formation. The signaling cascade initi-ated by CD40 can activate multiple transcription factors, such as Sp1, nuclear factorkappa-light-chain-enhancer of activated B cells (NF-κB), and nuclear factor of acti-vated T cells (NFAT), among others, which could lead to IL-10 production [66].

It has been widely demonstrated that in vitro stimulation via CD40 for 48–72 hoursenables B cells with B10 phenotype that do not produce IL-10 ex vivo to produce thiscytokine in response to stimulation with L+PI (referred to as B10pro). These B10procells have been characterized both in murine and human studies [31, 38]. Likewise, invitro stimulation via CD40 for 48–72 hours, with PI stimulation for the final 5 hours,has been used to induce IL-10 production by T2-MZP cells in murine studies [4].

In the EAE model, it was demonstrated that splenic B cells responded to stimulationwith a CD40 antagonist antibody by producing IL-10, whereas B cells from Cd40−/−

mice were unable to produce this cytokine, presented increased in clinical signs, andcould not induce disease remission [17].

In humans, the co-culture of CD19+CD38hiCD24hi cells from healthy controls withpreviously activated CD4+CD25− effector T cells inhibited IFN-γ and TNF-α produc-tion by T cells as well as the proliferation of these cells. The use of CD40L-blockingantibodies inhibited both IL-10 production in B cells and T-cell proliferation withoutaffecting IFN-γ or TNF-α production [27, 28].

Evidence suggests that the CD40-CD40L interaction plays a significant role in theregulation of the inflammatory manifestations, both in murine and human models. Itremains unknown whether the polymorphisms, both in CD40 and CD40L, observed inSLE patients could partially explain the regulatory defects observed in this and otherdiseases. It is also unknown in which context in vivo stimulation trough CD40 wouldfavor a regulatory response versus an effector response with isotype switching and im-munological memory.

Toll-like ReceptorsToll-like receptors (TLRs) are a well-preserved family of molecules specialized in rec-ognizing a wide variety of molecular patterns triggering the transduction of importantsignals both in the innate and adaptive immune responses. According to the subpop-

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

ulation, murine B cells have different levels of TLR-1, -2, -3, -4, -6, -7, -9, and RP105expression, whereas human B cells have a similar expression profile of TLRs with dif-fering TLR-5, TLR-8, and TLR-2 expression [67, 68].

It has been reported that CpG treatment in NZB/NZW lupus mice induces an in-crease in their survival accompanied by a decrease in proteinuria, nitrate/nitrite secre-tion, and glomerular pathology, although with significant increase in anti-dsDNA lev-els compared with untreated mice [69]. Similar results were observed in LPS-treatedmice prior to EAE induction, where a decreased T-cell proliferation, TNF-α produc-tion, and a delay in infiltration of T cells and macrophages in the central nervous sys-tem were observed compared with untreated mice [70]. Tlr-9 gene deletions favoredthe development of lupus manifestations in MRL lpr/lpr mice [71]. In humans, it hasbeen observed that Tlr-9 gene polymorphisms are related to low TLR-9 expression,which has been associated with a predisposition to develop SLE [72], possibly throughthe increase in levels of autoantibodies produced by B cells observed in this disease.

In the EAE model, the partial reconstitution of μMT mice with bone marrow froma mouse with deficiency of the molecule MyD88 (implicated in TLRs signaling), re-stricted to B cells, induced increased clinical manifestations and inhibition of diseaseremission, compared with wild-type bone marrow reconstitution. An increased pro-duction of IFN-γ and IL-17 by CD4+ T cells was observed in the presence of Myd88−/−

B cells in vitro using MOG, compared to wild-type cells [73]. Similar results were ob-served when mice were deficient for TLR2 and TLR4 only restricted to B cells [73].Likewise, IL-10 production resulting from B10 cells stimulation with LPS suggests thatstimulation by some TLRs has a significant role for the regulatory function carried outby B cells.

In humans, in vitro stimulation of spleen or peripheral blood B cells with CD40Lplus a TLR-1–9 agonist for 48 hours, together with PI in the last 5 hours, induced someIL-10 production. However, treatment with LPS and CpGs were responsible for an in-creased IL-10 production compared with other TLR ligands or with non-stimulatedcells [38]. These results indicate that at least the signals by LPS (through TLR4 andRP105) and CpG (TLR9) seem to play a significant role in IL-10 production by B cells.Alterations in the transduction of signals by these TLRs could hinder the effective ac-tivation of regulatory B cells and their subsequent participation in the resolution ofinflammatory manifestations.

B-cell ReceptorB-cell antigen specificity is determined by the B-cell receptor (BCR) complex, whichexists as an immunoglobulin molecule bound to the membrane associated to the Igα

and Igβ chains that are responsible for signal transduction. Upon recognizing the anti-gen, the complex induces the activation of multiple pathways leading to B-cell activa-tion.

In MD4 mice, which express hen-egg lysozyme-specific IgD and IgM, there weresimilar levels of B10 cells as well as a significant decrease in the percentage of IL-10+

B cells after ex vivo stimulation with L+PI that was observed compared with wild-typemice [31]. This suggests that the BCR diversity is critical for the normal generation andexpansion of IL–10-producing cells.

When B-cell adoptive transfer was performed from an anti-IgM-activated NODmice to NOD mice in diabetes-onset stage, disease development was delayed with alower incidence compared with control mice [10]. BCR-stimulated NOD mouse B cellsinduced high levels of IL-4 and IL-10, and low levels of IFN-γ by anti-CD3-stimulatedCD4+ T cells [10]. In a different study, in vitro stimulation with anti-IgM for 72 hoursand with PI for the final 5 hours induced IL-10 production in murine B cells, but in

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

a significantly lower proportion when compared with LPS or anti-CD40 stimulation[31].

These findings suggest that BCR stimulation could induce a regulatory pheno-type in B cells only when the CD40 and TLR signals are present, indicating that theligand-rich pro-inflammatory environments for BCR, CD40, and TLRs could favor thedevelopment of IL-10-producing regulatory B cells.

CD19CD19 is a B-cell membrane glycoprotein that belongs to the immunoglobulin super-family. CD19 participates, along with membrane Ig, complement receptor 2 (CD21),CD81, and CD225, in the processive amplification of the signals triggered by the BCRcomplex antigen recognition.

Cd19−/− mice develop a severe, chronic form of EAE with increased clinical signsand manifestations and are unable to enter disease remission, compared with wild-type mice. This is associated with a significant reduction in the percentage of IL–10-producing B cells ex vivo and in vitro. In contrast, mice with transgenic increased ex-pression of CD19 (hCD19Tg) had higher percentages of IL–10-producing B cells andunderwent a less severe form of EAE than Cd19−/− and wild-type mice [30].

CD19-deficient NZB/W lupus mice presented lower survival rate, marked renaldamage, and increased glomerulonephritis compared with wild-type mice. More-over, CD19-deficient mice presented a decrease in the frequency of cells with B10phenotype and in IL-10 production by these cells. The adoptive transfer of B10 cellsfrom wild-type mice to a Cd19−/− mouse decreased disease severity and increasedthe number of IL–10-producing CD4+CD25+Foxp3+ T cells [74]. Similar results wereobserved in a murine model of imiquimod-induced psoriasis and in chronic graft-versus-host disease models, in which Cd19−/− mice had an absence of B10 cells anda significantly lower number of IL-10+ B cells following ex vivo stimulation comparedwith wild-type mice [75, 76].

CD19 is required in order to control inflammatory manifestations and its deficiencyleads to a marked decrease in IL–10-producing B cells; the CD19 signaling pathwaycould be necessary for the generation and regulatory function of these cells. However,further studies are warranted to clarify this hypothesis.

CD1dCD1d is a membrane glycoprotein that belongs to the CD1 family, which is structurallysimilar to MHC-I; it has limited polymorphism and is expressed in APCs. Unlike MHCmolecules that present protein antigens, CD1d presents glycolipids that can be rec-ognized by the TCR of natural killer T (NKT) cells. In an autoimmune colitis model,B cells from TCR-α−/− mice (which spontaneously develop colitis) expressed IL-10 atthe transcriptional level, whereas B cells from TCR-α−/− Cd1d−/− mice did not presentthis expression and experienced increased inflammatory symptoms [77].

Concurrently, a study demonstrated that total B cells from peripheral blood fromhealthy controls induced the proliferation and activation (measured by the expressionof Ki65 and CD25) of the invariant (iNKT) cells; however, B cells of SLE patients pre-sented defects in the expression of CD1d and were unable to induce the proliferationand activation of iNKT cells [78]. Further, SLE patients responding to rituximab treat-ment presented a significant increase in the expression of CD1d in B cells and in thenumber of iNKT cells after B-cell repopulation, compared with patients that did notrespond to the treatment [78].

It has been observed that the T84 human cell line transfected with CD1d is able toinduce IL-10 production after binding to an anti-CD1d agonist antibody, whereas noIL-10 induction was observed when the same cell line was transfected with a CD1a/d

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

chimeric molecule (CD1a cytoplasmic tail) [79]. It was previously reported that theintracellular portion of CD1d serves as a tyrosine kinase substrate, inducing theactivation of a signaling cascade leading to IL-10 transcription [79], which could ex-plain the importance of CD1d expression on the regulatory function of B cells.

Other MoleculesOther molecules, besides those mentioned previously, seem to participate in the gen-eration, maintenance, expansion, or activation of regulatory B cells.

IL-21rAdoptive transfer of B10 cells from wild-type to Cd19−/− mice in the EAE model re-duced the clinical signs and induced disease remission, which was not observed whenusing B10 cells from IL-21r−/− mice. In addition, B10 cells from Il-21r−/− mouse wereunable to reduce IFN-γ and IL-17 production by CD4+ T cells with MOG-specific TCR[59]. It has been reported that the number of cells with a B10 IL-10+ phenotype ex-pands exponentially in vitro in the presence of IL-21, BAFF, and CD40L. The adoptivetransfer of these expanded B cells to wild-type mice with EAE resulted in a significantdecrease of the signs and a more rapid disease recovery, compared with mice withnon-B10 cells transfer [59]. These findings suggest the in vitro regulatory B-cell expan-sion as a possible therapeutic strategy to control inflammatory diseases.

Stromal interaction molecule 1 and 2 (STIM1 and STIM2)Recognition of a specific antigen by BCR leads to intracellular calcium mobilization,whose levels are detected by the STIM1/2 molecules, with the subsequent activationof transcription factors, such as NFAT, that may lead to IL-10 transcription [80]. In EAE,B cells from mice with deficiency in the calcium sensors STIM1 and STIM2 producedsignificantly lower levels of IL-10 compared with wild-type mice. Transfer of stim1−/−

B cells into μMT mice did not induce improvement in the severity of the disease due tothe defective activation of NFAT. B-cell transfer from non-deficient mice significantlyreduced the degree of autoimmune manifestations in EAE mice, which was associatedwith the production of IL-10 locates downstream of NFAT activation [80]. Further stud-ies are required to clarify the signaling involved in IL-10 production by B cells, whetherit is dependent or independent from calcium mobilization.

B-cell-activating factor receptorsThe B-cell-activating factor (BAFF) is a member of the TNF family and is important inperipheral B-cell survival, B-cell maturation processes, isotype switch recombination,and T-independent antibody production [81]. BAFF, also known as BLyS (B lympho-cyte stimulator), is either membrane-bound or produced in soluble form by T cells,APCs, and some epithelial cells. B cells express three BAFF receptors: CD267 (TACI),CD268 (BAFF-R, BR3), and CD269 (BCMA). BAFF was demonstrated to be able to in-duce IL-10 production in vitro by murine B cells with B10 phenotype, whereas additionof a soluble BAFF receptor to the culture neutralized the effect. These BAFF-inducedB10 cells inhibited in vitro IFN-γ production and proliferation of anti-CD3-stimulatedCD4+CD25− T cells [82].

B cells from healthy individuals stimulated in vitro with CpGs and BAFF signifi-cantly increased the expression of IL-10, TLR-9, and MHC-II compared with stimula-tion with CpGs alone [83], whereas stimulation with BAFF and CD40L induced matu-ration of IL–10-producing B10pro cells, which increase exponentially after stimulationwith IL-21 [59]. This suggests that BAFF, through its receptors and together with other

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

signals from TLRs or CD40, among other molecules, may participate in the develop-ment and maintenance of regulatory B cells.

CONCLUDING REMARKS

B cells with regulatory phenotype (Bregs) have the ability to modulate diverse inflam-matory manifestations, both in murine and human studies. The most widely studiedand understood mechanism to date is that which depends on IL-10 production. Inmurines, Breg cells inhibit TNF-α production by monocytes and the proliferation andproduction of proinflammatory cytokines, such as TNF-α, IFN-γ , and IL-17 in CD4+

T cells. In humans, Bregs induce similar effects to those observed in murines in CD4+

T cells; however, its mechanism is not completely dependent upon IL-10 production.In addition to IL-10, the production of TGF-β, IgM, and IgG4 and the expres-

sion of death-inducing molecules have been described as other potential mecha-nisms by which B cells are able to regulate the immune response. Anergic B cells alsoseem to have intrinsic regulatory abilities. In an Ars/A1 transgenic murine model ex-pressing IgM and IgD BCR with dual reactivity for hapten p-azophenylarsonate (Ars)and autoantigens (which include single-stranded DNA), it was found that adoptivetransfer of Ars/A1 B cells to Ars covalently conjugated to OVA- and HEL-immunizedmice, inhibited 95% of the production of anti-Ars IgG antibodies. Therefore, anergicB cells are thought to play an additional role in tolerance induction once the spe-cific antigen is recognized. This regulation was independent from IL-10 productionand IgM secretion, but required cell contact through the cognate interactions be-tween MHC-II and CD4+ T lymphocytes [84]. However, the contribution of each ofthese pathways to B–cell-mediated regulation and the pathophysiological contextsin which they participate remain unknown. Therefore, it is necessary to understandthe diverse regulatory mechanisms that participate and their type of activation inB cells for subsequent intervention as therapeutic targets in multiple pathologicalconditions.

To date, B-cell regulatory function is understood to be mainly exerted by CD40and TLR activation, as well as by antigen-presenting MHC and CD1d, and the anti-gen recognition signals from BCR and CD19. The absence of any of these moleculesleads to a marked defect in the regulatory capacity of B cells. These findings suggestthat the regulation mediated by these lymphocytes must be a highly refined and con-trolled process, having multiple checkpoints, and starting in inflammatory environ-ments where all of these signals coexist. However, it is still unknown whether Bregsbelong to a subpopulation that is inducible depending on the signals it receives, or ifthey are naturally part of this phenotype.

There is limited knowledge about the molecular mechanisms involved in IL-10 pro-duction by B cells and regarding their differentiation to Bregs. Initial studies have re-vealed the participation of diverse pathways in IL-10 production by B cells such asIRF4 [40, 85], p38 [86], STAT3, and ERK [87]. Foxp3 is a transcription factor involvedin the development and function of regulatory T cells and in the negative regulationof immune responses [88]. It was reported that Foxp3 is expressed in B cells [89, 90];however, the association of this factor with the regulatory function of B cells is not clearat this point. Therefore, it is essential to study this topic in depth in order to clarify thetranscriptional factors required for the regulatory function of B cells.

In addition, it is necessary to clarify other essential aspects in the activation of thesecells, such as the role of the CD1d molecule, whether there is any interaction betweenB cells and other cells such as iNKT, or whether a transcription factor is associatedwith the B–cell-mediated regulatory function, among others. Trying to answer thesequestions, there are studies on the interaction between regulatory B cells and iNKT

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

cells [78], CD11c+ splenic dendritic cells [91], tolerogenic dendritic cells [92, 93], andother interactions [94, 95]; however, the mechanisms and the implications that theseinteractions may have on the regulation exerted by Breg cells remain unknown.

To date, there is no marker or group of markers (other than IL-10 production) thatmake it possible to define Breg. The reported phenotypes, such as B10 and T2-MZPin murines and B10 and transitional-2 in humans, do not exclude the possibility thatthese two phenotypes belong to the same subpopulation, or that they are completelydifferent B cells.

The implication of the Breg role in controlling various diseases could be used as atherapeutic pathway, whether it is through its selective elimination in conditions suchas cancer or infections, or where its function perpetuates the abnormal state. Likewise,Breg amplification could be used to resolve or reduce clinical symptoms in chronicinflammatory diseases. With this in mind, it would be valuable to have more specificmarkers of these subpopulations that would allow for the design and development ofthese immunomodulatory strategies.

Evidence from patients treated with rituximab seems to support the prominenceof regulatory B cells. In some patients with autoimmune diseases such as RA andSLE, psoriasis was induced after rituximab treatment [96], as well as in patients withulcerative colitis, where the disease was exacerbated after treatment; this was as-sociated with local suppression of IL–10-producing B cells [97]. Evidence from pa-tients treated with rituximab seems to support the prominence of regulatory Bcells.

Repopulation of B cells in SLE patients treated with rituximab showed an increasein the frequency of transitional B cell [5], without evidence of increased production ofIL-10 to different stimuli (unpublished observation), suggesting that patients with au-toimmune diseases generate non-functional Breg cells. As mentioned, BAFF inducesthe expression of IL-10 on B cells, whereas neutralizing BAFF treatment with a solublereceptor prevented this effect [82], suggesting some role of BAFF in almost one of thepossible regulatory mechanism of Bregs. In a murine model of lupus, the silencing ofCD40 (siCD40) induced a reduction on CD40L gene expression on kidney cells andincreased the frequency of B10 cells [98], with a potential reduction in the functional-ity of Breg cells. These and other evidences suggest that therapeutic manipulation ofB cells might lead to alterations in both the number and functionality of Bregs. How-ever, in the clinical studies to date, there is no evidence of Breg functional alterationsafter B–cell-directed therapies. Therefore, it is suggested that the elimination of thesecells would favor the induction of autoimmune manifestations in humans. These dataare in agreement with results previously observed in Cd20−/− mice and support thenotion that a small percentage of regulatory B cells have great effects on the clinicalmanifestations of various autoimmune diseases [83].

It should be noted that most of the studies conducted in murine models on B–cell-mediated regulation mechanisms have been carried out with splenic cells. It was re-cently reported that peritoneal cavity B cells activated with an agonist antibody againstCD40 for 72 hours and restimulated with L+PI for the last 5 hours regulated the pro-duction of IFN-γ , IL-6, and TNF-α by CD4+ T cells in vitro [99]. Further research, how-ever, is necessary regarding the regulatory capacities (if there are any) of B cells fromother sites.

The evidence considered in this article suggests that culture, expansion, and thesubsequent transfer of regulatory cells would be a potential therapeutic strategy tocontrol various inflammatory diseases with minimal secondary effects and positivelyimpacting the quality of life of patients. Understanding the existing differences be-tween human and murine Bregs, their in vivo function, and characterizing the con-ditions in which they seem to be playing an important role in immunopathology

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

will allow the development of more personalized immunomodulatory therapeuticstrategies.

Declaration of Interest

The authors declare no financial or commercial conflict of interest. The authors aloneare responsible for the content and writing of the article.

This work received financial support by the grants (Colciencias project number111554431390) and (CODI Universidad de Antioquia, project E001600).

The project is also supported by the Programa de Sostenibilidad Universidad deAntioquia. 2013–2014 and the Joven Investigador Program of Colciencias 2014.

REFERENCES

[1] Ochsenbein AF, Fehr T, Lutz C, et al. Control of early viral and bacterial distribution and disease bynatural antibodies. Science 1999;286(5447):2156–2159.

[2] Radbruch A, Muehlinghaus G, Luger EO, et al. Competence and competition: the challenge of be-coming a long-lived plasma cell. Nat Rev Immunol 2006;6(10):741–750.

[3] Matsushita T, Yanaba K, Bouaziz JD, et al. Regulatory B cells inhibit EAE initiation in mice while otherB cells promote disease progression. J Clin Invest 2008;118(10):3420–3430.

[4] Blair PA, Chavez-Rueda KA, Evans JG, et al. Selective targeting of B cells with agonistic anti-CD40 isan efficacious strategy for the generation of induced regulatory T2-like B cells and for the suppressionof lupus in MRL/lpr mice. J Immunol. 2009;182(6):3492–3502.

[5] Palanichamy A, Barnard J, Zheng B, et al. Novel human transitional B cell populations revealed by Bcell depletion therapy. J Immunol. 2009;182(10):5982–5993.

[6] Morris A, Moller G. Regulation of cellular antibody synthesis effect of adoptively transferredantibody-producing spleen cells on cellular antibody synthesis. J Immunol 1968;101(3):439–445.

[7] Wolf SD, Dittel BN, Hardardottir F, Janeway CA, Jr. Experimental autoimmune encephalomyeli-tis induction in genetically B cell-deficient mice. The Journal of experimental medicine.1996;184(6):2271–2278.

[8] Mizoguchi A, Mizoguchi E, Smith RN, et al. Suppressive role of B cells in chronic colitis of T cellreceptor alpha mutant mice. J Exp Med 1997;186(10):1749–1756.

[9] Mauri C, Gray D, Mushtaq N, Londei M. Prevention of arthritis by interleukin 10-producing B cells. JExp Med 2003;197(4):489–501.

[10] Hussain S, Delovitch TL. Intravenous transfusion of BCR-activated B cells protects NOD mice fromtype 1 diabetes in an IL-10-dependent manner. J Immunol 2007;179(11):7225–7232.

[11] Lenert P, Brummel R, Field EH, Ashman RF. TLR-9 activation of marginal zone B cells in lupus miceregulates immunity through increased IL-10 production. J Clin Immunol 2005;25(1):29–40.

[12] Horikawa M, Minard-Colin V, Matsushita T, Tedder TF. Regulatory B cell production of IL-10inhibits lymphoma depletion during CD20 immunotherapy in mice. J Clin Invest 2011;121(11):4268–4280.

[13] Horikawa M, Weimer ET, DiLillo DJ, et al. Regulatory B cell (B10 Cell) expansion during Listeria in-fection governs innate and cellular immune responses in mice. J Immunol 2013;190(3):1158–1168.

[14] Jeong YI, Hong SH, Cho SH, et al. Induction of IL-10-producing CD1dhighCD5+ regulatory B cellsfollowing Babesia microti-infection. PloS One 2012;7(10):e46553.

[15] Correale J, Farez M, Razzitte G. Helminth infections associated with multiple sclerosis induce regu-latory B cells. Ann Neurol 2008;64(2):187–199.

[16] Siewe B, Stapleton JT, Martinson J, et al. Regulatory B cell frequency correlates with markers ofHIV disease progression and attenuates anti-HIV CD8(+) T cell function in vitro. J Leukoc Biol2013;93(5):811–818.

[17] Fillatreau S, Sweenie CH, McGeachy MJ, et al. B cells regulate autoimmunity by provision of IL-10.Nat Immunol 2002;3(10):944–950.

[18] Couper KN, Blount DG, Riley EM. IL-10: the master regulator of immunity to infection. J Immunol2008;180(9):5771–5777.

[19] Sabat R, Grutz G, Warszawska K, et al. Biology of interleukin-10. Cytokine Growth Factor Rev2010;21(5):331–344.

[20] de Waal Malefyt R, Abrams J, Bennett B, et al. Interleukin 10(IL-10) inhibits cytokine synthe-sis by human monocytes: an autoregulatory role of IL-10 produced by monocytes. J Exp Med1991;174(5):1209–1220.

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

[21] Willems F, Marchant A, Delville JP, et al. Interleukin-10 inhibits B7 and intercellular adhesionmolecule-1 expression on human monocytes. Eur J Immunol 1994;24(4):1007–1009.

[22] Groux H, Bigler M, de Vries JE, Roncarolo MG. Inhibitory and stimulatory effects of IL-10 on humanCD8+ T cells. J Immunol 1998;160(7):3188–3193.

[23] Groux H, Bigler M, de Vries JE, Roncarolo MG. Interleukin-10 induces a long-term antigen-specificanergic state in human CD4+ T cells. J Exp Med. 1996;184(1):19–29.

[24] Evans JG, Chavez-Rueda KA, Eddaoudi A, et al. Novel suppressive function of transitional 2 B cells inexperimental arthritis. J Immunol 2007;178(12):7868–7878.

[25] Carter NA, Rosser EC, Mauri C. Interleukin-10 produced by B cells is crucial for the suppression ofTh17/Th1 responses, induction of T regulatory type 1 cells and reduction of collagen-induced arthri-tis. Arthritis Res Ther 2012;14(1):R32.

[26] Carter NA, Vasconcellos R, Rosser EC, et al. Mice lacking endogenous IL-10-producing regulatory Bcells develop exacerbated disease and present with an increased frequency of Th1/Th17 but a de-crease in regulatory T cells. J Immunol. 2011;186(10):5569–5579.

[27] Blair PA, Norena LY, Flores-Borja F, et al. CD19(+)CD24(hi)CD38(hi) B cells exhibit regulatory capac-ity in healthy individuals but are functionally impaired in systemic Lupus Erythematosus patients.Immunity 2010;32(1):129–140.

[28] Lemoine S, Morva A, Youinou P, Jamin C. Human T cells induce their own regulation through acti-vation of B cells. J Autoimmun 2011;36(3–4):228–238.

[29] Flores-Borja F, Bosma A, Ng D, et al. CD19+CD24hiCD38hi B cells maintain regulatory T cells whilelimiting TH1 and TH17 differentiation. Sci Transl Med 2013;5(173):173ra23.

[30] Yanaba K, Bouaziz JD, Haas KM, et al. A regulatory B cell subset with a unique CD1dhiCD5+ pheno-type controls T cell-dependent inflammatory responses. Immunity. 2008;28(5):639–650.

[31] Yanaba K, Bouaziz JD, Matsushita T, et al. The development and function of regulatory B cellsexpressing IL-10 (B10 cells) requires antigen receptor diversity and TLR signals. J Immunol2009;182(12):7459–7472.

[32] Matsushita T, Horikawa M, Iwata Y, Tedder TF. Regulatory B cells (B10 cells) and regulatory T cellshave independent roles in controlling experimental autoimmune encephalomyelitis initiation andlate-phase immunopathogenesis. J Immunol 2010;185(4):2240–2252.

[33] Yanaba K, Yoshizaki A, Asano Y, et al. IL-10-producing regulatory B10 cells inhibit intestinal injuryin a mouse model. Am J Pathol 2011;178(2):735–743.

[34] Yang M, Deng J, Liu Y, et al. IL-10-producing regulatory B10 cells ameliorate collagen-induced arthri-tis via suppressing Th17 cell generation. Am J Pathol 2012;180(6):2375–2385.

[35] Mutnal MB, Hu S, Schachtele SJ, Lokensgard JR. Infiltrating regulatory B cells control neuroinflam-mation following viral brain infection. J Immunol 2014;193(12):6070–6080.

[36] Smith MR. Rituximab (monoclonal anti-CD20 antibody): mechanisms of action and resistance.Oncogene 2003;22(47):7359–7368.

[37] Hamaguchi Y, Uchida J, Cain DW, et al. The peritoneal cavity provides a protective niche forB1 and conventional B lymphocytes during anti-CD20 immunotherapy in mice. J Immunol2005;174(7):4389–4399.

[38] Iwata Y, Matsushita T, Horikawa M, et al. Characterization of a rare IL-10-competent B-cell subset inhumans that parallels mouse regulatory B10 cells. Blood. 2011;117(2):530–541.

[39] Zha B, Wang L, Liu X, et al. Decrease in proportion of CD19(+)CD24(hi)CD27(+) B cells and impair-ment of their suppressive function in Graves’ disease. PloS One 2012;7(11):e49835.

[40] Matsumoto M, Baba A, Yokota T, et al. Interleukin-10-producing plasmablasts exert regulatory func-tion in autoimmune inflammation. Immunity 2014;41(6):1040–1051.

[41] Neves P, Lampropoulou V, Calderon-Gomez E, et al. Signaling via the MyD88 adaptor proteinin B cells suppresses protective immunity during Salmonella typhimurium infection. Immunity2010;33(5):777–790.

[42] Li MO, Wan YY, Flavell RA. T cell-produced transforming growth factor-beta1 controls T cell toler-ance and regulates Th1- and Th17-cell differentiation. Immunity 2007;26(5):579–591.

[43] Tian J, Zekzer D, Hanssen L, et al. Lipopolysaccharide-activated B cells down-regulate Th1 im-munity and prevent autoimmune diabetes in nonobese diabetic mice. J Immunol. 2001;167(2):1081–1089.

[44] Singh A, Carson WFt, Secor ER, Jr., et al. Regulatory role of B cells in a murine model of allergic airwaydisease. J Immunol 2008;180(11):7318–7326.

[45] Natarajan P, Singh A, McNamara JT, et al. Regulatory B cells from hilar lymph nodes of tolerantmice in a murine model of allergic airway disease are CD5+, express TGF-beta, and co-localize withCD4+Foxp3+ T cells. Mucosal Immunol 2012;5(6):691–701.

[46] Amu S, Tarkowski A, Dorner T, Bokarewa M, Brisslert M. The human immunomodulatoryCD25+ B cell population belongs to the memory B cell pool. Scand J Immunol 2007;66(1):77–86.

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

H. Rincon-Arevalo et al.

[47] Kessel A, Haj T, Peri R, Snir A, Melamed D, Sabo E, et al. Human CD19(+)CD25(high) B regula-tory cells suppress proliferation of CD4(+) T cells and enhance Foxp3 and CTLA-4 expression inT-regulatory cells. Autoimmunity Rev 2012;11(9):670–677.

[48] Litvack ML, Post M, Palaniyar N. IgM promotes the clearance of small particles and apoptotic mi-croparticles by macrophages. PloS One 2011;6(3):e17223.

[49] Rieben R, Roos A, Muizert Y, et al. Immunoglobulin M-enriched human intravenous immunoglob-ulin prevents complement activation in vitro and in vivo in a rat model of acute inflammation. Blood1999;93(3):942–51.

[50] Lobo PI, Bajwa A, Schlegel KH, et al. Natural IgM anti-leukocyte autoantibodies attenuate excessinflammation mediated by innate and adaptive immune mechanisms involving Th-17. J Immunol2012;188(4):1675–1685.

[51] Kyaw T, Tay C, Krishnamurthi S, et al. B1a B lymphocytes are atheroprotective by secreting natu-ral IgM that increases IgM deposits and reduces necrotic cores in atherosclerotic lesions. Circ Res2011;109(8):830–840.

[52] Stoehr AD, Schoen CT, Mertes MM, et al. TLR9 in peritoneal B-1b cells is essential for produc-tion of protective self-reactive IgM to control Th17 cells and severe autoimmunity. J Immunol2011;187(6):2953–2965.

[53] Gronwall C, Akhter E, Oh C, et al. IgM autoantibodies to distinct apoptosis-associated antigens corre-late with protection from cardiovascular events and renal disease in patients with SLE. Clin Immunol2012;142(3):390–398.

[54] Nagata S, Suda T. Fas and Fas ligand: lpr and gld mutations. Immunol Today 1995;16(1):39–43.

[55] Lundy SK, Boros DL. Fas ligand-expressing B-1a lymphocytes mediate CD4(+)-T-cell apopto-sis during schistosomal infection: induction by interleukin 4 (IL-4) and IL-10. Infect Immun2002;70(2):812–819.

[56] Lundy SK, Lerman SP, Boros DL. Soluble egg antigen-stimulated T helper lymphocyte apoptosis andevidence for cell death mediated by FasL(+) T and B cells during murine Schistosoma mansoni in-fection. Infect Immun 2001;69(1):271–280.

[57] Zuniga E, Motran CC, Montes CL, Yagita H, Gruppi A. Trypanosoma cruzi infection selectively ren-ders parasite-specific IgG+ B lymphocytes susceptible to Fas/Fas ligand-mediated fratricide. J Im-munol 2002;168(8):3965–3973.

[58] Tanner JE, Alfieri C. Epstein-Barr virus induces Fas (CD95) in T cells and Fas ligand in B cells leadingto T-cell apoptosis. Blood 1999;94(10):3439–3447.

[59] Yoshizaki A, Miyagaki T, DiLillo DJ, et al. Regulatory B cells control T-cell autoimmunity throughIL-21-dependent cognate interactions. Nature 2012;491(7423):264–268.

[60] Mann MK, Maresz K, Shriver LP, et al. B cell regulation of CD4+CD25 +T regulatory cells andIL-10 via B7 is essential for recovery from experimental autoimmune encephalomyelitis. J Immun2007;178(6):3447–3456.

[61] Sznol M, Chen L. Antagonist antibodies to PD-1 and B7-H1 (PD-L1) in the treatment of advancedhuman cancer. Clin Cancer Res 2013;19(5):1021–1034.

[62] Bodhankar S, Galipeau D, Vandenbark AA, Offner H. PD-1 interaction with PD-L1 but not PD-L2 onB-cells mediates protective effects of estrogen against EAE. J Clin Cell Immunol 2013;4(3):143.

[63] van der Neut Kolfschoten M, Schuurman J, Losen M, et al. Anti-inflammatory activity of human IgG4antibodies by dynamic Fab arm exchange. Science 2007;317(5844):1554–1557.

[64] van de Veen W, Stanic B, Yaman G, et al. IgG4 production is confined to human IL-10-producing regulatory B cells that suppress antigen-specific immune responses. J Allergy Clin Immun2013;131(4):1204–1212.

[65] Shen P, Roch T, Lampropoulou V, et al. IL-35-producing B cells are critical regulators of immunityduring autoimmune and infectious diseases. Nature 2014;507(7492):366–370.

[66] Saraiva M, O’Garra A. The regulation of IL-10 production by immune cells. Nat Rev Immunol2010;10(3):170–181.

[67] Browne EP. Regulation of B-cell responses by Toll-like receptors. Immunology. 2012;136(4):370–379.

[68] Hornung V, Rothenfusser S, Britsch S, et al. Quantitative expression of toll-like receptor 1–10mRNA in cellular subsets of human peripheral blood mononuclear cells and sensitivity to CpGoligodeoxynucleotides. J Immunol 2002;168(9):4531–4537.

[69] Gilkeson GS, Ruiz P, Pippen AM, et al. Modulation of renal disease in autoimmune NZB/NZW miceby immunization with bacterial DNA. J Exp Med 1996;183(4):1389–1397.

[70] Buenafe AC, Bourdette DN. Lipopolysaccharide pretreatment modulates the disease course in ex-perimental autoimmune encephalomyelitis. J Neuroimmunol 2007;182(1–2):32–40.

[71] Lartigue A, Courville P, Auquit I, et al. Role of TLR9 in anti-nucleosome and anti-DNA antibody pro-duction in lpr mutation-induced murine lupus. J Immunol. 2006;177(2):1349–1354.

International Reviews of Immunology

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.

Regulatory B cells

[72] Tao K, Fujii M, Tsukumo S, et al. Genetic variations of Toll-like receptor 9 predispose to systemiclupus erythematosus in Japanese population. Ann Rheum Dis 2007;66(7):905–909.

[73] Lampropoulou V, Hoehlig K, Roch T, et al. TLR-activated B cells suppress T cell-mediated autoim-munity. J Immunol 2008;180(7):4763–4773.

[74] Watanabe R, Ishiura N, Nakashima H, et al. Regulatory B cells (B10 cells) have a suppressive rolein murine lupus: CD19 and B10 cell deficiency exacerbates systemic autoimmunity. J Immunol2010;184(9):4801–9.

[75] Yanaba K, Kamata M, Ishiura N, Shibata S, Asano Y, Tada Y, et al. Regulatory B cells suppressimiquimod-induced, psoriasis-like skin inflammation. J Leukoc Biol 2013;94(4):563–573.

[76] Le Huu D, Matsushita T, Jin G, et al. Donor-derived regulatory B cells are important for suppressionof murine sclerodermatous chronic graft-versus-host disease. Blood 2013;121(16):3274–3283.

[77] Mizoguchi A, Mizoguchi E, Takedatsu H, et al. Chronic intestinal inflammatory condition gen-erates IL-10-producing regulatory B cell subset characterized by CD1d upregulation. Immunity2002;16(2):219–230.

[78] Bosma A, Abdel-Gadir A, Isenberg DA, et al. Lipid-antigen presentation by CD1d(+) B cells is essen-tial for the maintenance of invariant natural killer T cells. Immunity 2012;36(3):477–490.

[79] Colgan SP, Hershberg RM, Furuta GT, Blumberg RS. Ligation of intestinal epithelial CD1d inducesbioactive IL-10: critical role of the cytoplasmic tail in autocrine signaling. Proc Natl Acad Sci U S A1999;96(24):13938–13943.

[80] Matsumoto M, Fujii Y, Baba A, et al. The calcium sensors STIM1 and STIM2 control B cell regulatoryfunction through interleukin-10 production. Immunity 2011;34(5):703–714.

[81] Liu Z, Davidson A. BAFF and selection of autoreactive B cells. Trends Immunol 2011;32(8):388–394.[82] Yang M, Sun L, Wang S, et al. Novel function of B cell-activating factor in the induction of IL-10-

producing regulatory B cells. J Immunol 2010;184(7):3321–3325.[83] Yehudai D, Snir A, Peri R, et al. B cell-activating factor enhances interleukin-6 and interleukin-10

production by ODN-activated human B cells. Scand J Immunol 2012;76(4):371–377.[84] Aviszus K, Macleod MK, Kirchenbaum GA, et al. Antigen-specific suppression of humoral immunity

by anergic Ars/A1 B cells. J Immunol 2012;189(9):4275–4283.[85] Rangaswamy US, Speck SH. Murine gammaherpesvirus M2 protein induction of IRF4 via the NFAT

pathway leads to IL-10 expression in B cells. PLoS Pathogens 2014;10(1):e1003858.[86] Mion F, Tonon S, Toffoletto B, et al. IL-10 production by B cells is differentially regulated by immune-

mediated and infectious stimuli and requires p38 activation. Mol Immunol 2014;62(2):266–276.[87] Liu BS, Cao Y, Huizinga TW, et al. TLR-mediated STAT3 and ERK activation controls IL-10 secretion

by human B cells. Eur J Immunol 2014;44(7):2121–2129.[88] Rudensky AY. Regulatory T cells and Foxp3. Immunol Rev 2011;241(1):260–268.[89] Leonardo SM, Josephson JA, Hartog NL, Gauld SB. Altered B cell development and anergy in the

absence of Foxp3. J Immunol 2010;185(4):2147–2156.[90] Noh J, Noh G, Kim HS, et al. Allergen-specific responses of CD19(+)CD5(+)Foxp3(+) regulatory B

cells (Bregs) and CD4(+)Foxp3(+) regulatory T cell (Tregs) in immune tolerance of cow milk allergyof late eczematous reactions. Cell Immunol 2012;274(1–2):109–114.

[91] Moore C, Sauma D, Reyes PA, et al. Dendritic cells and B cells cooperate in the generation ofCD4(+)CD25(+)FOXP3(+) allogeneic T cells. Transplant Proc 2010;42(1):371–375.

[92] Di Caro V, Phillips B, Engman C, et al. Involvement of suppressive B-lymphocytes in the mechanismof tolerogenic dendritic cell reversal of type 1 diabetes in NOD mice. PloS One 2014;9(1):e83575.

[93] Volchenkov R, Karlsen M, Jonsson R, Appel S. Type 1 regulatory T cells and regulatory B cells inducedby tolerogenic dendritic cells. Scand J Immunol 2013;77(4):246–254.

[94] Morva A, Lemoine S, Achour A, et al. Maturation and function of human dendritic cells are regulatedby B lymphocytes. Blood 2012;119(1):106–114.

[95] Georg P, Bekeredjian-Ding I. Plasmacytoid dendritic cells control B cell-derived IL-10 production.Autoimmunity 2012;45(8):579–583.

[96] Dass S, Vital EM, Emery P. Development of psoriasis after B cell depletion with rituximab. ArthritisRheumat 2007;56(8):2715–2718.

[97] Goetz M, Atreya R, Ghalibafian M, et al. Exacerbation of ulcerative colitis after rituximab salvagetherapy. Inflamm Bowel Dis 2007;13(11):1365–1368.

[98] Ripoll E, Merino A, Herrero-Fresneda I, et al. CD40 gene silencing reduces the progressionof experimental lupus nephritis modulating local milieu and systemic mechanisms. PloS ONE.2013;8(6):e65068.

[99] Margry B, Kersemakers SC, Hoek A, et al. Activated peritoneal cavity B-1a cells possess regulatory Bcell properties. PloS One 2014;9(2):e88869.

Copyright C© Informa Healthcare USA, Inc.

Int R

ev I

mm

unol

Dow

nloa

ded

from

info

rmah

ealth

care

.com

by

Mcg

ill U

nive

rsity

on

07/2

1/15

For

pers

onal

use

onl

y.