cx3cr1 defines functionally distinct intestinal mononuclear phagocyte subsets which maintain their...

CX3CR1 defines functionally distinct intestinalmononuclear phagocyte subsets which maintaintheir respective functions during homeostaticand inflammatory conditions

Benjamin Weber1, Leslie Saurer1, Mirjam Schenk1,2, Nina Dickgreber1

and Christoph Mueller1

1 Division of Experimental Pathology, Institute of Pathology, University of Bern, Bern,

Switzerland2 Division of Dermatology, Department of Medicine, David Geffen School of Medicine at

University of California, Los Angeles, CA, USA

Intestinal mononuclear phagocytes (iMNP) are critically involved in mucosal immunity

and tissue homeostasis. Two major non-overlapping populations of iMNP have been

identified in mice. CD1031 iMNP represent a migratory population capable of inducing

tolerogenic responses, whereas CX3CR11 iMNP are resident cells with disease-promoting

potential. CX3CR11 iMNP can further be subdivided based on differential expression of

CX3CR1. Using CX3CR1GFP/1�RAG2�/�mice, we demonstrate that CX3CR1hi and CX3CR1lo

iMNP clearly differ with respect to their morphological and functional properties.

Compared with CX3CR1hi iMNP, CX3CR1lo iMNP are polarised towards pro-inflammatory

responses already under homeostatic conditions. During a CD41 T-cell-induced colitis,

CX3CR1lo cells accumulate in the inflamed mucosa and upregulate the expression of pro-

inflammatory cytokines and triggering receptor expressed on myeloid cells-1 (TREM-1). In

contrast, CX3CR1hi iMNP retain their non-inflammatory profile even during intestinal

inflammation. These findings identify two functionally distinct iMNP subsets based on

differential expression of CX3CR1 and indicate an unanticipated stability of iMNP.

Key words: DC . Inflammation . Intestinal mucosa . Macrophages

Supporting Information available online

Introduction

One of the vital tasks of the intestinal immune system is to respond

to invading pathogens while tolerating food and commensal

bacteria. This critical balance is largely orchestrated by intestinal

mononuclear phagocytes (iMNP) which comprise both macro-

phages and DC. Defective DC functions and hyperresponsiveness

of intestinal macrophages are considered a principal disease-

promoting factor in the pathogenesis of inflammatory bowel

diseases (IBD) in humans [1, 2].

Recent studies in mice have substantially advanced our

knowledge on intestinal iMNP with respect to the identification of

different populations with distinct origins and functions. In the

murine lamina propria (LP), two prominent iMNP populations

exist that either express the integrin E a chain (CD103) or

the fractalkine receptor (CX3CR1). CD1031 (CX3CR1�) and

SHORT COMMUNICATION

Correspondence: Dr. Christoph Muellere-mail: [email protected]

& 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim www.eji-journal.eu

Eur. J. Immunol. 2011. 41: 773–779 DOI 10.1002/eji.201040965 Innate immunity 773

CX3CR11 (CD103�) cells represent non-overlapping populations

with their own distinct precursors [3, 4]. CD1031 iMNP share

traits with classical DC. They are short lived and travel via lymph

to mesenteric lymph nodes where they present antigen to T cells

and predominantly induce Foxp31 Treg [5, 6]. In contrast,

CX3CR11 iMNP are long-lived resident cells with slow turnover

rates. They are poor T-cell stimulators and are believed to modu-

late immune responses directly in the LP [7]. In an innate model of

experimental colitis, CX3CR11 iMNP were sufficient to induce

acute disease in mice previously depleted for all intestinal CD11c1

cells including CX3CR11 and CD1031 iMNP [3]. Hence, CX3CR11

iMNP display pro-inflammatory properties, and a delicately tuned

balance between the different subsets of DC and macrophages

seems to be instrumental for tissue homeostasis in the gut.

Intriguingly, CX3CR11 iMNP can be further subdivided into

CX3CR1lo and CX3CR1hi expressing subsets that are easily iden-

tifiable by the differential expression of GFP in CX3CR1GFP/1

mice [3, 7]. Whereas in the peripheral blood of mice and humans,

the presence of two main CX3CR1lo and CX3CR1hi monocyte

subsets with distinct functional properties has long been

acknowledged [8], no thorough functional characterisation of

CX3CR1lo and CX3CR1hi iMNP as two distinct subsets has so far

been undertaken. Since adoptive transfer of Ly6Chi (CX3CR1lo),

but not Ly6Clo (CX3CR1hi), monocytes gives rise to both subsets

of CX3CR1lo and CX3CR1hi iMNP [3], CX3CR1lo and CX3CR1hi

iMNP cannot necessarily be assumed to share the functional

traits of their corresponding peripheral blood monocyte

counterparts.

In the present study, we aimed to investigate the functional

properties of CX3CR1lo and CX3CR1hi iMNP during homeostatic

conditions and chronic intestinal inflammation in CX3CR1GFP/1

�RAG2�/� mice. Here we show that in spite of their common

precursor, CX3CR1lo and CX3CR1hi iMNP differ substantially in

their functional characteristics and that the functional dichotomy

between CX3CR1lo and CX3CR1hi iMNP is stably maintained

during intestinal inflammation.

Results and discussion

CX3CR11 iMNP subset composition changes duringintestinal inflammation

In transgenic mice expressing GFP under the control of the

CX3CR1 promoter (CX3CR1GFP/1 mice), among the CX3CR11

(GFP1) iMNP two distinct subsets of CX3CR1lo (GFPlo) and

CX3CR1hi (GFPhi) expressing cells can be identified in the

intestinal LP (Fig. 1 and Supporting Information Fig. 1) [3]. In

the colonic LP of healthy CX3CR1GFP/1�RAG2�/� mice, GFPhi

iMNP predominated compared with the GFPlo subset, while in the

small intestinal LP the two subsets of GFPlo and GFPhi iMNP were

present at comparable frequencies (Fig. 1A). GFPlo and GFPhi

iMNP from both colonic and small intestinal locations appeared

as homogeneous cell populations expressing high levels of

MHCII, CD80, CD86, CD11b and CCR2 (Supporting Information

Fig. 2). Both subsets also expressed CD115, CD68 and F4/80.

Notably, the GFPlo subset did not contain MHCII– Gr11 CD62L1

cells, arguing against a potential contamination with circulating

inflammatory monocytes (Supporting Information Fig. 2). While

GFPlo and GFPhi iMNP did not substantially differ with respect to

the surface markers analysed (with the exception of GFP), the

two subsets showed distinct differences in size as based on their

FSC properties (Fig. 1A) and cytospin as well as live cell images

of sorted GFPlo and GFPhi iMNP, irrespective of the colonic or

small intestinal origin of the cells (Fig. 1B). Thus, while both

GFPlo and GFPhi cells displayed a vacuolar cytoplasm, the GFPhi

subset was larger and retained this property also after 24 h

culture in vitro. These analyses indicate that GFPlo and GFPhi cells

can be considered as non-overlapping subsets of LP iMNP.

In order to investigate the potential changes in the cellular

composition of GFPlo and GFPhi cells in the intestinal LP under

inflammatory conditions, colitis was induced in CX3CR1GFP/1

�RAG2�/� mice by adoptive transfer of CD41CD45RBhi T cells.

Mice were sacrificed at the onset of clinical signs of colitis and the

relative frequencies of GFPlo and GFPhi iMNP in both the colonic

and small intestinal LP were analysed by flow cytometry. In colitic

CX3CR1GFP/1�RAG2�/� mice, GFPlo and GFPhi cells could still be

clearly discriminated as two distinct subsets (Fig. 1C) and distin-

guished from infiltrating Ly6Chi and Ly6Clo cells (likely repre-

senting monocytes and neutrophils) by their lack of Ly6C

expression (Supporting Information Fig. 3). However, in the

inflamed colonic LP the GFPlo cells were now prevailing over the

GFPhi cells and the mean ratio of GFPlo to GFPhi iMNP was

significantly increased in colitic compared with healthy control

mice (Fig. 1C and 1D). In the small intestine, where no distinct

histopathological signs of inflammation were observed, the relative

frequency of GFPlo to GFPhi cells was not substantially altered

(Fig. 1D). In order to investigate whether the observed increase in

GFPlo cells in the inflamed colons was due to a selective loss of the

GFPhi subset, absolute cell numbers of GFPlo and GFPhi iMNP

isolated from colons of control and colitic mice were determined. A

marked overall accumulation of both GFPhi (�10-fold) and

GFPlo iMNP (�30-fold) was noted in the intestinal LP of colitic

mice compared with control mice. However, in the colon of

colitic mice, GFPlo cells considerably outnumbered the GFPhi cells

(Fig. 1E). Collectively, these results demonstrate a selective accu-

mulation of GFPlo iMNP in the colonic mucosa during intestinal

inflammation.

TREM-1 expression is restricted to GFPlo iMNP

Triggering receptor expressed on myeloid cells (TREM)-1 is a

potent amplifier of inflammatory responses in neutrophils,

monocytes and macrophages [9]. We have previously reported

that surface TREM-1 expression is absent on resident macro-

phages isolated from the normal human intestinal LP while a

significant increase in TREM-1-expressing macrophages can be

observed in the inflamed LP of patients with IBD [10, 11]. The

selective accumulation of GFPlo iMNP in the LP of colitic mice

Eur. J. Immunol. 2011. 41: 773–779Benjamin Weber et al.774


prompted us to also analyse TREM-1 expression in GFPlo and

GFPhi murine iMNP. Similar to what has been observed for

human intestinal macrophages, TREM-1 was almost completely

absent on GFPlo and GFPhi iMNP isolated from the LP of healthy

control mice (Fig. 2A). However, when iMNP were isolated from

the inflamed colons of colitic CX3CR1GFP/1�RAG2�/� mice,

surface TREM-1 was clearly expressed on the GFPlo subset of

iMNP (Fig. 2B). TREM-1 expression was also detected on GFPlo

iMNP derived from the small intestine of colitic mice, albeit at

lower levels. In contrast, the GFPhi iMNP subset consistently

lacked TREM-1 expression even during intestinal inflammation

(Fig. 2). A screening for additional differentiation markers

revealed a comparable expression pattern for TLR2 as for

TREM-1. Thus, TLR2 was expressed only by GFPlo iMNP in the

inflamed, but not in the healthy colon, whereas TLR2 surface

expression could not be detected on GFPhi iMNP isolated from

healthy and inflamed intestinal mucosa (Supporting Information

Figs. 2 and 4).

GFPlo and GFPhi iMNP exhibit a distinct gene expres-sion profile

The selective expression of TREM-1 by the GFPlo, but not GFPhi,

subset of iMNP during intestinal inflammation strongly suggested

that GFPlo and GFPhi iMNP not only differed in their phenotypical

but likely also in their functional properties. In order to gain

insight into additional functional attributes of GFPlo and GFPhi

iMNP, the two subsets were FACS-sorted from the colons and

small intestines of healthy and colitic CX3CR1GFP/1�RAG2�/�

mice, and the expression of pro-inflammatory and regulatory

candidate genes was assessed by qRT-PCR. In the colon and small

intestine of healthy mice, higher mRNA expression levels of IL-6,

iNOS, IL-1b and IL-1f9 were noted in the GFPlo subset (Fig. 3A).

In contrast, the expression of mRNA for IL-10, Hmox-1 and

TREM-2 was clearly more prominent in GFPhi iMNP (Fig. 3A).

Since the expression of TREM-2 has previously been associated

with alternatively activated macrophages in vitro and in vivo

[12, 13], YM-1/ECF-L, Fizz1/RELM-a, Arginase 1 (Arg-1) and

Mannose receptor 1 (Mrc1) were analysed as additional markers.

Except for the expression of Mrc1, these transcripts were not

enriched in GFPhi compared with GFPlo iMNP (Supporting

Information Fig. 5).

A distinct change in gene expression was noted in iMNP

isolated from the colons of colitic mice. However, while both

GFPlo and GFPhi colonic iMNP upregulated expression of mRNA

for IL-6, TNF-a, IL-1a, IL-1f9 and iNOS, the expression of these

genes was most prominent in the GFPlo subset of iMNP compared

with GFPhi iMNP (Fig. 3A). Moreover, in colitic mice, GFPhi cells

retained the expression of mRNA for IL-10, Hmox-1 and TREM-2,

albeit at slightly lower levels. Gene expression was not substan-

tially altered in iMNP isolated from the small intestine of colitic

Figure 1. The ratio of GFPlo to GFPhi colonic iMNP increases during experimental colitis. (A) Representative FACS plots of LP cells isolated from thecolon and small intestine of healthy CX3CR1GFP/1�RAG2�/� mice. Numbers indicate percentages of GFPlo and GFPhi subsets, respectively, relativeto the parental gate defined by backgating analyses of GFP1 cells. (B) Colonic and small intestinal lamina propria GFPlo and GFPhi iMNP subsetsfrom healthy mice were sorted based on their GFP expression and gates shown in (A). Cells were centrifuged onto glass slides and stained withhemacolor (top) or cultured for 24 h in vitro for the analysis by confocal microscopy in the easy 3D view mode (bottom). Numbers indicate therespective photomultiplier voltage (bottom). (C) Representative FACS plots of LP cells isolated from the colon and small intestine of coliticCX3CR1GFP/1�RAG2�/� mice. (D) Ratios of GFPlo/GFPhi iMNP as determined by flow cytometry analysis of their relative frequencies in the colonicand small intestinal LP of healthy and colitic mice. Symbols represent values for individual mice. (E) Absolute cell numbers of colonic GFPlo andGFPhi iMNP subsets recovered from healthy and colitic CX3CR1GFP/1�RAG2�/� mice (n 5 6) were determined by cell counts of LP preparations andFACS analysis. Data show mean1SD from a total of four independent experiments. �po0.001; ns, not significant (Student’s t-test).

Eur. J. Immunol. 2011. 41: 773–779 Innate immunity 775


mice, in line with the absence of severe inflammation at this

intestinal site (Fig. 3A).

GFPlo iMNP are potent producers of pro-inflammatorycytokines

To ascertain the functional relevance of the findings described

above, GFPlo and GFPhi iMNP isolated from healthy and colitic

CX3CR1GFP/1�RAG2�/� mice were cultured for 24 h and

cytokine secretion was determined by Luminexs Technology.

Even in the absence of intestinal inflammation, GFPlo iMNP

produced elevated amounts of IL-6, IL-12 and TNF-a compared

with the GFPhi iMNP subset, irrespective of the colonic or small

intestinal origin of the cells (Fig. 3B). Secretion of the pro-

inflammatory cytokines IL-6, IL-12 and TNF-a by the GFPlo subset

of iMNP was further substantially increased when cells were

isolated from the inflamed colon, but not from the small intestine,

of colitic mice (Fig. 3B). In contrast, GFPhi iMNP predominantly

produced IL-10 and barely upregulated the production of IL-6,

IL-12 and TNF-a during intestinal inflammation (Fig. 3B).

Concluding remarks

Recent evidence has led to the consensus that the intestinal LP of

mice contains two major non-overlapping populations of iMNP,

CD1031 (CX3CR1�) cells, which exhibit typical traits of DC, and

CD103� (CX3CR11) cells, which are considered to represent non-

migratory, tissue-resident cells. The further existence of two

subsets (CX3CR1lo and CX3CR1hi) within the CX3CR11 popula-

tion of iMNP has long been acknowledged from flow cytometry

data, yet functional characterisations have so far largely relied on

the analysis of CX3CR11 as an entity of cells. Our findings now

demonstrate a clear functional dichotomy within the CX3CR11

(GFP1) population of iMNP. Accordingly, the capacity to secrete

pro-inflammatory cytokines segregates with the CX3CR1lo

(GFPlo) subset while CX3CR1hi (GFPhi) cells exhibit a somewhat

opposite profile with an increased production of IL-10. These

functional differences, which are apparent under homeostatic

conditions and even more distinct during intestinal inflammation,

are intriguing, considering that GFPhi and GFPlo iMNP are not

direct reciprocal descendants of CX3CR1hi (‘‘resident-type’’) and

CX3CR1lo (‘‘inflammatory-type’’) monocytes but in fact share a

common precursor of Ly6Chi (CX3CR1lo) monocytes [3]. In line

with this notion, we noted a distinct increase of Ly6Chi, but not

Ly6Clo, peripheral blood monocytes in colitic compared with

healthy mice (data not shown), which may account for the

observed accumulation in both GFPlo and GFPhi iMNP in the

affected LP during colitis.

There currently lies considerable interest in the clear identi-

fication of disease-promoting versus regulatory populations

among iMNP. A disease-promoting role in experimental colitis

has previously been assigned to several populations of iMNP,

including Ly6Chi graft-derived CX3CR11 cells, E-cadherin1

CD11chi inflammatory DC and F4/801 TLR21 CCR21 Ly6Chi

macrophages [3, 14, 15]. Although the precise interrelationship

of these populations described in the literature cannot easily be

established due to divergent experimental procedures and gating

strategies, the monocytic origin and the production of pro-

inflammatory cytokines appear to be shared traits. In colitic

CX3CR1GFP/1�RAG2�/� mice, GFPlo cells are predominant over

GFPhi cells and produce substantially increased levels of TNF-a,

IL-6 and IL-12. In contrast to the pro-inflammatory profile of

GFPlo iMNP, GFPhi cells in the intestinal LP are characterised by

their preferential expression of genes associated with regulatory

functions and inhibitory receptors. An important role for intest-

inal macrophage-derived IL-10 in the induction and maintenance

of Treg activity and a crucial function for TREM-2-expressing

macrophages in colonic mucosal wound repair were recently

reported [13, 16, 17]. However, in the absence of cell engraft-

ment protocols that allow for selective generation of GFPlo versus

GFPhi iMNP, we can at best speculate about potential disease-

promoting versus possible immunoregulatory roles of GFPlo and

GFPhi iMNP during experimental colitis.

One of the most striking findings of the present study is the

observed functional stability of GFPlo and GFPhi iMNP during

intestinal inflammation. Accordingly, in colitic mice, GFPhi iMNP

Figure 2. TREM-1 is selectively expressed by GFPlo iMNP during colonicinflammation. Surface TREM-1 expression (black line) on colonic andsmall intestinal LP-derived GFPlo and GFPhi iMNP subsets of (A) healthyand (B) colitic mice was determined by flow cytometry. An antibody ofirrelevant specificity was used as an isotype control (filled histograms).Representative data of one out of three independent experiments withthe analysis of pooled cells from 2 to 3 mice are shown.



not only lack pronounced secretion of pro-inflammatory cyto-

kines but also fail to upregulate TREM-1 and TLR2. This stable

phenotype of GFPhi iMNP differs from the previously reported

acquisition of inflammatory functions by the otherwise tolero-

genic CD1031 MLN DC during intestinal inflammation [18].

Thus, lineage-specific variations in the plasticity of iMNP may

exist. Alternatively, the extent and duration of experimentally

induced inflammation may be a critical parameter in determining

potential adaptations of iMNP subsets. The stable functional

characteristics of GFPhi and GFPlo iMNP, however, are highly

reminiscent of the findings by Platt et al. who have also described

two distinct TLR21 and TLR2� iMNP subsets that retain their

Figure 3. GFPlo iMNP are polarised towards pro-inflammatory responses. GFPlo (filled bars) and GFPhi iMNP (open bars) were FACS-sorted from thecolonic and small intestinal LP of healthy and colitic CX3CR1GFP/1� RAG2�/� mice. (A) Expression of pro-inflammatory and regulatory-type (TGF-b1, IL-10, Hmox1, TREM-2) candidate genes was determined by qRT-PCR. Data show mean1SD for healthy (n 5 4) and colitic (n 5 7) mice from fourindependent experiments. (B) FACS-sorted iMNP subsets were cultured in vitro for 24 h. Cytokine levels in culture supernatants were analysed byLuminex. Representative data from one out of three experiments using pooled cells from 4 to 5 mice are shown as mean1SEM of 3–4 replicatewells.



discrete functional profiles under inflammatory conditions [15].

Taken together, these findings indicate that phenotypical prop-

erties may indeed reliably associate with distinct functions.

Hence, efforts towards the identification of clearly defined iMNP

subsets with specialised functions in mice and humans may hold

promise for a better understanding and potential selective

targeting of these cells during intestinal disorders.

Materials and methods

Mice

CX3CR1GFP/1�RAG2�/� mice were obtained by crossing

CX3CR1GFP/GFP�RAG2�/� mice with RAG2�/� mice [19].

CX3CR1GFP/GFP�RAG2�/� mice were a generous gift from F.

Geissmann (Paris, France). Mice were bred and maintained

under SPF conditions in the central animal facility of the Medical

School, University of Bern. All animal experiments were

approved by the committee for animal experimentation of the

state of Bern (license number: 79/08).

CD41 T-cell transfer model of colitis

Colitis was induced in CX3CR1GFP/1�RAG2�/�mice by adoptive

transfer of 2� 105 CD41CD25�CD45RBhi FACS-sorted T cells as

described previously [20]. Mice were sacrificed at 10–12 days

post CD41 T-cell transfer at the onset of clinical signs of colitis

(diarrhea, weight loss, symptoms of abdominal pain).

Cell isolations

For the isolation of iMNP, colon and small intestine were opened

longitudinally and cut into small pieces. The epithelium was

removed by incubation in HBSS/HEPES containing 5% horse

serum, 5 mM EDTA and 2 mM DTT at 371C for 3�30 min under

magnetic stirring. LP cells were obtained by subsequent digestion

with 200 U/mL collagenase (Type IV; Sigma-Aldrich) and 50 U/

mL DNase (Type I, grade II; Roche) for 2� 45 min. The LP

fraction was filtered through a 40-mM cell strainer and GFPlo and

GFPhi expressing iMNP were purified by FACS-sorting (FACSAria,

BD Biosciences).

Flow cytometry

Fc receptors were blocked using supernatant from the hybridoma

2.4G2. The following antibodies were used: TREM-1 (174031,

R&D); MHCII (M5/114.15.2), CD115 (AFS98), F4/80 (BM8),

Gr1 (RB6-8C5), NK1.1 (PK136) from eBioscience; CD80 (16-

10A1), CD86 (GL1) from Pharmingen; CD68 (FA-11), TLR2

(T2.5) from BioLegend; CD11b (M1/70), CD62L (MEL-14)

purified from hybridoma supernatants; CCR2 (MC-21) a gift

from M. Mack, University of Regensburg, Germany. Cells

were acquired on a LSRII flow cytometer (BD Biosciences)

and analysed using FlowJo software (Tree Star). Due to the

reported heterogeneous expression of CD11c by various iMNP

subpopulations in the intestinal LP and the consistent absence of

CD103 on CX3CR1-GFP1 cells [7], these markers were not used

for gating of CX3CR1-GFP1 cells. Instead, analyses of CX3CR1-

GFP1 cells were based on an initial FSC/SSC backgating of

CX3CR1-GFP1 cells and subsequent analysis of backgated

CX3CR1-GFP1 cells against FSC. CX3CR1-GFPlo and GFPhi

subsets, respectively, were discriminated based on the differential

expression of GFP.

Microscopy

FACS-sorted GFPlo and GFPhi iMNP subsets were centrifuged

onto Superfrost Plus glass slides (Thermo Scientific), fixed and

stained with Microscopy Hemacolor (Merck). In parallel, sorted

iMNP were cultured in m-slides (Ibidi) for 24 h. Fixed and live

cells were analysed by light or confocal microscopy, respectively,

with 40� magnification (IX81, Olympus). Z-stacks were visua-

lised using the Easy 3D view mode (Imaris software version

6.1.3).

RNA isolation and quantitative real-time PCR

Total RNA was isolated from sorted iMNP subsets using RNA

isolation reagent (Tri-Reagent, Molecular Research Center). DNA

was digested using DNase I (Ambion), and cDNA was generated

using High Capacity cDNA Reverse Transcription Kit (Applied

Biosystems). Expression of genes was analysed using RT2 Profiler

PCR Array (PAMM-052A, SABiosciences) and Qiagen Quantitect

Primer Assays (TREM-2, Fizz1, YM-1, Arg-1 and Mrc1) on a 7500

Real-time PCR System (AB Biosystems). The house-keeping genes

Gusb, Hprt1, Hspcb, Actb and GAPDH were used for the

normalisation of gene expression.

Cell culture and analysis of produced cytokines

Sorted GFPlo and GFPhi iMNP were cultured in 96-well U-bottom

plates at 105 cells per well and supernatants were collected

after 24 h incubation. IL-6, TNF-a, IL-12p40/p70 and IL-10

were determined using a Bio-Plex Suspension Array system

(Bio-Rad) and combined murine Singleplex Bead Kits

(Invitrogen).

Acknowledgements: The authors thank Bernadette Wider for

excellent assistance with FACS sorting and Daniela Kassahn for



help with confocal microscopy. This work was supported by Swiss

National Science Foundation Grant 3200-122560.

Conflict of interest: The authors declare no financial or

commercial conflict of interest.

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20 Dayer Schneider, J., Seibold, I., Saxer-Sekulic, N., Paredes, B. E., Saurer, L.

and Mueller, C., Lack of TNFR2 expression by CD4(1) T cells exacerbates

experimental colitis. Eur. J. Immunol. 2009. 39: 1743–1753.

Abbreviations: IBD: inflammatory bowel diseases � iMNP: intestinal

mononuclear phagocytes � LP: lamina propria � Mrc-1: mannose

receptor 1 � TREM-1: triggering receptor expressed on myeloid cells-1

Full correspondence: Dr. Christoph Mueller, Institute of Pathology,

University of Bern, Murtenstrasse 31, CH-3010 Bern, Switzerland

Fax: 141-31-381-8764

e-mail: [email protected]

Received: 18/8/2010

Revised: 25/11/2010

Accepted: 20/12/2010

Accepted article online: 4/1/2011



cx3cr1 defines functionally distinct intestinal mononuclear phagocyte subsets which maintain their...

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