imm335 fish review

8/12/2019 IMM335 Fish Review

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Jak Family:

- four kinds of Jaksstructurally related kinases (common domains)Jak1, Jak2,Jak3, Tyk2

- FERM domainmediates binding to cytokine receptor-

Kinase domain- Enzymatically inactive pseudokinase domain- SH2 domain

Stat Family:

- 7 kinds of stats (Stats 1-6, with 5a and 5b)- Have tyrosine and serine residues that are phosphorylated- DNA-binding domain (since its a TF)- Transactivation domain has the tyrosine and serine residues that are

phosphorylated

- Has coiled-coil domain, SH2, and N-terminal domain (dont think this needs to bememorized)

Cytokines and T Cell

ActivationCytokines Activate T cells

T helper 1produces IFN, deals with intracellular pathogens

T helper 2produces IL-4, IL-5, deals with extracellular pathogensT reg cellsuppresses regulationsuppresses effector response (prevents autoimmunity)

T helper 17proinflammatory cytokines (IL-17)TH1, TH2, and TH17 = effector T helper triad

Balance between Effector and Suppressor

More T(reg) suppressors than T effectors = tolerance (because it suppresses immuneresponse)

More T effectors than T (reg) = graft rejection (excessive immune response)

Balance between effectors and suppressors.

Cytokine action following infectionVirus comes in via skin, respiratory tract, whatever route

Viruses replicate rapidly so they need a rapid immune response.APC (usually dendritic) takes up virus, contain TOLL-LIKE RECEPTORS (TLRs)

(TLRs recognize nucleic acids of viruses).

TLRs can be on cell surfaces, endosomes, or in the cytoplasm.TLR activation triggers signal cascade.

APC makes IL-12, and IL-18, which are secreted.


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Virus in APCAg is presented by MHC IInave T cell is activated by presentation

to TCR (expresses one of IL-12 receptor subunits on surfacethe other subunit is

inducible, talk about later).When IL-12 binds its receptor, activates the Jak-Stat pathway.

Stat4 is activated here, translocates into the nucleus, makes IFN-active, which is

secreted and binds its own receptor, activating Stat-1, which activates T-bet, which driveschromatin remodeling.

The point: Not a single signaling cascade, EVER. Always multiple pathways activating

simultaneously.

Pathways here:

Presentation of Ag induces IL-12R2receptor.Thelper1 pathway: IL-12 binds receptorstat4IFN- IL-18 also helps in thispathway

IFN-binds receptorstat1T-betchromatin remodeling

**Must be a high affinity event with MHC II and TCR.

IFN-(key in Thelper 1 pathway) negatively regulates the potential to become a Thelper2 cellit drives Th1 commitment.The cytokines that T cells secrete drive different immune responses.

Cytokines involved in speciation of dif ferent cell s

IFN-speciates Thelper 1 cells,secretes IFN- , LT

IL-4 speciates Thelper 2 cells, secretes IL-4, IL-5, IL-T3TGF- and IL-6 speciate Thelper 17 cells secretes IL-17A, IL-17F, IL-6

TGF- speciates T(reg) cells

Thelper 17 Cells Vs. Adaptive T(r eg) cel ls

Depends on the presence of a mature or immature DC.Immature DCs cannot secrete IL-6.

Mature DCs can secrete IL-6.IL-6 distinguishes whether it differentiates into a T(reg) cell or an inflammatory TH-17.

The Jak-stat pathway is used here.

In the presence of Ag,immature DCs make nave T cells differentiate into T(reg) cells in

the presence of TGF- .

In the presence of Ag, mature DCs make nave T cells differentiate into Thelper 17cells

because of IL-6, which also allows IL-23 to help.

T cell li neage commitmentT cells recognize MHC molecules loaded with antigen peptides on the surface of APCs

(here, DCs).Immunogenic DCs stimulate CD4+ T cells into TH1/TH2, and CD8+ cells into CTLs.

Regulatory DCs trigger apoptosis/anergy of Ag-specific T cells, inducing T(reg cells).

DC:T cell contact factors

1. Affinity of MHC for TCR


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2. Level of costimulatory molecules3. Length of DC:T contact4. DC:T cell ratio5. Cytokines secreted by DCs and neighboring cells

TH1 Expression

A high affinity event, a lot of antigen, and a lot of IFN-

TH2 Expression

A lower affinity event, less antigen.

TH17 Expression

Mature DC, IL-6, IL-23, IL-21

Regulatory T cell s

Immature DC

T Folli cular Helper Cell PathwayIL-21

Human I L -12

Not just alpha or beta tertiary structurea mosaic structure.IL-12 receptortwo subunits, 1 and 2.

Remember IL-12 elicits a TH1 response.

Jaks: Tyk2 and Jak2Stats: Stat4/Stat4

When TLR recognizes virus, IL-12 made.

MHC meets TCR, evokes a functional IL-12 receptor.

IL-12R1 subunitis shared also in IL-23 receptor (for making TH17 cells).So nave T cell can express one receptor constitutively, and the other one must be

induced to make functional receptor complex.

IL-12 and IL-23 also use the same Jak kinases.

Human IL -1

-sheets.Cofactor for T and B cell activation.

Induces inflammatory response.

Also important for breakdown of cartilage.

3 IL-1 proteins: IL-1, IL-1, and IL-ra (receptor antagonist).IL-1, IL-1 = agonists

Needs to associate with IL-1RacPreceptor accessory protein.

Comes together with IL-1R1 (receptor) to help bind agonists.

IL-1R2the outside is like the IL-1R1 receptor but inside there is nothing, so it binds upagonist but no intracellular response.

Mechanisms to suppress IL-1 response (Regulation)1. IL-1R2no signal


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2. Receptor antagonist binding IL-1R1 receptor3. Soluble decoy receptors that bind up agonist, so they can reach IL-1R1

Human IL -2

Helical bundles.Receptor with 3 subunits, ,

Promotes clonal expansion of T cells.

IL-2R (receptor) - , are constitutively expressed, IL-2R is inducible (disturbs

energy?)3 sites of contact with receptor (interloop), (N-terminus), (C-terminus)

Importantthe -chain is shared with many different receptors.

This chain would recruit the same kind of factors, so the inducible chains are forspecificity.

The conformational change induced by cytokine binding to receptor exposes certain

amino acidsspecificity of response.

IL-2 in the Jak-Stat Pathway

(inducible), (Jak-1), (Jak-3)

( is always Jak-3).Typical Jak-stat pathway activates transcription of IL-2 proteins. Dont forget it also

activates translation.

Downstream signals also trigger the Map-kinase pathway

I nterferons (I FNs) and Vir uses

IFNs very effective at clearing viruses.

3 types:

1. Type 1IFN, IFNa. Inhibit viral replicationb. Dendritic Cells

2. Type 2 - IFN-a. Functionally active as a dimer, 4 subunits of receptor (think of everything

as double)

b. Receptors ubiquitously expressed on all cells because this IFN is soimportant

c. Macrophages express3. Type 3IFN-lambda

a. Wont really talk aboutIFN- Pathway

Helical bundles.Jaks: Jak1 (2 of them) and Jak2 (2 of them)


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Stat: Stat 1

Typical Jak-stat pathway mechanism

Type 1 I nterf eron Signali ngMany many different stat combinations (herecan be heterodimers)Each stat complex binds two different elements (in nucleus?)

1. ISREusually antiviral proteinsa. ONLY type I activate ISGF3 (stat 2:1:IRF9)

2. GAS sequencegamma activated sequencemany different functionsconsensus sequence

TLR detects virus, binds, triggers signaling cascadeType 1 IFN.

Type 1 IFN == primary response to all virusesAttacks multiple steps of replication, triggers immune response.

Typical TFN ResponseVirus in endosomal compartment (for example)TLRsignal inducedIFN produced

and secreted (cytokine)short half lifecan only interact with neighborsbinds its

receptortranscriptional activationtriggers MORE IFNs for secretionthese can

directly activate lymphocytesDC cellsTH1 Cell response.

The IFN, in addition to triggering lymphocytes/differentiation, secretes antiviral proteins,

which target viral replication, prevent viruses from coming in, block uncoating of virus,cleave viral genetic protein, etc etc.

NoteIFNs can inhibit growth of cells, so they are human cancer therapy targets.

Importance of Stat/Jak proteins

Without stats, lack of IFN response = defect in antimicrobial defenses, embyronic lethal,

etc.Without Jaks, perinatal lethal, or embryonic lethal.


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Cytokines and B Cell

ActivationHuman IL -7Helical bundles

Receptor: Specific -chain (Jak3) and common chain (Jak1)Important for stromal and epithelial cellsPre-pro-B cellpro-B cellearly pre-B cel

(important for first three stages)

Stat5 also activated (Jak-stat signaling).

Principle Cytokines for B CellsIL-4IgE production

IL-5IgA productionIL-6B cell differentiation

IL-7survival, proliferation, differentiation

RecallTH1 cellssecrete IFN-. Negatively regulates TH2production.

TH2 cellsreleases IL-3, IL-4, IL-5, IL-6, IL-7. Negatively regulates TH1 production.

Human IL -4

Helical core, loop regions determine contact with receptor.

Important for differentiation and IgE switching.

Produced by activated CD4+ TH2 cells, exhibits anti-tumor activity.Receptor: Specific -chain and common chain

Stat6 activation.

sIL-4R soluble decoy receptor that catches IL-4 so it cant bind.Remember that IFN- downregulates TH2. This is how it does it by downregulating

IL-4R expression.

IL-4R chain also present in IL-13 receptor.


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Cytokines and Macrophage

ActivationMacrophage activationIFN- is the main macrophage activating agent.

Expression depends on cytokines secreted.

T cell activation leads to macrophage activation.

Macrophage Types

Two types of macrophages: M1 and M2 (a,b,c).Type M1 classical macrophage. TH2 cell response - IFN-

Type M2a TH2 cell response IL-4Type M2b TH1 cell response IL-10

Type M2c T(reg) cell response IL-10

Can screen for certain cytokines for type identification.

Cytokines In Hematopoiesis

Lineage DeterminationControl mitigated by environment and stimulis.

Four major CSFs involved (Colony Stimulating Factors):

IL-3, GM-CSF (neutrophils), G-CSF (granulocytes), M-CSF (macrophages).

Early stage: IL-3 and GM-CSF (helical bundle)

Late stage: G-CSF and M-CSF.

IL-5: eosinophil production

IL-4: mast cell production

Epo:Clinically significant, clones were developed to treat patients with kidney

failure where erthyrocytes tanked. Its now used for patients on dialysis.

IL-3Secreted by CD4+ TH1 and TH2

IL-3R and creceptor (this is a shared receptor)Stat 5 activation (with IL-5 as well)


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IL-5Homodimer is active.

CD4+ TH2 cells are source.Eosinophils and basophils

IL-5R and creceptor (this is a shared receptor)

Stat 5 activation.Alpha chains determine specificity.

Cytokines In InflammationInflammatory TriadIL-1, IL-6, TNF-

Rapidly produced (inflammation), a link between innate and adaptive responses.Theres ALWAYS a local inflammatory response, but sometimes theres a systemic

response as well.

Brain: fever responseLiver: acute phase proteins (APP) associated with rapid response, triggered by

inflammatory triad.

Thymus: thymic evolution.

Chemokines: another huge class of key playerstrafficking.

IL-6

Helical bundles

Functions: CTL differentiation, B cell differentiation, Overexpression, Induction of acutephase reactants.

IL-6 is produced by a wide variety of cells.

IL-6Rhas transmembrane receptor unit gp130.Jaks: JAK1, JAK2, TYK2, phosphorylate gp130 as well.

Overproduction of IL-6: induction of TH17 cells, acute and chronic inflammation (acute

phase proteins), bone and cartilige destruction.

TNF Cytokine Superf amily

Beta sheets.

TNF only active as trimer, interacts with trimeric receptor.

Important receptor subunit: TNFR1Binding of ligand to TNFR1 activates death domains (DDs)which are recruitment sites.

3 proteins come together: TRADD, TRAF2, RIP.TRADD itself has a DD that recruits TRAF2 and RIP.

NOT Jak-stat pathway.

NFkB activationthrough NFkB element in nucleus.


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There are TWO COMPLEXES that can be activated by TNFs.

Complex I pathway: TRADD, TRAF2, RIP (above) - NFkB

Complex II Pathway: caspasesapoptosis.

Pro-inflammatory IL-1 Response

Unrelated to TNF family.Also uses Traf-6.Vital accessory protein IL-1R-AcPrecruits traf.

IL-1R-AcPIRAK (kinase)Nik (NFkB inducing kinase)

NFkB activation is always linked to some pro-inflammatory response.

AutoimmunityAutoimmunity targets specific tissues, more prevalent in women.

Arthritis: bone + cartilige, etc.

Anti-inflammatory meds (makes sense)also B cell, IL, Jak, inhibitors throughbiologicals

Autoimmune diseases: RA (rheumatoid), OA (osteo), scleroderma (skin), psoriatic (skin),

ankylosing spondylitis (spine).

RARheumatoid Arthritis

Swollen and fluid filledsynovial fluid shows inflammatory cells.

Pro-inflamm cells play a role: TNF, IL-1, IL-17, IL-6.TH17 secretes IL-17.

Rheumatoid spreads over time whereas osteo is wear and tear

Can score swollen and inflamed joints for deformation.

Therapies for RAMultiple targets.

Abataceptprevents APC from delivering to T cell, and limits co-stimulation to T cell.Anakirablocks IL-1.

Rituximabblocks T cell activation

TocilizumabIL-6 inhibitorTofacitinibJAK inhibitor (almost FDA approved)

Anti-TNF inhibitors have revolutionized rheumatoid therapyas theres a central role of

TNF- in RA.

There is a disequilibrium of cytokines in joints of patients with RA.Need to shut down the immune response so that its not persistant.

A very large subset of pro-inflamm cytokines use Jak-stat pathways, so inhibit JAK

(Tofacitinib).

If you have antibodies staining for STATS, there is much stain in an RA synovium, butnone in a normal synovium.


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CCR5

- have many tyrosine residues in intracellular domain- use the Jak/Stat pathway- Associated with G-proteins (GTP/GDP exchange factors)- A few different pathways: G-protein, Jak/Stat, Map kinase

Bone RemodellingBone remodelling and bone loss are controlled by a balance of TNF mol OPGL and its

DECOY receptor, OPGutility in osteoperosis

Synthesis of bone matrix with osteoblasts and osteoclastsmust be tightly which is why

decoy receptor is needed.OPGL expression is induced by AG, activated T cells.

OPG blocks bone losslook at this through bone densityPeople with arthritis have

little bone density.

OPG prevents cartilige destruction and even restores it.

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