Immune EffectorsKathleen Kelly kkelly@mednet.ucla.edu6-5562

ReadingImmunobiology (5th Edition) Janeway, Travers, Walpert and Capra

Chapter 10 (p. 381-402) and Chapter 8 (p. 295-340)

Agnello D, et al. Cytokines and transcription factors that regulate T helper cell differentiation: new players and new insights. J Clin Immunol. 23:147-161, 2003.

Mak, TM & Lohoff. Roles of Interferon Regulatory Factors in T-helper-cell Differentiation. Nature Reviews Immunol. 5:125-135, 2005.

Russell, JH & Ley, TJ. Lymphocyte-mediated cytotoxicity. Annu. Rev. Immunol. 323-370, 2002.

Formation of Effector T Cells

T Effector Cells T cell subsets are the armed assassins of the

adaptive immune response CD8

Cytotoxic T cells (CTL) Effector function is to lyse target cells (infected,

tumor) CTL - effector molecules are lytic granules

perforin/granzyme pathway CD4

T helper cells Effector function is to produce certain cytokines Th1 - effector cytokine is IFN

• - Activate MQ & FasL/FADD mediated cytotoxicity Th2 - effector cytokine is IL-4

• - help B cells/Ab production

Different Classes of PathogensElicit Different T Effector Subsets

Effector Function of CTLEffector function is to

lyse target cells Virus infected Tumor

MHC Class I restrictedContact-dependentPerforin/Granzyme

mediated cytotoxicity Lytic granules are

produced & released from CD8+ CTL

Granules induce apoptosis

Pathways of Apoptosis

Russell, JHAnn. Rev. Immunol.20:323, 2002

Cytotoxicgranules

Granzyme B but not FADD (FasL) Pathway is Necessary for MHC Class I Restricted Responses (GvH)

Granzyme B-/-

FasL-/-

WildType

FasL & Granzyme B-/-

Syngeneic

Graubert, TA et al. J Clin Invest. 100:904, 1997

FADD (FasL) but not Perforin/Granzyme B Pathway is Necessary for

MHC Class II Restricted Response

Granzyme B-/-

FasL-/-

FasL & Granzyme B-/-

Syngeneic

Perforin-/-

Graubert, TA et al. J Clin Invest. 100:904, 1997

CTL Lytic GranulesLytic granules:

Are synthesized de novo after initial T cell activation (1-3 days) (NK cell killing is immediate)

After activation CTL can kill multiple cells, ie multiple times.

Requires post-translational modification Perforin (action is Ca++ dependent)

Similar in structure to C9, which polymerizes to form membrane pores on target cell surface by binding to perforin receptors that are induced by IFN

Granule Exocytosis Pathway

Effector molecules are preformed in granules and undergo granule exocytosis pathway PI-3 kinase

RAC-1

PAC-1

MAPK kinase

ERK Russell, JH, Ann. Rev. Immunol.20:323, 2002

cation-dependentMannose-P-6 R

CTL Lytic GranulesLytic granules:

Granzymes Serine proteases

• Granzyme B cleaves caspase 3

Other enzymes with undefined function Granulysin Orphan granzymes

Action of Granzyme B

Russell, JHAnn. Rev. Immunol.20:323, 2002

Focal Delivery of Effector Molecules TCR : MHC-peptide complexes

induces reorientation of cytoskeleton to contact site

Microtubule-organizing center (MTOC) and golgi apparatus then follows

Enhanced binding of LFA-1 (CD11a/CD18) to ICAM-1(CD54) forms a molecular seal.

Effector molecules are delivered within the sealed area

CD8

Perforin/Granzyme is Needed to Clear CMV Infected Cells

Eur. J. Immunol. 30:1350, 2000

Mice infected with MCMV

Day 15 Day 30

Effector Function of Th1 Cells

Th1 cells activate macrophages to induce intracellular killing of organisms that grow in vesicles

MHC class II restricted response Endosomal processing pathway

Th1 cells produce membrane-associated proteins soluble cytokines

Effector Molecules of Th1 Cells

Membrane bound CD40 ligand - sensitizes macrophages to respond

to IFN Fas ligand - induces apoptosis of target cell

Soluble IFN- activates macrophages & MHC class I & II

and co-stimulatory molecules TNF- activates macrophages & induces NO

production GM-CSF - activates macrophages LT, TNF- - activates macrophages & induces NO

production

Th1 Cytokines

Leishmania: The Poster Child for Th1-mediated Infections.

Immunity 4:283, 1996

Production of Th1 Effector Molecules

Effector molecules must be synthesized – for each killing event 1-2 hrs after TCR stimulation.

TCR receptor triggering induces Expression of CD40L Cytokines are made de novo

This process minimizes “by-stander” activation BUT FasL receptor killing is more promiscuous that

CTL granule release because it can occur in the absence of TCR stimulation.

IFN mRNA contains (AUUUA)n sequence in untranslated 3’ region that reduces the 1/2 life of mRNA

Function of Other Th1 Effector Molecules

Granulomas Form When Microbes Resist Th1-Mediated Killing

Effector Function of Th2 CellsHelp B cells produce antibody

Linked recognition - T & B cells must “see” the same antigen but not identical epitopes

MHC - class II antigen presentation activates Th2 cell to express CD40L

CD40L - drives B cells into cell cycle

IL-4, IL-5, IL-10, IL-13 - drives B cell proliferation (IL-6) & differentiation

Isotype switching

Th2 Cytokines

Interaction Between Th2 Cells and B cells

Focal Delivery of Effector Molecules

CD4 T Cell Differentiation

Process that occurs following the activation of naïve CD4 cells which directs Th1 or Th2 cell development

Influenced by: Cytokines

Th1: IL-12 & IFN Th2: IL-4

Co-stimulatory molecules on APC Nature of the peptide:MHC ligand (dose, affinity)

CD4 T Cell Differentiation

Different patterns of cytokines were produced by T cell clones R. Coffman & T. Mosmann (1986) JI 136:2348

Listeria infection of macrophages induced IL-12 production which was necessary for Th1 cell development K. Murphy (1993) Science 260:547-549

Lysteria monocytogenes: A model for inducing Th1 Differentiation

Hsieh, C-S Science260:547, 1993

Influence of Cytokines on T Helper Cell Differentiation

IL-4

IL-12, IL-23, IL-27 & type I IFNs

IL-4, MCP-1?

IL-12

Th1

Th2

IL-2ThP

IFNIL-2LT (TNF)

IL-4IL-5IL-10IL-13

IL-17IL-6TNFa

ThIL-17

DTH & MQactivation

Inflammatorypathology

Allergic reactions & Eosinophilic inflammation

Th0 progresses to Th1 or Th2

PNAS 29:7565, 1995

Cytokines signal via JAK/STAT Pathway

Jak2Tyk2↑IL-12

Jak1Jak3↑IL-4

Cytokine Receptor Families

Influence of Transcription Factors on T cell subset Differentiation

IL-12 APC

T-BET

IFN

IFNR

TCR

1) STAT1

2)STAT4IFNIL-23p19 chainIL-12p40

IL-12R(p40 chain)

CD4 cell

Th1

IL-18RIL-18

CXCR3

PSGL-1Receptor

Th17

CXCR5

CCL9, 10 & 11

CXCL13

IL-17

What are the progenitors for Th17?

Bettelli, E & Kuchroo, V.K. J. Exp. Med. 201:169-171, 2005

Influence of Co-stimulatory Molecules on Differentiation

B7.1

B7.2, Ox40ICOS, T1/ST2

Th1

Th2

IL-2

ThP

IFNIL-2LT (TNF)

IL-4IL-5IL-13

Th1 cell Transcription Factors

Szabo, S, Cell 100:655, 2000

Influence of Transcription Factors on Th2 Cell Differentiation

IL-4

APC

STAT6

GATA-3

C-maf (IL-4 transcription factor)

NFAT

IL-4IL-5IL-13

IL-4R

TCR

IL-12IL-12R

CD4 cell

Th2

Expression of GATA-3 During Th2 Cell Differentiation

Immunity 9:745, 1998

Epigenetic Regulation of T cell Differentiation

JCI 109:431, 2002

Nucleosomes/HistonesAcetylatedMethylatedPhosphorylated

T helper Cell Differentiation

type 1 IFNs IL-23IL-27IFNIL-12

IL-4

TCR

IL-12RIL-4R

DC DC

IL-4

STAT4

STAT6T-BET

IFN

IL-18R

NFB

c-maf

GATA-3

IL-10

IFNR

STAT1

A Dominant Th1 vs. Th2 Response Alters the Outcome of Infection

A Dominant Th1 vs. Th2 Response Alters the Outcome of Infection

Th1/Th2 Differentiation is linked to cell division

Immunity 9:229, 1998

Papers for Discussion 5/12/05

P1. 1). Murphy CA, Langrish CL, Chen Y, Blumenschein W, McClanahan T, Kastelein RA, Sedgwick JD, Cua DJ.Divergent pro- and antiinflammatory roles for IL-23 and IL-12 in joint autoimmune inflammation.J Exp Med. 2003 Dec 15;198(12):1951-7.

P2. Langrish CL, Chen Y, Blumenschein WM, Mattson J, Basham B, Sedgwick JD, McClanahan T, Kastelein RA, Cua DJ

IL-23 drives a pathogenic T cell population that induces autoimmune inflammation. J Exp Med. 2005 Jan 17;201(2):233-40.