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Immune Effectors
Kathleen Kelly [email protected]
6-5562
Reading
Immunobiology (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-helpercell 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 IFNg
• - Activate MQ & FasL/FADD mediated cytotoxicity
Th2 - effector cytokine is IL-4
• - help B cells/Ab production
Different Classes of Pathogens
Elicit Different T Effector Subsets
Effector Function of CTL
 Effector function is to
lyse target cells


Virus infected
Tumor
 MHC Class I restricted
 Contact-dependent
 Perforin/Granzyme
mediated cytotoxicity


Lytic granules are
produced & released
from CD8+ CTL
Granules induce apoptosis
Pathways of Apoptosis
Cytotoxic
granules
Russell, JH
Ann. Rev. Immunol.
20:323, 2002
Granzyme B but not FADD (FasL) Pathway
is Necessary for MHC Class I Restricted
Responses (GvH)
Syngeneic
FasL &
Granzyme B-/Wild
Type
FasL-/-
Granzyme B-/-
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
Syngeneic
FasL &
Granzyme B-/-
FasL-/-
Granzyme B-/-
Perforin-/-
Graubert, TA et al. J Clin Invest. 100:904, 1997
CTL Lytic Granules
Lytic 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 IFNg
Granule Exocytosis Pathway
 Effector molecules are preformed in
granules and undergo granule exocytosis
pathway

PI-3 kinase

RAC-1

PAC-1

MAPK kinase

ERK
cation-dependent
Mannose-P-6 R
Russell, JH,
Ann. Rev. Immunol.
20:323, 2002
CTL Lytic Granules
Lytic granules:

Granzymes
Serine proteases
• Granzyme B cleaves caspase 3

Other enzymes with undefined function
Granulysin
Orphan granzymes
Action of Granzyme B
Russell, JH
Ann. 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
Mice infected
with MCMV
Eur. J. Immunol.
30:1350, 2000
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
IFNg
Fas ligand - induces apoptosis of target cell
 Soluble




IFNg - activates macrophages &  MHC class I & II
and co-stimulatory molecules
TNFa - activates macrophages & induces NO
production
GM-CSF - activates macrophages
LT, TNF-b - 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.
 IFNg 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 Cells
 Help 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 & IFNg
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 IL12 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 Science
260:547, 1993
Influence of Cytokines on T Helper
Cell Differentiation
IL-4
IL-12, IL-23, IL27 &
type I IFNs
Th1
IL-2
ThP
ThIL-17
DTH & MQ
activation
Inflammatory
pathology
IL-17
IL-6
TNFa
IL-12
Th2
IL-4, MCP-1?
IFNg
IL-2
LT (TNFb)
IL-4
IL-5 Allergic reactions
IL-10 & Eosinophilic
IL-13 inflammation
Th0 progresses to Th1 or Th2
PNAS 29:7565, 1995
Cytokines signal via
JAK/STAT Pathway
Jak2 Jak1
Tyk2 Jak3
↑IL-12 ↑IL-4
Cytokine Receptor Families
Influence of Transcription Factors
on T cell subset Differentiation
Th1
IL-12 TCR
APC
IL-12Rb
(p40 chain)
IFNg
IL-18
2)STAT4
IFNgR
IL-18R
IL-23
p19 chain
IL-12p40
1) STAT1
T-BET
CXCL13
CXCR5
CCL9, 10 & 11
CXCR3
IFNg
Th17
PSGL-1
Receptor
IL-17
CD4 cell
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
Th1
IL-2
IFNg
IL-2
LT (TNFb)
ThP
Th2
IL-4
IL-5
IL-13
Th1 cell Transcription Factors
Szabo, S, Cell 100:655, 2000
Influence of Transcription Factors
on Th2 Cell Differentiation
IL-12R
Th2
IL-4R
IL-4
APC
TCR
IL-12
STAT6
GATA-3
IL-4
IL-5
IL-13
C-maf (IL-4 transcription factor)
NFAT
CD4 cell
Expression of GATA-3 During
Th2 Cell Differentiation
Immunity 9:745, 1998
Epigenetic Regulation of T cell
Differentiation
JCI 109:431, 2002
Nucleosomes/Histones
Acetylated
Methylated
Phosphorylated
T helper Cell Differentiation
type 1 IFNs
IL-23
IL-27
IFNg
IL-12
IL-12R
IL-18R
DC
DC
IL-10
IFNgR
STAT1
T-BET
STAT4
NFkB
IFNg
IL-4
TCR
c-maf
IL-4R
STAT6
GATA-3
IL-4
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 IL23 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.