Transcript Characteristics of Immune Response

Immunology 101
Richard T Maziarz, MD
September 13, 2013
Basic concepts
• Self vs nonself recognition
• Response to danger signals- Inflammation
– sterile vs nonsterile
• Components of the immune system
• Impact of transplantation on immune
system.
• Immune reconstitution.
• Harnessing the immune system
Self vs non-self admission is
evolutionarily conserved
Characteristics of Mamnalian
Immune Response
• Self: Nonself Recognition
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Protection from foreign pathogens
Elimination of malignant transformed cells
Rejection of foreign allografts
Failure of tolerance--> Autoimmune disorders
MHC molecules
• MHC class I
– HLA-A,B,C
• E, F, G, H
– Ubiquitous expression
• MHC class II
– HLA-DR,DP,DQ
• DO,DX
– Limited expression
• Antigenic Diversity
Crystal structure
MHC Molecules : Diversity
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Genetic structure : exon crossover events
Molecular structure : point mutations
Peptide binding pocket
TAP
Protein degradation and processing
End result: Tissue specific antigens
Future: Peptide specific therapies, vaccines?
Immune System
• Adaptive immune system vs innate immune
system
Pathogen associated molecular
patterns (PAMPs)
• Bacterial components
• Viral components
• Endogenous sources
– Uric acid
– DNA
– RNA
Toll like receptor activation
Components: Immune System
• Lymphocytes (Specificity) : B cells, T cells,
NK cells
• Non-Specific Elements
– NK Cells
– APC’s: Monocytes/macrophages; endothelial
cells; B cells; Dendritic cells; Other- microglia,
Langerhan’s cells, etc
– Neutrophils
– Soluble mediators: cytokines, lymphokines,
chemokines
Effector cells
Immunologic specificity
• Antigen-specific receptors on cell surfaces
– T lymphocytes: antigen specific T cell receptor
– B lymphocytes: surface IgM or IgM + IgD
• Antibodies in serum after secretion by
plasma cells
Cluster of Differentiation
Antigen Nomenclature
• Nomenclature defines the “name” of the
antigen : (CD1 – CD326)
• Developed to clarify the biology of
responses associated with antigen
• All CD designations are not necessarily
independent molecules
– Examples : CD3, CD11/CD18 are peptides;
CD15 defines CHO sidechain
“T cell and B cell clones are
actually individual tissues. The
comlexity of the immune system
is simplified by the recognition
that there are billions of tissues in
circulation contributing to
immune surveillance”
T cells
• Intrathymic vs Extrathymic differentiation
• Thymus differentiation : well ordered
pathway - cortex--> medulla and out
– CD34--> CD34 CD7--> CD2CD7(triple
negative)--> CD2CD3 (double negative)-->
CD2CD3CD4CD8 (double positive)-->
CD2CD3CD4 or CD2CD3CD8
• TCR rearrangement accompanies positive
and negative selection
CD4 and CD8 Co-Receptors
• Adhesion molecules :
– CD4:MHC II
– CD8: MHC I
• Recognition of MHC - conserved sequences
• Co-stimulatory function to augment TCR
signalling (associated with lck)
• Defines subpopulation of effector T cells
– Helper and cytotoxic T cells
T Cells in the thymus
• Positive Selection
– Low affinity TCR for self can mature and
migrate to periphery
• Negative Selection
– High affinity TCR for self are deleted following
TCR ligation
• Actual Mechanism remains unclear
– Signal intensity vs Developmental stage
Age Related Change in Thymus
Haynes, Ann Rev Imm, 2000
Age Related Change in Thymus
• Age
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0-1
2-10
11-25
26-49
>50
%TE space
93
88
63
45
18
Thymus out
>109
8.8 x 108
6.3 x 108
4.5 x 108
1.8 x 108
Haynes, Ann Rev Imm, 2000
Costimulation
• TCR and CD28 simultaneous activation leads to T cell
proliferation and target cell death
• TCR and CD152 (CTLA4) binding can limit a T cell
proliferative response
• The lack of cell surface CD80 and CD86 can lead to T cell
programmed cell death or to induction of peripheral
tolerance (e.g. anergy).
– Absence of CD80 on tumor can induce tolerance
– Heterotypic antibodies binding CD3 and CD28 can
overcome peripheral tolerance
– OKT3 treatment in renal transplants can render T cells
refractory to stimulation
• Immunologic Memory:
– Antigen exposure--> proliferation and
differentiation; small # of cells may proceed to
memory state
– Secondary Antigenic Challenge : anamnestic
response
• Amplification of Immune Response
– Cell: Cell interactions
– Cell: soluble mediator interactions
Cytokine Expression by T cell
populations
• Naïve T cells
– IL2, lo induction of DC IL12
• Memory T cells
– T-CM:(CCR7+):
• IL2, induce DC IL12
– T-EM:(CCR7-):
• lo IL2, IL4, IL5, IFN-G,
Sallusto, Nature, 1999
Memory/Effector T cells
• Effector T cells :
– Conventional: Precursor of memory cells?
– Hypothesis: Downstream cell after
differentiation of T central memory cell?
• Supported by telomere shortening observations
– Phenotype: CD45RO+CCR7+ and
CD8+CD45RA+CCR7-CD62Llo
subpopulation(?)
Naïve T cells: Molecular
Determination
• Chromosome 14 is home of alpha and delta
TCR
• Rearrangement of TCR alpha locus during
thymic maturation splices out TCR delta
locus
• T cell receptor excision circles (TREC):
maintained episomally and do not replicate
• Antigen driven T cell expansion does not
expand TREC
• Two classes of TCR
• TCR are polypeptides with two functionsexternal antigen recognition and signal
transduction
• TCR engage antigen on the cell surface of
other cells
• TCR recognize antigen in context of MHC
• TCR families can be associated with
diseases
– Vβ2 in toxic shock (super antigen)
– Vβ12, 17 in multiple schlerosis (auto antigen)
Generation of TREC
TREC : Clinical Applications
• Decreases with age, but persists into 7th
decade -Douek, Nature, 1999
• Decreased in HIV-infected pts
• Increased with aggressive antiviral therapy
in HIV
• Increased in thymic transplants for
DiGeorge syndrome, coincident with
increase CD45RA+, CD62L+ -Markert, NEJM,
1999
Recovery of CD4 and CD8 T Cells
after AutoTx for MM
CD4= opaque
CD8= open
CD34s=circle
Douek, Lancet 2000
T Cell Receptor Analysis
Normal V-β Family Expression
CDR3 Size-Pattern Analysis
Normal
In vitro
Ag stim
HIV
T cell line
Manfras, J Imm Met, 1997
CDR3 Size-Pattern Analysis in
Transplantation
• Gorski, JI, 1994:
– Repertoire stability
– Rate of repertoire recovery
– Impact of opportunistic infections
• Memon, AAI, 2000:
– Correlated with CD4+, CD45RA+ T cell
recovery
TCR signal transduction
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Activation of T cell
Render T cells refractory to stimulation
Costimulation (CD3 : CD28)
Targets for therapy of T cell diseases
Genetic defects (SCIDS and others)
– Zap 70 deficiency
– CD3 gamma or epsilon deletion
Second Signals
T cell sub-subsets
• CD4 T cells differentiate into separate
subpopulations of T cell
– Th1 are important for cellular responses and
resistance to infection; IL-2, IFN-G, TNF-alpha
are produced
– Th2 are important for humoral responses and
can increase susceptibility to infection; IL-4,
IL-5, Il-6, IL-10, IL-13, GM-CSF; can
downregulate Th1 responses
• CD8 effector cell subpopulations like CD4
cells have been identified.
Helper T cell subsets
CD4 T cell subsets
Natural killer cells
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Killer inhibitory receptors (KIR)
Diversity
HLA recognition
May impact leukemia outcome
Clinical relevance- recognition of herpes
virus family members
Impact of transplantation
conditioning on host immunity
• Myeloablative
• Immune suppressive
• Quantitative and qualitative deficits
Tumor Cell Escape from T cell
Immunosurveillance
• Loss of expression of MHC antigens
– Transcriptional repression (-) of gene
expression
– Intracellular competition with β2M
– Loss of trans activating + factors for expression
– Altered TAP transporter
– Chromosomal Deletion
• Production of inhibitory cytokines e.g.
IL10, TGF-β
Tumor Cell Escape from T cell
Immunosurveillance
• Induction of Zeta chain translocation and
anergy
• Loss of adhesion molecules
• Lack of costimulatory molecules (CD80,
CD86, CD40)
• Lack of TSTA, TAA
• Secretion of soluble antigen to create
tolerance
Immune reconstitution
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Population
% Lymphs
Count/ul %
Total T cells(CD3+) 59.8
316 L
CD3+ CD4+
23.4
124 L
CD3+ CD8+
30.9
163 L
CD3+CD4-CD8-(Doub.neg) 4.8
CD3+CD4+8+(Doub. pos) 0.0
CD4+CD45RO- (naive)
4.6
NKT
6.9
NK cells (CD56+CD3-) 38.4 203
Total B-Cells (CD19+) 0.0
0L
Lymphs count/ul
55-82% 800-3500
20-60% 500-2000
15-30% 300-900
NA
<6%
NA
<2%
NA
8-50%
<3%
5-20% 75-500
5-15% 70-450
Immune reconstitution
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% of B-cells
% of B-cells
IgD+ CD27- Naive B-cells 0.0 L 58-80%
IgD+ CD27+ Non-switched memory B 0.0 L 7-21%
IgG+ CD27+ Switched, memory B 0.0 L 9-19%
Activation Indicators
Patient Results
Reference Ranges CD4:CD8 ratio 0.8 L 1.0-3.3
%Lymphs
CD3+CD4+CD8beta+
0.0 L
CD3+HLA-DR+
8.7
CD4+CD25+
2.2
CD8beta+CD69+
1.9 H
% of CD4+ T cells
• CD4+CD25+ bright(T regs)
12.0 H
%Lymphs
<1.5%
<10%
<7%
<1%
<10%
Harnessing the immune system
• Antibody therapy
– IvIg
– BITEs
• Cellular therapies
– LAK + NK-T
• IL2/ cytokine ex vivo expanded cell populations
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TIL
Tregs
Dendritic cell vaccines-Provenge®
CAR-T cells
Generation of TIL (tumor infiltrating
lymphocytes)
Novel antibody therapy
Hematologic RFS – MRD persistence or relapse of ALL
(A) 20 evaluable patients; (B) subset 9  allo HSCT; (C) subset 11  chemo only
T cell engaging, bispecific single chain (BiTE) ab
Topp M S et al. Blood 2012;120:5185-5187
©2012 by American Society of Hematology
Chimeric antigen receptor- T
(CAR-T) cells
CAR-T cell applications
CAR-T: mechanism of killing
Clinical Response in the Patient.
Porter DL et al. N Engl J Med 2011;365:725-733.
Expansion and Persistence of Chimeric Antigen Receptor T Cells In Vivo.
Porter DL et al. N Engl J Med 2011;365:725-733.
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