Immune Responses to Tumors and Transplants William Hildebrand Chapter 10 Abbas and Lichtman

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Immune Responses to Tumors and
TransplantsWilliam HildebrandChapter 10Abbas
and Lichtman
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Objectives

• Introduction
• Different types of tumors
• Nature of immune response
• Antigens of cancer cells
• Cancer immune evasion
• Immunotherapy

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Cell Growth
Control of cell growth
Growth-restricting Tumor-suppressor genes
Growth-promoting Proto-oncogenes
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Molecular Basis of Cancer
Radiation Chemical (Carcinogen) Virus
Mutations
Uncontrolled cell growth
Proto-oncogenes
Tumor-suppressor genes
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There are Different Types of Tumors

• Chemically-induced tumors
• Each tumor induced by a carcinogen (e.g.
  benzopyrene) injected at various sites expresses
  a unique Ag.
• Thus difficult to develop vaccine.
• Virus-induced tumors
• Tumors induced by same virus express same tumor
  Ag.
• Induce a strong immune response.
• e.g. Gardasil vaccine Human Papilloma Virus
  (HPV) induced cervical cancer
• UV-induced tumors
• UV radiation---gtmelanomas
• Highly tumorigenic

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Genetic Implications Cancer

• Genetic factors mutations, translocation,
  amplifications
• conversion of proto-oncogenes (potential for cell
  transformation) to oncogenes (cell
  transformation)
• alteration in tumor suppressor genes

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Immunological SurveillanceBurnet, Thomas

• Hypothesis Tumors are constantly arising. A
  major role of the immune system is to eliminate
  this threat. Only non-immunogenic tumors are
  successful.
• Evidence
• Pro Incidence of cancer is higher in conditions
  of immunosuppression (transplant recipients, AIDS)

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The Immune System Controls Tumors
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Virus-induced tumors e.g.SV40
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Chemical-induced tumors e.g. methylcholanthrene
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• Tumor antigens have been shown to cross-react
  immunologically in cases of
• tumors induced by chemical carcinogens
• tumors induced by RNA viruses
• all tumors
• tumors induced by irradiation with ultraviolet
  light
• tumors induced by the same chemical carcinogen on
  two separate sites on the same individual

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B Immunologic cross-reactivity has been
demonstrated only in cases of virally induced
tumors (caused by either RNA or DNA viruses).
Tumors induced by chemical or physical
carcinogens do not exhibit cross-reactivity, even
if induced by the same carcinogen on separate
sites on the same individual.
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Tumor Antigens

• Tumor-specific antigens
• Expressed by tumors ONLY
• Tumor-associated antigens
• Preferentially expressed by tumors
• Oncofetal antigen
• Expressed by tumors in adult, but also expressed
  by fetal (not adult) tissues

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Types of Tumor Antigens Recognized by T cells
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Ocogene Product bcr-abl fusion gene
Constitutively Active Tyrosine Kinase CML, AML,
ALL
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Drugs that target protein kinases and the
receptors that activate them
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Non-Specific Proteins or Markers Related to
Malignant Cells

• Oncofetal proteinsexpressed by cells as they
  de-differentiate and take on embryonic
  characteristics
• a-FPHCC, testicular, ovarian cancer
• CEAmany GI tumors

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Colorectal Cancer

• Carcinoembryonic antigen (CEA)
• fetal glycoprotein found on cell surfaces,
  produced by fetal GI tract, liver, and pancreas
• Normal serum and tissue fluid valuelt3.0 ng/ml
• Circulating half-lifeweeks
• Detect early relapse of colorectal cancer and
  prognostic indicator
• In 2/3 of patients an elevated CEA may be the 1st
  indication of relapse

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CEA

• Found also in 3050 of breast cancer, small cell
  lung cancer, mucinous cystadenocarcinoma of
  ovary, adenocarcinoma of cervix
• Elevation (lt10 ng/ml) in smokers, COPD,
  inflammatory or peptic bowel disease, liver
  inflammation or cirrhosis, renal failure,
  fibrocystic breast disease

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Viral Cancer Antigen
the primary function of the E7 protein is to
inactivate members of the pRb family of tumor
suppressor proteins
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Objectives

• Introduction
• Different types of tumors
• Nature of immune response
• Antigens of cancer cells
• Cancer immune evasion
• Immunotherapy

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Induction of CTL Responses to Tumor Antigens
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Mechanisms of Tumor Escapefrom Immune Responses

• Loss of HLA or TAP
• Lack of tumor antigen
• Secretion of immunosuppressive factors
• E.g. TGF-b, IL-10
• Exhaustion of T cells
• T regulatory cells suppress anti-tumor responses

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Down Regulation of HLA Class I

• Down regulation of HLA class I expression is
  frequently seen in human tumors
• Loss of HLA-I as a mechanism for tumor escape
  from CTL-mediated elimination (longitudinal study
  of melanoma patients)
• Four HLA altered phenotypes found in tumor tissues

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HLA Loss
Total loss
HLA allelic loss
Haplotype loss
HLA-A or B locus-specific loss
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Lack of Tumor Antigen
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Antigen Loss
HER-2
tumor
Herceptin
tumor
Loss
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Mechanisms of Tumor Escapefrom Immune Responses

• Loss of MHC or TAP
• Lack of tumor antigen
• Secretion of immunosuppressive factors
• E.g. TGF-b, IL-10
• Exhaustion of T cells
• T regulatory cells suppress anti-tumor responses

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How does a tumor escape immune surveillance?

• Generation of Regulatory cells (CD4CD25 FoxP3
  T cells) or Myeloid-derived suppressor
  cells(Gr-1 CD11b)
• Secrete immunosuppressive molecules Ex
  Transforming growth factor beta (TGF-b),
  interleukin-10 (IL-10), etc.

T regs
CTL
MDSC
IL-10, etc
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• Tumors may fail to express costimulatory
• molecules involved in T cell activation.

Tumors escape the action of CTL by not expressing
B7 which provides 2nd signal involved in T cell
activation
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Active ImmunotherapyVaccination
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APC 8015 (Provenge) Vaccine Therapy with Pulsed
Dendritic Cells
Dendritic-cell precursors are harvested by
leukapheresis
APC Antigen presenting cells
MHC
Pulse with PAP-GM-CSF fusion protein for 40 hrs
Purified Dendritic Cells with prostate-specific
peptides
Inject Back Into Prostate Cancer Patient
Prostate Cancer Patient
Phase I/II results published show safety and a
clear dose-related biologic activity
prostatic acid phosphatase PAP
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Tumor Immunity

1. Tumors may be distinguished by CTL
2. Tumors may modulate immune recognition
3. Emerging methods for the delivery of tumor immune
   targets

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Passive ImmunotherapyAnti-tumor monoclonal
antibodies (a billion dollar business)
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Antibody-dependent cellular cytotoxicity
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FDA-approved therapeutic monoclonal antibodies
CD20
Her2
CD33
CD52
CD20
CD20
EGF-R
VEGF
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One minute review

• Tumor Antigens Mostly Cellular Gene Products
• Oncogenes (bcr-abl)
• mutated genes/tumor suppressor genes (p53)
• over-expressed genes (telomerase, tyrosinase)
• oncofetal genes (CEA, Alpha-Feto protein)
• Transforming viruses (HPV, Hepatitis viruses)

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One minute review

• Anti-tumor mechanisms (Abs, CTLs, NK cells)
• Immune evasion
• Decrease or loss of MHC expression
• Lack of co-stimulation
• Antigen loss variants
• Suppression of immune response (TGFbeta)
• Immunotherapies for tumors
• Experimental T cell therapies, mAb
• T cell vaccines

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Immune Responses to Tumors and
TransplantsWilliam HildebrandChapter 10Abbas
and Lichtman
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MHC AND TRANSPLANTATION Categories of
Grafts
Transplantation - the grafting of tissue, usually
from one individual to another. Autograft - to
another site on the same individual
(Autologous) Isograft - to a genetically
identical individual (syngeneic or
syngraft) Allograft - to a genetically disparate
member of the same species (allogeneic) Xenograft
- to a different species
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• A 42-year-old auto mechanic has been diagnosed
  with end-stage renal disease. His identical twin
  brother has the same HLA alleles at all loci, and
  volunteers to donate a kidney to his brother.
  Which of the following terms correctly describes
  the proposed organ transplant?
• A. Allograft
• B. Autograft
• C. Heterograft
• D. Syngeneic graft
• E. Xenograft

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Immune Recognition of Transplants

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Acute graft rejection is mediated by T cells...
Strain A and strain B mice differ only in their
MHC molecules
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Immune Recognition of Transplants

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Acute graft rejection is mediated by T cells...
Modified from Kuby Figure 21-3
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Kuby Figure 21-7
Transplant Rejection is T Cell Driven
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Allorecognition TCR MHC

• TCR interact with allogeneic MHC molecules and
  are activated
• 10-30 of an individuals T cells can respond to
  allogeneic MHC

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Characterization of Immune Responses to Grafts
Transplant rejection if primarily driven by T
cell responses, although hyperacute rejection is
antibody mediated

• In solid tissue transplantation, there are three
  major types of graft rejection
• 1. Hyperacute rejection minutes to hours for
  transplant to be rejected
• 2. Acute rejection Days to weeks for transplant
  to be rejected
• 3. Chronic rejection Transplant rejected
  slowly, months to years

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Minutes hours Weeks Months
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Acute graft rejection is mediated by T cells...
Strain A and strain B mice differ only in their
MHC molecules Acute rejection takes days to
weeks (immune suppression may lengthen to
several weeks) Second-set or accelerated
rejection immune memory
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Minutes hours Weeks Months
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• A person rejects a kidney within 10 minutes of
  getting the graft.
• A person accepts the graft, then develops edema
  a few weeks later. The reaction ocurring is
  between the donor macrophages and cytotoxic T
  Cells.
• Same person from 2 gets another graft and
  rejects it twice as fast because of Memory
  T-cells.
• Person gets a graft, and is ok for six months,
  then develops fibrinoid necrosis and ischemia
• Choices
• Hyperacute
• Acute
• Chronic
• Accelerated

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Summary of the three major forms of tissue
rejection
Hyperacute rejection Acute rejection
Chronic rejection Incidence Rare (1)
due to Common (50) Common (50)
pretransplant depending on increases
with HLA Ab screen preventive
increased episodes measures of acute
rejection Time of Minutes to days Days
to weeks Usually within 5-10 onset
post-transplant lt 1year post- years, but can
be as transplant early as weeks
post- transplant Histo-
Thrombosis, Escalating leukocytic Leukocytic
infiltration pathology platelet and
infiltration, edema, may be present,
neutrophil tissue necrosis interstitial
fibrosis, accumulation occlusion of
blood vessels Primary
Antibodies, T-cells Ab, T-cells,
cytokines, mediators Complement tissue
growth factors
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Transplant Immunology

1. T cell driven phenomenon
2. Direct or indirect allorecognition
3. Abs contribute
4. Different types of grafts - autologous,
   syngeneic, allogeneic
5. Different pace of rejection - hyperacute, acute,
   chronic

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Limiting Transplant Rejection

• Pre-transplant
• HLA match donor and recipient (acute chronic)
• Screen for antibodies to HLA (hyperacute)
• Post-Transplant
• Immunosuppressive drugs
• Immune modifiers

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Match donor recipient by HLA typing

1. Type class I and class II HLA by DNA
2. Phenotype class I and class II HLA

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Location of amino acid variability that results
in multiple different HLA class I molecules
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HLA Genotyping

• Type HLA-A, -B, and C, alpha chain, exons 2-3
• Type HLA-DR, exon 2, beta chain
• Type HLA-DP DQ, alpha beta, exon 2
• PCR ARMS typing
• PCR followed by probe hybridization
• PCR followed by DNA Sequencing

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Class I HLA Typing Via Serologic Methods
Phenotype Genotype
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Limiting Transplant Rejection

• Pre-transplant
• HLA match donor and recipient (acute chronic)
• Screen for antibodies to HLA (hyperacute)
• Post-Transplant
• Immunosuppressive drugs
• Immune modifiers

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Screen Recipient for Ab to HLA
Organ recipient
HLA class I/II
Or donor cells
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Limiting Transplant Rejection

• Pre-transplant
• HLA match donor and recipient (acute chronic)
• Screen for antibodies to HLA (hyperacute)
• Post-Transplant
• Immunosuppressive drugs
• Immune modifiers

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Steroids block IL-1
View Notes
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Major Steps in Immune Responses

• 1- Antigen recognition
• 2- IL-1 production
• 3- IL-2 and other cytokine expression
• 4- lymphocyte proliferation differentiation

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Three Signal Model of T cell Activation
Antigen Presenting Cell

• MHC II B7
• 
  Antigen Interleukin-2
• CD45 CD4 CD3 CD28
  Interleukin-receptor
• T Lymphocyte Target lymphocyte

Signal 1
Signal 2
Signal 3
TCR

Purine
Synthesis
Calcineurin Pathway
TOR Pathway
Cytokine gene nucleus
Cell Cycle
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Sites of Action of Immunosuppressive Medications
Antigen Presenting Cell

• MHC II B7
• 
  Interleukin-2
  
• CD45 CD4 CD3
  CD28 Interleukin-2 receptor
• T Lymphocyte Target lymphocyte

Steroids
Signal 1
Signal 2
Signal 3
Anti-IL-2R
ATG
Belatacept
OKT3
TCR

Purine
Synthesis
Sirolimus
TOR Pathway
Cyclosporine Tacrolimus
Calcineurin Pathway
MMF
Steroids
Cytokine gene nucleus
Cell Cycle
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• Question Tumors may escape immunosurveillance
  by any of the following EXCEPT
• A. lack of cells recognizing the tumor antigen.
• B. inability of patients MHC to present that
  particular tumor antigen.
• C. antigenic modulation or masking.
• D. local overexpression of cytokines IL-2 and/or
  TNF.
• E. failure to provide costimulation to develop
  anti-tumor immunity.

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• Question Tumors may escape immunosurveillance
  by any of the following EXCEPT
• A. lack of cells recognizing the tumor antigen.
• B. inability of patients MHC to present that
  particular tumor antigen.
• C. antigenic modulation or masking.
• D. local overexpression of cytokines IL-2 and/or
  TNF.
• E. failure to provide costimulation to develop
  anti-tumor immunity.

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GVHD

• Graft versus host disease occurs in bone marrow
  transplants when the transplanted cells from the
  bone marrow donor attack the recipient
• Histoidentical siblings preferred as donors
• Vigorous immunosuppression required

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• Which of the following statements regarding GVH
  disease is incorrect?
• GVH can result from MHC differences between donor
  and recipient
• GVH requires immunocompetent donor cells
• GVH may result from infusion of blood products
  that contain viable lymphocytes into an
  immunologically incompetent recipient
• GVH requires natural killer cells
• GVH may occur in an immunosuppressed individual

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D. GVH disease is caused by the destruction of
cells or tissue of an immuno-incompetent
recipient by immunocompetent lymphoid cells
transferred from a histo-incompatible donor. The
GVH reaction does not require natural killer
cells.
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Cromwell, a 5-month-old boy who was diagnosed
with Wiskott-Aldrich syndrome, received a bone
marrow transplant from a HLA-matched unrelated
donor. He was doing well until two weeks after
the transplant, when he developed a rash.
Subsequently, he developed diarrhea, an enlarged
liver and spleen and jaundice. Answer
These symptoms are consistent with GVH. Other
organs that may be involved include the heart,
lung, and CNS. The mortality rate is high.
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Graft versus host disease
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One minute review

• Organ Transplants
• Autograft (autologous)
• Isograft (syngeneic)
• Allograft (allogeneic)
• Transplant Rejection
• - Hyperacute Rejection (preformed Abs)
• Acute Rejection (T cell driven)
• Chronic Rejection (T cells and Abs)
• GVHD during BMT
• Immunosuppressive drugs and antibodies
• Target T cells at different stages of maturation
• Tissue typing
• DNA for HLA class I and class II genotyping
• Microcytotoxicity for phenotype (complement-based
  assay)