Download Anti-tumor immune mechanisms

27. Tumour immunology - tumour antigens, mechanisms of defence.
28. Alloimmune reaction. Types of transplantations and immunological
examination before transplantation. Immunologically privileged tissues.
29. Types of graft rejection and their mechanisms. GvH. Principle of maternofoetal tolerance. Rh incompatibility
30. IgG and IgM based immunopathological reaction (reaction of
hypersensitivity type II).
31. Immunocomplex based immunopathological reaction (reaction of
hypersensitivity type III).
Tumour immunology
Tumor antigens
a) Tumor – specific antigens (TSA)

complexes of MHCgp I with abnormal fragments of cellular proteins
(chemically induced tumors, leukemia with chromosomal translocation)

complexes of MHC gp with fragments of oncogenic viruses proteins
(tumors caused by viruses: EBV, SV40, polyomavirus…)

abnormal forms of glycoproteins
(sialylation of surface proteins of tumor cells)

idiotypes of myeloma and lymphoma
(clonotyping TCR and BCR)
Tumor antigens
b) Tumor - associated antigens (TAA)
 present also on normal cells
 differences in quantity, time and local expression
 auxiliary diagnostic markers
Tumor - associated antigens

onkofetal antigens -on normal embryonic cells and some tumor cells
 -fetoprotein (AFP) - hepatom
 carcinoembryonic antigen (CEA) - colon cancer

melanoma antigens - MAGE-1, Melan-A

antigen HER2/neu -receptor for epithelial growth factor, mammary
carcinoma

EPCAM – epithelial cell adhesion molecule, metastases

differentiation antigens of leukemic cells - present on normal cells of
leukocytes linage
 CALLA -acute lymphoblastic leukemia (CD10 pre-B cells)
Anti-tumor immune mechanisms
Immune control
 tumor cells normally arise in tissues
and are eliminated by T cells
Immune surveillance of tumours
Anti – tumor immune response
 tumor cells are weakly immunogenic
 occurs when tumor antigens are presented to T cells
by dendritic cells activated in the inflammatory
environment
Regulatory T cells prevents removal of cancer cells and
thus contribute to the development of the tumor.
Anti-tumor immune mechanisms
If tumor cells are detected, in defense may be
involved non-specific mechanisms (neutrophilic
granulocytes, macrophages, NK cells, complement) and
antigen-specific mechanisms (TH1 and TC cells,
antibodies).
Anti-tumor immune mechanisms
 DC are necessary for activation of antigen specific mechanisms
 predominance of TH1 (IFN g, TNF)
 specific cell-mediated cytotoxic reactivity – TC
 activation of TH2 → stimulation of B cells→ tumor specific
antibodies production (involved in the ADCC)
 tumor cells are destroyed by cytotoxic NK cells (ADCC)
 interferons - antiproliferative, cytotoxic effect on tumor cells
- INFg - DC maturation
Mechanisms of tumor resistance to the
immune system
 high variability of tumor cells
 low expression of tumor antigens
 sialylation
 some anticancer substances have a stimulating effect
 production of factors inactivating T lymphocytes
 expression of FasL → T lymphocyte apoptosis
 inhibition of the function or durability dendritic cells (NO, IL-10,
TGF-b)
Transplantation
Transplantation
= transfer of tissue or organ
 autologous - donor = recipient
 syngeneic - genetically identical donor and recipient
(identical twins)
 allogeneic - genetically nonidentical donor of the
same species
 xenogenic - the donor of another species
 implant - artificial tissue compensation
Allotransplantation

differences in donor-recipient MHC gp and secondary
histocompatibility Ag
 alloreactivity of T lymphocytes - the risk
of rejection and graft-versus-host disease
Tests prior to transplantation
 ABO compatibility (matching blood group)
-risk of hyperacute or accelerated rejection
(= formation of Ab against A or B Ag on graft vascular endothelium)
 HLA typing (matching tissue type)
- determining of HLA alelic forms by phenotyping or genotyping
 Cross-match - detection of preformed alloantibodies
(after blood transfusions, transplantation, repeated childbirth)
 Mixed lymphocyte reaction - testing of T lymphocytes
alloreactivity
HLA typing
= determmination of HLA antigens on the surface of
lymphocytes
 Carry out during the testing before transplantation
and in determination of paternity
 serotyping
 genotyping
Serotyping (microlymfocytotoxic test)
Serotyping (microlymfocytotoxic test)

Allospecific serums (obtained from multiple natal to 6 weeks after birth, or
commercially prepared sets of typing serums (monoclonal antibodies))

Principle - the incubation of lymphocytes with typing serums in the
presence of rabbit complement, then is added the vital
dye which stained dead cells
-
cells carrying specific HLA are killed by cytotoxic Ab
against the Ag, the percentage of dead cells
is a measure of serum toxicity

In positive reaction is more than 10% dead cells
(serological typing can be done also by flow cytometry)
Molecular genetic methods - genotyping
a) PCR-SSP
(Polymerase chain reaction with sequential specific
primers)
 Extracted DNA is used as a substrate in a set of PCR reactions
 Each PCR reaction contains primers pair specific for a certain
allele (or group of alleles)
 Positive and negative reactions are evaluated by electrophoresis
Molecular genetic methods genotyping
b) PCR-SSO
 PCR reaction with sequence-specific oligonucleotides
 Hybridization with enzyme or radiolabeled oligonucleotides
probes specific for individual alleles
Molecular genetic methods - genotyping
c) PCR-SBT
 Sequencing based typing
 We get the exact sequence of nucleotides, which compares
with a database of known sequences of HLA alleles
Tests prior to transplantation
Cross-match testing
 determination of preformed alloantibodies
 recipient serum + donor lymphocytes + rabbit complement
→ if cytotoxic Ab against donor HLA Ag are present in recipient serum ,
Ab activate complement → lysis of donor lymphocytes.
Dye penetration into lysis cells.
 positive test = the presence of preformed Ab → risk of hyperacute
rejection! → contraindication to transplantation
Tests prior to transplantation
Mixed lymphocyte reaction (MRL)
 determination of T lymphocytes alloreactivity
 mixed donor and recipient lymphocytes → T lymphocytes
after recognition of allogeneic MHC gp activate and proliferate
One-way MRL
 determination of recipient T lymphocytes reactivity against donor cells
 donor cells treated with chemotherapy or irradiated lose the ability of
proliferation
One-way MRL
Immunologically privileged sites and tissues
 Transplantation of some tissues doesn´t lead to the induction
of allogeneic reactivity
 Evolutionarily significant- protection of vital organs
(brain, eye, gonads)
 Factors protecting immunologically privileged structures
 isolation from the immune system (minimal content of lecocytes)
 preference of TH2 reactoin, supression of TH1 reaction
 FasL expression
 production of TGFb
Rejection
 hyperacute
 accelerated
 acute
 chronic
Hyperacute rejection
 minutes to hours after transplantation
 humoral mediated immune response
mechanism:
 if in recipients blood are present preformed or natural Ab (IgM anti-
carbohydrate Ag) before transplantation → Ab + Ag of graft (MHC gp
or endothelial Ag) → graft damage by activated complement
 the graft endothelium: activation of coagulation factors and platelets,
formation thrombi, accumulation of neutrophil granulocytes
prevention:
 negative cross match before transplantation, ABO compatibility
Accelerated rejection
 3 to 5 days after transplantation
 caused by antibodies that don´t activate complement
 cytotoxic and inflammatory responses triggered by
binding of antibodies to Fc-receptors on phagocytes and
NK cells
prevention:
 negative cross match before transplantation,
ABO compatibility
Acute rejection
 days to weeks after the transplantation or after a lack of
immunosuppressive treatment
 cell-mediated immune response
mechanism:
 reaction of recipient TH1 and TC cells against Ag
of graft tissue
 infiltration by lymphocytes, monocytes, granulocytes
around small vessels → destruction of the transplant tissue
Chronic rejection
 from 2 months after transplantation
 the most common cause of graft failure
mechanism is not fully understood:
 non-immunological factors (tissue ischemia) and TH2 response
with production alloantibodies, pathogenetic role of cytokines
and growth factors (TGFβ)
 fibrosis of the internal blood vessels of the transplanted tissue,
endothelial damage →impaired perfusion of graft → gradual loss
of its function
 dominating findings: vascular damage
Rejection
Factors:
 The genetic difference between donor and recipient,
especially in the genes coding for MHC gp (HLA)
 Type of tissue / organ - the strongest reactions against vascularized
tissues containing many APC (skin)
 The activity of the recipient immune system – the immunodeficiency
recipient has a smaller rejection reaction; immunosuppressive therapy
after transplantation – suppression of rejection
 Status of transplanted organ - the length of ischemia, the
method of preservation, traumatization of organ at collection
Graft-versus-host (GvH) disease
 after bone marrow transplantation
 GvH also after blood transfusion to immunodeficiency
recipients
 T-lymphocytes in the graft bone marrow recognize
recipient tissue Ag as foreign (alloreactivity)
Acute GvH disease
 days to weeks after the transplantation of stem cells
 damage of liver, skin and intestinal mucosa
 prevention: appropriate donor selection, the removal
of T lymphocytes from the graft and effective
immunosuppression
Chonic GvH disease
 months to years after transplantation
 infiltration of tissues and organs by TH2 lymphocytes,
production of alloantibodies and cytokines → fibrosis
 process like autoimmune disease: vasculitis, scleroderma,
sicca-syndrome
 chronic inflammation of blood vessels, skin, internal
organs and glands, which leads to fibrosis, blood circulation disorders
and loss of function
Graft versus leukemia effect (GvL)
 donor T lymphocytes react against residual
leukemick cells of recipient (setpoint response)
 mechanism is consistent with acute GvH
 associated with a certain degree of GvH
(adverse reactions)
Immunologic relationship
between mother
and allogenic fetus
Immunologic relationship between
mother and allogenic fetus
fetal cells have on the surface alloantigens
inherited from his father
Pregnancy = „semiallogenic transplantation“
Immunologic relationship between mother
and allogenic fetus
Tolerance of fetus by mother:

the relative isolation of the fetus from maternal immune
system (no mixing of blood circulation)

trophoblast - immune barrier witch protects against mother
alloreactive T lymphocytes (don´t express classical MHC gp,
expresses non-classical HLA-E and HLA-G)
 suppressin of TH1 and preference of TH2 immune mechanisms
in pregnancy
• transfer of small doses of fetal antigens in maternal circulation
causes tolerance ...
Rh incompatibility
 Complications in pregnancy: production of anti-RhD
antibodies by RhD- mother carrying an RhD+ fetus
(hemolytic disease of newborns)
 During childbirth or abortion (after 8 weeks of
gestation) fetal erythrocytes can penetrate into the
bloodstream of mother → immunization,
formation of anti-RhD antibodies
Rh incompatibility
Rh incompatibility
 After childbirth, investigate Rh factor of born child, if is child Rh+,
mother (Rh-) gets up to 72 hours after birth injection of anti-RhD
antibodies (administered after abortion too)
 Anti-Rh(D) antibodies bind to RhD Ag on baby´s red blood cells,
this Ag than can´t bind to BCR and can´t activate B lymphocytes,
this immune comlexes also inhibit B lymphocytes
Rh incompatibility
 During next childbirths, if fetus is Rh+ and mother
produce anti-Rh antibodies, this Abb destroy red blood
cells of fetus, which can lead to fetal death, or in severe
postpartum anemia (anemia neonatorum) and neonatal
jaundice (icterus gravis neonatorum)

For each pregnant woman during the first trimester investigate blod Rh
factor and the presence of antibodies, in Rh- women performed a test for
antibodies also in II. and III. trimester
Immunopathological
reactions
Immunopathological reactions
 Immune response which caused damage to the body
(Consequence of immune response against pathogens,
inappropriate responses to harmless antigens;
autoimmunity)
Immunopathological reactions
Classification by Coombs and Gell
Immunopathological reactions: immune response, which caused damage
to the body (secondary consequence of defense responses against pathogens,
inappropriate responses to harmless antigens, autoimmunity)
IV types of immunopathological reactions:
Type I reaction - response based on IgE antibodies
Type II reaction - response based on antibodies, IgG and IgM
Type III reaction - response based on the formation of immune complexes
Type IV reaction - cell-mediated response
Immunopathological reactions based on
antibodies IgG and IgM (reaction type II)
Cytotoxic antibodies IgG and IgM bind to antigens
on own cell:
 complement activation
 binding to Fc receptors on phagocytes and NK cells
(ADCC)
Examples of immunopathological reaction
Type II
 Transfusion reactions after administration
of incompatibile blood:
binding of antibodies to antigens on erythrocytes →
activation of the classical pathway of complement →
cell lysis
 Hemolytic disease of newborns:
caused by antibodies against RhD antigen
Examples of immunopathological reaction
Type II
Autoimmune diseases:
 organ-specific cytotoxic antibodies (antibodies against erythrocytes,
neutrophils, thrombocytes, glomerular basement membrane ...)
 blocking or stimulating antibodies
Graves - Basedow's disease - stimulating antibodies against the
receptor for TSH
Myasthenia gravis - blocking of acetylcholin receptor→ blocking
of neuromuscular transmission
Pernicious anemia - blocking the absorption of vitamin B12
Antiphospholipid syndrome - antibodies against fosfolipids
Fertility disorder - antibodies against sperms or oocytes
Immunopathological reactions based
on immune complexes formation
(reaction type III)
 caused by IgG antibodies → bind to antigen → creation
of immune complexes
 immunocomplexes - bind to Fc receptors on phagocytes
- activate complement
 immune complexes, depending on the quantity and structure,
are eliminated by phagocytes or stored in tissues
Immunopathological reactions type III
 pathological immunocomplexes response arises when is a large dose
of antigen, or antigen in the body remains; arise 10-14 days after
aplication of Ag and induced inflamation (can get to chronic state)
 immune complexes are deposited in the kidneys (glomerulonephritis),
on the surface of endothelial cells (vasculitis) and in synovie joint
(arthritis)
Serum sickness
 the therapeutic application of xenogeneic serum
(antiserum to snake venom)
 creation of immune complexes and their
storage in the vessel walls of different organs
 clinical manifestations: urticaria, arthralgia, myalgia
Systemic lupus erythematosus
 antibodies against nuclear antigens, ANA, anti-dsDNA
Farmer's lung
 IgG antibody against inhaled antigens (molds, hay)
Post-streptococcal glomerulonephritis, cryoglobulinemia,
revmatoid arthritis, post-infectious arthritis
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