Transcript 09.12.2011

Anti-tumor immunity
Malignant transformation
 Failure of regulation of cell division and regulation
of "social" behavior of the cells
The uncontrollable proliferation, dissemination
to other tissues
Mutations in protoonkogenes and antionkogenes
Mutagens (carcinogens)
- physical (eg various forms of radiation)
- chemical (eg aromatic hydrocarbons)
- biological (mainly various oncogenic
viruses)
Anti-tumor immune mechanisms
Hypothesis of immune control
 tumor
cells normally arise in tissues and are eliminated
by T lymphocytes (probably wrong hypothesis)
Defensive immune response
 tumor
cells are weakly immunogenic
 occurs when tumor antigens are presented to T lymphocytes
by activated dendritic cells
 in defense may be involved: non-specific mechanisms
(neutrophilic granulocytes, macrophages, NK cells, interferons)
and antigen-specific mechanisms (complement activating antibodies
or ADCC, TH1 and TC)
 cancer-associated antigens are processed by DC and
recognized by T lymphocytes in complex with HLA I. and II. class
with providing costimulus signals
 predominance of TH1 (IFN  TNF)
 specific cell-mediated cytotoxic reactivity – TC
 activation TH2 → support B lymphocytes→ tumor specific
antibodies (involved in the ADCC)
 tumor cells are destroyed by cytotoxic NK cells (low MHC gpI
expression on tumor cells)
 interferons - antiproliferative, cytotoxic effect on tumor cells
- INFγ - DC maturation
Tumor antigens
Antigens specific for tumors (TSA)
a) complexes of MHCgp I with abnormal fragments of cellular proteins
- chemically induced tumors
- leukemia with chromosomal translocation
b) complexes of MHC gp with fragments of proteins of oncogenic viruses
- tumors caused by viruses (EBV, SV40, polyomavirus)
c) abnormal forms of glycoproteins
- Sialylation of surface proteins of tumor cells
d) idiotypes of myeloma and lymphoma
- clonotyping TCR and BCR
Antigens associated with tumors (TAA)
- also on normal cells
- differences in quantity, time and local expression
- auxiliary diagnostic markers
a) onkofetal antigens
- on normal embryonic cells and some tumor cells
- -fetoprotein (AFP) - hepatom
- canceroembryonal antigen (CEA) - colon cancer
b) melanoma antigens
- MAGE-1, Melan-A
c) antigen HER2/neu
- receptor for epithelial growth factor
- mammary carcinoma
d) EPCAM
- epithelial adhesion molecule
- metastases
e) differentiation antigens of leukemic cells
- present on normal cells of leukocytes linage
- CALLA -acute lymphoblastic leukemia (CD10 pre-B cells)
Mechanisms of tumors resistance to immune
system
 high variability of tumor cells
 low expression of tumor antigens
 sialylation
 tumor cells do not provide costimulus signals → T lymphocyte
anergy
 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-
Tumor immunotherapy
Therapy - surgical removal of tumor
- chemotherapy or radiotherapy
- immunotherapy
Immunotherapy - induction of anti-tumor immunity, or the use
of immune mechanisms to targeting drugs
to the tumor site
Immunotherapy using antibodies
Antibodies functions - opsonization
- activation of complement
- induction of ADCC
- carriers of drugs or toxins
1) Monoclonal antibodies
- against TAA
- mouse and humanised antibodies
- imunotoxins, radioimunotoxins
- the possibility of damage surrounding tissues
- HERCEPIN - Ab against HER2/neu, breast cancer
- RITUXIMAB - Ab against CD20, lymphoma
2) Bispecific antibodies
- bind a tumor antigen and the T lymphocyte or NK cell
- Fc fragment of antibody binds to Fc receptors on phagocytes
and NK cells
3) Elimination of tumor cells from the suspension of bone
marrow cells
using monoclonal antibodies for autologous transplantation
Immunotherapy using cell-mediated
mechanisms
1) stimulation of inflammation at the tumor site
2) stimulation of LAK and TIL
- isolation of T and NK cells, stimulation by cytokines, and return
to the patient
- LAK (lymphokine activated killers)
- TIL (tumor infiltrating lymphocytes)
3) improving of tumor cells antigenpresenting function
- genetic modification of tumor cells - expression of CD80, CD86
- production of IL-2, GM-CSF
- modified cells are irradiated and returned to the patient
4) the dendritic cell immunotherapy
- in vitro cultivation of monocytes in an appropriate cytokine
environment (GM-CSF, IL-4) → transformation into dendritic cells
- cultivation of dendritic cells with tumor antigens
5) tumor vaccines
- in vitro stimulation of TH1 cells and TC with tumor antigens
6) immunotherapy by donor T lymphocytes
- after allogeneic transplantation
- causing graft-versus-host disease
7) immunotherapy by immune system products
- IL-2 - renal cell carcinoma
-IFN  - hematoonkology
8) Anti CTLA-4 antibody
- Treg inhibition, longer activation of effector T cells
Transplantation
Transplantation
= transfer of tissue or organ
• autologous - donor = recipient
• syngeneic - genetically identical donor recipient (identical
twins)
• allogeneic - genetically nonidentical donor of the same
species
• xenogenic - the donor of another species
• implant - artificial tissue compensation
Allogeneic
- differences in donor-recipient MHC gp and secondary histocompatibility Ag
- alloreactivity of T lymphocytes - the risk of rejection and graft-versus-host
- direct recognition of alloantigens – recipient T lymphocytes recognize
the different MHC gp and non-MHC molecules on donor cells
- indirect recognition of alloantigens - APC absorb different MHC gp from
donor cells and present the fragments to T lymphocytes
- CD8+ T cells recognize MHC gp I.
- CD4+ T cells recognize MHC gp II.
Recognition of alloantigens
Testing before transplantation
ABO Compatibility -risk of hyperacute or accelerated rejection =
formation of Ab against A or B Ag on graft vascular endothelium)
HLA typing (determining of MHC gp alelic forms) phenotyping and
genotyping by PCR
Cross-match - lymfocytotoxic test - testing preformed Ab
(after blood transfusions, transplantation, repeated childbirth)
Mixed lymphocyte test - testing of alloreactivity T lymphocytes
monitor for reactivity of lymphocytes to allogeneic HLA
HLA typing
a) phenotyping: Evaluation of HLA molecules using typing
serums
Typing antiserums = alloantiserums of multipar (created cytotoxic
Ab against paternal HLA Ag of their children), serum of patients
after repeated blood transfusions, monoclonal Ab
- molecules HLA class I: separated T lymphocytes
- molecules HLA class II: separated B lymphocytes
b) genotyping: evaluation of specific alleles
DNA typing of HLA class II: DR, DP, DQ by PCR.
Cross-match test
• determination of preformed antibodies
• recipient serum + donor lymphocytes + rabbit complement
→ if cytotoxic Ab against donor HLA Ag are present
in recipient serum (called alloantibodies = Ab activating
complement) → lysis of donor lymphocytes. Visualization of
dye penetration into lysis cells.
• positive test = the presence of preformed Ab → risk of
hyperacute rejection! → contraindication to transplantation
Mixed lymphocyte reaction (MRL)
• determination of alloreactivity T lymphocytes
• mixed donor and recipient lymphocytes → T lymphocytes
after recognition allogeneic MHC gp activate and proliferate
• the total proliferation of lymphocytes is measured by adding
[3H]-thymidine to the culture medium and monitoring its
integration to DNA of new cells
One-way MRL
• determination of recipient T lymphocytes reactivity against
donor cells
• donor cells treated with chemotherapy or irradiated lose
the ability of proliferation
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 much APC (skin)
The activity of the immune system of the recipient - the
immunodeficiency recipient has a smaller rejection reaction;
immunosuppressive therapy after transplantation – suppression of
rejection
Status transplanted organ - the length of ischemia, the method of
preservation, traumatization of organ at collection
Hyperacute rejection
• minutes to hours after transplantation
• antibodies type of immune response
mechanism:
• in recipients blood are present before transplantation
preformed or natural Ab (IgM anti-carbohydrate Ag)
→ Ab + Ag of graft (MHC gp or endothelial Ag) → graft
damage by activated complement (lysis of cells)
• the graft endothelium: activation of coagulation factors
and platelets, formation thrombi, accumulation of neutrophil
granulocytes
prevention:
• negat. 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 activated
by antibodies binding 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:
• recipient TH1 and TC cells response against Ag of graft tissue
• infiltration of lymphocytes, mononuclears, granulocytes
around small vessels → destruction of 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
responses with production alloantibodies, pathogenetic role
of cytokines and growth factors (TGF β)
• replacement of functional tissue by connective tissue,
endothelial damage →impaired perfusion of graft → gradual
loss of its function
dominating findings: vascular damage
Bone marrow transplantation
• hematopoetic stem cell collection
• myeloablation
• transplantation
• engraftment
• rejection
• graft versus host disease
Graft-versus-host disease (GVHD)
• after bone marrow transplantation
• GVHD also after blood transfusion to immunodeficiency
recipients
• T-lymphocytes in the graft bone marrow recognize recipient
tissue Ag as foreign (alloreactivity)
Acute GVHD
•
days to weeks after stem cells transplantation
•
damage of liver, skin and intestinal mucosa
•
Prevention: appropriate donor selection, T lymphocytes removal
from the graft and effective immunosuppression
Chronic GVHD
• months to years after transplantation
• TH2 lymphocytes infiltration of tissues and organs, production
of alloantibodies and production of cytokines → fibrotization
• process like autoimmune disease: vasculitis, scleroderma,
sicca-syndrome
• chronic inflammation of blood vessels, skin, internal organs
and glands, which leads to fibrotization, blood circulation
disorders and loss of function
Graft versus leukemia effect (GVL)
• donor T lymphocytes react against residual
leukemick cells of recipient
• mechanism is consistent with acute GVHD
• associated with a certain degree of GVHD (adverse
reactions)
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 IgG and IgM antibodies
Type III reaction - response based on the formation of immune
complexes
Type IV reaction - cell-mediated response
Immunopathological reaction based
on IgG and IgM antibodies (reaction type II)
Cytotoxic antibodies IgG and IgM:
• complement activation
• ADCC
• binding to phagocytes and NK cells Fc receptors
Haemolytic reactions after transfusion of ABO incompatible blood:
Binding of antibodies to antigens of erythrocytes → activation
of the classical way of complement → cell lysis
Hemolytic disease of newborns:
Caused by antibodies against RhD antigen
Autoimmune diseases:
• organ-specific cytotoxic antibodies (antibodies against
erythrocytes, neutrophils, thrombocytes, glomerular basement
membrane ...)
• blocking or stimulating antibodies
Graves - Basedow disease - stimulating antibodies against the
TSH receptor
Myasthenia gravis - blocking of acetylcholin receptor→ blocking
of neuromuscular transmission
Pernicious anemia - blocking of vitamin B12 absorption
Antiphospholipid syndrome - antibodies against fosfolipids
Fertility disorders - antibodies against sperms or oocytes
Immunopathological reactions based on immune
complex formation (reaction type III)
• caused by IgG antibodies → bind to antigen → creation
of immunecomplexes
• immunocomplexes - bind to Fc receptors on phagocyte
- activate complement
• immune complexes (depending on the quantity and structure)
are eliminated by phagocytes or stored in tissues
• pathological immunocomplexes response arises when is a large
dose of antigen, or antigen in the body remains
• immune complexes are deposited in the kidneys (glomerulonephritis),
on the endothelial cells surface (vasculitis) and in synovial joints
(arthritis)
Serum sickness
• after 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 antibodies against inhaled antigens (molds, pollens)
• Poststreptococcal glomerulonephritis
Immunopathological delayed-type reaction
(reaction type IV)
• delayed-type hypersensitivity (DTH)
• local reaction caused by TH1 cells and monocytes / macrophages
(physiologically – elimination of macrophage intracellular parasites)
• antigen immunization → formation of antigen specific TH1 cells
(and memory cells)
• 12-48 hours after next contact with antigen arise local reaction –
granuloma (TH1 and macrophage infiltration)
Tuberculin reaction
Tissue damage in tuberculosis and leprosy
Sarcoidosis
Subtype IV - Cellular cytotoxic response
(Tc activation)
• similar to DTH reaction
• TH1 cells activate CD8 + T lymphocytes
viral rashes
viral hepatitis
acute rejection of transplanted organ
some autoimmune thyroiditis
contact dermatitis
Contact dermatitis
• is a localized rash or irritation of the skin caused
by contact with alergen (nickel , chromium,
ingredients in cosmetic products , plant allergens and other)
• the first is senzitization
• appears in 24 – 48 hours after second contact with alergen
• diagnosis : patch test
Patch test
• patch test is a method used to determine
if a specific substance causes allergic
inflamation of the skin
•
Allergens are applied to special
hypoallergenic patch on the back skin
• Results are evaluated after
48 and 72 hours
• In positive reaction appears eczema
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