Antitumour immunity

J. Ochotná

Malignant transformation

• Failure of cell division regulation and regulation of cells "social" behavior

•The uncontrollable proliferation, dissemination to other tissues

•Mutations in protoonkogenes and antionkogenes

Tumour antigens

Tumour specific antigens (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 oncogenic viruses proteins

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

Tumour associated antigens (TAA)

•expressed also on normal cells•differences in quantity, time and local of 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 cell adhesion molecule

• metastases

e) differentiation antigens of leukemic cells

• present on normal cells of leukocytes linage

• CALLA -acute lymphoblastic leukemia (CD10, pre-B cells)

Anti-tumor immune mechanisms

Hypothesis of immune control

• tumor cells normally arise in tissues and are eliminated by T lymphocytes

• DC are necessary for activation of antigen specific mechanisms

• cancer-associated antigens are processed by DC and presented to T lymphocytes in complexes with HLA I. and II.

• predominance of TH1 (IFN TNF); IFN support DC

maturation

• tumor cells are eliminated by TC

• TH2 activation → support B lymphocytes→ tumor specific

antibodies (involved in the ADCC)

• tumor cells are also destroyed by NK cells (low MHC gpI expression on tumor cells)

• interferons - antiproliferative, cytotoxic effect on tumor cells - INF - DC maturation

Mechanisms of tumor resistance

high variability of tumor cells

low expression of tumor antigens

sialylation

tumor cells do not provide costimulatory signals → T lymphocyte anergy

some antitumor substances have a stimulating effect on tumor

production of factors inactivating T lymphocytes

expression of FasL → T lymphocyte apoptosis

inhibition of the dendritic cell functions and durability (NO, IL-10, TGF-

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 other species

• implant - artificial tissue compensation

Allogeneic transplantation

•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 APC

•indirect recognition of alloantigens - APC absorb different MHC gp fromdonor cells and present the fragments to T lymphocytes

•CD8+ T cells recognize MHC gp I.

•CD4+ T cells recognize MHC gp II.

Tests prior to transplantation

ABO Compatibility -risk of hyperacute or accelerated rejection =

formation of Ab against A or B Ag on graft vascular endothelium)

HLA typing (determination 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 reaction - test for T lymphocytes alloreactivity

HLA typing

a) phenotyping: evaluation of HLA molecules using typing serumsTyping antiserums = alloantiserums of multipar (created cytotoxic Ab against paternal HLA Ag of their children), serum of patients after repeated blood transfusions, monoclonal Ab

b) genotyping: PCR – SSP PCR – SSO PCR – SBT

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 T lymphocyte alloreactivity

• 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 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 rejectionHyperacute rejection

Accelerated rejection

• 3 to 5 days after transplantation

• caused by antibodies that don‘t activate complement

• cytotoxic and inflammatory responses activated by antibodies which bind 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

• occures after 2 months from 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 fibrous 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 → 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

• 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

•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 determineif 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