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Saturday, 7 September 2013

Immunology VII. TUMOR IMMUNOLOGY

 Tumor Immunology involves the antigenic properties of the transformed cell, the host immune response to the tumor cells, the effect of the growth of the tumor may have on the body, and the potential manipulation of the immune response to eradicate the tumor.
Cancer results from a single cell that has undergone multiple mutations that lead to uncontrolled cell growth. Tumors can be benign (encapsulated, local, and limited in size), malignant (continually increasing in size and encroaching on adjacent tissues), or metastatic (spreading out from the primary tumor to form secondary tumors often at distant sites). Exposure to chemicals, radiation, viruses, or accumulated errors during replication can facilitate the malignant transformation.
Immune recognition of cancers
1. Malignant tumors express molecules that may be recognized by the immune response. Tumor specific antigens are expressed on tumor cells, but not on normal cells (e.g., viral proteins). Tumor-associated antigens are expressed on tumor cells but can also be found on normal cells, although often in smaller amounts or on cells of a different developmental stage (e.g., p53 and CT antigens).
2. MHC class I chain-related (MIC) proteins are stress-induced proteins that are often expressed on the surface of transformed epithelial cells, which can then be recognized by NK cells and CTLs. Tumor cells that express tumor antigens via class I MHC are recognized and killed by CTLs. Tumor cells that alter gene expression to reduce class I MHC presentation are recognized and killed by NK cells.
3. Several types of cancers are associated with chronic viral infections. By preventing infection, vaccinations protect against cancers caused by those viruses (e.g., human papillomavirus vaccine and hepatitis B vaccine).

Monoclonal antibodies directed against tumor antigens can be used for diagnosis and therapy, either alone via typical antibody-mediated mechanisms or conjugated to cytotoxic drugs or radioactive isotopes.
Examples include rituximab (Rituxan), trastuzumab (Herceptin), and ibritumomab (Zevalin, conjugated to Indium-111). (Cancer Chemotherapy will be discussed later)


Ref: Comprehensive Pharmacy Review

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