Adaptive immunity is a characteristic feature of jawed vertebrates (Gnathostomata). Immune response is controlled by MHC (Major Histocompatibility Complex) gene products (in hu-mans termed HLA). Each individual (except for monozygotic twins) expresses a unique set of MHC proteins, the histocompatibility antigens, on its nucleated cells. These immunological differences among various individuals represent the main cause of failure in organ transplan-tation. However, the actual role of MHC proteins is to control selection of T lymphocyte sub-populations and to present them with foreign antigens. Therefore they play an important role in anti-infectious defence and protection against cancer, as well as in autoimmune diseases.
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© Orig. I. Trebichavský