Cell-mediated immunity plays a major role in the resistance of host to many bacteria, fungi, and protozoa, all of which have the capacity to live and multiply in the mononuclear phagocytes. Cell-mediated immune mechanisms can be functioned by collaboration with helper T cells (Th), cytotoxic T cells (Tc, CTL), macrophages and natural killer cells. Tdth that funcions as effector cells for delayed-type hypersensitivity reaction, is generated from Th, of which surface antigen is termed as L3T4 for mouse and CD 4 for human, in response to antigenic stimulus. One of lymphokines, macrophage activating factor (MAF) which is now referred to γ-interferon (IFN-γ) , is secreted from Tdth, and activate macrophage for increased capacity for microbicidal activity and tumor cytotoxicity. CTL with specificity for viral antigen is generated that inhibit the virus from propagating by killing the infected host ells as well as by secreting IFN-γ. CTL is generated also during tumor growth, and allograft rejection. In graft rejection, CTL is directed mainly to class I alloantigens which serve as the main stimulus for its generation. In contrast, Th is reacting mostly with the class II alloantigens found in cells of the graft. CTL plays roles for destruction of tumor cells and allograft by adhering to target cells. CTL function is restricted in major histocompatibility complex (MHC) products and is collaborated with Th and macrophages.
細胞性免疫と生体防御
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