What is the role of T-lymphocyte surveillance in neoplastic disease?
Abstract
Dramatic advances have recently been made in our comprehension of how thymus-derived (T) lymphocytes function. Principles of both antigen-specific and nonspecific modes of their action in cell-mediated immunity are summarized as follows. First, different functions are carried out by distinct, separable populations of T lymphocytes. Second, all T-cell responses depend on interaction between cells of different functional subclasses. Thus, target cell killing of cytotoxic T lymphocytes depends on separate, coincident recognition of antigen by pre-cytotoxic T lymphocytes and by amplifier T cells that supply a nonspecific but critical lymphokine. Immunosuppressive drugs such as cyclosporin A and dexamethasone block this interaction at different points. Antigen-specific amplifier T cells also secrete various polypeptide factors that augment the impact of macrophage cytotoxicity, and immune interferon, which stimulates natural killer (NK) cells. Thus, even in cases where T cells are not the effectors, activation of T cells can potentiate host defenses. However, immune paralysis can result from stimulation of antigen-specific suppressor T cells. These act on effector cells directly or on their amplifier cells. The route of immunization...Continue Reading
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