AGE-RELATED EFFECTS IN T-CELL ACTIVATION AND PROLIFERATION

Age-associated thymic involution manifests its effects in a variety of ways that are related to a loss of T cell function. These include the appearance of a non-functional subset of T cells that increase in rep resentation with age. Moreover there is a loss of T cell proliferative ability, a decline in the synthesis and release of interleukin-2 (IL- 2), a decline in the ability of the T cell to express the IL-2 recepto r, and a loss of control activity. This loss of control is demonstrate d by the age-related appearance of autoantibodies and an increase in t he elaboration of inflammatory cytokines such as TNF, IFN, IL-6, and T GF. A major part of the basis for the loss of T cell function is an in ability of the T cell to respond to activation signals that are transm itted through the membrane binding of specific stimulatory signals. Tr ansduction events, differentiation signals, and a loss of control mech anisms are all parts of a complicated picture of age-related immune de ficiencies.