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During senescence the immune system undergoes profound alterations associated with a progressive decline of immune responsiveness to exogenous antigens and increasing incidence of autoimmune phenomena. Helper T cell (Th) activity decreases with aging mainly as a result of the reduced capacity to produce lymphokines and to express receptors for these molecules. The decline in Th cell activity is concomitant with thymus involution and decrease in concentration of thymic hormones that sustain the maturation of T cell precursors. Th cell activity can be restored in old mice by injection of synthetic thymosin alpha(1), a 28 aminoacids peptide identified in a bovine thymus extract (Fraction 5). Immune responses are magnified by Th cells and modulated by suppressor T cells (Ts). Suppression is mediated by a complex series of molecular and cellular interactions involving inducer, transducer, and effector Ts cells which are organised in cellular circuits. Aging has been found to affect the recognition repertoire implicated in the interactions within the inducer, transducer, and effector Ts cell circuit. The use of immunomodulators is promising but requires very accurate protocols to reach two antithetic objectives, such as an increased immune responsiveness against exogenous antigens and the prevention or mitigation of autoimmune phenomena.

Additional information

Authors: DORIA G, ENEA C.R.E., Casaccia, Roma (IT);FRASCA D, ENEA C.R.E., Casaccia, Roma (IT)
Bibliographic Reference: Paper presented: International Symposium on Immunoregulatory Mechanisms and their Clinical Implications, Budapest (HU), Nov 20-21, 1988
Availability: Available from (1) as Paper EN 34352 ORA
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