Effects of thymosin on cytotoxicity and virus production in AKR mice.

The cytotoxic potential and ability to produce endogenous ecotropic virus(es) of thymic-, splenic-, and lymph node-derived lymphocytes were significantly (and differentially) altered following thymosin treatment of young (nonleukemic) and aged (preleukemic) AKR mice. Thymosin administration markedly enhanced the cytotoxic potential of both splenic and lymph node lymphocytes from aged animals, but effected a moderate increase only in the spleens of young mice. Thymosin enhanced the production of endogenous virus(es) by thymocytes from aged mice, with the opposite effect noted in young animals. Splenectomy generally reduced the cytotoxic activity and virus titers of lymphocytes from both groups, and thymosin administration further reduced the cytotoxic response. These findings probably reflect overall effects on both regulatory lymphocyte subpopulations and different endogenous viruses in young and aged mice.