Reversible restoration by thymosin of antigen-induced depression of spleen DNA synthesis in NZB mice.

Antigen-induced depression of spleen DNA synthesis was studied in NZB and CBA/J mice. This phenomenon, a measure of T suppressor cell activity, normally decreases as a consequence of aging. However, NZB mice have an accelerated loss of antigen-induced depression that can be restored by treatment with thymosin or injection of 1-month-old NZB thymocytes. The restoration by thymosin declined between 1 and 2 weeks after treatment, but could be induced again after a second exposure to thymosin. These results suggest a potential for reversible but repeatable restoration of suppressor cell activity in NZB mice.