Testosterone inhibits the immunostimulant effect of thymosin fraction 5 on secondary immune response in mice.
The purpose of the present investigation was to examine the in vivo influence of testosterone on the immune properties of a thymic factor (thymosin fraction 5, TF5) a partially purified thymic preparation in male Swiss IOPS/OF1 mice (5-10 weeks old). Testosterone administration (100 micrograms/ml) significantly inhibited the enhanced anti-sheep red blood cell antibody response induced by TF5 (100 micrograms/ml); this inhibition was only observed on the secondary antibody response and not on the primary. These results suggest that gonadal steroids can affect the immune response by modulating the activity of thymic factors.