Effect of synthetic thymic humoral factor (THF‐γ2) on T cell activities in immunodeficient ageing mice

Immunodeficient ageing (C57BL/10 x DBA/2)F1 mice were treated by a single injection of synthetic thymic hormones and 4 days later their thymus and spleen cells were assayed in vitro for T cell activities. A few nanograms of THF-γ2 were found to raise the frequency of mitogen-responsive T cells in thymus and spleen cell populations as well as the frequency of cytokine-producing splenic T cells, up to the levels observed in young mice. Moreover, injection of THF-γ2 was found to restore T cell growth factor (TCGF) production by mitogen-stimulated spleen cells. Also, the helper activity of spleen cells was enhanced by this treatment and increased with increasing the THF-γ2 dose over a wide range. Similarly, the effects of thymopentin and thymosin-α1 on T helper cell activity increased with increasing the injected dose, but the efficiencies of THF-γ2 and thymopentin were, respectively, 400-fold and eight-fold greater than that of thymosin-α1.