Studies of rabbit testes infected with Treponema pallidum. III. Immunosuppressive activity of infiltrating mononuclear cells.

When mononuclear cells infiltrating rabbit testes infected with Treponema pallidum were cocultured with autologous or homologous peripheral blood lymphocytes spontaneous stimulation and that induced by concanavalin A were suppressed. The inhibition was not due to the cytotoxic effect of the mononuclear cells or to their interference with the active site of concanavalin A (competitive inhibition). The suppressor activity was present in both T and non-T cells but was not affected by pretreatment of the mononuclear cells with indomethacin, a prostaglandin synthetase inhibitor. The suppressor activity may be intrinsic to the mononuclear cells or acquired by the cells in the testicular environment.