Potentiation of autoimmune response in rats infected with Toxoplasma gondii. Inhibition of suppressor system and impairment of thymic cellular populations.

In the present work we studied the influence that an infection with Toxoplasma gondii in thymus proximity produces on the suppression of autoimmune response to autoantigen of rat male accessory glands (RAG). The suppression was achieved injecting syngeneic animals with low doses of autoantigen of RAG previous to the immunization with chemically modified rat male accessory glands (MRAG). Rats were infected in thymus proximity with 3 x 10(3) trophozoites of T. gondii before or after to be suppressed. Controls were rats only infected or only suppressed. The delayed hypersensitivity response against MRAG, (DTH test), was significantly potentiated in rats only infected and in the animals suppressed before the infection (p less than 0.001). The suppression was not inhibited in the animals suppressed after infection. The suppression of humoral response against MRAG studied by ELISA and passive hemagglutination test was prevented in rats infected before as well as in rats infected after the induction of suppression (p less than 0.001). Decrease of CD4+ CD8+ and Ox18+ (class I MHC antigen) and increase of CD4+ CD8- and CD4- CD8- thymocytes was observed in the rats where the DTH response was potentiated. These results indicate that the infection with T. gondii in thymus proximity was able to inhibit the suppression of response to autoantigen of RAG producing selective impairment in thymic suppressor influence.