Taenia taeniaeformis: inhibition of mitogen induced proliferation and interleukin-2 production in rat splenocytes by larval in vitro product.

Splenocytes from rats infected with Taenia taeniaeformis showed an early decreased proliferative response to the mitogen concanavalin A with larval growth. When larvae culture supernatant (in vitro product) was added to normal rat splenocytes, there was a decrease in the proliferative response to concanavalin A and phytohemagglutinin. The ability of infected rat splenocytes to produce interleukin-2 was decreased with larval growth. Addition of in vitro product to culture medium significantly depressed interleukin-2 production by normal as well as infected rat spleen cells. Culturing normal rat splenocytes with in vitro product for 3 days induced a suppressor cell population. When these cultured cells were admixed with fresh normal rat splenocytes plus concanavalin A, the proliferative response of the fresh cells was significantly reduced. The present results suggest that in vitro product secreted by larvae in hepatic cysts causes subversion of the cellular immune response in the host. Induction of a suppressor cell population could suppress interleukin-2 production which may lead to the inhibition of differentiation and proliferation of specific cytotoxic T lymphocytes.