Evaluation of spleen lymphocyte responsiveness to a T-cell mitogen during early infection with larval Taenia taeniaeformis.

The effect of taeniid infection on the in vitro cellular response of the host was investigated. Infections of Taenia taeniaeformis decreased the ability of spleen cells from susceptible C3H/He mice to respond to the T-cell mitogen concanavalin A (Con A) as early as 2 days postinfection (pi) reaching a suppression peak at day 12 pi. Similar experiments performed with spleen cells from infected BALB/c mice, resistant to the infection, revealed little or no suppression of Con A stimulation. The results suggested that susceptibility to the parasite may be due to its ability to induce a partial suppression of the host's immune system. The role of adherent splenocytes from infected C3H/He mice in the production of a deficient response to Con A during early infection was studied by coculturing experiments. These experiments demonstrated that adherent populations from infected mice did not play a direct role in the Con A-suppressor mechanisms. Concomitant with the suppressor activity an increased background proliferation was observed with nonstimulated splenocytes from C3H/He mice infected with T. taeniaeformis. Plasma from infected mice was able to suppress the response of normal spleen cells to Con A and to stimulate a proliferative response in cultured splenocytes from noninfected animals. The results suggest the presence of factors in the plasma of infected mice which may be modulating the immune response to the parasite.