Lymphocyte activation induced by Trichinella spiralis infection reflected as spontaneous DNA synthesis in vitro

Spleen cells from mice, infected with Trichinella spiralis, were cultured in micro and macrocultures without stimulatory agents. As controls, various polyclonal T and B cell activators were used. During the course of the infection the cells exhibited an increased spontaneous DNA synthesis compared to the cells from uninfected controls. It was also found that the relative proportion of theta and Ig-positive cells and macrophages was not significantly affected by the infection. To characterize the in vivo stimulated cells one week after infection various techniques were used. Autoradiography combined with immunofluorescence revealed that virtually all labelled cells were Ig-negative. Removal of macrophages by silica powder decreased the spontaneous DNA synthesis but not to the level of the controls. Spleen cells from infected nude mice did not show any increased spontaneous DNA synthesis, whereas the effluent cells obtained after separation on Ig-complexed columns still showed an enhanced spontaneous DNA synthesis. These results indicate that T. spiralis infection causes a macrophage dependent activation of T cells which in vitro is detectable as spontaneous DNA synthesis.