The response of the mouse R-E system to infection with Toxoplasma gondii.

Groups of mice were inoculated with strains of Toxoplasma gondii of either high or low virulence strains. The response of the lymph nodes, speen and thymus was studied histologically and antibodies were assessed by the dye-test technique. The low-virulence strain induced changes in all three organs indicative of an immunological response, both in respect of cellular and humoral immunity. The high-virulence strain produced rapid lymphoid depletion in lymph nodes, spleen and thymus with areas of necrosis. It is suggested that the high-virulence strain has a toxic effect on the Reticulo-Endothelial system allowing urestricted proliferation of the organism with eventual death.