"<I>Toxoplasma gondii </I>is an obligate intracellular parasite that infects all mammalian cells. Several
antigens such as excreted/secreted antigens have been identified as potential vaccine candidates. The main
goal of the present study was to determine how excreted/secreted antigens from peritoneal exudates of infected
mice (mESA) stimulate cell-mediated immune responses and protective immunity against toxoplasmosis in the
murine model. The supernatants produced from the peritoneal fluids were fractionated by precipitation with
ammonium sulphate solution (30-80% saturated). For induction of cell-mediated immune responses, Delayed
type hypersensitivity was measured in injected footpad measured in injected footpad. By adding [ H] thymidine
to cell cultures, their radioactivities were measured. Nitric oxide was measured by Griess method. For
immunization, Balb/c mice were immunized 2 times with mESA, mESA-40% and Toxoplasma Lysate Antigen
(TLA). The virulent RH strain of <I>Toxoplasma gondii </I>was used for challenging. The pattern of lymphocyte
responsiveness was dependent on the kind of antigen employed for induction of the blastogenesis. In
sensitized mice, those received mESA-40% displayed higher counts per minute than mice that stimulated by
mESA (p&lt;0.05). The highest amounts of nitric oxide were observed in macrophages, which received mESA-40%
and mESA (p&lt;0.05). Mice immunized with mESA-40% survived longer than those immunized with mESA and
other antigens (p&lt;0.05). As fraction 40% (mESA-40%) showed a good result in induction of cell-mediated
responses in the murine model, for getting better response, this antigen have to be purified further."