partial purification of a potent immunosuppressive factor excreted from leishmania major promastigote and amastigote

recent scientific evidence indicates that distinct patterns of susceptibility in balb/c mice to leishmania major infection are attributable to the differential expansion of distinct cd4+ t-cell subsets and their cytokines production. production of the th1 cytokine ifn-g is associated with resistance, whereas production of the th2 cytokines il-4 and il-10 are associated with extreme susceptibility. the major host immune defense mechanism against leishmania is activation of macrophages by inf-γ derived from t cells. the inability of susceptible hosts to mount the immune response necessary to activate macrophage and destroy the parasites may be due to the parasite-specific proteins that are able to suppress the immune system. in the present study, we have semi-purified the excreted antigens of leishmania major promastigote and amastigote by column chromatography. the isolated fraction showed a potent immunosuppressive activity on normal balb/c mice lymphocytes stimulated with mitogens. fifteen microgram of the isolated fraction caused 81% suppression of lymphocyte proliferation. these data may suggest that the parasite by secreting immunosuppressive factor down regulate the immune system and as a result survive in the body