Immunosuppressive Activity of Leishmania major Culture Supernatant

Balb/c mice are highly susceptible to infection with the protozoan para ite leishm ania major. this susceptibility has beenattribu ted in part to the expansion of th2 cells and production of their cytokines, il-4 and il-io and down-regulation ofth l cytokine, inf-y. the inability of susceptible hosts to mount the immune response necessary to activate macrophageand destroy the parasites can be due to the parasi te-specific proteins that are able to modulate the immune system. in thisreport, we monitored the culture supernatant of the paras ite in order to show the existence of inununosuppressive factor.the l. major parasites were isolated from lesion of infected balb/c mice. amastigotes were grown at 35 °c andpromastigotes at 22-25°c in th presence of 10% fcs. culture supernatants were harvested after 72 h of incubation andused for lymphocyte proliferation assay using lymph node and spleen cells stimulated with mitogens. we have shown thatthe excretory materials of promastigotes and axen ic amastigotes have a potent immunosuppres sive activity. culturesupernatants can suppress the proliferation of rnitogen-stimulated lymph node lymphocytes (74%) or spleen cells (90%) in adose-dependent manner. this result may show that parasite by excretory materials can influence inf-y production by tcells and macrophag e activation in order to survive within the macrophage and propagating inside the phagolysosome.