IFN-GAMMA IS DIRECTLY CYTOSTATIC TO THE EXTRACELLULAR FORM (PROMASTIGOTE) OF LEISHMANIA-DONOVANI

We investigated the effect of various human cytokines on the in vitro growth of Leishmania donovani (L. donovani) promastigotes. rhIFN-alpha , rhIFN-beta, rhIL-1, rhIL-2, rhIL-3, rhIL-4, rhIL-6 and rhM-CSF had n o effect. By contrast, rhIFN-gamma was directly growth inhibitory to L . donovani promastigotes in a dose-dependent manner. Anti-IFN-gamma an tibody, but neither anti-IFN-alpha nor anti-IFN-beta antibody, abolish ed this promastigote growth inhibitory effect of rhIFN-gamma. L. donov ani promastigotes were not lysed by rhIFN-gamma as determined by Cr-51 -release assay. These data indicate that rhIFN-gamma is cytostatic, no t cytotoxic, to L. donovani promastigotes.