Human PBMC proliferative response to Leishmania infantum promastigotes is inhibited by anti-IFN-gamma mAb gamma 123.

PBMC from individuals both exposed and non-exposed to leishmaniae proliferative and produce interferon-gamma (IFN-gamma) following stimulation with Leishmania antigens. We studied the kinetics of the proliferative response of PBMC from non-exposed individuals and from patients recovering from visceral leishmaniasis due to Leishmania infantum, using heat-killed stationary-phase promastigotes of L. infantum as stimulating agent. The kinetics of both groups followed a similar temporal pattern, with higher values in the patient's group. Moreover, we observed that in both groups the activation was dose-dependently inhibited following the addition of gamma 123 anti-IFN-gamma monoclonal antibody. These results indicate the need for IFN-gamma in the activation process of PBMC induced by Leishmania antigens and stress the role of IFN-gamma in the immune response to leishmaniasis. The relevance of the elucidation of the immune response mechanism in human leishmaniasis for therapy and vaccination is briefly discussed.