Immunobiological studies on experimental visceral leishmaniasis. III. Cytokine-mediated regulation of parasite replication.

The role of T-cell-derived cytokines in the regulation of Leishmania donovani replication was studied in a murine model. It was observed that in H-2d mice at the early and later stages of the disease IFN-gamma-secreting T cells predominate, whereas in between the above stages IL-4-secreting T cells predominate. Possibly, IL-4 abrogates the protective ability of IFN-gamma and thereby exponential parasite growth is ensured at the active stage of the disease. By contrast, H-2b mice were possibly incapable of inducing IL-4-secreting T cells and therefore parasite replication remains under control at any point post infection.