IL-2-stimulated splenocytes reduce infections by Leishmania donovani in vivo

The traditional treatment of infections produced by the obligate intramacrophage protozoan Leishmania donovani involves the use of antimonial drugs. Because these drugs may have toxic side effects (and are sometimes ineffective), the potential efficacy of alternative therapy with lymphokine-stimulated leucocytes was assessed. Macrophage-depleted C57BL/6 splenocytes from mice inoculated 2 wk earlier with L. donovani were stimulated in vitro with the interleukin-2-containing supernatant of MLA 144 cells and transferred intravenously into syngeneic infected mice. Compared to infected mice that had received unstimulated normal or infected spleen cells, animals treated with lymphokine-stimulated splenocytes had significantly reduced parasite loads. Efficacy was further enhanced significantly by supplementary intraperitoneal injections of the MLA 144 supernatant; the effector function of the stimulated splenocytes was dose dependent. The rescue of animals infected by L. donovani from parasite-induced down-regulation of immunity could be an important part of a strategy for the effective treatment of kala azar; lymphokine-stimulated cells are potential candidate agents to restore curative immune responses of experimental visceral leishmaniasis.