Mechanisms of protective immunity in experimental cutaneous leishmaniasis of the guinea-pig. II. Selective destruction of different Leishmania species in activated guinea-pig and mouse macrophages.

Macrophages activation as the effector mechanism in destroying L. enriettii in the guinea-pig, and L. tropica in the mouse, was tested in vitro. Activated guinea-pig macrophages, with enhanced anti-Listeria capacity had no effect on the survival of intracellular L. enriettii, irrespective of the antigen used. Activated mouse macrophages, on the other hand, destroyed ingested L. enriettii within 24-48 hr but had no effect on L. tropica during the same time period. It is suggested that the pathogenicity of a Leishmania parasite in a given host depends on the ability of the parasite to survive in the host's activated macrophages. The possible mechanisms by which L. enriettii evades destruction in activated guinea-pig macrophages are discussed.