Blood monocytes: differing effector role in experimental visceral versus cutaneous leishmaniasis

Irrespective of the tissue infected or the strain involved, all Leishmania species selectively parasitize and replicate within the resident tissue macrophage. Henry Murray here discusses the role of a second mononuclear phagocyte, the blood monocyte, which is also attracted to leishmanial lesions, but which appears to play quite different roles in experimental visceral versus cutaneous infection: in visceral disease, the monocyte is a critical host defense effector cell, in cutaneous disease, it may, paradoxically, serve to perpetuate intracellular infection.