The third component of complement (C3) is responsible for the intracellular survival of Leishmania major.
Leishmania are obligate intracellular parasites of mononuclear phagocytes. We and others have shown that the promastigote form of all species of leishmania activates complement from non-immune serum and that this activation can result in parasite lysis. This work, as well as earlier in vivo studies, suggested that complement is an important component of host defence against leishmaniasis. We now present evidence that parasite complement fixation, in addition to increasing parasite phagocytosis, is required for the intracellular survival of leishmania in macrophages. We specifically show a strong correlation between parasite C3 fixation and intracellular survival. We attribute this survival, in part, to a decrease in the magnitude of the macrophage respiratory burst which is triggered by complement-coated, as opposed to uncoated, parasites.
D000818:Animals; D001769:Blood; D003167:Complement Activation; D003176:Complement C3 / Q000276:immunology*; D003574:Cytochrome c Group / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D007895:Leishmania tropica / Q000276:immunology / Q000502:physiology*; D008264:Macrophages / Q000276:immunology* / Q000469:parasitology / Q000502:physiology; D051379:Mice; D009895:Opsonin Proteins / Q000276:immunology; D010084:Oxidation-Reduction; D010587:Phagocytosis
D003176:Complement C3; D003574:Cytochrome c Group; D009895:Opsonin Proteins