Endogenous IL-13 Plays a Crucial Role in Liver Granuloma Maturation During Leishmania donovani Infection, Independent of IL-4Rα-Responsive Macrophages and Neutrophils

Previous studies comparing interleukin 4 receptor alpha (IL-4R alpha)(-/-) and interleukin 4 (IL-4)(-/-) BALB/c mice have indicated that interleukin 13 (IL-13), whose receptor shares the IL-4R alpha subunit with IL-4, plays a protective role during visceral leishmaniasis. We demonstrate that IL-13(-/-) BALB/c mice were less able to control hepatic growth of Leishmania donovani compared with wild-type mice. This correlated with significantly retarded granuloma maturation in IL-13(-/-) mice, defective interferon gamma (IFN-gamma) production, and elevated IL-4 and interleukin 10 (IL-10) levels. L. donovani-infected IL-13(-/-) mice also responded poorly to sodium stibogluconate-mediated chemotherapy compared with wild-type BALB/c mice. Because murine lymphocytes do not have IL-13 receptors, we examined the ability of macrophage/neutrophil-specific IL-4R alpha(-/-) mice to control primary infection with L. donovani and to respond to chemotherapy. Macrophage/neutrophil-specific IL-4R alpha(-/-) mice were as resistant to leishmaniasis as wild-type mice, and chemotherapy retained its efficacy. Consequently, in L. donovani infected BALB/c mice, IL-13 promotes hepatic granuloma formation and controls parasite burdens independently of direct effects on macrophages/neutrophils.