Effective clearance of intracellular Leishmania major in vivo requires pten in macrophages

Abstract

Leishmaniases are a major international public health problem, and macrophages are crucial for host resistance to this parasite. To determine if phosphatase and tensin homologue deleted on chromosome ten (Pten), a negative regulator of the PI3K pathway, plays a role in macrophage-mediated resistance to Leishmania, we generated C57BL/6 mice lacking Pten specifically in macrophages (LysMCrePtenflox/flox mice). Examination of lesions resulting from Leishmania major infection showed that LysMCrePtenflox/flox mice were more susceptible to the parasite than wild-type (WT) mice in the early phase of the infection, but were eventually able to eliminate the pathogen. In vitro Pten-deficient macrophages showed a reduced ability to kill parasites in response to IFN-γ treatment, possibly because the mutant cells exhibited decreased TNF secretion that correlated with reductions in inducible nitric oxide synthase expression and nitric oxide production. In response to various TLR ligands, Pten-deficient macrophages produced less TNF and IL-12 but more IL-10 than WT cells. However, analysis of cells in the lymph nodes draining L. major inoculation sites indicated that both LysMCrePtenflox/flox and WT mice developed normal Th1 responses following L. major infection, in line with the ability of LysMCrePtenflox/flox mice to eventually eliminate the parasite. Our results indicate that the efficient clearance of intracellular parasites requires Pten in macrophages. © 2008 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.