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J Immunol. 2010 Jun 15;184(12):7047-56. doi: 10.4049/jimmunol.0903273. Epub 2010 May 12.

Type I IFN receptor regulates neutrophil functions and innate immunity to Leishmania parasites.

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  • 1Department of Microbiology and Immunology, Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.


Type I IFNs exert diverse effector and regulatory functions in host immunity to viral and nonviral infections; however, the role of endogenous type I IFNs in leishmaniasis is unclear. We found that type I IFNR-deficient (IFNAR-/-) mice developed attenuated lesions and reduced Ag-specific immune responses following infection with Leishmania amazonensis parasites. The marked reduction in tissue parasites, even at 3 d in IFNAR-/- mice, seemed to be indicative of an enhanced innate immunity. Further mechanistic analyses indicated distinct roles for neutrophils in parasite clearance; IFNAR-/- mice displayed a rapid and sustained infiltration of neutrophils, but a limited recruitment of CD11b+Ly-6C+ inflammatory monocytes, into inflamed tissues; interactions between IFNAR-/-, but not wild-type (WT) or STAT1-/-, neutrophils and macrophages greatly enhanced parasite killing in vitro; and infected IFNAR-/- neutrophils efficiently released granular enzymes and had elevated rates of cell apoptosis. Furthermore, although coinjection of parasites with WT neutrophils or adoptive transfer of WT neutrophils into IFNAR-/- recipients significantly enhanced infection, the coinjection of parasites with IFNAR-/- neutrophils greatly reduced parasite survival in WT recipients. Our findings reveal an important role for type I IFNs in regulating neutrophil/monocyte recruitment, neutrophil turnover, and Leishmania infection and provide new insight into innate immunity to protozoan parasites.

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