RESEARCH ARTICLE Exposure to Leishmania braziliensis Triggers Neutrophil Activation and Apoptosis

Background Neutrophils are the first line of defense against invading pathogens and are rapidly recruited to the sites of Leishmania inoculation. During Leishmania braziliensis infection, depletion of inflammatory cells significantly increases the parasite load whereas co-inoculation of neu-trophils plus L. braziliensis had an opposite effect. Moreover, the co-culture of infected mac-rophages and neutrophils also induced parasite killing leading us to ask how neutrophils alone respond to an L. braziliensis exposure. Herein we focused on understanding the inter-action between neutrophils and L. braziliensis, exploring cell activation and apoptotic fate. Methods and Findings Inoculation of serum-opsonized L. braziliensis promastigotes in mice induced neutrophil ac-cumulation in vivo, peaking at 24 h. In vitro, exposure of thyoglycollate-elicited inflammatory or bone marrow neutrophils to L. braziliensismodulated the expression of surface molecules such as CD18 and CD62L, and induced the oxidative burst. Using mCherry-expressing L. braziliensis, we determined that such effects were mainly observed in infected and not i