Human and Mouse Macrophages Collaborate with Neutrophils To Kill

Macrophages are multifunctional cells that are active in TH1- and TH2-mediated responses. In this study, we demonstrate that human and mouse macrophages collaborate with neutrophils and complement to kill the parasite Strongyloides stercoralis in vitro. Infection of mice with worms resulted in the induction of alternatively activated macrophages (AAM) within the perito-neal cavity. These cells killed the worms in vivo and collaborated with neutrophils and complement during the in vitro killing process. AAM generated in vitro killed larvae more rapidly than naive macrophages, which killed larvae after a longer time period. In contrast, classically activated macrophages were unable to kill larvae either in vitro or in vivo. This study adds macro-phages to the armamentarium of immune components that function in elimination of parasitic helminths and demonstrate a novel function by which AAM control large extracellular parasites. Macrophages play an integral part in both pro- and anti-in-flammatory responses, as well as in maintaining homeosta-sis. These cells exhibit a multiplicity of functions, including phagocytosis (1), antigen presentation (2), immune regulation (3), and pathogen clearance (4, 5). The plasticity of macrophages is most evident in type 1 helper T cell (TH1) responses, where classically activated macrophages (CAM) are induced, and type 2 helper T cell (TH2) responses, where alternatively activatedmac