NOS2 and infection: Activated macrophages or M1 macrophages, which express the iNOS enzyme and produce proinflammatory mediators, are effective for killing A. fumigatus [27,28]; anti-inflammatory or M2 macrophages that express arginase 1 (Arg1) also have a phagocytic profile in an in vivo infection, but their killing capabilities have not been addressed [29].