IL4R and infection: 46 sheds new light on the potential contribution of macrophages to nematode killing. Using mice that lack antibodies (JH−/−) or activating Fc receptors (FcRγ−/−), they demonstrate in a model of secondary H. polygyrus infection that antibodies activate macrophages to trap and immobilize infective larvae. Arginase was important for killing as discussed below. In this setting, the ability of antibodies to induce arginase was independent of the IL-4Rα, but in its absence macrophages fail to accumulate at the infection site 46.