Infections by adult stages of B. malayi induce the production of IL-4 by the host, promoting the appearance of suppressive cells known as IL-4-dependent F4/80+ macrophages (or nematode elicited macrophages (NeMφ)), which exert an anti-proliferative effect on lymphocytes, mediated by cell-to-cell contact [164,165], and at the same time act as antigen-presenting cells (APC) to stimulate naïve T cells and induce their differentiation towards Th2 and IL-4-producing cells [166]. The gene discussed is IL4; the disease is infection.