Alternatively activated macrophages are thought to be important in infections with other nematodes such as Brugia malayi and Litomosiodes sigmodontis, where infection induces the recruitment of F4/80+ cells, along with the up-regulation of the associated alternatively activated genes, Retnla (RELMα/FIZZ1) and Chi3l3 (Ym1), at the site of infection (7). The gene discussed is RETNLB; the disease is infection.