Several recent reports have specifically examined the role of IgM in protection from malaria, caused by infection with parasites of the genus Plasmodium. Mice selectively deficient in IgM experience greater parasitemia and mortality compared with wild-type mice upon infection with Plasmodium chabaudi, a model for uncomplicated Plasmodium falciparum infection (Couper et al., 2005). Here, CD40LG is linked to parasitic infectious disease.