Induced FasL expression and IL-10 production by CD5+ B cells, which are well-documented to have autoreactive and poly-reactive antibody specificities, may be an important mechanism behind the correlations between schistosome infection and protection from autoimmunity and asthma described below (Lundy et al., 2005; Lundy and Fox, 2009). This evidence concerns the gene FASLG and asthma.