Mice deficient for the IL-21R (Il21r−/−) showed reduced accumulation of immune subsets in the intestine, including lymphocytes, and reduced sizes and numbers of intestinal granuloma following helminth infections, suggesting a critical requirement of the IL-21/IL-21R axis for mounting TH2 responses (Frohlich et al., 2007). This evidence concerns the gene IL21R and helminthiasis.