FOXP3 and helminthiasis: Both cytokines are, for instance, critical for helminth infection-associated intestinal mucus production (38, 39), Trichinella spiralis–dependent host inducible nitric oxide synthase expression (40, 41), positive regulation of the Foxp3+ T cell populations with the tissue-dwelling parasites Schistosoma mansoni and Nippostrongylus brasiliensis (42), and optimal Heligmosomoides polygyrus expulsion (43).