IL33 and infection: A central function for IL-33 in host defence was established by several studies demonstrating that mice lacking either IL-33 or the IL-33 receptor ST2 displayed increased intestinal parasite burdens in Strongyloides venezuelensis [22], Nippostrongylus brasiliensis [24], and Heligmosomoides polygyrus [25] infection, increased muscle larval burdens during Trichinella spiralis [26] infection and elevated microfilaremia during Litomosoides sigmodontis [27] infection.