In these conditions, it is thought that Th9 cells produce IL-9 that stimulate the mucosal mast cells production that contribute in mucus production and increase the muscle contraction as well as intestinal permeability [21,77], while IL-9-deficient mice during lung parasitic infection caused by Schistosoma mansoni only decreased the mucus production and no effect on granuloma formation for parasitic egg removal [78]. This evidence concerns the gene IL9 and parasitic infectious disease.