– IL-9 is a pleiotropic cytokine that influences various distinct functions of different target cells such as T cells, B cells, mast cells and airway epithelial cells by activating STAT1, STAT3 and STAT5. Because of its pleiotropic functions, IL-9 has been demonstrated to be involved in several diseases, such as cancer, autoimmunity and other pathogen-mediated immune-regulated diseases. In this review, we focus on the role of Th9 and IL-9-producing cells in allergic asthma. IL-9 Protein, Mouse, Recombinant (hFc) is expressed in HEK293 mammalian cells with C-hFc tag. The predicted molecular weight is 40.9 kDa and the accession number is P15247.