IL9 and allergic disease: Primarily produced by T cells, (TH1 and TH17), LT-α shares redundant features with TNF-α, acting on TNFRI and RII, but the effects of LT-α are less robust than TNF-α.32,52 IL-9, produced by TH9 cells, TH2 cells Tregs, and TH17 cells, was originally defined as a T-cell growth factor, but is now known to have pleiotropic functions in allergy, cancer and autoimmune diseases.53 Thus, each of these cytokines can also be produced by TH17 cells.