TNF and ulcerative colitis: While Th1 and Th17 cells are involved in IBD-associated inflammation, with the secretion of cytokines, such as TNF-α, IFN-γ, and IL-6 by Th1, and IL-17, IL-22, and IL-21 by Th17, Th2 cells contribute to intestinal mucosa inflammation in ulcerative colitis (UC) by secreting IL-4 [40].