CD4 and inflammatory bowel disease: Naïve CD4+ T cells differ according to cytokine-producing T-helper (Th) subsets, including Th1 (interferon-gamma, IFN-γ, TNF-α), Th2 (IL-4, IL-5, IL-6, IL-13), and Th17 (IL-17) cells, which are implicated in the dysregulation of colonic mucosa in IBD patients [43,44].