CD4 and inflammatory bowel disease: CD4+ T cells are also important for pathological processes of autoimmune diseases, such as systemic lupus erythematosus (SLE) [50, 51], autoimmune type 1 diabetes (T1D) [52, 53], multiple sclerosis (MS) [54, 55], rheumatoid arthritis (RA) [56–58], inflammatory bowel disease (IBD) [59, 60], and allergic responses or atopic diseases [61–63].