CD4 and colitis: In this model, remission could be induced by systemic anti-CD4 mAb treatment, depleting the circulating CD4+ T cells, and after treatment stopped, mice relapsed spontaneously, indicating a potential role of tissue-resident CD4+ TRM cells not only in colitis induction but also in relapsing disease, which may have escaped anti-CD4 mAb-mediated depletion [112,113].