Their significant functions in the gut are the intestinal epithelial barrier, as well as the modulation of immunity and anti-inflammatory effects, that evidenced from the conversion of intraepithelial CD4+ T helper cells into Treg lymphocytes and inhibition of Th17 cell polarization in mice33, and spermidine was reported as a protective role in an animal model of autoimmune diseases of multiple sclerosis and psoriasis52,53. Here, CD4 is linked to autoimmune disease.