CD31, also known as platelet endothelial cell adhesion molecule-1 (PECAM-1), is a receptor on endothelial cells for clostridium perfringens beta-Toxin (CPB). It also functions as an ER-MP12 antigen and connects mechanical stress, metabolism, and inflammation. The CD31 peptide promotes phosphorylation of CD31 ITIM 686 and SHP2, thereby inhibiting TCR-induced T-cell activation [1]-[5].