Moreover, the presence of the protein tyrosine phosphatase nor receptor type 22 (PTPN22)-encoded Lyp phosphatase (Lyp620W) variant increases the risk of autoimmunity by promoting the calpain-mediated cleavage of Lyp/Pep (Pep is the human PTP ortholog in mice) (PTPN22), decreasing Lyp/Pep levels in hyperresponsive lymphocytes and DCs during a steady state [229,230]. This evidence concerns the gene PTPN22 and Autoimmunity.