PTPN22 and type 1 diabetes mellitus: One of these non-HLA genes, IDDM-2, is the insulin gene, and the other non-HLA gene IDDM-3, maps close to CTLA4, which has a regulatory role in the immune response (chromosome 15q26).[78, 79] Also, PTPN22 (protein tyrosine phosphatase, non-receptor type 22), and the regions around the interleukin 2 receptor alpha (IL2RA/CD25) and interferon-induced helicase 1 genes shows association with type 1 diabetes.[25] The defined and putative genetic factors for type 1 diabetes are presented in Table 1.