PTPN22 and type 1 diabetes mellitus: These studies have found convincing evidence of associations of several loci with T1D: HLA class II genes on chromosome 6p21, INS on 11p15, CTLA4 on 2q33, PTPN22 on 1p13, the IL2Rα region on 10p15 and the IFIH1 region on 2q24.