CTLA4 and type 1 diabetes mellitus: Recent genome-wide association studies (GWAS) revealed many T1D association loci located in genes related to T1D autoimmunity, including PTPN22, CTLA4, IL2RA, INS, CD69, ERBB3, CYP27B1, PTPN2, UBASH3A and IL2RB (Barrett et al., 2009, Bradfield et al., 2011, Burren et al., 2011).