PTPN22 and type 1 diabetes mellitus: Other genes that have also been associated with T1D are IL-2 receptor α [65], cytotoxic T lymphocyte antigen (CTLA4) [66], protein tyrosine phosphatase non-receptor 22 (PTPN22) [67], intercellular adhesion molecule 1 (ICAM1) [68], and the insulin gene (INS) [69].