Autoimmune diseases are also caused by the strong association of the human leukocyte antigens, HLA class I and class II alleles, with specific autoimmune diseases, and genetic mutations in CTLA4, a suppressor receptor for T cell responses, and PTPN22, which acts as a negative regulator of T cell receptor signaling [29,30]. The gene discussed is PTPN22; the disease is autoimmune disease.