CTLA4 and autoimmune disease: Recent studies have shown that polymorphisms of the T-cell regulatory gene (cytotoxic T-lymphocyte-associated antigen 4) are associated with PAS.[65] Evidently, the immunological mechanisms are crucial in the development of the autoimmune disease, and the intervention of activated self-reacting T cell is considered to be necessary in the majority of the cases to achieve complete destruction of the target organ.[66]