CTLA4 and autoimmune disease: Lipopolysaccharide‐responsive and beige‐like anchor protein (LRBA) controls intracellular trafficking of Cytotoxic T‐lymphocyte protein 4 (CTLA‐4), and a loss of LRBA causes the insufficient CTLA‐4 expression on the surface of Tregs, resulting the development of autoimmune diseases.