CTLA4 and Autoimmunity: In contrast to previous reports which described the development of autoimmunity and exacerbation of autoimmune diseases by CTLA-4 deficiency, subsequent studies showed that CTLA-4 ablation in adult mice resulted in complete or transient resistance to experimental autoimmune encephalomyelitis (EAE), which was interpreted as a consequence of increased expansion of thymic Treg as a result of CTLA-4 deletion (24, 25).