A role for CTLA-4 in autoimmune diseases is suggested by the observation that blockade of B7/CTLA-4 interaction via administration of anti-CTLA-4 mAb exacerbates autoimmune diseases in animal models such as experimental autoimmune encephalomyelitis [11] and type 1 diabetes (T1D) [12, 13]. Here, CTLA4 is linked to type 1 diabetes mellitus.