Pmel-1 CTLA-4^–/– mice develop autoimmune vitiligo at an accelerated rate compared with pmel-1 CTLA-4^+/+ mice. Development of autoimmune vitiligo in a pmel-1 CTLA-4^–/– mouse. Pictured are pmel-1 CTLA^+/+ (right) and pmel-1 CTLA-4^–/– (left) littermates at 6 weeks of age. Autoimmune vitiligo is present over more than 75% of the body surface of the pmel-1 CTLA-4^–/– mouse.