CTLA4 and atherosclerosis: Studies have shown that single programmed cell death protein 1(PD-1) (13), T cell immunoglobulin and mucin domain 3 (Tim-3) (14), or cytotoxic T-lymphocyte antigen-4 (CTLA-4) (15) pathway signaling has anti-atherogenic effects during the progress of murine atherosclerosis.