CTLA-4 

Cytotoxic T-lymphocyte-associated protein 4 (CTLA-4), also known as CD152, is an inhibitory receptor belonging to the CD28 immunoglobulin subfamily. CTLA-4 is expressed primarily by T cells. The ligands of CTLA-4, CD80 and CD86, are typically found on the surface of antigen-presenting cells and can either bind CD28 or CTLA-4. The interactions of the ligands with CTLA-4 serve to inhibit T cell responses. Because of its dampening effect, CTLA-4 is a crucial regulator of T-cell homeostasis and self-tolerance. The mechanisms by which CTLA-4 exerts its inhibitory function can be categorized as either cell-intrinsic (affects the CTLA-4 expressing T-cell) or cell-extrinsic (affects secondary cells). CTLA-4 is well recognized as a key immune checkpoint and has gained significant momentum as a therapeutic target in the field of autoimmunity and cancer.