Human CTLA-4 (also known as Cytotoxic T lymphocyte-associated antigen-4, CD152) is a structural homologue of T cell co-stimulatory receptor CD28. CTLA-4 binds to the same ligands (CD80 and CD86) as CD28 but with much higher avidity. It is expressed at very low levels on the cell surface of activated T cells, and is found primarily in the post-Golgi or endosomal compartments of the cell. There is a high degree of overall homology between human and mouse CTLA-4 (>70 % ), and the cytoplasmic domains of the human, mouse and rabbit sequences are completely conserved. CD152 antibodies have shown both stimulatory and negative regulatory roles in functional experiments.Synonyms: CTLA-4, Cytotoxic T-lymphocyte protein 4, Cytotoxic T-lymphocyte-associated antigen 4