CD152 [CTLA-4] (human) (rec.) (His)

CD152 (Cytotoxic T-lymphocyte-associated protein 4; CTLA-4) is an inhibitory receptor belonging to the CD28 immunoglobulin subfamily, expressed primarily by T-cells. Its ligands, CD80 and CD86, are typically found on the surface of antigen-presenting cells and can either bind CD28 or CTLA-4, resulting in a costimulatory or a co-inhibitory response, respectively. Because of its dampening effect, CTLA-4 is a crucial regulator of T-cell homeostasis and self-tolerance. While CD28 promotes T-cell activation and proliferation, CTLA-4 is reported to dampen T-cell responses through a variety of mechanisms. Prior to activation, conventional T-cells (Tconv) express low levels of CTLA-4, predominantly in intracellular compartments. Upon activation, CTLA-4 expression is upregulated and becomes increasingly detectable on the cell surface. In Tregs on the other hand, transmembrane CTLA-4 is constitutively expressed and plays an important role in Treg homeostasis and function. In general, T-cell CTLA-4 is largely constrained to intracellular expression although some surface expression may be detectable owing to the rapid, continuous shuttling of CTLA-4 between intracellular compartments and the plasma membrane. Recently, roles of CTLA-4 have been demonstrated in dendritic cells and tumors, showing that CTLA-4 plays nonredundant and critical roles in thymic development, T-cell priming, peripheral tolerance, and a variety of other critical immunoregulatory functions as an immune checkpoint in Immuno-oncology research.