Clusters of differentiation of the B7 family

The B7 family protein is present on the activated antigen presenting cells (APC)surface, and it interacts with the CD28 or CD152 (CTLA-4) receptor on the T cell surface, can produce a costimulatory signal or a coinhibitory signal to enhance or decrease the activity of a MHC-TCR signal between the APC and the T cell, respectively. Besides being present on activated APCs, B7 is also found on T-cells themselves.
The B7 family consists of structurally related, cell-surface proteins that regulate immune responses by delivering costimulatory or coinhibitory signals through their ligands. Ten family members have been identified to date including CD80, CD86, CD274, CD273, CD275, CD276, and others. B7 ligands are expressed on both lymphoid and nonlymphoid tissues. The importance of the B7 family in regulating immune responses is clear from their demonstrated role in the development of immunodeficiency and autoimmune diseases.
CD80 and CD86 are both type I proteins that are members of the immunoglobulin (Ig) superfamily. Both CD80 and CD86 are capable of binding the receptors, CD28 and CD152 (CTLA-4). CD28 plays a role in activation, whereas CD152 functions as an inhibitory receptor important for down-modulating the immune response.