 B7 (protein)

B7 is a type of peripheral membrane protein found on activated antigen-presenting cells (APC) that, when paired with either a CD28 or CD152 (CTLA-4) surface protein on a T cell, 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.Binding of the B7 of APC to CTLA-4 of T-cells causes inhibition of the activity of T-cells.