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CD272, also known as BTLA （B- and T-lymphocyte attenuator）, is an inhibitory receptor belonging to the CD28 immunoglobulin superfamily. It is a type I transmembrane glycoprotein expressed by most lymphocytes, including T and B cells. BTLA shares structural and functional similarities with CTLA-4 and PD-1, but it is distinct in that it interacts with the tumor necrosis factor receptor superfamily member 14 （TNFRSF14）, also known as herpesvirus entry mediator （HVEM）, rather than just the B7 family of cell surface receptors. This interaction plays a crucial role in negatively regulating T-cell immune responses. BTLA is involved in maintaining lymphocyte homeostasis and preventing excessive immune activation. It has potential implications in various diseases, including cancer and autoimmune disorders, where immune regulation is critical.