B-and T-lymphocyte attenuator (BTLA) is also known as B-and T-lymphocyte-associated protein, CD antigen CD272. BTLA is a inhibitory molecule which belongs to the Ig superfamily that attenuates BCR and TCR-mediated signaling, and thereby functions as a negative regulator of lymphocyte activation. BTLA contains one Ig-like V-type (immunoglobulin-like) domain. As a lymphocyte inhibitory receptor, BTLA / CD272 inhibits lymphocytes during immune response. BTLA is not expressed by naive T cells, but it is induced during activation and remains expressed on T helper type 1 (T(H)1) but not T(H)2 cells.