Inhibitory receptor on lymphocytes that negatively regulates antigen receptor signaling via PTPN6/SHP-1 and PTPN11/SHP-2 (PubMed:12796776, PubMed:14652006). May interact in cis (on the same cell) or in trans (on other cells) with TNFRSF14 (PubMed:19915044). In cis interactions, appears to play an immune regulatory role inhibiting in trans interactions in naive T cells to maintain a resting state. In trans interactions, can predominate during adaptive immune response to provide survival signals to effector T cells (PubMed:19915044). Interacts with tyrosine phosphatases PTPN6/SHP-1 and PTPN11/SHP-2 (PubMed:12796776, PubMed:14652006). Interacts with TNFRSF14/HVEM (via cysteine-rich domain 1) (PubMed:19915044). Expressed in splenic T- and B-cells as well as lymph node tissues but very weakly in somatic tissues. Also expressed in macrophages, NK cells and dendritic cells. A polymorphic tissue distribution between several strains is seen. Phosphorylated on Tyr residues by TNFRSF14 and by antigen receptors cross-linking, both inducing association with PTPN6 and PTPN11. N-glycosylated. Mice exhibit no developmental defects in T- or B-cells in thymus or bone marrow, but increased antibody responses and sensitivity to antigen-induced 'experimental autoimmune encephalomyelitis'. T-cells lacking Btla show increased proliferation with a heightened response to anti-CD3 and a slightly greater response to stimulation with anti-IgM.