Inhibits the proliferation of CD4 and CD8 T-cells activated by anti-CD3 antibodies, T-cell metabolism and IL2 and IFNG secretion. Widely expressed (at protein level). In the thymus, restricted to the corticomedullary junction, but not confined solely to epithelial cells (at protein level). Significant expression on naive B-cells, splenic natural killer cells, dendritic cells and peritoneal macrophages (at protein level). Negligible expression on naive T-cells up-regulated on activated T-cells (at protein level). N-glycosylated. Belongs to the immunoglobulin superfamily. BTN/MOG family.