NTBA (NK-, T-, and B-cell Antigen) is a 60 kD type I transmembrane glycoprotein. It is a member of Ig superfamily belonging to CD2/CD150 subfamily, also known as SLAMF6 (SLAM family member 6), LY108, TCOM, or SF2000. This antigen is expressed on NK cells, T cells (upregulated upon activation), and B cells. NTBA is its own ligand. The homophilic interaction of NTBA is involved in the induction of NK cytotoxicity, CD28 independent T cell costimulation, triggering Th1 cytokines production, and regulation of B cell tolerance. It may play a role in the regulation of autoimmune diseases.