SLAM family member 6, also known as Activating NK receptor, NK-T-B-antigen, NTB-A, SLAMF6, KALI and Ly18, is a single-pass type I membrane protein which belongs to the CD2 subfamily of the immunoglobulin superfamily. SLAMF6 / Ly18 contains one Ig-like (immunoglobulin-like) domain. It is expressed by all (resting and activated) natural killer cells (NK), T- and B-lymphocytes. SLAMF6 / Ly18 triggers cytolytic activity only in natural killer cells (NK) expressing high surface densities of natural cytotoxicity receptors. SLAMF6 / Ly18 is a homodimer. It interacts with PTN6 and, upon phosphorylation, with PTN11 and SH2D1A/SAP. SLAMF6 / Ly18 undergoes tyrosine phosphorylation and associates with the Src homology 2 domain-containing protein (SH2D1A) as well as with SH2 domain-containing phosphatases (SHPs). It may function as a coreceptor in the process of NK cell activation. SLAMF6 / Ly18 can also mediate inhibitory signals in NK cells from X-linked lymphoproliferative patients.