Signaling Lymphocytic Activation Molecule Family member 7 (SLAMF7), also known as CS1 or CD319. SLAMF7 is a cell surface glycoprotein that is highly and uniformly expressed on multiple myeloma cells and plasma cells, with relatively restricted expression on normal tissues (mainly NK cells and a subset of other immune cells). In normal NK cell biology, SLAMF7 acts as a self-ligand that provides a costimulatory activation signal. In multiple myeloma, its high expression is associated with tumor cell adhesion, survival, and interaction with the bone marrow microenvironment.