CD2 family receptors are immunoglobulin (Ig) superfamily, type I transmembrane, glycosylated proteins characterized by an N-terminal variable (V) domain lacking disulfide bonds and a truncated Ig constant 2 (C2) domain with two disulfide bonds in the extracellular region. CD84, also known as Ly-9B, is a member of the CD150/SLAM (signaling lymphocyte activation molecule) subfamily of the CD2 family and is designated SLAMF5. It is expressed on B cells, T cells, monocytes and platelets, and is self-associating.