CD84 is a 64- to 82 kDa cell surface glycoprotein and is also known as SLAMF5. It belongs to the CD2 subgroup (SLAM family) of the immunoglobulin superfamily, which has similar patterns of conserved disulfide bonds and functions in cell-cell interaction. Cell surface expression of CD84 is predominantly found on B cells, a subset of T cells, monocytes, macrophages, and dendritic cells. CD84 forms a homodimer via its extracellular domain and plays the role of an adhesion receptor in homophilic interactions or cell clustering.