CD15/signaling lymphocytic activation molecule (SLAM) is a cell surface sialylated phosphoglycoprotein and belongs to the CD2 subset of the Ig superfamily of type I transmembrane glycoproteins. The CD15 receptor is expressed on thymocytes, activated and memory T cells, B cells, platelets, natural killer T cells, and mature dendritic cells, and is also detected on tumor cells of Hodgkin's lymphoma (HL) and diffuse large B-cell lymphoma with an activated B cell phenotype. Additionally, it is the immune cell receptor for measles virus (MV). As a self-ligand, CD15 performs diverse immunologic functions including T/B-cell costimulation, induction of IFN-&gamma in Th1 T-cell clones, redirection of Th2 clones to a Th1 or Th phenotype, and inhibition of apoptosis in B cells. Furthermore, CD15 was shown to be the second receptor for measles virus in addition to CD46, and the distribution of SLAM on various cell lines is consistent with their susceptibility to clinical isolates of measles virus.