CD150 is a member of a family of genes that encode glycoproteins on the surface of hematopoietic cells

Human CD150 (SLAM) is a glycoprotein expressed on the surface of T, B, natu ral killer, and dendritic cells. The extracellular domain of CD150 is the r eceptor for measles virus and CD150 acts as a co-activator on T and B cells . We characterized the mouse and human CD150 genes, each of which comprises seven exons spanning approximately 32 kb. Mouse CD150 mRNA was detected in T cells and in most thymocyte subsets, except CD4(-)8(-) cells. Surprising ly, the CD4(-)8(-) thymocytes of CD3 gamma delta (null) mice, but not of Ra g(null) or severe combined immunodeficiency mice, expressed CD150. Whereas high levels of CD150 were found in Th1 cells, only small amounts were detec table in Th2 cells. CD150 expression was up-regulated upon in vitro activat ion of mouse T cells by anti-CD3. The complete mouse CD150 gene is highly h omologous to its human orthologue in terms of nucleotide sequences and intr on/exon organization. The human genomic sequences indicate that all isoform s detected so far have arisen from alternative splicing events. As judged b y fluorescence in situ hybridization, mouse CD150 mapped to Chromosome (Chr ) 1, band 1H2.2-2.3, and human CD150 was found on Chr 1q22. Human and mouse CD150 share sequence homologies with six other genes, five of which - CD84 , CD229 (Ly-9), CD244 (2B4), CD48, and 19A - are localized in a 250-kb segm ent in close proximity to the human gene. Their location and their sequence similarities strongly suggest that the CD150 family of cell surface recept ors arose via successive duplications of a common ancestral gene.