CD84 leukocyte antigen is a new member of the Ig superfamily

Abstract

cDNA isolated from a human B-cell line Raji library was ana- (CD48 and HumLy9) have been mapped. CD84 monoclonal lyzed and shown to encode the full-length cDNA sequence antibodies (MoAbs) were shown to react with cells transof a novel cell-surface glycoprotein, initially termed HLy9-b. fected with the cloned cDNA. These MoAbs were further The predicted mature 307-amino acid protein was composed used to show that CD84 is expressed as a single chain cellof two extracellular Ig-like domains, a hydrophobic trans- surface glycoprotein of Mr 64,000 to 82,000, which was membrane region, and an 83-amino acid cytoplasmic do- highly glycosylated. CD84 had a unique pattern of expresmain. The extracellular Ig-like domains presented structural sion, being found predominantly on lymphocytes and monoand sequence homology with a group of members of the Ig cytes. Thus, the glycoprotein HLy9-b is recognized by MoAbs superfamily that included CD2, CD48, CD58, and Ly9. North- previously clustered as CD84 and represents a newly identiern blot analysis showed that the expression of HLy9-b was fied member of the Ig superfamily that may play a significant predominantly restricted to hematopoietic tissues. Chromo- role in leukocyte activation.