Molecular cloning of CD31, a putative intercellular adhesion molecule closely related to carcinoembryonic antigen

cDNA clones encoding CD31 have been isolated by transient expression. The sequence of CD31 expressed on human umbilical vein endothelial cells (HUVEC) is identical to that expressed on the monocyte-like cell line HL60. In HUVEC. CD31 is concentrated in regions of cell-cell contacts. CD31 is a member of the Ig superfamily and is most closely related to the carcinoembryonic antigen CEA, consisting of four contiguous C2 domains. The localization of CD31 to regions of cell-cell contacts, and the sequence similarity to CEA, a known intercellular adhesion molecule (ICAM), strongly suggest that CD31 may function as an ICAM, possibly mediating endothelial cell-cell contacts and also promoting interactions between leukocytes and endothelial cells.