Endothelial leukocyte adhesion molecule 1: Direct expression cloning and functional interactions

A cDNA for endothelial leukocyte adhesion molecule 1 (ELAM-1) was isolated by transient expression in COS-7 cells of a subtracted cDNA library from cytokine-treated human umbilical vein endothelial cells (HUVECs), with selection of ELAM-1-expressing clones by adhesion of transfected cells to the human promyelocytic cell line HL-60. This cloning method requires neither antibody nor purified ligand. ELAM-1-expressing COS cells bind the promyelocytic cell line HL-60 by a Ca2+-dependent but temperature-independent mechanism. Although ELAM-1 is homologous to mammalian lectins, its interaction with HL-60 cells is not inhibited by simple carbohydrate structures. ELAM-1-expressing COS cells also bind human neutrophils and the human colon carcinoma cell line HT-29, but not the B-cell line Ramos. However, Ramos cells adhere to cytokine-treated HUVECs but not control HUVECs, confirming the existence of other inducible adhesion molecules. In addition, the binding of HL-60 cells or neutrophils to ELAM-1-expressing COS cells is not inhibited by a monoclonal antibody (60.3) directed to an inhibitory epitope on CD18, indicating that the ELAM-1 ligand, although uncharacterized, is not a member of the CD11/CD18 family