A peptide from ICAM-2 binds to the leukocyte integrin CD11a/CD18 and inhibits endothelial cell adhesion.

Numerous leukocyte functions depend on adhesive intercellular interactions. The leukocyte-specific integrins CD11a/CD18 (lymphocyte function-associated antigen-1 (LFA-1)) and CD11b/CD18 (complement type 3 receptor (Mac-1)), which bind to the intercellular adhesion molecules ICAM-1 and ICAM-2, play a key role in adhesion. Little is known about the binding in molecular detail. We have now defined a peptide region from the first immunoglobulin domain of ICAM-2 that is specifically involved in binding to CD11a/CD18. A synthetic peptide from this part of ICAM-2, covering residues 21-42, bound to purified CD11a/CD18 and inhibited the adhesion of endothelial cells to this integrin. It also inhibited the binding of B lymphoblastoid cells to endothelial cells. Leukocytes bound to the peptide coated on plastic. Several shorter peptides from the same region showed less or no activity.