A PEPTIDE FROM ICAM-2 BINDS TO THE LEUKOCYTE INTEGRIN CD11A CD18 AND INHIBITS ENDOTHELIAL-CELL ADHESION/

Numerous leukocyte functions depend on adhesive intercellular interact ions. The leukocyte-specific integrins CD11a/CD18 (lymphocyte function -associated antigen-1 (LFA-1)) and CD11b/CD18 (complement type 3 recep tor (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 b inding in molecular detail. We have now defined a peptide region from the first immunoglobulin domain of ICAM-2 that is specifically involve d in binding to CD11a/CD18. A synthetic peptide from this part of ICAM -2, covering residues 21-42, bound to purified CD11a/CD18 and inhibite d the adhesion of endothelial cells to this integrin. It also inhibite d the binding of B lymphoblastoid cells to endothelial cells. Leukocyt es bound to the peptide coated on plastic. Several shorter peptides fr om the same region showed less or no activity.