Inhibition of Molt-4-endothelial adherence by synthetic peptides from the sequence of ICAM-1.

Previous studies have shown that inflammatory pathologies are mediated by lymphocyte adhesion to endothelium and subsequent transmigration through the endothelial monolayer. Lymphocyte-endothelial adherence is, in part, caused by the leukocyte integrin LFA-1 binding to ICAM-1, its ligand on endothelial cells. Synthetic peptides based on specific amino acid sequences of human ICAM-1 inhibit the adherence of a lymphocytic cell line, Molt-4, to cytokine-stimulated endothelial cells. A total of 26 peptides spanning the extracellular domains of ICAM-1 were evaluated for their inhibitory activity in two cell adhesion assays. Binding of fluorescently labeled Molt-4 cells to TNF-stimulated human umbilical vein endothelial cells was inhibited reproducibly by peptides ICAM1-20, ICAM26-50, ICAM40-64, ICAM132-146, and ICAM345-375. Three overlapping sequences of the peptide ICAM40-64, KELLLPGNNRKVYELSNVQEDSQPM, were synthesized and tested as well, and the sequence KELLLPGNNRKV showed the greatest inhibition. The inhibitory activity of these peptides was confirmed using a second assay, inhibition of aggregation of the Epstein-Barr virus-transformed B-lymphoblast line JY. Polyclonal antibodies were developed in rabbits by immunization with two of the peptides and characterized for their ability to inhibit lymphocyte-endothelial adherence. These studies predict potential sites for interaction of the integrin receptor, LFA-1, with its ligand, ICAM-1. Thus lymphocyte-endothelial interaction, and resulting inflammation, may be partially mediated by the association of ICAM-1 with LFA-1 at the specific molecular locations identified in this study.