A PEPTIDE DERIVED FROM NEUTROPHIL INHIBITORY FACTOR (NIF) BLOCKS NEUTROPHIL ADHERENCE TO ENDOTHELIAL-CELLS

Objective and Design: Peptides derived from neutrophil inhibitory fact or (NIF), a known antagonist of Mac-1. were evaluated as inhibitors of neutrophil adherence. Material: In vitro assays of adherend employed: 1) human polymorphonuclear cells (PMN), 2) human umbilical vein endot helial cells (HUVEC), and 3) CHO cells expressing ICAM-1 (CHO-ICAM cel ls). Treatment: Cells, pretreated with NIF-derived peptides (0.1-100 m u M) for 10 minutes, were permitted to adhere for 20 min in the contin ued presence of peptide. Methods: Cell-based assays: 1) PMN adherence to HUVEC, 2) PMN adhesion to immobilized human serum proteins, and 3) adherence of CHO-ICAM cells to immobilized Mac-1. Results: A NIF-deriv ed peptide of 29 amino acids blocked PMN adherence to HUVEC, but behav ed somewhat differently than the parent NIF protein. NIF specifically antagonized Mac-1 dependent adherence, but the peptide blocked neutrop hil adherence that was dependent upon both Mac-1 and LFA-1 integrins. CHO-ICAM adherence to Mac-1 was blocked by NIF, but not by the peptide . Binding studies with NIF and the peptide indicate that the molecules bind to different sites. Conclusions: A peptide derived from NIF bloc ks PMN adherence but, unlike NIF, the mechanism of action is not media ted by direct antagonism Mac-1.