Decreased leukocyte adhesion with anti-CD18 monoclonal antibodies is mediated by receptor internalization.
BACKGROUND
Adhesion of polymorphonuclear leukocytes (PMNs) to endothelial cells is mediated partially by CD11/CD18 integrins. The purpose of this study was to define (1) the response of PMNs to anti-CD18 monoclonal antibody binding, and (2) the mechanism responsible for anti-CD18 monoclonal antibody-mediated decreases in PMN adhesion to endothelial cells.


METHODS
Canine PMN O2- production, myeloperoxidase, and lysozyme release in response to the anti-CD18 monoclonal antibody IB4 were measured by standard assays. To examine endocytosis of CD18 receptors, PMNs incubated with IB4 and a fluorescein isothiocyanate secondary antibody were analyzed by flow cytometry.


RESULTS
Treatment of PMNs with IB4 did not stimulate O2- production or degranulation but decreased adhesion of 51Cr-labeled PMNs to ex vivo canine aorta. Incubation of PMNs at 25 degrees C resulted in a decrease in fluorescence intensity that was not affected by NaN3 or vanadate but was blocked by NaF, 4 degrees C, and bafilomycin, which prevents endosomal acidification. Treatment with an antifluorescein antibody decreased the fluorescence intensity in NaF and 4 degrees C, but not in bafilomycin-treated neutrophils.


CONCLUSIONS
IB4 decreases PMN-endothelial cell adhesion but does not stimulate neutrophil oxidative metabolism or degranulation. These data suggest that reduced adhesion may be the result of internalization of the CD18/IB4 complex. Anti-CD18 monoclonal antibodies may be useful in preventing PMN adhesion without the potentially deleterious effects of cell activation.
Rubin
B B
BB
Department of Pathology, Toronto Hospital, Ontario, Canada.
Rotstein
O D
OD
Lukacs
G
G
Bailey
D
D
Romaschin
A
A
Walker
P M
PM
D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology*; D015703:Antigens, CD / Q000276:immunology*; D001011:Aorta; D001666:Binding Sites, Antibody; D018821:CD18 Antigens; D002448:Cell Adhesion; D015550:Cell Degranulation; D004285:Dogs; D004705:Endocytosis; D008024:Ligands; D009504:Neutrophils / Q000378:metabolism / Q000502:physiology*; D011971:Receptors, Immunologic / Q000378:metabolism*; D016028:Receptors, Leukocyte-Adhesion / Q000276:immunology; D013481:Superoxides / Q000378:metabolism
D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D018821:CD18 Antigens; D008024:Ligands; D011971:Receptors, Immunologic; D016028:Receptors, Leukocyte-Adhesion; D013481:Superoxides