Monoclonal antibody-defined functional epitopes on the adhesion- promoting glycoprotein complex (CDw18) of human neutrophils

We have evaluated the functional and immunochemical activities of three monoclonal antibodies (MoAbs) minimally reactive with adherence- defective neutrophils (PMN) from a patient with recurrent bacterial infections. In studies with normal PMN, MoAbs OKM1 and 60.1 both precipitate the same 165kd alpha-subunit (alpha M) within an alpha-beta heterodimer complex (CD11). The CD11 complex is part of a larger complex composed of four glycoproteins (CDw18) precipitated by MoAb 60.3, with properties suggesting that the CDw18 complex is equivalent to the Mac-1, LFA-1, p150, 95 glycoprotein family implicated in adherence-dependent leukocyte functions. PMN adherence to endothelium, spreading on surfaces, aggregation, and phagocytosis of zymosan particles were all inhibited in a dose-dependent fashion by MoAb 60.1 (analogous to previous studies with MoAb 60.3) while MoAb OKM1 had no effect. These findings unify previously disparate observations and suggest that a functionally active site on the adherence promoting glycoprotein complexes CD11 and CDw18 is distant from the alpha M epitope recognized by MoAb OKM1 but closely associated with the alpha M epitope recognized by MoAb 60.1 and the beta-epitope (or epitope created by alpha-beta quaternary structure) recognized by MoAb 60.3.