Identification of a Cell‐Surface Glycoprotein Mediating Adhesion in Human Granulocytes

Abstract

Previous studies have shown that monoclonal antibody 60.3 reacting with a surface antigen common to human leukocytes inhibits phorbol ester-induced adhesion among blood mononuclear cells and precipitates from these cells three surface polypeptides with apparent molecular weights of 90,000, 130,000 and 160,000. Now we report that the same antibody, either as purified IgG or Fab fragments, also inhibits the extensive adhesion among granulocytes induced by phorbol ester. Inhibition of cell aggregation was not observed with monoclonal antibodies to C3b receptor, common leukocyte antigen T200, C3bi receptor, brain granulocyte-T lymphocyte antigen, IgG Fc receptor, class I transplantation antigen, or a granulocyte-specific antigen. Intercellular adhesion induced by either the chemotactic tripeptide N-formylmethionyl-leucyl-phenylalanine (FMLP) or the ionophore A23187 was also inhibited by antibody 60.3. However, this antibody did not affect phorbol ester-induced superoxide (O2-) generation or lysozyme release. Two major surface glycopolypeptides with apparent molecular weights of 92,000 and 155,000 were immunoprecipitated from granulocytes. Dissociation of the protein complexes obtained from blood mononuclear cells and granulocytes indicated the presence of the epitope on the 90,000-92,000 molecular-weight components. It is thus concluded that the smallest glycopolypeptides mediate adhesion in human granulocytes and mononuclear leukocytes.