Characterization of cell surface glycoproteins recognized by the granulocyte-specific monoclonal antibody, AHN-1

Major surface-iodinated proteins of Mr 105,000 and 145,000 of normal human neutrophils are immunoprecipitated by a number of monoclonal antibodies (AHN-1 to AHN-6), which react specifically with granulocytes among peripheral blood cells and selectively inhibit phagocytosis. These proteins, and an Mr 60,000 component, were purified by monoclonal antibody affinity chromatography, molecular sieve chromatography, and preparative polyacrylamide gel electrophoresis. Each of the three purified proteins was immunoprecipitated by all six antibodies. Nevertheless, tryptic peptide maps of the three proteins indicated that each was a distinct component. AHN-1 to AHN-6 also bound to glycolipid fractions of human neutrophils, and the binding of each antibody to human neutrophils was blocked by the carbohydrate sequences, lacto-N-fucopentaose III. The data indicate that a predominant antigenic determinant of human neutrophils is lacto-N-fucopentaose III, or related carbohydrates, present on three distinct proteins as well as glycolipids. At least one of these molecules appears to be involved in the process of phagocytosis.