Monoclonal antibodies PMN 6, PMN 29, and PM-81 bind differently to glycolipids containing a sugar sequence occurring in lacto-N-fucopentaose III

Three monoclonal antibodies, PMN 6, PMN 29, and PM-81, bind myeloid cells. Antibodies PMN 6 and PMN 29 bind specifically to granulocytes but differ in their ability to bind some other cell lines E. D. Ball, R. F. Graziano, L. Shen, and M. W. Fanger (1982) Proc. Natl. Acad. Sci. USA 79, 5374-5378]. Antibody PM-81, in addition to granulocytes, also binds to eosinophils, monocytes, and most acute myelocytic leukemia cells E. D. Ball, R. F. Graziano, and M. W. Fanger (1983) J. Immunol. 130, 2937-2941]. Despite these differences, the binding of all three antibodies to cells was inhibited by the oligosaccharide, lacto-N-fucopentaose III Gal beta 1-4(Fuc alpha 1-3)GlcNAc beta 1-3Gal beta 1-4Glc]. Solid-phase radioimmunoassays using purified glycolipids containing sugar sequences found in lacto-N-fucopentaose III demonstrated different binding characteristics for each antibody. PM-81 bound lower concentrations of glycolipids than PMN 29, while PMN 6 required the highest concentration of glycolipids for binding. Autoradiography of thin-layer chromatograms of glycolipid antigens supported these results. The binding of these monoclonal antibodies to cells probably depends on the density of antigens on the cell surface, each antibody requiring a different density. Thus, cells containing antigen below a certain threshold concentration may not bind low-affinity antibodies.