Differences in the Fine Specificities of Monoclonal (Class A) Antibodies to Human Myeloid Cells

Among 13 monoclonal antibodies to human myelomonocytic cells, six could be assigned to a group designated Class A with the following properties: (a) they react almost exclusively with granulocytes among cells of the peripheral blood, (b) they resemble the previously described anti-granulocyte antibodies, VEP8 and VEP9, and the anti-mouse embryo, anti-SSEA-1, in their strong reactions with human meconium glycoproteins and ovarian cyst mucins of non-secretor type and (c) they recognize the carbohydrate antigen 3-fucosyl-N-acetyllactosamine (alpha 1----3fucosylated Type 2 blood group chains). The binding of these anti-myeloid antibodies is more strongly inhibited by lacto-N-fucopentaose III than by the trisaccharide-fucosyl-N-acetyllactosamine, in contrast to anti-SSEA-1 which is more strongly inhibited by the trisaccharide. These observations suggest that the myeloid Class A antibodies recognize additional determinants on the neolacto (Gal beta 1----4GlcNAc beta 1----3Gal beta 1----4) backbone of the pentasaccharide which occurs on the glycoproteins and glycolipids of myeloid cells. However, no two of the anti-myeloid antibodies were identical in their inhibition patterns with the glycoproteins and the two oligosaccharides. They also differed in their cellular reactivities, for example, the proportion of cells in the K-562 cell line reacting with each antibody ranged from 15-57%.