Monoclonal antibody 91.9H raised against sulfated mucins is specific for the 3'-sulfated Lewisa tetrasaccharide sequence

The IgG1hybridoma antibody, 91.9H, was originally raised against sulfatedmucins isolated from normal human colonic mucosa. Previous studies haveshown that the 91.9H antigen is expressed on normal colonic epithelialcells and the sulfomucins that they produce, but not in the normal smallintestine and stomach. Tissue-specific changes occur in 91.9H antigenexpression in disease: the antigen diminishes in colonic carcinomas,whereas in regions of gastric mucosa showing intestinal metaplasia and ingastric carcinomas, the antigen is expressed as a "neo-antigen." Thisreport is concerned with elucidation, by the neoglycolipid technology, ofthe determinant recognized by antibody 91.9H using sulfated and sialyloligosaccharides of Lewisa(Lea) and Lextypes, and analogs that lacksulfate, sialic acid, or fucose. Binding experiments with the lipid-linkedoligosaccharides immobilized on chromatograms or on microwells, andinhibition of binding experiments with free oligosaccharides based on di-,tri- and tetrasaccharide backbones, show that the 91.9H antigenicdeterminant is based on a trisaccharide backbone, and consists of the3'-sulfated Leatetrasaccharide sequence, which is a potent ligand for theE- and L-selectins. The antibody gives a relatively low signal with the3'-sulfated non-fucosylated backbone, and has no detectable cross- reactionwith the 3'-sulfated Lexisomer, nor with sialyl-Leaand - Lexanalogues.Antibody 91.9H is a valuable addition, therefore, to the repertoire ofreagents for mapping details of the distribution, and determining therelative importance of sulfated and sialyl oligosaccharides as ligands forthe selectins, in normal and pathological epithelia and endothelia.