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

which is a potent ligand for the E- and L-selectins. The antibody gives a relatively low signal with the 3 4-sulfated non-fucosylated backbone, and has no detectable cross-reaction with the 34-sulfated Le x isomer, nor with sialyl-Le a and -Le x analogues. Antibody 91.9H is a valuable addition, therefore, to the repertoire of reagents for mapping details of the distribution, and determining the relative importance of sulfated and sialyl oligosaccharides as ligands for the selectins, in normal and pathological epithelia and endothelia.