Free, monovalent, SLeX (Neu5Ac alpha 2-3Gal beta 1-4(Fuc alpha 1-3)-GlcNAc), SLn (Neu5Ac alpha 2-3Gal beta 1-4GlcNAc) and corresponding BSA-conjugated forms--displaying different ratios of SLeX and SLn to protein--were tested for their ability to inhibit binding of HL-60 cells to immobilized E-selectin.