Anti-L-selectin oligonucleotide ligands recognize CD62L-positive leukocytes: binding affinity and specificity of...

Oligonucleotide aptamers generated against purified LS-Rg, a human L-selectin/IgG fusion protein, bound human CD62L-positive leukocytes. FACS analysis of lymphocytes or neutrophils stained with fluorescently labeled aptamers indicated specificity and sensitivity for cellular L-selectin similar to that observed with anti-L-selectin antibody. Univalent aptamers were compared to bivalent aptamers as well as to the anti-adhesion, anti-L-selectin antibody DREG56. Equilibrium and kinetic binding experiments were performed to examine the affinity and kinetic binding parameters of L-selectin aptamers to evaluate their binding to CD62L-positive leukocytes and to test their potential as L-selectin antagonists. Binding experiments indicated that bivalent aptamers approached the affinity and the dissociation rate of bivalent antibody, and preferentially recognized cellular compared to soluble L-selectin, a potentially useful distinction in vivo. Anti-L-selectin aptamers also inhibited L-selectin dependent self-adhesion of neutrophils suggesting that in vitro univalent and bivalent aptamers provided anti-adhesion activity similar to that observed with blocking antibody and indicated a direct blocking mechanism of action during inhibition of L-selectin-dependent trafficking of lymphocytes observed in vivo.