Antisera specificities to beta-D-galactopyranoside cluster ligands

Mono-, di-, and tri-beta-D-galactopyranosides of 2-(5-hydrazinocarbonylpentanamido)-2-(hydroxymethyl)-1,3-propan edi ol [(Gal)n-TA] have been conjugated to bovine serum albumin (BSA), and used to study the binding specificities to the Gal receptors of liver parenchymal cells. In this study, rabbit antisera produced to the (Gal)n-TA-BSA were characterized by using an enzyme-linked, immunosorbent assay under conditions that allow only the antibodies directed to the carbohydrate part of the antigen to react with the solid-phase (Gal)n-TA-BSA antigens. Inhibition assays using (Gal)n-TA-BSA conjugates showed a relative specificity of the antisera for the number of Gal residues on the TA bridging group to the BSA carrier-protein, indicating that antibodies having specificities to oligosaccharide branch points can be produced. Inhibition assays with (Gal)n-TA haptens, Gal, and methyl beta-D-Gal indicated that the antibody combining-sites interact mainly with the Gal units; no inhibition was observed with the TA bridging group used as a hapten inhibitor. The spatial distances of the Gal units were apparently important for interaction with the anti-(Gal)n-TA-BSA antibody-combining-sites, as (Lac)3-TA-BSA and (Lac)3-TA exhibited relatively little inhibitory activity.