Immunochemical studies on dextrans. Cross-reaction of synthetic linear dextrans with rabbit anti-N4 dextran

Alpha (1 Leads to 6) specific anti-dextran antibody was raised in rabbits by injecting N4 dextran-concanavalin A conjugate, and the interactions of five synthetic linear dextrans (alpha(1 Leads to 6)-D-glucopyranans) with rabbit anti-N4 dextran were studied. The ability of glucans to precipitate antibody depended on their average molecular weight, samples with higher molecular weight precipitating more antibody nitrogen under the same conditions. This phenomenon was shown to be due to solubility of the antigen-antibody complex. Oligosaccharide inhibition assay indicated that the maximum size of the alpha(1 Leads to 6)-specific antibody combining site corresponded to isomaltopentaose. The precipitated antibody class was shown to be IgG immunoglobulin, and it was mostly directed to linear non-terminal glucosidic linkages. Determination of antibody nitrogen and glucan in the precipitates indicated that the ratio of antibody molecule to numbers of glucose residues was 1:16 in the extreme antibody excess region.