Affinity chromatography of two sets of isomeric antibodies having specificity for different oligosaccharide units of gum arabic

Two sets of antibodies directed against different carbohydrate units of gum arabic were isolated from the sera of rabbits immunized intramuscularly with gum arabic and Freund's complete adjuvant. The isolation was affected by affinity chromatography on two columns attached in series and containing an adsorbent of AH-Sepharose 4B with ligands of partially hydrolyzed gun arabic in the first column and an adsorbent of AH-Sepharose 4B with ligands of native gum arabic in the second column. The two populations of anti-gum arabic antibodies were obtained and have been designated as Set 1 and Set 2 on the basis of their mobilities on agar diffusion. The antibodies of Set 1 consisted of 4 isomeric antibodies and those of Set 2 consisted of 11 isomeric antibodies. Native gum arabic samples were oxidized with periodate or reduced with sodium borohydride and carbodiimide under standard conditions and the modified samples were totally inactive in the precipitin test. On the basis of methylation data and immunological results it was concluded that terminal disaccharide moieties of the gum having the structure β-d-glucosyluronic acid-(1→6)-d-galactose and α-l-arabinofuranosyl-(1→4)-d-glucuronic acid were the immunodeterminant groups for Set 1 and Set 2 antibodies, respectively.