Immunochemical Studies on Dextrans

Human and rabbit antidextrans of α(1 → 2) specificity have been further characterized as to their combining sites based on oligosaccharide inhibition assays with three trisaccharides: 1) αdGlc(1 → 2)αdGlc(1 → 6)dGlc, 2) αdGlc·(1 → 6)αdGlc(1 → 2)dGlc and 3) αdGlc(1 → 2)[αdGlc(1 → 6)]dGlc. After absorption of α(1 → 6) specific antibody, the human antidextran sera contained antibodies complementary to trisaccharide 1 while the rabbit antisera contained antibodies complementary to both trisaccharides 1 and 2. With human antidextrans with non-α(1 → 2) specificity these trisaccharides were not the best inhibitors. The various rabbit antisera studied with dextrans of predominantly α(1 → 6) linkages showed combining site sizes with upper limits complementary to IM5, IM4 and IM3. The cross-reaction of horse antipneumococcal type XII antiserum was best inhibited by trisaccharide 1.