Immunochemical Studies on Cross-Reactions of Antipneumococcal Sera

Abstract

Summary A variety of dextrans cross-react with Types IX and XII antipneumococcal sera and, to the extent of their cross-reactivity, remove the same fraction of anti-SIX or anti-SXII. Dextrans with high proportions of 1,6 linkages cross-react poorly with anti-SIX whereas some dextrans with high proportions of 1,3-like linkages precipitate the largest quantitites of antibody N and three dextrans with high proportions of 1,2 linkages precipitate about two-thirds of this cross-reacting antibody. Inhibition studies of the cross-reaction of anti-SIX with a dextran with 38% 1,2 linkages and 12% 1,4 linkages (B1299-S-3) show that a trisaccharide, 4-O-α-d-glucopyranosyl-3-O-α-d-glucopyranosyl-d-glucopyranose (T2), was the best inhibitor tested; maltose, kojibiose and nigerose were the best disaccharide inhibitors of this cross-reaction, all three being poorer than T2 and about equal to one another. Inhibition studies of the cross-reaction of anti-SIX with a dextran with a high proportion of 1,3-like linkages (B1355-S-4) show that nigerose is a much more effective inhibitor than either maltose or kojibiose and as good, on a molar basis, as either T2 or 3-O-α-d-glucopyranosyl-4-O-α-d-glucopyranosyl-d-glucopyranose, indicating a heterogeneity in the specificity of the anti-SIX involved in the cross-reactions. Dextrans with high proportions of 1,2 linkages precipitate the most antibody N from anti-SXII whereas dextrans with high proportions of 1,6 linkages precipitate the least and kojibiose was found to be the best inhibitor of the cross-reaction of anti-SXII with a dextran with a high proportion of 1,2 linkages (B1299-S-3). Trehalose was almost as effective as kojibiose in inhibiting the cross-reaction of anti-SXII with B1355-S-4 (no 1,2 linkages), also indicating heterogeneity in the specificity of the cross-reacting fraction of anti-SXII. The results of the dextran-anti SXII cross-reaction closely parallel findings in the reaction of dextran with human antidextran of specificity involving the 1,2 linkage. The data are discussed in relation to the information provided concerning the structural units on SIX and SXII involved in the cross-reactions. N-acetylglucosamine and glucuronic acid may be involved in the specificity of the cross-reacting fraction of anti-SIX and N-acetylglucosamine may be involved in the specificity of the cross-reacting fraction of anti-SXII.