IMMUNOLOGICAL CROSS-REACTION BETWEEN A NATURALLY-OCCURRING GALACTAN, AGAROSE, AND AN LPS LOCUS FOR IMMUNE LYSIS OF NEISSERIA-MENINGITIDIS BY HUMAN-SERA

Abstract

An immunological cross-reaction between agarose, a naturally-occurring galactan, and an antigenic determinant which is a locus for human bactericidal antibody within the LPS [lipopolysaccharide] of group Y strains of N. meningitidis was investigated. Bactericidal antibody in the convalescent serum of a child from whom a group Y, type IX strain was isolated could be absorbed by highly purified agarose in bead form (Sepharose), but not by a dextran gel (Sephadex). It was inhibited by agarose as a linear polymer and by the strain''s LPS, but not by a heterologous LPS from a group B, type II strain of N. meningitidis, nor by the homologous capsular polysaccharide. Both LPS contained galactose; neither was anti-complementary. Agarose antiserum, raised in a rabbit, was bactericidal for the group Y strain, but not for the group B strain. Bactericidal activity in the agarose antiserum could be inhibited by agarose. Immunization with agarose induced hemagglutinating antibody against the group Y strain''s LPS which could be absorbed by the group Y, but not the group B strain and could be reduced by absorption with Sepharose. Absorption with Sepharose also removed the lytic activity against group Y strains of serotypes II and IV from a normal human serum without group Y capsular polysaccharide antibody. The cross-reaction probably resides in the fine structure of the galactose constituent of the group Y strains'' LPS.