[Immunogenicity of the surface polysaccharide of serotype A meningococci possessing different physico-chemical properties].

The influence of changes in the physico-chemical parameters of serogroup A meningococcal polysaccharide on its immunogenicity for mice was studied by means of passive local hemolysis in gel and the passive hemagglutination test. The polysaccharide was depolymerized by heating at 100 degrees C for 5, 30 and 120 minutes; during this process the progressing decrease of the molecular weight and the content of O-acetyl groups in the preparation could be observed. Mice showed high sensitivity to changes in the above-mentioned physico-chemical parameters, which was manifested by a sharp drop in the intensity of the immune response of the animals to the heated samples of the antigen.

[Immunologic tolerance to surface polysaccharides of serogroup A and C meningococci].

A single intravenous injection to mice of surface polysaccharides of meningococcal A and C serogroups in doses of 25--50 micrograms induces immunologic tolerance: the animals did not respond to the optimal dose (0.5 micrograms) of homologous antigens but were capable to form normal response to the heterologous polysaccharide Vi-antigen S. typhi.

[Primary and secondary immune response of mice to polysaccharide antigens of meningococcal serogroups A and C].

The peculiarities of the primary immune response, the formation of immunological memory and the secondary immune response to serogroup A and C meningococcal polysaccharides were studied in 7 strains of inbred mice, hybrids F1 and in noninbred animals. The passive local hemolysis test and the passive hemagglutination test indicated that the intensity of immune response to A and C polysacchardies depended on the genotype of the animals: both antigens induced the most intense response in CBA and BALB/c mice. The primary immune response to the both antigens was characterized by a short latent period, a rapid (by days 4-5) increase in the amount of antibody-producing cells in the spleen and in antibody titer in the blood serum to the maximum level, and a pronounced decrease inantibody formation by days 6-7 followed by a gradual extinction of the response.