Abstract
The immune response to the lipopolysaccharide (LPS) somatic antigen of Shigella paradysenteriae was studied at the levels of humoral antibody and individual antibody-forming cells. Mice immunized with various doses of either LPS or wholecell vaccine rapidly developed serum agglutinins to the bacteria. Antibody activity was due to IgM globulins throughout the primary and secondary responses. LPSsensitized ovine erythrocytes permitted assessment of the serum antibody response and were useful for detection and enumeration of specific antibody plaque-forming cells in spleens of immunized animals. Antibody-forming cells rapidly appeared after immunization and peaked on days 5 and 6. Only 19S IgM antibodyforming cells were stimulated by the shigella antigen. Immunologic tolerance to shigella LPS was induced by injection of a relatively large inoculum into neonatal mice and persisted for at least six to eight weeks, with markedly depressed cellular and humoral antibody responses after challenge. Extracts rich in ribonucleic acid (RNA) from spleens of normal immune and tolerant donor mice transferred antibody-forming activity to normal or shigella-primed mice. Immunogenic activity of these RNA extracts was abolished by in-vitro treatment with RNAase or specific antibody to Shigella; thus both RNA and a persisting antigen fragment appear to contribute to biologic activity. The significance of immunogenic RNA extracts during immunogenesis and tolerogenesis was studied.
Published Version
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