Abstract
Summary
The number of specific antibody plaque-forming cells appearing in spleens of mice immunized with various concentrations of the lipopolysaccharide somatic antigen derived from Serratia marcescens was studied in detail. Maximum numbers of antibody-forming cells appeared 4–5 days after intraperitoneal injection of 50 μg of antigen. Fewer plaque-forming cells appeared in spleens of mice treated with a lower concentrations of antigen. Furthermore, mice injected with 500 μg of the lipopolysaccharide also had relatively few plaque-forming cells, indicative of a marked depression of the immune response.
The “nonspecific” response to sheep erythrocytes was enhanced in spleens of mice injected with the highest concentrations of antigen, as compared to animals receiving smaller amounts. The specificity of the antibody-plaque response was readily demonstrated by inhibition experiments using either specific antigen or anti-mouse globulin in the test agar plates. Plaques were inhibited when 10-100 μg of Serratia lipopolysaccharide, but not Salmonella or E. coli antigen, was incorporated into the agar.
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