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Some Physical Properties of K Antigens of Escherichia coli Related to Their Biological Activity

Department of Bacteriology, Wright-Fleming Institute, St. Mary's Hospital Medical School, London, England

ABSTRACT

The ability of K antigens from Escherichia coli to inhibit the agglutination of sheep red cells by rabbit antibody has been taken as a measure of the ability of such antigens to render strains of E. coli O-inagglutinable, resistant to complement and to phagocytosis, and to increase their virulence for mice. Analysis of K antigens by chromatography on Sepharose and diethylaminoethyl cellulose columns and by immunoelectrophoresis suggested that agglutination-inhibiting activity was directly related to molecular size rather than charge. The effect of alkali treatment showed inhibitory activity to be independent of K-specific antigenic determinants and confirmed its relation to molecular weight.