Antigenicity of protein and lipopolysaccharide from Yersinia enterocolitica

The rabbits infected intravenously with viable Yersinia enterocolitica (Y.e.) produced the precipitating antibodies against a protein component as well as lipopolysaccharide of the organism. The production of the precipitins against protein antigen persisted for a long period of time even after the O-agglutinins had disappeared. The rabbits infected orally with the organism produced only the precipitins against protein antigen, and the amount of the antibody was equal to or greater than that of intravenous infection. The same precipitins that rabbits produced were detected even in human patients with yersiniosis showing O-agglutinin titers as low as less than or equal to 1:20. The antibody titers of mice infected with Y.e. were markedly lower than those of rabbits.