The relationship between the protective and cross-reacting antigens of Brucella spp., Yersinia enterocolitica 0:9 and Salmonella serotypes of Kauffmann-White group N.

Vaccination with killed cells of Brucella abortus, Yersinia enterocolitica 0:9 and Salmonella neusdorf evoked cross-reacting antibodies in guinea pigs but only the homologous antigen effectively produced protective immunity to Br. abortus. None of these preparations induced protective immunity to Y. enterocolitica in gerbils but all stimulated protective immunity to S. landau in Balb/c mice. The antigenic determinants responsible for protective immunity to salmonella infection were located on the cross-reacting lipopolysaccharide-peptide agglutinogens of the brucella, yersinia and salmonella organisms. The protective effect could be passively transferred by serum and was probably mediated by IgM antibodies.