[Immunological interrelations between Shigella sonnei differing in enzymatic activity and colicinogenicity].

For the first time immunological interrelations between S. sonnei differing in enzymatic activity and colicinogenicity were studied. Specific postinfectious immunity against Shigella pneumonia in intranasally infected mice was used as a model for testing S. sonnei strains, biovars II and III, with colicinogenic markers designated S5 and IE2, respectively. The development of homologous and heterologous immunity was shown to occur in the animals; immunity to the more virulent strain II S5 proved to be significantly more intense than in comparison with immunity to the less virulent strain III IE2. The unequal effectiveness of immunity to these strains (the more virulent were the strains, the more effective immunity they produced) was due to the fact that their populations contained different amounts of organisms in phase I responsible for infective action and immunity, and also, which was heretofore unknown, for the sensitivity of these bacteria to immunological action: the greater their virulence, the greater their sensitivity.