Morphological changes in the immunocompetent organs of white mice with experimental plague infection manifested in activation of the immune response of different degree and pathological process of different severity that depended on the plasmid composition of Y. pestis. Widening of the T-dependent zones in the immune organs of white mice infected with isogenic strains of Y. pestis with different plasmid composition attests to activation of cellular immunity. Our findings allow considering Y. pestis subsp. altaica I-2948/3, Y. pestis subsp. pestis I-3479 and Y. pestis subsp. pestis I-3480 as promising candidates for vaccine strains.
Keywords: Yersinia pestis; experimental animals; immunocompetent organs; plasmids.