[The mutagenic effect of polymorphonuclear leukocytes on Yersinia pestis]

As the result of in vitro experiments, Y. pestis auxotrophic mutants have been obtained under the influence of polymorphonuclear lymphocytes obtained from guinea pigs, previously immunized with Y. pestis strain EV. The mutagenic effect has been found to occur at minute 45 of phagocytosis. The control treatment of the bacteria with the lysate of neutrophils, homologous serum, penicillin (antibiotic-influenced selection) has not been found to lead to the appearance of auxotrophicity. These data suggest that the polymorphonuclear leukocytes of animals, having a set of powerful cytocidal systems, play an active role in the process of the natural variability of Y. pestis.