Immunologic phenomena in experimental rodentiosis. II. Cellular and humoral factors in immunity to infection with Yersinia pseudotuberculosis.

Humoral and cellular mechanisms of immunity to infection with Y. pseudotuberculosis bacilli in mice were studied. Development of delayed hypersensitivity, measured by the footpad test and macrophage migration inhibition test, was significantly correlated with immunity, expressed by elimination of Y. pseudotuberculosis cells from the organs of infected mice. Passive transfer of hypersensitivity and immunity was possible only by using peritoneal cells, while specific serum was inactive in this respect. Macrophages from immunized animals were more active in limiting intracellular multiplication of rodentiosis macroorganisms than macrophages from sensitive animals. Immunity in rodentiosis appears to be associated mainly with activation of cellular mechanisms.