ネズミチフス症における生菌免疫成立機序に関する研究

Abstract

The present study was carried out to elucidate the mechanism by which living cells of Salmonella typhimurium confer long-lasting immunity in mice against murine typhoid. Living cells of either virulent or avirulent organisms of S. typhimurium induced higher levels of mouse protection of which the duration correlated with the persistence of each bacterium in the liver as a L form. In contrast, S. schottmülleri, of which O antigenicity is identical to that of S. typhimurium, induced only short-term protection, since L forms of the bacteria existed in the liver only over a short period. The capacity of salmonella L forms to persist in the liver was attributable to the ability of salmonella organisms to produce cytotoxin and they changed into L forms. This cytotoxin was toxic only to macrophages and polymorphonuclear leukocytes in vitro. The persistence of L forms in mice resulted in high production of both the tumor necrosis factor and membrane associated interleukin 1 upon challenge with virulent S. typhimurium, which would lead to the initiation of S. typhimurium-specific immunity. These results suggest that the persistence of salmonella L forms in mice might be required for longer-lasting immunity against murine typhoid after immunization with live-cell vaccines.