Antigenic Determinants of <i>Salmonella</i> for Production of “Clearance” Factor in Mouse Typhoid

ABSTRACT The “clearance” factor produced in the peritoneal cavity of mice immunized with killed vaccines prepared from Salmonella typhimurium or S. enteritidis was identified as the specific antibodies elicited by the O side chain of the cell wall polysaccharides in the organisms used as immunogens. After immunization of mice with vaccines prepared from virulent Salmonella strains, complement‐dependent antibacterial antibodies in the serum and “clearance” factors in the peritoneal cavity were found to appear coincidentally, to last for more than one year, and to have the same specificity against the virulent bacterial strains. The relationship between the complement‐dependent antibacterial antibodies and “clearance” factor, and the mechanisms of bactericidal action of these antibacterial agents in experimental typhoid were discussed.