Studies on Immunity of Experimental Typhoid

Abstract

When mice passively immunized with anti-O serum were challenged intravenously by virulent organisms of Salmonella enteritidis, a slight inhibition of bacterial multiplication could be observed only in the blood, and the bacteria in the liver and spleen multiplied as rapidly as in controls. The antilethal effect of the passive immunization was recognized only against an intravenous challenge with a small dose (5×10-7 mg) of bacteria.When challenge infection was carried out through the subcutaneous (10-4 mg bacteria) or per oral (2-4 mg) routes, no inhibition of bacterial multiplication was noted at all either inregional lymph nodes or in liver and spleen of the immunized mice.The hitherto obtained deta concerning the effect of killed vaccines in experimental typhoid of mice, which was shown to be antilethal only when immunized mice were challenged intraperitoneally, have been discussed with the above-mentioned results.Since the marked clearance phenomenon by antibodies could be observed only in the peritoneal cavity, it seemed reasonable to assume that an antilethal effect was obtained when the clearance was so extensive that very few bacteria could escape from loco to organs. On the contrary, after challenge through various routes other than peritoneal cavity, bacteria, not receiving marked “clearance” effects at loco, easily multiplied in organs of the immunized mice.