Resistance to Experimental Infection and Mobilization of Granulocytes in Irradiated Mice Treated With Bacterial Endotoxin

Abstract

The ability of mice to respond to an intraperitoneal injection of Salmonella typhosa endotoxin with increased resistance to experimental Pseudomonas infection was studied over a period of 3 weeks following just sublethal irradiation, with and without lead shielding of the hind legs. In general, the increase in resistance paralleled the ability to mobilize granulocytes. No increase in resistance was observed 3 days after irradiation in the unshielded mice, while in the shielded mice the increase was only slightly less than in nonirradiated mice. In nonirradiated mice given a series of endotoxin injections, increased resistance to the infection persisted in the absence of a granulocytic response. This effect could be abolished by an intervening exposure to sublethal radiation. An intraperitonial injection of zymosan also increased resistance to the infection without producing a granulocytosis. The rapidly developing resistance to infection following an endotoxin injection was transitory and apparently is not responsible for the recently reported increase in survival of lethally irradiated mice.