Increased Survival in Irradiated Animals Treated With Bacterial Endotoxins

Abstract

A single injection of endotoxin derived from Gram negative bacteria caused an increased survival in lethally irradiated animals when given immediately after or 24 hours before irradiation. Mice responded better to the injection before irradiation and hamsters to the injection after irradiation. The effect was associated with a reduction in infection, very pronounced in the case of α-streptococcus or Proteus and still significant in the case of Pseudomonas infection. No beneficial effect was obtained when mice were given three endotoxin injections during 1 week or six injections during 2 weeks prior to irradiation. The beneficial effect is not necessarily associated with the granulocytosis which begins within a few hours after the endotoxin injection, or with the conditions under which nonirradiated animals show an increased resistance to bacterial challenge.