Anaphylactic reactions to endotoxin in guinea-pig tissues: relationship to endotoxin toxicity.

1 A lipopolysaccharide extract of Escherichia coli 026:B6 cells (026:B6(B) endotoxin) was shown to be toxic to normal adult guinea-pigs. 2 The agent had no action on isolated preparations of ileum and heart taken from normal adult guinea-pigs. 3 Ileal segments from animals actively immunized against 026:B6(B) endotoxin showed dose-dependent contractions when exposed to endotoxin. Desensitization phenomena were demonstrated. 4 Reactivity of 026:B6(B) endotoxin was transferred to isolated preparations of ileum and heart from normal animals by passive transfer of immune serum. 5 Tissue responses to 026:B6(B) were associated with release of ileal spasmogen into the bath medium. Mepyramine blocked the effects of this spasmogen at bath concentrations which caused little change in ileal responses to carbachol. 6 It is concluded that E. coli endotoxin can elicit anaphylactic reactions, and that this process may potentiate endotoxin toxicity in sensitized animals. However, endotoxin toxicity in guinea-pigs does not appear to depend on this kind of allergic process.