Relationship between Escherichia coli endotoxin toxicity and the immunization status of normal adult guinea-pigs.

Lipopolysaccharide extracts of E. coli (endotoxins) were toxic to normal adult guinea-pigs, yet no evidence was found of serological reactivity to endotoxins or of "immediate" dermal reactivity in vivo. In contrast, testing of the serum of experimentally immunized animals provided evidence of precipitins, agglutinins and haemolysins. It is concluded that endotoxin exerts toxic effects in the absence of significant antibody production. This suggests that endotoxin toxicity is independent of immune processes not involving cell-mediated responses.