Immunoradiometric assay of endotoxin in serum

We describe an immunoradiometric assay for the specific detection and quantitation of endotoxin from Escherichia coli 026, with use of 125I-labeled antibody. The sensitivty of this assay is 1 microgram/L.E. coli 026 endotoxin was detected in serum of rats for as long as 24 h after intraperitoneal injection of 0.1 mg of endotoxin per 100 g body weight. The assay is specific for the O-polysaccharide portion of this endotoxin, as confirmed by results after protein digestion and oxidation of the endotoxin, as well as by failure to detect endotoxin in serum after similar injections of E. coli 0127 and Salmonella typhosa 0901 endotoxins.