Permeability factor-like skin reaction in rabbits induced by endotoxin of Salmonella sp

An inflammatory skin reaction similar to the permeability factor (PF) described for the thermolabile (TL) enterotoxin of Escherichia coli was induced in rabbits inoculated intradermally with supernatants from cultures of Salmonella typhimurium and S. enteritidis. This PF-like activity was observed with both crude supernatants as well as those which were submitted to gel filtration through Sephadex G-100. PF-like activity was found only in fraction 1 (F1) of the chromatographed materials. It was resistant to boiling, proteolytic enzymes and wide variations of pH. Serological studies based on agglutination and immunodiffusion tests demonstrated that F1 materials were closely related to the somatic antigen of group B Salmonella. No specific TL activity, as detected by the Y-1 adrenal cell assay and the passive immune haemolysis test, could be demonstrated. Furthermore, F1 materials were not enterotoxigenic as assayed by the rabbit ileal loop assay, and no neutralization of PF-like activity could be obtained in tests carried out using F1 preparations pre-incubated with either anti-F1 or cholera antitoxin. Based upon these findings, it seems reasonable to suppose that most PF reactions, already reported as being caused by a TL-like enterotoxin produced by Salmonella, are probably due to endotoxin. In fact, this possibility was reinforced by the Sanarelli-Shwartzman phenomenon which was produced in rabbits inoculated with F1 materials.