The protein moiety of the endotoxin of Pseudomonas aeruginosa

Release of cytokines induced by Salmonella typhimurium porins

Salmonella typhimurium SH5014 porins induce the release of tumor necrosis factor alpha (TNF-alpha), interleukin 1 alpha (IL-1 alpha), and IL-6 by human monocytes and of gamma interferon (IFN-gamma) and IL-4 by human lymphocytes. Porins at 1 microgram/ml induce the greatest release of TNF-alpha, IL-1 alpha, and IL-6 by monocytes and of IL-4 by lymphocytes, while porins at 5 micrograms/ml induce the greatest release of IFN-gamma by lymphocytes. The R form of lipopolysaccharide (LPS-R) induces the greatest release of TNF-alpha and IL-1 alpha by monocytes when used at a low concentration (1 microgram/ml). At higher concentrations (5 and 10 micrograms/ml, respectively), LPS-R induces the maximal release of IL-6 from monocytes and the maximal release of IL-4 from lymphocytes. The S form of LPS (LPS-S) induces the greatest release of TNF-alpha, IL-1 alpha, and IL-6 by monocytes and that of IL-4 by lymphocytes when used at a concentration of 1 microgram/ml. After stimulation with LPS-S, the largest quantity of TNF-alpha and IL-1 alpha released was less than that obtained after stimulation with LPS-R at the same concentration, while the quantity of IL-6 released was found to be slightly higher than that obtained after stimulation with porins or LPS-R. LPS-S (1 microgram/ml) induces IFN-gamma release from lymphocytes in notably smaller quantities than that obtained with LPS-R and slightly larger quantities than that obtained with porins. The preparation of porins used was found to be contaminated with 10 pg of LPS per 10 micrograms of porins, a quantity which was found to have no biological effect; furthermore, porin preparations with the addition of polymyxin B gave the same results.

Activation of complement system by porins extracted from Salmonella typhimurium

The effect of porins purified from Salmonella typhimurium on the complement system was investigated both in vitro and in vivo. Incubation of porins with either human or guinea pig serum resulted in the consumption of the total complement activity when an amount of porins ranging from 8 to 10 micrograms per 100 microliters of serum was used. The activation of the complement system was temperature dependent, suggesting an active process rather than passive adsorption of the complement components by porins. In addition, the activation had a fast kinetic and proceeded mainly through the classical pathway. This conclusion is supported by the consumption of C1s and C4 in normal human serum treated with porins and also by the depletion of C3 activity in the C1s-deficient serum which was marked only when purified C1s was added to the serum before incubation with porins. Injection of 100 micrograms of porins into guinea pigs induced profound complement consumption at 6 h postinjection that persisted up to 12 h. We conclude from this study that porins can effectively contribute to complement activation and to subsequent biological events induced by gram-negative bacteria.

Neutralizing antibody to Pseudomonas aeruginosa exotoxin in human sera: evidence for in vivo toxin production during infection

Antibody to Pseudomonas aeruginosa exotoxin was detected in human sera by using a cytotoxicity-neutralization assay. Serum antitoxin was present in high titer in all 14 patients who recovered from serious pseudomonas infections (log2 of 50% neutralization titer, mean +/- standard deviation = 6.0 +/- 1.2). In contrast, serum antitoxin was present in lower titer in four of seven patients with fatal pseudomonas infections (3.3 +/- 2.7, P less than 0.005), in 3 of 7 patients with non-pseudomonas infections (1.4 +/- 0.6 P less than 0.001), and in 6 of 14 normal control subjects (2.0 +/- 1.3, P less than 0.001). Fourfold or greater serum antitoxin rises were demonstrated in two survivors of acute infections, and toxin-neutralizing activity was associated with the immunoglobulin G fraction of human sera. Immunization of rabbits with purified exotoxin also induced high antitoxin titers.

Endotoxin protein: a B-cell mitogen and polyclonal activator of C3H/HeJ lymphocytes

A cell wall protein that is ordinarily complexed to the lipopolysaccharide endotoxin in gram-negative bacteria has been separated by the use of aqueous phenol. The protein is active as a B-cell mitogen and polyclonal activator of murine lymphocytes including the C3H/HeJ strain which is a nonresponder to lipoplysaccharide or lipid A.