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Some culture filtrates or enterotoxin preparations from enterobacteria that activate the adenylate cyclase system (vibrio cholerae, LT fraction from escherichia coli and klebsiella pneumoniae, shigella dysenteriae type 1) exibit an inhibiting effect on ADP-induced platelet aggregation, while other enterotoxin preparations not effective on adenylate cyclase system, don't interfere with this model. The A. propose the platelet aggregation as cellular assay to detect enterotoxin fractions effective upon adenylate cyclase system.

The in vitro effect of a virulent and a non virulent strain of Leptospira interrogans serotype icterohaemorrhagiae on human peripheral mononuclear cells was investigated. After addition of bacteria to citrated whole blood the production of mononuclear cell procoagulant activity (tissue factor) was observed. Indeed mononuclear cells isolated from whole blood-bacteria mixtures after prolonged incubation shortened the recalcification time of normal plasma. The virulent strain induced a significantly higher procoagulant activity than non virulent and this effect was dependent on the number of bacteria. The production of tissue factor, a potent trigger of blood clotting, by Leptospira icterohaemorrhagiae could help to understand the mechanism(s) responsible for the activation of intravascular coagulation sometimes associated with leptospirosis.

Shigella sonnei lipopolysaccharide (LPS) was injected intravenous (iv) or into the lateral cerebral ventricle (icv) of freely moving rats. Iv injection of 320 micrograms/Kg reduced arterial blood pressure, increased heart rate and did not change pressor response and reflex bradycardia induced by iv bolus injection of phenylephrine (5 micrograms/Kg). Iv injection of 640 micrograms/Kg reduced arterial blood pressure and heart rate, and altered baroreceptor reflexes. Icv injection of LPS (up to 50 micrograms/rat) neither changed resting blood pressure and heart rate nor modified phenylephrine induced pressor response and reflex bradycardia. Results suggest that S. sonnei endotoxin determines cardiovascular changes mainly through baroreceptor resetting. Data also seem to rule out a central nervous system involvement.

The A.A. have examined by Limulus endotoxin assay some LPS preparations from R. typhi, R. slovaka, C. burnetti phase I and II, as a demonstration of endotoxicity. All the preparations tested were able to gel the Limulus amoebocyte lysates, even if to a different degree of reactivity. The results add credibility to the hypothesis that LPS from Rickettsiaceae can represent at least in part the pathogenetic mediators of some manifestations described in Rickettsiosis; however, without endotoxin assay in the blood of patients, one cannot assume to this be true.

Administration of E. coli LPS prior to 3.5 mg/Kg dose of thiourea has been reported to protect rats against pulmonary edema and pleural effusion. However, LPS of Shigella sonnei (either in phase I or II) did not show any protective effect. These data might suggest a different mechanism of endotoxins on membranes.

Human neutrophils produce small amounts of superoxide anion when stimulated with the chemotactic peptide FMLP; preincubating neutrophils with low concentrations of lipopolysaccharides (LPS) markedly increases this response, an effect referred to as priming. In this work LPS from Coxiella burnetii either phase I (virulent) or phase II (avirulent) were examined for their ability to induce priming. Results clearly show that only LPS from phase II microorganism was able to increase the release from neutrophils upon subsequent stimulation with FMLP. This effect was abolished by preincubation of LPS with polymyxin B. This finding may account for the ability of Coxiella burnetii phase I to escape intracellular phagocyte killing during persistent infections.

The newly recognized spirochete, Borrelia burgdorferi, the causative agent of Lyme Disease, has been examined for endotoxin-like activities as measured by the standard Farmacopea Ufficiale della Republica Italiana rabbit fever test and the Limulus amoebocyte lysate assay. The suspension of heat-killed microorganism caused a febrile response at a dose of 1 X 10(8) bacteria pro kilo. Similar results were obtained in the Limulus assay where the heat-killed spirochetes stimulated formation of solid clot until the concentration of 1 X 10(5) per ml. Both in pyrogen test and in Limulus assay heat-killed Escherichia coli exhibited a higher degree of potency. These results show that LD-Borrelia possess endotoxin-like activities which could help in understanding the pathogenesis of the clinical symptomatology of the disease.

The injection in the peritoneum of Limulus amebocyte lysate at the same time of inoculation of lethal dose of E. coli LPS is able to protect the rats against endotoxin lethality.

Yogurt lactic-acid-bacteria (LAB) consisting of Lactobacillus bulgaricus and Streptococcus thermophilus were evaluated for their capacity to bind to human peripheral blood lymphocytes (PBL). These micro-organisms adhere to human T lymphocytes, and bind to B lymphocytes, in high and low frequencies, respectively. In addition, a quantitative analysis of LAB binding to PBL was carried out using the same parameters previously applied to a Salmonella model. The effect of yogurt LAB on the natural anti-bacterial activity exerted by PBL was examined. Lymphocyte pretreatment with bacteria did not affect such functions. These findings are discussed in the light of the well known ability of yogurt LAB to modulate the immune response.

Lipoglycans represent a special type of lipopoly-saccharide that differs in structure from the well-known gram-negative bacteria lipopolysaccharide. After briefly describing their most important characteristics, the authors take into consideration the in vitro interaction between lipoglycans from Acholeplasma granularum, Acholeplasma oculi, and Acholeplasma axanthum and human leukocytes in terms of production of procoagulant activity. The results obtained show that the examined lipoglycans possess, similarly to lipopolysaccharides, the capacity to induce the production of procoagulant activity, thromboplastin-like, from human mononuclear cells. However, the pathophysiological significance of this endotoxin-like activity remains to be established.

Protection against endotoxin challenge. The AA. have summarized shortly some experimental data dealing with trials of protection against endotoxin challenge pointing out, mostly, the effects of phosphate-containing compounds, as well as dextrane, anticoagulants, platelets, polymyxin B, and serum antiendotoxin and Lipid A antiserum. They have reported some experiments carried out by means of Limulus amebocyte lysate.

Some effects of bacterial endotoxin on leukocytes and platelets are reviewed. The release of two mediators, Leukocyte Inhibiting Factor (LIF) and Tissue Factor (TF) from human mononuclear cells are described. These factors may play either beneficial effects (LIF) or noxious activities (TF liberation in certain pathological conditions). Regarding the activities of LPS on platelets the AA. report some personal data about the electrokinetic modification of platelets due to endotoxin. This LPS effect can be performed directly or via a lymphokine release, Platelet Slowing Factor (PSF). In the light of all the mentioned considerations, a scheme of interaction LPS/platelets is suggested.

Endocarditis is a rather frequent complication of Q fever caused by Coxiella burnetii. We examined the ability of phase I (virulent) or phase II (avirulent) C. burnetii to coagulate blood in the presence of human blood mononuclear cells in vitro. After incubation for 4 h, virulent phase I C. burnetii was an effective stimulant for mononuclear cells. Since this interaction is a potent trigger of blood coagulation through the extrinsic pathway, it could be responsible for the local deposition of fibrin on the surface of infected valves and the development of large vegetations in cases of endocarditis complicating Q fever.

Ten atopic subjects, sensitive to intradermal injection of less than or equal to 10 protein nitrogen units of ragweed or grass pollen antigen, underwent paired antigen and buffer skin chamber incubation over the base of denuded skin blisters. The chamber fluids were sampled over a 6-hr period for histamine and activated Hageman factor and plasma kallikrein which were complexed to C1 inhibitor. In 9 of 10 subjects significantly (p less than 0.01) increased histamine levels (74 +/- 11 ng/ml vs 1.5 +/- 0.55 ng/ml) and kallikrein-C1 inhibitor complexes (2.15 +/- 0.78 ng/ml/hr vs 0.51 +/- 0.09 ng/ml/hr, p less than 0.25) were detected at antigen sites compared with buffer sites, respectively. Increased levels of activated Hageman factor (ng/ml/hr) were detected at antigen sites (1.35 +/- 0.60) compared with buffer sites (0.11 +/- 0.05), (p less than 0.01), in 8 of 10 subjects. Whereas peak levels of histamine were obtained after 1 hr of challenge, both Hageman factor and kallikrein activation, as assessed by complex formation, tended to peak later from the 2nd to the 5th hr. This represents the first demonstration that cutaneous IgE-mediated allergic responses are associated with local activation of the intrinsic plasma coagulation-kinin pathways.