K. S. Kristensen

Bacteria and endotoxin enhance basophil histamine release and potentiation is abolished by carbohydrates

Histamine release caused by anti‐IgE, specific antigens and calcium ionophore A23187 was examined in leukocyte suspensions from healthy individuals and patients allergic to house dust mite and birch pollen. Staphylococcus aureus and LPS from Salmonella typhimurium were found to cause a synergistic enhancement of the release. The potentiation of mediator release by the bacteria and the endotoxin depends on a binding to the basophilocyte, followed by a non‐transient event, since the potentiating effect persists after preincubation of the cells with the LPS followed by washout and leaving the cells for 30 min at 37°C before stimulation with anti‐IgE. The potentiation was abolished or reduced by galactose (10−7 and 10−6 M) and N‐acetylglucosamine (10−6 and 10−5 M), acting by a binding to the basophil cell membrane, demonstrated by the persistence of effect after preincubation and washout of unbound sugar.

Carbohydrates inhibit the potentiating effect of bacteria, endotoxin and virus on basophil histamine release

Histamine release caused by calcium ionophore A23187 and anti-IgE was examined in leukocyte suspensions from 8 healthy individuals.Staphylococcus aureus, lipopolysaccharide (LPS) fromSalmonella typhimurium and influenza A virus were found to enhance the histamine release but did not release histamineper se. The potentiation of mediator release depends on a non-transient signal since the potentiating effect was also obtained by preincubation of the cells with LPS followed by wash-out and stimulation of the cells with anti-IgE. The potentiation was abolished or reduced by galactose, N-acetyl-glucosamine, α-methyl-d-glucoside, α-methyl-d-mannoside, N-acetylneuraminic acid and lactose, but not by glucose. These findings indicate that the enhancement of mediator release by bacteria, endotoxin, and virus depends on a sugar-mediated reaction.

Virus, bacteria and lipopolysaccharide increase basophil cell response to histamine releasing stimulators and calcium : examination of allergic and normal individuals

Histamine release from human basophil leukocytes from allergic patients or controls was induced by specific antigens, anti‐IgE or calcium ionophore A23187, Influenza A virus, S. aureus and lipopolysaccharide from S. typhimurium increased the maximum release of histamine and caused a shift lo the left of the dose‐response curves showing increased cell sensitivity and lowering of the threshold to these stimuli. The mechanism of action was elucidated by examining the mediator release as a function of increasing extracellular concentration of calcium, in these experiments the dose‐response curves were changed by the microorganisms and lipopolysaccharide as before. This indicates that the microorganisms and lipopolysaccharide change the basophil cell response to IgE‐dependent and non‐immunological stimuli by causing a change in the subcellular handling of calcium.

Fungal spores enhance basophil histamine release

The effects of whole spores from moulds were examined concerning histamine release using leukocyte suspensions from normal (non-atopic) individuals and grass pollen-allergic patients. Spores fromChaetomium globosum, Mucor racemosus andAspergillus terreus caused no histamine release in concentrations up to 0.1 or 1 mg/ml, but they enhanced mediator release triggered by both IgE-dependent stimuli (grass-pollen allergen and anti-IgE antibody) and non-immunological stimuli (Staphylococcus aureus and calcium ionophore). Organic dust contains microfungi as well as bacteria and endotoxins. Earlier we have shown that bacteria release mediators from human lung cells and that bacteria and their endotoxins potentiate mediator release. It is now demonstrated that fungal spores also have potentiating ability. The content of all these microorganisms in dust may therefore be responsible for the symptoms observed after occupational exposure to organic dusts.

Influenza A virus enhances basophil histamine release and the enhancement is abolished by carbohydrates

Basophil histamine release was studied in leukocyte suspensions from normal individuals and from patients allergic to house dust mite or birch pollen. Mediator release caused by IgE‐mediated reactions was examined by stimulating the cells with anti‐IgE or specific antigens, and the calcium ionophore A23187 was used for a non‐immunological histamine release. In all experiments influenza A virus caused a synergistic enhancement of the mediator release and the potentiation was abolished by galactose (10 −2 to 10−6 M) and by 10−6 to 10−3 M of N‐acetylglucosamine, alpha‐methyl‐D‐glucoside, alpha‐methyl‐D‐mannoside, N‐acetylneuraminic acid and lactose, but not by glucose. Wash‐out experiments show that the sugars prevent the aggravation of mediator release by a binding of sugar to the basophil cell membrane, thereby causing a blockade of binding sites responsible for the potentiating effect of virus.

Increased numbers of circulating basophils with decreased releasability after administration of rhG-CSF to allergic patients

Preliminary studies in hematological patients have indicated that treatment with rhG-CSF reduces basophil releasabilityex vivo. We examined this phenomenon further, in allergic patients. Ten patients with grass pollen rhinoconjunctivitis were given rhG-CSF (5 μg/kg/day s.c.) for 5 days, and examined before and after treatment. Basophil counts increased from 5 to 19×109/l (P<0.01). Total blood histamine increased from 80 to 160 μg/l (P<0.01), corresponding to a decrease in average basophil histamine content from 1.5 to 0.81 pg/cell (P<0.01). Isolated mononuclear cells showed a significantly decreased histamine release (HR) when stimulated with A23187 and grass. Whole blood experiments showed a similar decreased HR to grass and anti-IgE (P<0.01). However, we found an increase in total blood histamine. We conclude that treatment with rhG-CSF (1) increases the number of circulating blood basophils, (2) reduces the average histamine content per basophil, and (3) reduces the basophil releasability. These findings could be due to the mobilization of immature basophils from the bone marrow.

Cytokines modulate IgE-mediated histamine liberation from human basophils

The effect of recombinant human IL-1α, IL-1β, IL-2, IL-3, Il-4, IL-6, TNF, LT, IFNα, IFNγ, GM-CSF and M-CSF on human basophil histamine release induced by anti-IgE antibody was examined in seven healthy donors using washed whole blood and a glass microfibre assay. The blood was preincubated for 20 min with cytokines and incubated for another 60 min after addition of the antibody. IL-3, GM-CSF and M-CSF were found to enhance the IgE-mediated response by 60–80%, whereas the other cytokines did not affect the mediator release to any significant degree.

Histamine-releasing serum factors as a predictor of the outcome of insect sting reactions. Results from a multicentre study*

Cord blood cells were incubated (passively sensitized) with sera from 27 patients with previous systemic reactions to insect stings. Histamine release (HR) from these cells was measured following exposure to venom extracts at increasing concentrations. The aim was to see whether this parameter could predict more efficiently than RAST and skin test the outcome of a subsequent re‐sting. Results showed that HR from passively sensitized cells tended to reflect skin sensitivity and specific IgE levels. If patients were not re‐stung during the follow‐up period, HR from the passively sensitized cells frequently decreased whereas an increase was seen (in 6/13) when using sera collected after re‐sting. In conclusion HR from passively sensitized cord blood cells could not satisfactorily predict re‐sting reactions in the serum donors.

Granulocyte-macrophage colony-stimulating factor enhances basophil histamine release induced by non-IgE-dependent stimulators

Some cytokines are known to affect IgE-mediated basophil histamine release. The effect of the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF) on human basophil and masct cell histamine release was studies further. Blood leukocytes with approximately 2% basophils from 9 healthy individuals were incubated with recombinant human GM-CSF (0.3–30 U/ml) in combination with A23187 (10−7–10−6M) or washedStaphylococcus aureus whole bacteria (0.3–2.5 mg/ml). Histamine release was measured spectrofluorometrically. GM-CSF in itself did not induce histamine release. The addition of GM-CSF to cells stimulated with A 23187 caused a dose-dependent enhancement amounting to mean 70% at 3 U/ml and mean 170% at 30 U/ml (P<0.05). GM-CSF enhanced the bacteria-induced histamine release by 30% at U/ml and by 65% at 3 U/ml (P<0.05). The enhancement did not depend on cell-bound IgE or LPS contamination. In preliminary mast cell experiments with lung tissue we did not find an enancing effect of GM-CSF on IgE-mediated histamine release.

Measurement of histamine in nasal lavage fluid after challenge with anti-IgE antibody andStaphylococcus aureus

Experimentsin vitro have shown that bacteria induce histamine release and potentiate IgE-mediated histamine release. In the present study, these events were examined in allergic patients by anin vivo model using nasal challenge. Nasal spray with 56 mgStaphylococcus aureus triggered histamine release in the nasal cavity in 4 of 13 patients, whereas no response was obtained by 28 and 112 mg bacterium. These findings indicate that bacteria containing peptidoglycan may release histaminein vivo. To avoid allergens, we used anti-IgE antiserum. In six patients nasal challenge with anti-IgE (112000 IU) caused an, increased histamine level in the nasal fluid which was not obtained by a control preparation without anti-IgE antibodies. The IgE-mediated mediator release was potentiated by the bacterium in only 2 of 22 patients.