Anti-IgE-Induced Histamine Release from Human Basophilic Leukocytes: Inhibition Depends on Nature and Concentration of Inhibitor and Secretagogue

Histamine release from human basophilic leukocytes was induced by increasing concentrations of anti-IgE in the presence of various concentrations of 2-deoxyglucose (2-DOG), the histamine H2-receptor agonist dimaprit, theophylline, or enprofylline (a new antiasthmatic xanthine derivative). The results show that the degree of inhibition produced by each agent differed with the concentration of anti-IgE used and with the nature and concentration of the inhibitor. These data indicate that great care should be used when characterizing an inhibitor of mediator release by simply giving a figure for the per cent inhibition of release observed in its presence.     

Inhibitory Effect of Calcium Antagonists on Histamine Release from Human Leukocytes

A study was made of the influence of calcium antagonists on human basophil histamine release induced in vitro by specific antigen, anti-IgE or the calcium ionophore A23187. Both verapamil, nifedipine, and nimodipine were found to inhibit the release, and a similar effect was also observed after peroral administration of verapamil and nifedipine. The inhibitory effect of the drugs on histamine release seems to depend on interaction with calcium at different sites. The anti-allergic effect might explain the improvement found with calcium antagonists in exercise-induced asthma.     

Inhibitory Effect of Cyclosporin A on Histamine Release from Human Leukocytes and Rat Mast Cells

The influence of cyclosporin A (CyA) on human basophil histamine release induced in vitro by specific antigen, anti-IgE, calcium ionophore A23187, or concanavalin A (Con A) was studied. CyA inhibited the release induced by these four stimulators. It is suggested that the drug acts directly on the target cell, since similar effect was obtained with isolated peritoneal rat mast cells. The basophil histamine release was not changed by a non-immunosuppressive cyclosporin derivate.     

Basophil Histamine Release in Cord Blood Regulatory Role of IgE

Thirty-two cord blood samples were studied for histamine releasing capability by using a sensitive glass microfibre-based histamine analysis. Histamine was obtained after challenge with anti-IgE in 24 of the 32 samples. However, the net release in cord blood was only 25% of that in adult blood and no relationship was found between histamine release response, total IgE in cord plasma, and a family history of atopic diseases. The low histamine release in cord blood seemed to be associated with the immunological IgE receptor complex activation and not with an immature basic cell function, since the calcium ionophore A23187 which bypasses the receptor complex induced identical histamine release curves in cord and adult blood. Furthermore, when comparing the results of passive sensitization of basophils from new-born and adult persons, the new-born basophils possessed a significant fraction of free IgE receptors, whereas in adults most of the receptors were occupied by IgE.     

3H-Histamine Release from Human Leukocytes

A rapid, simple, and inexpensive method for large scale screening of patients suspected of type I allergy has been developed. The method is based on in vitro incorporation of 3H-histamine in the leukocytes of the patient, whereafter release of labelled histamine is measured after provocation of the cells with the suspected allergen. The new method was compared with the conventional basophil histamine release technique by in vitro provocation of six asthmatic patients under suspicion of type I allergy against animal dander, house dust, and mite, and an almost identical release of histamine was observed in both assays.     

Influence of Bacterial Endotoxins on Basophil Histamine Release Potentiation of Antigen- and Bacteria-Induced Histamine Release

The histamine-releasing capability of lipopolysaccharides (LPS) was examined in human leukocyte suspensions. LPS alone did not release histamine, but was found to enhance the histamine release caused by anti-IgE. Also the IgE-mediated histamine release caused by specific antigens (allergens or bacteria) in sensitized individuals was enhanced by LPS. The potentiating effect of LPS was observed in grass pollen and dog dander allergic patients as well as in patients sensitized to E. coli or Staph. aureus bacteria. No potentiation was obtained by exposure to unspecific allergens or bacteria to which the persons were not sensitized. Bacteria can release histamine by immunological or nonimmunological mechanisms, and only the immunological histamine release was found to be potentiated by LPS. It is speculated that endotoxins reinforce release of histamine caused by allergens in allergic patients or by bacteria in persons sensitized to these microorganisms.     

Influence of Neuraminidase and N-Acetylneuraminic Acid on Basophil Histamine Release in Vitro

Since N-acetylneuraminic acid (NANA) in cell membrane glucocalyx mediates or modulates a variety of actions, such as mediator release, we examined a possible modulating role of this amino sugar in histamine release from human basophil leukocytes. Removal of NANA from the cell membrane by the enzyme neuraminidase caused a dose-dependent histamine release. Removal of smaller amounts of NANA enhanced histamine release induced by anti-IgE, Concanavalin A and the calcium ionophore A23187, and reduced the interval between addition of antigen and initiation of histamine release. Pretreatment with free NANA had the opposite effects, i.e. a diminished and delayed maximal histamine release. The hypothesis that NANA in the cell membrane modulates the cellular response to stimulation was further substantiated by demonstrating that the altered response was reflected by a change in the sensitivity of the cell to extracellular calcium. NANA in the cell membrane glucocalyx thus seems to modulate the basophil response to stimulation by modulating transmembraneous calcium transport.     

The Glucocorticosteroid, Budesonide, Partially Blocks Histamine Release from Human Lung Tissue in Vitro

IgE-receptor dependent, but not A23187-induced, histamine release from passively sensitized chopped human lung tissue, or from a dispersed lung cell population obtained from the tissue after enzymatic digestion, is reduced after incubation overnight of cells/tissue with the glucocorticosteroid budesonide (10(-7) M). Since the inhibitory effect of budesonide is reduced in the continuous presence of diluted reagin-rich serum used for passive sensitization, but not in the presence of heat-inactivated serum, it is suggested that the glucocorticosteroid acts by reducing the binding of IgE-antibody to the target cell(s).     

Histamine Release from Human Leucocytes by IgG4 Subclass in the Sera of Allergic Children

Our studies on histamine release from normal washed leucocytes sensitised with sera of children allergic to various inhaled and ingested allergens show that besides IgE, IgG4 present in these sera was capable of sensitising leucocytes of normal donors, and these leucocytes released histamine on challenge with anti-IgG4. By contrast, antisera of other subclasses of IgG released very small amounts of histamine from sensitised leucocytes. A discordant correlation between skin tests and RAST IgE was observed in some children. Significantly greater amounts of histamine were released from normal leucocytes sensitised with serum from these children when challenged with anti-IgG4 compared to anti-IgE. These studies indicate that IgG4 merits further study as a reaginic marker in atopic diseases of the children with possible prognostic significance.     

Complexity of Lectin-Mediated Reactions in Bacteria-Induced Histamine Release

We have earlier suggested that bacteria-induced histamine release is caused by different mechanisms, including allergic and non-immunological mechanisms, and that the latter probably depends on lectin-mediated reactions. Two possibilities of lectin-mediated reactions were examined in this study, bacterial surface lectins bind to sugars on the basophil cell membrane leading to histamine release, and the reverse reaction where bacterial aminosugars react with lectins on the basophil cell surface. In the bacterial histamine release caused by the Staph. aureus strain Wood 46 it was possible to demonstrate a reverse reaction, but not a bacterial lectin-mediated reaction. The reaction seems to be complex, as lower concentrations of sugars might potentiate the release of histamine by binding to the target cell or bacteria, while the release is inhibited by higher concentrations.     

Effect of nitrendipine on histamine release from human basophil leukocytes

The effect of the new calcium antagonist nitrendipine on in vitro basophil activation was evaluated in 10 subjects. The histamine release induced by calcium ionophore A23187, f-met peptide and anti-IgE was inhibited, in a dose-dependent fashion, by nitrendipine in the concentration range of 1-100 microM. The activity of this calcium antagonist seems complex and related to an interference with calcium at multiple sites. At concentrations higher than 200 microM, nitrendipine causes histamine release from basophil leukocytes. This histamine secretion is likely to be due to a cytotoxic effect, since it is associated with an increase in LDH levels in the cell supernatant.     

Evidence for a Glucocorticoid Receptor in Human Leukocytes

The glucocorticoid uptake in vitro by human periferal leukocytes was studied. The uptake showed 2 main components, one saturable and one non-saturable. The saturable component was compared with the uptake by the specific glucocorticoid receptor in rabbit granulocytes. The similarities with the rabbit receptor in structural specificity, time course of uptake at 37° C, sensitivity to metabolic inhibition by PCMS and the physiological concentration for half saturation indicate that the saturable component corresponds to a specific glucocorticoid receptor. Cells from chronic lymphatic leukemia and chronic myeloic leukemia were also studied. Only the former had a saturable glucocorticoid uptake.     

Regulation of histamine release from human basophil leucocytes: role of H1, H2 and H3 receptors

A novel class of histamine receptors (H3), controlling histamine synthesis and release, was described in rat and human brain and peripheral nerve endings. The present study was undertaken to evaluate whether H3 receptors contribute to the regulation of histamine release from human basophils. Basophil leucocytes were incubated with a H3 antagonist (thioperamide; concentrations ranging from 1 nM to 10 microM) or with a H3 ((R)alpha methyl-histamine; concentrations ranging from 1 to 100 mM), and subsequently were stimulated with optimal doses of anti-IgE and formyl-methionyl-leucyl-phenyl-alanine (f-met peptide). No significant modifications of histamine release were observed after incubation either with the H3 agonist or with the H3 antagonist. By contrast, a H2 antagonist (cimetidine; concentrations ranging from 1 to 100 microM) exerted a dose-dependent enhancing effect on anti-IgE- and, to a lesser extent, on f-met peptide-induced histamine release. A H1 antihistamine (chlorpheniramine; concentrations ranging from 100 nM to 1 microM), at the highest concentration employed, displayed an inhibitory activity on IgE-dependent and IgE-independent histamine release. Exogenous histamine was shown to exert a dose-dependent inhibitory effect on two-staged anti-IgE-induced histamine release. Taken as a whole, these results suggest that H3 receptors are not involved in the regulation of histamine release from human basophils; by contrast, H2 receptors participate in controlling histamine release from human basophils, as previously demonstrated by other authors.     

Effect of Cimetidine on Exogenous Histamine Inhibition of Histamine Release in Vivo

We previously reported that exogenous histamine inhibits in vivo histamine release and eosinophil accumulation in ragweed-challenged skin sites of sensitive human subjects. The mechanism(s) involved were unclear. In this study, we repeated similar approaches in four of the same subjects pretreated for 3 days with cimetidine, an H2 receptor antagonist. The pattern of exogenous histamine effects was now different in that local exogenous histamine (50 ng/ml) did not significantly alter ragweed-induced mast cell alteration, histamine release, or the degree of eosinophil accumulation in skin challenge sites. These findings suggest that the observed exogenous histamine inhibitory effects may be mediated through the H2 receptor.     

Role of Phospholipase A2 Activation in Histamine Release from Human Basophils

The present experiments were undertaken to investigate the role of phospholipase A₂ (PLA₂) activation in histamine release from human basophils. A PLA₂ inhibitor, P-bromophenacyl bromide (BPB), inhibited IgE-mediated anti-IgE-induced histamine release from human basophils with a concentration of drug required to produce 50% inhibition (IC₅₀) of 1.5 × 10^?6 m when leukocytes were preincubated with this agent for 15 min. Histamine release induced by calcium ionophore A23187 and formyl-l-methionyl-l-leucyl-l-phenylalanine was also blocked by BPB with IC₅₀ of 4.1 × 10^?6 m, and 3.5 × 10^?6 m, respectively. A PLA₂ activator, 12–0-tetradecanoylphorbol-13-acetate (TPA) caused basophil histamine release with a dose-dependent fashion. BPB inhibited TPA-induced histamine release (IC₅₀: 2.5 × 10^?6 m). However, another PLA₂ activator, melittin, and PLA₂ did not release histamine through non-cytotoxic mechanisms. Collectively, these results suggest that PLA₂ activation plays a central role in histamine release from human basophils via generation of lysophosphatidylcholine or products of the lipoxygenase pathway of arachidonic acid metabolism.     

Passive sensitization of basophil leukocytes from a non-atopic adult by plasma from allergic children

Basophil leukocytes from a non-atopic donor, who responded well to anti-IgE, were depleted of their native membrane-bound IgE by acid treatment and passively sensitized with plasma containing either Phleum pratense-, Dermatophagoides pteronyssinus- or dog dander- specific IgE obtained from 18 allergic children. Histamine release was then performed on the passively sensitized cells and the results were compared with those of bronchial provocation test (BPT), allergen-specific serum IgE (RAST), skin prick test (SPT), and conventional histamine release test (HR). A high coincidence rate was found between BPT, RAST and histamine release after passive sensitization (HR-PS), but compared to HR, it was lower. This could be because several of the patients had non-responding basophils (i.e. no release after challenge with anti-IgE) in the conventional histamine release assay. The lower rate was not related to a lack of antigen-specific IgE, since after passive sensitization of basophils, anti-IgE and allergen provocation could induce release. It is concluded that plasma from allergic children with non-responding basophil leukocytes contain antigen-specific IgE capable of binding to Fc-receptors on the basophils of a non-atopic donor. In addition it was found that the plasma could change the cell reactivity (maximal histamine release) of the donor cells, since the amount of histamine released varied according to the plasma used for passive sensitization. The lack of histamine release response in some patients could be because their own membrane-bound IgE is unable to induce mediator release or, more likely, activation of one or more of the subcellular steps involved in the release is impaired.     

Sustained Inhibition of Antigen-Induced Histamine Release from Human Lung by the β2-Adrenoceptor Agonist Terbutaline

Antigen-induced histamine release from passively sensitized human lung tissue was inhibited in the presence of the β₂-adrenoceptor agonist, terbutaline. A sustained and statistically significant suppression was detected in the concentration interval 3 × 10⁻⁸-1 × 10⁻⁶ M. Fifty per cent inhibition IC₅₀, was obtained at an interpolated concentration of 5.3 × 10⁻⁸± 0.4 × 10⁻⁸ M ( n = 13), when the histamine secretion was elicited with optimum concentration of antigen. Histamine release induced with a suboptimum concentration of antigen was inhibited to a greater extent than release initiated with optimum concentration. The data in the present investigation support the concept that terbutaline-induced inhibition of mediator release from human lung tissue can contribute to the clinical effectiveness of the drug during treatment of allergic asthma.     

Effect of interleukin 2 on basophil histamine release

Accumulating evidence suggests a link between immediate hypersensitivity and cellular immunity. In this study, we examined the effect of interleukin 2 (IL-2) on basophil histamine release. Histamine-releasing activity of IL-2 was very weak with % histamine release of 2.9 +/- 1.3 (mean +/- SEM, n = 9) at 1:12 dilution. IL-2 at 1:1200 dilution slightly inhibited anti-IgE-induced histamine release by 22.4 +/- 18.6% (P greater than 0.05). There was a significant potentiation of release at 1:12 dilution of IL-2 with % enhancement of 78.7 +/- 42.2 (P less than 0.05). IL-2 enhanced the calcium ionophore A23187-induced histamine release in a dose-dependent fashion. IL-2 at 1:12 dilution significantly potentiated release by 28.8 +/- 6.3% (P less than 0.05). There was a slight suppression of formyl-methionyl-leucyl-phenylalanine (FMLP)-induced histamine release at 1:1200 dilution with % inhibition of 23.4 +/- 7.4 (P greater than 0.05). At 1:12 dilution, IL-2 significantly potentiated FMLP-induced release by 73.7 +/- 41.6% (P less than 0.05). Recombinant IL-2 (RIL-2) augmented anti-IgE-induced histamine release with a significant enhancement at 200 units/ml. Conventional IL-2 was more potent than RIL-2 in enhancing release. These results indicate that IL-2 enhances basophil histamine release and some part of the effect of IL-2 on basophils is derived from other factors contained in conventional IL-2.     

Anti-Anaphylactic and Bronchodilating Action of a Beta-Adrenoceptor Stimulator, KWD 2131, in Human Lung Tissue

The beta-adrenoceptor stimulating agent KWD 2131 has been studied with regard to inhibitory effect on allergen-induced histamine release from passively sensitized human lung tissue and relaxing effect on contracted small (diameter = 1 mm) and large (diameter greater than 3 mm) isolated human bronchi. The dose for 50% inhibition of the allergen-induced histamine release was 2 x 10(-11) M. The potency of KWD 2131 was approximately 0.15 times that of terbutaline and 0.05 times that of isoprenaline in this respect. The bronchodilating potency of KWD 2131 was 0.02-0.03 times that of terbutaline. The data indicate that KWD 2131 is a compound with preferably anti-anaphylactic potency in the human lung.     

Inhibitory Effect of MY-1250 on Histamine Release from Rat Peritoneal Mast Cells and Guinea Pig Lung Fragments: The Elucidation of the Mechanism

When the effect of MY-1250 (5, 6-dihydro-7, 8-dimcthyl-4, 5dioxo-4 H-pyrano [3, 2-c] quinolinc-2-carboxylic acid) on histamine release from rat peritoneal mast cells induced by compound 48/80 was studied, MY-1250 caused a significant inhibition of histamine release at concentrations higher than 3 _pM. Furthermore, the compound inhibited not only 45C _a uptakc into the mast cells but also Ca²⁺ release from thc intraccllular Ca store at a concentration of 10 _pM in both cases. By contrast. MY-1250 did not affect either histarnine release from permeabilized mast cells induced by TPA, IP3 and GTPyS or Ca²⁺ release from the endoplasmic reticulum induced by IP3. In the chopped lung preparations, MY-1250 at doses of 10 and 100 _pM caused a significant inhibition in histarnine release from thc pieces of actively scnsitizcd guinea pigs exposed to antigen and simultaneously prevented a decrease in intracellular CAMP contents taking place in association with antigen-antibody reaction. No significant changes were effected by MY-1250 in a-chymotrypsin activity and phospholipasc A2 activity. Also, no antagonistic effects on LTD4 and PAF were observed.