Nasal response to a single antigen challenge in patients with allergic rhinitis - inflammatory cell recruitment persists up to 48 hours.

BACKGROUND: Allergen challenge in some patients with respiratory allergy is followed by an early and a late reaction. OBJECTIVE: To evaluate the duration of mediator release and inflammatory cell recruitment during the late antigen-induced nasal response. METHODS: Eight patients with seasonal allergic rhinitis due to grass pollen underwent local challenge with the relevant allergen, a non-relevant allergen (Parietaria judaica), and nebulized saline solution. Nasal lavages were performed at baseline and 6, 24, 48, 72 h after challenge. Eosinophil cationic protein (ECP), leukotriene C4 (LTC4), leukotriene B4 (LTB4) myeloperoxidase (MPO) and prostaglandin D2 (PGD2) levels were radioimmunoassayed and histamine concentration was measured by an automated fluorometric method. RESULTS: Nasal challenge with the relevant antigen induced a response 6 h after stimulation, which subsided within 24 h. Eosinophilia, observed in the nasal lavages collected from 6 to 24 h after this challenge, was accompanied by ECP release. Neutrophilia were found in the nasal lavages collected from 6 to 24 h after challenge. The increase in neutrophil number correlated with MPO levels and LTB4 concentrations, but not with the intensity of nasal obstruction. Antigen challenge also induced significant recruitment of mononuclear cells 48 h after provocation. The challenge significantly raised histamine, but not PGD2, levels in the nasal lavages collected 6 h after provocation. A trend towards an increase in LTC4 levels in the nasal lavages collected 6 h after specific antigen challenge was also found. Nasal challenge with a non-relevant allergen or with saline solution did not cause either inflammatory cell recruitment or mediator release. CONCLUSION: Nasal challenge with the relevant antigen can induce a late response characterized by local accumulation of eosinophils, neutrophils and mononuclear cells persisting for 48 h and accompanied by release of ECP, MPO, LTB4 and histamine. These results indicate that a single antigen challenge in patients with allergic rhinitis causes prolonged inflammatory alterations which may contribute to the development of airway hyperreactivity.

N-acetyl-aspartyl-glutamic acid inhibits cellular recruitment and mediator release during the late allergen-induced nasal reaction.

OBJECTIVE: N-acetyl-aspartyl-glutamic acid (NAAGA) was effective in the treatment of allergic rhinitis, with an action on early allergen-induced nasal symptoms and mediator release. The aim of this study was to evaluate the clinical activity of NAAGA and its effects on the late antigen-induced reaction in the nose. METHODS: Ten patients with allergic seasonal rhinitis were included in this randomized double-blind crossover trial of a 6% wt/vol solution of NAAGA (daily dosage 84 mg) versus placebo (lactose). The drug and placebo were administered intranasally five times daily for 1 week, with a 2-week interval between treatments. RESULTS: Treatment with NAAGA, but not with placebo, significantly reduced the late antigen-induced nasal symptoms, mainly nasal obstruction. Eosinophil numbers in the nasal lavages collected 6 h and 24 h after challenge were significantly lower after NAAGA than after placebo. Active treatment also significantly reduced the neutrophil count 6 h after antigen challenge, and significantly lowered eosinophil cationic protein and myeloperoxidase levels in nasal lavages 6 h and 24 h after antigen challenge. CONCLUSION: These results indicate that treatment for 1 week with NAAGA can reduce the late antigen-induced reaction in the nose. This is accompanied by a reduction in eosinophil and neutrophil recruitment and release of eosinophil cationic protein and myeloperoxidase.

Reduced priming effect of interleukin 3 on IgE mediated basophil histamine release in patients with systemic sclerosis.

OBJECTIVE: To determine the capacity of interleukin 3 (IL-3) to induce and enhance basophil histamine release in patients with systemic sclerosis (SSc). METHODS: Leukocyte suspensions prepared by dextran sedimentation of peripheral venous blood were stimulated with anti-IgE (10 microg/ml), N-formyl-methionyl-leucyl-phenylalanine (fMLP, 1 microM), and IL-3 (0.1 to 10 ng/ml). The priming effect of IL-3 on anti-IgE and fMLP induced histamine release was evaluated. Histamine release was measured by an automated fluorometric method. RESULTS: No significant difference was found between patients with SSc (n = 12) and control subjects (n = 16) regarding spontaneous IL-3 and fMLP induced histamine release. IL-3 was a weak basophil agonist in both populations, since net histamine release did not exceed 10% of total histamine content in any case. Anti-IgE induced histamine release was lower in patients with SSc than in controls (13.09 +/- 4.8 vs 30.2 +/- 6.2%; p = 0.048). IL-3 enhanced anti-IgE and fMLP induced histamine release in a dose dependent fashion. However, the enhancement of anti-IgE induced histamine release by IL-3 was significantly lower in patients with SSc than in controls (p < 0.01 at 0.1 ng/ml IL-3; p < 0.05 at 1 and 10 ng/ml IL-3). In contrast, no difference was found between the 2 populations regarding the enhancement of fMLP induced histamine release by IL-3. CONCLUSION: Basophil response to anti-IgE and the priming effect of IL-3 on IgE mediated basophil histamine release are lower in patients with SSc than in controls. These alterations could be related to chronic activation of the IgE/basophil system in patients with SSc.

In vivo and ex vivo inhibitory effects of loratadine on histamine release in patients with allergic rhinitis.

BACKGROUND: The aim of this study was to evaluate the in vivo and ex vivo effects of the H1-antagonist loratadine on histamine release. METHODS: The study was designed as a double-blind, crossover trial. Ten patients with allergic rhinitis due to Dermatophagoides pteronyssinus were treated with loratadine (10 mg daily p.o.) and with placebo for 1 week, with a 2-week interval between the two treatments. Nasal lavages with saline solution were done before and after challenge with the relevant allergen at the end of treatments with loratadine and placebo. Venous blood was taken after treatments, and basophil histamine release induced by anti-IgE (10 microg/ml), N-formyl-methionyl-leucyl-phenylalanine (fMLP, 1 microM), and Ca2+ ionophore A23187 (1 microM) was evaluated by an automated fluorometric method. RESULTS: Treatment with loratadine attenuated early antigen-induced nasal obstruction, rhinorrhea, and itching. Nasal symptoms were accompanied by a significant histamine release in the nasal lavages collected 5 min after stimulation when the patients received placebo (median 4 ng/ml, range 1-28; P < 0.05). After treatment with loratadine, histamine release in the 5-min postchallenge lavages was almost abrogated (median 0.5 ng/ml, range 0-3; P < 0.01 vs placebo). Median anti-IgE-induced histamine release from basophils was 41.9% (range 27.8-79.2) after placebo and 30.0% (range 1.7-73.3, P < 0.05) after loratadine. Active treatment exerted an inhibitory effect also on basophil histamine release induced by fMLP and Ca2+ ionophore A23187. CONCLUSIONS: Treatment for 1 week with loratadine reduces allergen-induced nasal symptoms and inhibits in vivo and ex vivo histamine release in patients with allergic rhinitis.

Priming and inducing effects of interleukin-3 on histamine release from cord-blood basophils.

The effect of interleukin-3 (IL-3) on histamine release from cord and adult blood basophils were evaluated. Leukocyte suspensions, obtained from adult patients with respiratory allergy (n = 15), normal adult subjects (n = 15), and neonates with (n = 15) and without (n = 19) atopic disposition, were stimulated with anti-IgE, fMLP, and IL-3. IgE-mediated histamine release was significantly higher in adult patients, either allergic or normal, than in neonates with or without atopic disposition. A trend toward higher fMLP-induced histamine release was found in allergic adult subjects. IL-3 had a weak direct histamine-releasing activity in allergic adult subjects and in neonates, but not in normal adult donors. A significant enhancing effect of IL-3 on histamine release induced by anti-IgE was observed in neonates with and without atopic disposition and in normal adult subjects, but not in atopic adult patients. IL-3 exerted a priming effect also when basophils were stimulated with fMLP, without any significant difference between neonates and adult subjects. Passive sensitization with IgE-rich serum resulted in a significant increase in anti-IgE-induced, but not in IL-3-induced, histamine release from cord-blood basophils. In conclusion, IL-3 primes cord-blood as well as adult blood basophils for a consecutive anti-IgE- or fMLP-induced histamine release and its activity is not limited by the low density of membrane IgE in cord-blood basophils.

Defective inhibition of sodium on basophil histamine release in patients with allergic rhinitis and bronchial asthma.

The aim of this study was to evaluate whether Na+ exerts its inhibitory effect on basophil histamine release induced by immunoglobulin E (IgE)-dependent (anti-IgE) and IgE-independent (N-formyl-methionyl-leucyl-phenylalanine (FMLP), interleukin-3 (IL-3)) stimuli in patients with allergic rhinitis (n = 24) and allergic bronchial asthma (n = 10). Peripheral blood leucocytes were stimulated with anti-IgE, FMLP and IL-3 in the presence of high and low Na+ concentrations, and histamine release was measured using a fluorometric method. In standard Na(+)-containing medium, spontaneous and stimulated histamine release was higher in allergic patients (n = 34) (both rhinitic and asthmatic) than in healthy subjects (n = 41). Na+ removal from extracellular medium and its isosmotic substitution with choline chloride or with N-methyl-D-glucamine led to a significant increase of anti-IgE-, FMLP- and IL-3-induced histamine release in normal subjects, but not in allergic patients. The increase in Na+ concentration in the extra-cellular medium was accompanied by a dose-dependent decrease of anti-IgE- and FMLP-induced histamine release in normal subjects, but not in allergic patients. The behaviour of atopics and healthy subjects was different and not related to the basophil responsiveness to activating signals. The incubation of basophils from healthy subjects with sera from allergic patients did not have a significant influence on the inhibitory effect of Na+. Basophils from healthy subjects and atopic patients respond differently when stimulated in a low Na+ medium. The reduced sensitivity to the inhibitory effect of Na+ may contribute to basophil dysfunction in patients with respiratory allergy.

Enhancement of basophil histamine release by interleukin-3: reduced effect in atopic subjects.

The inducing and enhancing effects of interleukin-3 (IL-3) on basophil histamine release in patients with respiratory allergy (n = 28) and in normal subjects (n = 22) were compared. Leukocyte suspensions, prepared by dextran sedimentation, were stimulated with anti-IgE (1/5000), N-formyl-methionyl-leucyl-phenylalanine (FMLP, 1 microM), and IL-3 (0.1-10 ng/ml), and histamine concentration was measured by an automated fluorometric method. A trend toward higher histamine release after challenge with anti-IgE, FMLP, and IL-3 was found in atopic subjects. Preincubation of basophils with IL-3 resulted in a dose-dependent increase of anti-IgE- and FMLP-induced histamine release, with a more marked effect in nonatopic than in atopic subjects. Mean net enhancement of anti-IgE-induced histamine release by 10 ng/ml IL-3 was 2.5 +/- 5% in atopic subjects and 29.6 +/- 4.2% in nonatopic subjects (P < 0.001). The enhancement of FMLP-induced histamine release by IL-3 was 10.3 +/- 3.9% in atopic patients and 29 +/- 2.4% in nonatopic subjects (P < 0.01). In atopic subjects, a negative correlation was found between anti-IgE- or FMLP-induced histamine release and net enhancement by IL-3 (r = -0.45, P < 0.02; r = -0.48, P < 0.01, respectively). The results of this study indicate that in atopic subjects IgE-mediated histamine release can scarcely be enhanced by a basophil response modifier such as IL-3. It is conceivable that the frequent basophil stimulation in atopic patients leads to a reduced sensitivity to the enhancing effect of IL-3.

Impairment of the inhibitory effect of sodium on basophil histamine release in patients with systemic sclerosis.

It has been demonstrated that Na+ down-regulates IgE-dependent and IgE-independent histamine release from basophils of normal subjects. The aim of this study was to evaluate whether Na+ exerts its inhibitory effect on basophil histamine release in patients with systemic sclerosis (SSc). Peripheral blood leucocytes were stimulated with anti-IgE, n-formyl-methionyl-leucyl-phenylalanine (fMLP) and IL-3 in the presence of high and low Na+ concentrations, and histamine release was measured by a fluorometric method. The dose-response curves of histamine release induced by the above stimuli were similar in SSc patients (n=15) and in normal subjects (n=39). Na+ removal from the extracellular medium and its isosmotic replacement with choline chloride led to a significant increase of anti-IgE-and fMLP-induced histamine release in normal subjects, but not in SSc patients. In the former population, histamine release induced by an optimal dose of anti-IgE (1/5000) was 26.4+/-3.1% in high Na+ and 59.3+/-3.5% in low Na+ (mean+/-s.e.m., P<0.0001), whereas in the latter population mean histamine release was 20.4+/-5.1% in high Na+ and 15.8+or-2.9% in low Na+ (p NS). A similar trend was observed when basophils were stimulated with fMLP. Na+ exerted a dose-dependent inhibitory effect on anti-IgE- and fMLP-induced histamine release in normal subjects, but not in SSc patients. IL-3-induced histamine release from basophils of SSc patients was increased in a low-Na+ solution, but to a lesser extent when compared with normal controls. Therefore basophils from normal subjects and SSc patients behave in a different way when stimulated in a low-Na+ medium. The inhibitory effect of Na+ on basophil histamine release is impaired in SSc patients, and this abnormality could contribute to basophil dysfunction.

Nasal neutrophilia and release of myeloperoxidase induced by nasal challenge with platelet activating factor: different degrees of responsiveness in atopic and nonatopic subjects.

BACKGROUND: Nasal challenge with platelet activating factor (PAF) is able to induce local neutrophilia, with a different degree of responsiveness in atopic subjects and in nonatopic subjects. We investigated whether nasal accumulation of neutrophils induced by PAF is accompanied by the release of neutrophil-derived mediators. METHODS: Nasal lavages were performed before and after challenge with PAF (500 nmol), lyso-PAF (500 nmol), and saline solution in 10 patients with allergic rhinitis and 10 normal subjects to evaluate changes in neutrophil counts and the release of myeloperoxidase (MPO) and immunoreactive leukotriene B4. RESULTS: PAF caused neutrophilia, which appeared after 30 minutes in atopic subjects and after 3 hours in nonatopic subjects. Furthermore, when compared with saline insufflation, PAF caused a significant release of MPO in the nasal lavage fluids collected 30 minutes, 3 hours, and 24 hours after challenge in atopic subjects and 3 hours after challenge in nonatopic subjects, with higher values in the former than in the latter. Neutrophil counts correlated with MPO levels in the nasal lavages collected after PAF challenge. A lower degree of neutrophilia was found 3 hours after stimulation with lyso-PAF in both groups of subjects, with a marginal release of MPO in atopic subjects only. No significant increase of immunoreactive leukotriene B4 levels in nasal lavages was found after challenge with either PAF or lyso-PAF. CONCLUSION: These results indicate that PAF-induced neutrophilia in the nose is accompanied by the release of MPO, which appears earlier and is more marked in atopic subjects than in nonatopic subjects.

IL-3-induced histamine release from human basophils. Dissociation from cationic dye binding and down-regulation by Na+ and K+.

The effect of recombinant human IL-3 on human basophils from normal subjects was evaluated by the decrease of toluidine blue-positive basophils (TB+) and by histamine release. IL-3 (0.001 to 100 ng) caused the decrease of TB+ without concomitant histamine release, whereas anti-IgE-induced TB+ decrease was accompanied by histamine release. IL-3 enhanced both anti-IgE-induced TB+ decrease and histamine release. IL-3-induced TB+ decrease was dose- and Ca2+-dependent and related to the time of incubation (detectable after an incubation of 5 min and maximal after incubation of 2 h). When extracellular Na+ was replaced isosmotically with choline, N-methyl-D-glucamine, or glucose, histamine release also was observed after direct stimulation with IL-3. The effect was dose dependent, related to the time of incubation (detectable after 30 min and maximal after 60 min), and required extracellular Ca2+. The increase in extracellular Na+ or K+ concentrations was accompanied by a reduction of histamine release, with a more marked effect on IL-3- than on anti-IgE-induced histamine release. In line with these results, the Na+ ionophore gramicidin D, which increases Na+ influx, and the K+ channel blocker 4-aminopyridine, which decreases K+ efflux, dose-dependently inhibited anti-IgE- and IL-3-induced histamine release. The inhibitory effects on Na+ and K+ were slightly additive, suggesting an action via the same pathway, which most probably is membrane potential. These results indicate that: 1) IL-3 can induce TB+ decrease without concomitant histamine release, 2) basophils from normal subjects can release histamine on challenge with IL-3 once the inhibitory effect of Na+ is removed, and 3) Na+ and K+ down-regulate IL-3 as well as anti-IgE-induced histamine release.

Antiallergic activity of loratadine: inhibition of leukotriene C4 release from human leucocytes.

The H1 antagonist loratadine has the capacity to inhibit histamine release from human basophils. The aim of this study was to investigate whether loratadine can also inhibit leukotriene C4 (LTC4) release from human leucocytes. Basophil-enriched mononuclear cell suspensions were prepared by centrifugation of peripheral venous blood (n = 10) on discontinuous Percoll gradients. Leucocytes were stimulated with anti-IgE, N-formylmethionyl-leucyl-phenylalanine (FMLP) and Ca2+ ionophore A23187; immunoreactive (i) LTC4 release in the cell supernatant was measured by a competitive radioimmunoassay and histamine release was evaluated by an automated fluorometric technique. Loratadine, in the concentration range of 1-50 microM, exerted a dose-dependent inhibitory effect on IgE-mediated and IgE-independent histamine and iLTC4 release. The concentrations inhibiting 50% of histamine release were 30 microM (anti-IgE), 27 microM (FMLP) and 19 microM (Ca2+ ionophore A23187). The concentrations inhibiting 50% of iLTC4 release were 2.3 microM (anti-IgE). 11 microM (FMLP) and 1.7 microM (Ca2+ ionophore A23187). The inhibitory activity on iLTC4 release was optimal after preincubation for 2 h at 37 degrees C, and was no longer evident when leucocytes were stimulated 2 h after cell washing. Increased extracellular Ca2+ concentrations reduced the inhibitory activity of loratadine. These results indicate that loratadine has the capacity to inhibit the release of preformed and newly generated mediators from human basophil-enriched mononuclear cell suspensions.

Ionic regulation of human basophil releasability. III. Effects of Na+ and Ca2+ on histamine release induced by different stimuli.

The effects of Na+ and Ca2+ ions on histamine release from human basophils stimulated by anti-IgE, N-formyl-methionyl-leucyl-phenylalanine (FMLP), 4 beta-phorbol 12-myristate 13-acetate (PMA) and Ca2+ ionophore A23187 were evaluated. Isosmotic replacement of Na+ in the extracellular medium with the nonpermeant Na+ analogue choline+ or with glucose led to a significant increase in anti-IgE- (1/5000: 43.7 +/- 7.3% in high Na+ vs 68.9 +/- 7.3% in low Na+, mean +/- SEM, n = 8, P < 0.001), FMLP- (1 microM: 37.9 +/- 2.3% vs 49.5 +/- 4.3%, n = 8, P < 0.01) and PMA-(160 nM: 12.7 +/- 0.9% vs 27.3 +/- 4.3%, n = 8, P < 0.05) induced histamine release, whereas A23187-induced histamine release was reduced (1 microM: 90.4 +/- 2.4% vs 45.4 +/- 3.4%, n = 8, P < 0.0001). The progressive increase in extracellular Na+ concentration was accompanied by a decrease of basophil response to anti-IgE, FMLP and PMA; in contrast, A23187-induced histamine release was up-regulated by Na+. The Na+/H+ exchanger monensin, in the concentration range of 10(-8)-10(-4) M, exerted a dose-dependent inhibitory effect on anti-IgE-, FMLP- and PMA-induced histamine release, but not on A23187-induced histamine release. Extracellular Ca2+ up-regulated the histamine release induced by all the above stimuli. Removal of extracellular Na+ lowered the requirement of extracellular Ca2+ for anti-IgE, FMLP- and PMA-induced histamine release. In contrast with previous observations showing that Na+ supports histamine release from rat peritoneal mast cells and rat basophilic leukaemia cells, these results indicate that Na+ strongly inhibits histamine release from human basophils stimulated by anti-IgE, FMLP and PMA, whereas it enhances Ca2+ ionophore A23187-induced histamine release. The effects of Na+, which are probably related to modulation of membrane potential and/or intracellular pH, vary depending on the cell type and the stimulus employed for cell activation.

Inhibitory effect of the H1 antagonist loratadine on histamine release from human basophils.

Loratadine is a powerful H1 antagonist commonly employed in the treatment of allergic disorders. The present study was performed to investigate whether loratadine, in addition to anti-H1 activity, is able to modulate histamine release from human basophils. Leukocyte suspensions were prepared by dextran sedimentation of peripheral venous blood drawn from 10 normal subjects. Leukocytes were stimulated with anti-IgE (1/5,000), N-formyl-methionyl-leucyl-phenylalanine (FMLP; 10 microM) and the Ca2+ ionophore A23187 (1 microM), and histamine release in the cell supernatants was measured by an automated fluorometric method. Loratadine, at concentrations ranging from 1 to 50 microM, exerted a dose-dependent inhibitory effect on IgE-mediated and IgE-independent histamine release. The concentrations inhibiting 50% of histamine release were 30 microM (anti-IgE), 29 microM (FMLP) and 24 microM (Ca2+ ionophore A23187). The inhibitory activity of loratadine was optimal after incubation for 2 h at 37 degrees C and the effect of the drug was no longer evident when leukocytes were stimulated 2 h after cell washing. Increased extracellular Ca2+ concentrations reduced the inhibitory activity of loratadine, indicating that external Ca2+ and loratadine have antagonistic effects on basophil histamine release. These results indicate that loratadine, in addition to H1 receptor blocking activity, has the capacity to inhibit histamine release from human basophils.

Nasal eosinophilia induced by PAF-acether is accompanied by the release of eosinophil cationic protein.

It has been demonstrated that platelet-activating factor (PAF)-acether can induce nasal neutrophilia and eosinophilia, with a different degree of responsiveness in atopic and in nonatopic subjects. The aim of this study was to evaluate whether PAF can also induce the release of secondary mediators in the human nose. Ten patients with allergic rhinitis and 10 normal subjects underwent nasal challenge with PAF (500 nmol), lyso-PAF (500 nmol) and saline solution. Nasal lavages were performed before and after challenge to evaluate changes in nasal cytology and release of histamine, immunoreactive leukotriene (iLT) C4 and eosinophil cationic protein (ECP). PAF caused neutrophilia and eosinophilia, which appeared earlier in atopic than in nonatopic subjects (30 min vs 1 h), and peaked 3 h after challenge in both groups. Lyso-PAF caused mild neutrophilia, which appeared 3 h after challenge in both groups; an increase in eosinophil counts was observed 3 h after challenge in atopic subjects, but not in nonatopic subjects. PAF insufflation caused a significant release of ECP in nasal lavage fluids 30 min and 3 h after challenge in atopic subjects, and 3 h after challenge in nonatopic subjects. ECP levels in the nasal lavages collected 30 min and 3 h after challenge with PAF were higher in atopic than in nonatopic subjects. Eosinophil counts correlated with ECP levels in the nasal lavages collected 30 min after PAF challenge in atopic subjects. Nasal challenge with lyso-PAF did not provoke any release of ECP. No significant increase of histamine and iLTC4 levels in nasal lavages was found after challenge with either PAF or lyso-PAF.(ABSTRACT TRUNCATED AT 250 WORDS)

Nasal neutrophilia and eosinophilia induced by challenge with platelet activating factor.

BACKGROUND: It has been demonstrated that in vitro platelet activating factor-acether (1-O-hexadecyl-2-acetyl-sn-glycero-3-phosphorylcholine; PAF) has the capacity to attract eosinophils and neutrophils. We investigated whether the same applies when human nasal airways are stimulated with PAF. METHODS: Symptom scores and cytologic changes in nasal lavage fluids were evaluated in 10 atopic and 10 nonatopic subjects after nasal challenge with PAF, its precursor and metabolite, 1-O-hexadecyl-sn-glycero-3-phosphorylcholine (lyso-PAF), or saline solution. RESULTS: Nasal obstruction was reported by all the atopic subjects and seven of the 10 nonatopic subjects after nasal challenge with PAF; other symptoms such as rhinorrhea, itching, and sneezing were generally mild. PAF induced neutrophilia, which appeared after 30 minutes in atopic subjects and after 1 hour in nonatopic subjects, and peaked at 3 hours in both. Less neutrophilia was found 3 hours after stimulation with lyso-PAF in both groups of subjects. PAF also induced eosinophilia, which appeared after 30 minutes in atopic subjects and only after 3 hours in nonatopic subjects. An increase in eosinophil counts was observed 3 hours after lyso-PAF stimulation in atopic but not in nonatopic subjects. CONCLUSION: PAF can attract neutrophils and eosinophils into human nasal airways; however, the recruitment of inflammatory cells is more rapid in atopic than in nonatopic subjects, suggesting a different degree of responsiveness to PAF challenge in the two groups of subjects.

Ionic regulation of human basophil releasability. II. Non-releasing basophils are converted into releasing basophils in a low-Na+ medium.

The effects of different extracellular Na+ and Ca2+ concentrations on histamine release from human basophils were investigated. Isosmotic replacement of extracellular Na+ either with choline+, a non-permeant Na+ analogue, or glucose significantly increased spontaneous and anti-IgE-induced histamine release. Basophils from 12 of 49 normal subjects, which were found not to release histamine upon challenge with an optimal dose of anti-IgE in a 135 mM NaCl buffer, were converted into releasing basophils when stimulation with anti-IgE was performed in a low-Na+ medium. The increase in Na+ concentration in the extracellular medium was accompanied by a reduction in the magnitude of basophil response to anti-IgE, which was significantly more pronounced in non-releasers than in releasers (per cent inhibition by 70 mM NaCl 75.5 +/- 3.2 vs 43.5 +/- 9.0, P < 0.01). At higher Na+ concentrations a progressive and almost complete abrogation of histamine release was observed in non-releasers, but not in releasers (maximal per cent inhibition at 140 mM NaCl 97.3 +/- 1.3 vs 50.4 +/- 8.6). The Na+/H+ exchanger monensin had a dose-dependent inhibitory effect on anti-IgE-induced histamine release, and the concentration inhibiting 50% of histamine release was 1.5 x 10(-7) M. When basophils were challenged in the presence of different Na+ and Ca2+ concentrations, it was shown that the two cations have antagonistic effects, which is to say that they down-regulate and upregulate histamine release, respectively. Moreover, the requirement of extracellular Ca2+ was lowered in a low-Na+ medium.(ABSTRACT TRUNCATED AT 250 WORDS)

Ionic regulation of human basophil releasability. I. Inhibitory effect of copper.

The effects of copper (CuSO4 and CuCl2) on in vitro histamine release from human basophils stimulated by anti-IgE and Ca2+ ionophore A23187 were evaluated. Both CuSO4 and CuCl2 caused a dose-related inhibition of histamine release, which was more pronounced on anti-IgE- than on Ca2+ ionophore-induced histamine release. The concentration which produced 50% inhibition of anti-IgE-induced histamine release was 1.3 microM for CuSO4 and 1.5 microM for CuCl2; the maximal inhibition of Ca2+ ionophore-induced histamine release was 33% for CuCl2 (4 microM) and 51% for CuSO4 (16 microM). The inhibitory effect on anti-IgE-induced histamine release persisted also when extracellular Cu2+ was removed by cell washing before stimulation, whereas no inhibition of Ca2+ ionophore-induced histamine release was found when extracellular Cu2+ was removed. The activity of Cu2+ was independent of any effects of deuterium oxide and colchicine, two agents known to interact with microtubules. Increased extracellular Ca2+ concentrations reduced the inhibitory effect of CuCl2 on Ca2+ ionophore-induced histamine release, and Schild plot analysis demonstrated that Cu2+ ions are competitive antagonists of Ca2+ ions. These results indicate that Cu2+ ions in the micromolar range down-regulate anti-IgE- and Ca2+ ionophore-induced histamine release. Since Cu2+ concentration in human plasma is in the micromolar range (30 microM with 10-30% of free Cu2+), it is conceivable that Cu2+ ions contribute to the in vivo regulation of histamine release from human basophils.