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.     

Clinical significance of specific IgE determination on nasal secretion

The clinical use of RAST on the nasal secretions was investigated in seventeen atopic patients, with asthma or rhinitis, who had shown at a first diagnostic screening, some difficulties in the identification of the responsible allergen(s). The results of the skin tests, of the RAST on the serum and on the nasal secretions and of the specific provocation test (bronchial or nasal) were compared. In some cases the basophil degranulation test was performed. The results of the RAST on the nasal secretions were in perfect agreement with the provocation test. The skin tests and the RAST on the serum showed many discrepancies, particularly for Dermatophagoides, epidermal derivatives of cat and dog and moulds, and less frequently for Graminaceae and other pollens. It is concluded that RAST analysis on nasal secretions is useful in clinical diagnosis of allergy especially for Dermatophagoides, epidermal derivatives and moulds. Most false positive results were observed with the RAST on serum; in fifteen cases it was positive, while all the other tests, basophil degranulation test included, were negative. The data suggest that IgE may have a low affinity for basophil receptors.     

Plasma of normal, but not atopic persons reducing basophil degranulation induced by anti-IgE

The response to anti-IgE serum of basophils from allergic and normal persons in the presence of whole plasma or as washed cells in Tyrode solution was examined to detect any inhibiting activity of human plasma. A factor reducing the potential of anti-IgE serum to degranulate basophils was present in plasma of normal but not of allergic persons. It is considered that this property of plasma could contribute to homeostatic control in immediate hypersensitivity.     

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 ± 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.     

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 CV²⁺ 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 l.5 × 10^?7M. When basophils were challenged in the presence of different Na⁺ and C²⁺ 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. These results suggest that Na⁺ and Ca⁺ ions contribute with opposite effects to the modulation of basophil response to anti-IgE and that non-releasing basophils are converted into releasing basophils in a low-Na ⁺ medium.     

Correlation of the specific IgE in serum and nasal secretions with clinical symptoms in atopies

In an unselected population of 133 young adults studied by prick testing to common allergens three groups were identified: eleven subjects with positive skin test responses and clinical symptoms of allergy; ten subjects only with positive skin tests and the remainder with negative skin tests. All subjects with positive skin tests (with and without symptoms) were studied by RAST on the serum and nasal secretions. Specific and non-specific bronchial provocation tests (BPT) were also carried out. The serum RAST was positive in all subjects with positive skin tests, and there was good correlation between high levels of circulating specific IgE and the presence of clinical symptoms. The RAST of nasal secretions was negative in most symptom-free subjects and as a diagnostic lest it was slightly better than the serum RAST. BPTs with extracts of the relevant allergens caused bronchospasm in every subject with a positive nasal secretion RAST. Only two subjects out of fifteen with a positive response were clinical asthmatics. Our results cast doubt on the clinical relevance of the BPT as it is usually conducted.     

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 1–50μM, 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 μM (anti-IgE), 27μM (FMLP) and 19μM (Ca²⁺ ionophore A23187). The concentrations inhibiting 50% of iLTC₄ release were 2–3 μM (anti-IgE). 11 μM (FMLP) and 1.7μM (Ca²⁺ ionophore A23187). The inhibitory activity on iLTC₄ release was optimal after preincubation for 2h at 37°C, and was no longer evident when leucocytes were stimulated 2h 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.     

Study of the effects of paf-acether on human nasal airways

In 6 normal subjects and 6 patients with allergic rhinitis, nasal response to insufflation of paf-acether (paf, platelet-activating factor), lyso-paf and histamine was evaluated. Nasal challenge with paf, at doses of 300 and 600 nM, induced nasal obstruction, associated with an increase in nasal airway resistances, measured by anterior passive rhinomanometry. Maximum increase in nasal airway resistance was observed at 30 min after challenge (mean percent change + 481 with 600 nM paf; P less than 0.05). Other symptoms induced by paf insufflation were rhinorrhea (6 out of 12 subjects), itching (8 out of 12), sneezing (4 out of 12) and a burning sensation (6 out of 12). No differences were observed between normal and rhinitic subjects, concerning nasal sensitivity to paf. Neither nasal symptoms nor changes in nasal airway resistance were observed after nasal challenge with lyso-paf (300 and 600 nM); by contrast, histamine (100 nM) induced sneezing, nasal obstruction, itching and rhinorrhea in all the studied subjects, associated with an increase in nasal airway resistance (maximum 5 min after challenge; percent change + 358; P less than 0.02). Nasal effects of paf were not mediated by histamine, since no increase in histamine levels was observed in nasal washings following paf insufflation. We conclude that paf may have pathogenetic relevance in allergic rhinitis.