Eosinophils, mast cells, and basophils in induced sputum from patients with seasonal allergic rhinitis and perennial asthma: Relationship to methacholine responsiveness,☆☆,

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Abstract

Objectives: We attempted to determine whether inflammation is present in induced sputum of patients with seasonal allergic rhinitis (AR) as compared with those with perennial asthma (AS) and examined its relationship with bronchial responsiveness to methacholine. Methods: Sputum was induced in 30 patients with seasonal rhinitis in response to grass pollens only and in 15 patients with stable, asymptomatic asthma. The AR group was divided according to methacholine PD20 value: the AR– group (n = 15) had a methacholine PD20 greater than 24 μmol; the AR+ group (n = 15) had a methacholine PD20 ranging between 2.2 and 19.6 μmol. In the AS group, methacholine PD20 ranged between 0.42 and 2.6 μmol. The percentage of eosinophils and metachromatic cells (alcian blue–positive) was assessed in sputum by light microscopy. Tryptase-positive cells and EG2+ cells were identified by immunocytochemistry with the mouse anti-human mast cell–tryptase monoclonal antibody and the monoclonal anti-eosinophil cationic protein antibody. Results: We found that the number of eosinophils in the AS group was greater than that in the AR+ group (p < 0.05) and in the AR– group (p < 0.01). Moreover, the eosinophil count was lower in the AR– group compared with the AR+ group (p < 0.05). Similarly, the number of EG2+ cells was greater in the AS group than in the AR group (p < 0.02) and the AR– group (p < 0.05). Moreover, the EG2+ cell count was lower in the AR– group than in the AR+ group (p < 0.05). The number of mast cells and basophils in the AS group was greater than that in the AR group (p  < 0.05 and p < 0.01, respectively). Mast cells in sputum were tryptase-positive. Basophils were present in sputum from 23% of patients with AR and 53% of patients with asthma. There was a significant correlation between methacholine PD20 and eosinophils (p < 0.005) and mast cells (p < 0.02) but not with basophils in those patients showing a measurable methacholine PD20 (AR+ and AS groups). Conclusions: Inflammatory cells are present not only in the airways of patients with asthma but also in airways of patients with seasonal AR, even outside natural exposure. Moreover, we provide evidence for the presence of basophils in sputum of patients with asthma even during clinical remission. The presence of bronchial responsiveness is associated with an increase in the number of eosinophils and metachromatic cells. Our findings are consistent with the hypothesis that eosinophils, as well as mast cells, contribute to bronchial responsiveness not only in AS but also in seasonal AR. (J Allergy Clin Immunol 1997;100:58-64.)

Section snippets

Patients

We selected two groups of consecutive patients who were referred to our outpatient clinic: patients with a history of seasonal AR in response to grass pollen without asthma (AR group) and patients with AS (AS group).

Inclusion criteria for patients with rhinitis were: (1) a history of seasonal rhinitis without cough, wheezing, or shortness of breath during natural exposure, lasting 3 to 5 years; (2) positive skin test responses to grass pollens only; and (3) baseline FEV1 greater than 80% of

Results

Characteristics of patients with AR and asthma, who successfully accomplished sputum induction, are shown in Table I. We studied 30 patients with AR and 15 patients with asthma. Four patients in each group were former smokers. Seven patients with asthma were using inhaled β2-agonists as needed. The two groups were not different in regard to gender, age, and baseline FEV1. Methacholine PD20 values in the AR group were different from those of the AS group (p < 0.001, Table I). Patients in the AR

Discussion

In this study we demonstrated that eosinophils and metachromatic cells are present in induced sputum from patients with seasonal AR even outside exposure to the sensitizing antigen. In these patients, cell counts differed from those of patients with asthma. We found that metachromatic cells in induced sputum had the features of both mast cells and basophils. An important and new observation of this study was that basophils were present in seven of 30 (23%) sputum samples from patients in the AR

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    From Servizio di Fisiopatologia Respiratoria, Modulo di Allergologia ed Immunopatologia Polmonare, Sesto San Giovanni, and Istituto di Clinica delle Malattie dell'Apparato Respiratorio, Università di Parma.

    ☆☆

    Reprint requests: Antonio Foresi, MD, Servizio di Fisiopatologia Respiratoria, Viale Matteotti 83, 20099 Sesto San Giovanni, Italy.

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