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

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 micromol; the AR+ group (n = 15) had a methacholine PD20 ranging between 2.2 and 19.6 micromol. In the AS group, methacholine PD20 ranged between 0.42 and 2.6 micromol. 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.