Elevated Circulating CD4⁺CD25⁺CD127^-/low Regulatory T Cells in Patients with Non-asthmatic Eosinophilic Bronchitis

Non-asthmatic eosinophilic bronchitis (NAEB) is a common cause of chronic cough. It is characterized by sputum eosinophilia like asthma but lacks airway hyperresponsiveness. Regulatory T cells (Tregs) are recognized as immune suppressors and are involved in the pathogenesis of asthma. However, the relationship between Tregs and NAEB remains unknown. This study aimed to preliminarily explore the role of Tregs in NAEB by comparing circulating Tregs levels to asthma and healthy controls.

Fractional exhaled nitric oxide (FeNO), spirometry with bronchial provocation test, sputum induction and blood routine test were performed in all subjects. Peripheral blood mononuclear cells were used to detect the Tregs (CD4⁺CD25⁺CD127^-/low) by flow cytometry. Relationship between the levels of circulating Tregs and clinical indexes was also observed.

A total of 15 patients with NAEB, 20 patients with asthma and 11 healthy controls were included. The absolute numbers of circulating Tregs in the NAEB group (49.8 ± 18.9 × 10³ cells/ml) and asthma group (53.3 ± 18.7 × 10³ cells/ml) were higher than that in healthy control group (32.7 ± 11.6 × 10³ cells/ml) (both P < 0.01). In total, the level of circulating Tregs showed positive correlation with FeNO (r = 0.30, P < 0.05).

Tregs may play a key role not only in asthmatic patients, but also in patients with NAEB, as reflected by the elevated Tregs in peripheral blood.