Extracellular interleukin (IL)-26 protein was enhanced in patients with uncontrolled asthma compared with patients with controlled asthma, according to study findings published in the Journal of Allergy and Clinical Immunology.

A total of 32 patients with asthma (13 with controlled asthma and 19 with uncontrolled asthma) as well as 8 healthy volunteers were included in the study. Participants reported weekly respiratory symptoms and underwent clinical characterization and bronchoscopy. Bronchial and transbronchial biopsies were followed by bronchoalveolar lavage.

Patients with uncontrolled asthma had a lower median forced expiratory volume in 1 second percent predicted compared with the subgroup of patients with controlled asthma (3.2 vs 4.1, respectively; P =.009). In addition, patients with uncontrolled asthma were more responsive to methacholine (n=18 vs n=11). The pooled group of patients with asthma had lower median concentration of extracellular IL-26 in bronchoalveolar lavage fluid compared with healthy individuals (P =.029).

There was no correlation between extracellular IL-26 protein concentration and score on the asthma control test in the pooled cohort of all patients with asthma (r = -0.23; P =.21). In patients with uncontrolled asthma, however, the median asthma control test score was lower in patients with low extracellular IL-26 protein concentrations vs patients with high extracellular IL-26 protein concentrations. The researchers also observed lower median immunoreactivity for IL-26 in the parenchymal tissue in all patients with asthma vs healthy volunteers (% area; P =.045). There were also higher concentrations of IL-26 mRNA in bronchoalveolar lavage cells in patients with uncontrolled vs controlled asthma.

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A limitation of the study was the small sample size.

The researchers concluded that glucocorticoid therapy inhibits IL-26 protein in lung fibroblasts in vitro, suggesting that “[inhaled corticosteroids] may account for the average decrease in extracellular IL-26 protein that we observed in the pooled group of all patients with asthma.”

Reference

Tufvesson E, Jogdand P, Che KF, et al. Enhanced local production of interleukin-26 in uncontrolled compared with controlled adult asthma [published online July 6, 2019]. J Allergy Clin Immunol. doi:10.1016/j.jaci.2019.06.035