Role of interferon-gamma as a marker of asthma severity and control

Background: Role of interferon-gamma (IFNγ) in asthma remains controversial. While certain studies found association of this cytokine with severe asthma and bronchial hyperresponsiveness, the other ones established its rather beneficial effect on mucin secretion and asthma development. Objectives: The aim of the study was to investigate IFNγ levels in exhaled breath condensate (EBC) of asthma patients. Methods: The study included 46 patients with asthma (mostly newly diagnosed - 52% and moderate - 30%) and 23 patients with chronic bronchitis. Mean age of patients was 38.1±1.60 years. Among asthma patients, 78% had uncontrolled disease according to ACQ5. Lung function was tested by spirometry. IFNγ was measured in EBC by BD cytometric bead array method with enhanced sensitivity. Results: Asthma patients had higher level of IFNγ than patients of control group (2654 (1328.9; 3123.9) fg/ml vs. 1872 (1707.8; 2506.3) fg/ml) but the difference was not significant. IFNγ was increased in moderate asthma (2199 (1764.8; 2519) fg/ml) compared to newly diagnosed asthma (1666 (928.8; 2048.5), p=0.01). Moreover, IFNγ was positively correlated with ACQ5 score (R=0.39, p=0.01). In uncontrolled asthma concentration of the cytokine was more than two times higher compared to patients with partially or fully controlled disease (2807 (1512.9; 3123.9) fg/ml vs. 1158 (995.5; 1589.6) fg/ml, p=0.02). 10-days treatment with oral glucocorticoids decreased IFNγ from the initial (2654 (1328.9; 3123.9) fg/ml) to “normal” values (1790 (1124.4; 3070.1) fg/ml, p=0.08). Conclusions: Our observations suggest detrimental effect of IFNγ in asthma pathogenesis. The study was supported by RFBR (#18-54-53019).