Role of interleukin 4 and its receptor in clinical presentation of chronic extrinsic allergic alveolitis: a pilot study

BACKGROUND Th-2 cytokine milieu including interleukin 4 (IL-4) was detected in fibrotic lung diseases. Chronic extrinsic allergic alveolitis (EAA) may be also accompanied by marked fibrogenesis. The aim of this study was to determine if IL-4 and its receptor (IL-4R-alpha) play any role in the clinical presentation and pathogenesis of chronic EAA. METHODS Twenty patients originally investigated for interstitial lung disease and finally diagnosed affected with chronic EAA and sarcoidosis were prospectively enrolled into the study. Concentrations of IL-4, IL-4R-aplha and total protein were assessed in the bronchoalveolar lavage fluid (BALF) of all enrolled subjects as well as high resolution computed tomography (HRCT) scores and pulmonary function tests. RESULTS BALF IL-4R-alpha and total protein concentrations were significantly higher in chronic EAA patients (p < 0.05). Concentrations of BALF IL-4R-alpha were significantly higher in men than in women (p < 0.05) in EAA group. Total protein BALF levels were significantly elevated in ex-smokers with EAA compared to nonsmokers (p < 0.05). A positive correlation (p < 0.01) between IL-4R-alpha BALF concentrations and HRCT interstitial scores were observed in chronic EAA group; the IL-4R-alpha/total protein ratio showed the same significant positive correlation. A negative correlation between lung function results and IL-4R-alpha, and IL-4R-alpha/total protein as well, was also found (p < 0.05). CONCLUSIONS We suggest a clinical relevance for the IL-4/IL-4R axis in the etiopathogenesis of chronic EAA. IL-4R-alpha could serve as a potential biomarker of lung fibrogenesis.