Clarissa Hilzendeger,1 Jane da Silva,2 Monique Henket,1 Florence Schleich,1 Jean Louis Corhay,1 Tatiana Kebadze,3 Michael R Edwards,3 Patrick Mallia,3 Sebastian L Johnston,3 Renaud Louis1 1Department of Respiratory Medicine, Centre Hospitalier Universitaire (CHU) Liege, Groupe Interdisciplinaire de Génoprotéomique Appliquée (GIGA) I3 University of Liege, Belgium; 2Department of Medicine, Post-graduate Program in Health Sciences, University of Southern Santa Catarina, Palhoça-SC, Brazil; 3Airway Disease Division, Airway Disease Infection Section, National Heart and Lung Institute, Imperial College, London, UK Background: Exacerbations of COPD are frequent and commonly triggered by respiratory tract infections. The purpose of our study was to investigate innate immunity in stable COPD patients.Methods: Induced sputum was collected from 51 stable consecutive COPD patients recruited from the COPD Clinic of CHU Liege and 35 healthy subjects. Expression of interferons beta (IFN-β) and lambda1 (IL-29), IFN-stimulated genes (ISGs) MxA, OAS, and viperin were measured in total sputum cells by reverse transcription quantitative polymerase chain reaction (RT-qPCR). The presence of Picornaviruses was assessed by RT-PCR, while potential pathogenic microorganisms (PPM) were identified by sputum bacteriology.Results: Expression of IL-29 was found in 16 of 51 COPD patients (31%) and in nine of 35 healthy subjects (26%), while IFN-β was detected in six of 51 COPD patients (12%) and in two of 35 healthy subjects (6%). ISGs were easily detectable in both groups. In the whole group of COPD patients, OAS expression was decreased (P