We next used a semiquantitative RT‐PCR method to profile the expression of MMP‐2/MMP‐9/MMP‐12, NGAL and IL‐6 transcripts in PBMCs isolated from blood samples of 19 COPD‐S patients and 12 healthy‐S participants (for the patients’ characteristics, see the Table S3). The gene discussed is LCN2; the disease is chronic obstructive pulmonary disease.