Real-time quantitative PCR analyses of CLCA1 mRNA expression in induced sputum cells. Induced sputum samples were obtained from non-smokers (circles, n = 13), smokers without COPD (triangles, n = 5), and COPD patients (squares, n = 20), as described in Methods. Group mean values are shown by horizontal lines. CLCA1 mRNA expression (normalized to that of GAPDH mRNA) was significantly greater for COPD patients’ cells than for non-smokers’ cells. * p ≤ 0.05, Student’s t-test.