Concentrations of 14 cytokines in serum samples from control subjects and patients with COPD. The number of subjects in each group was never-smokers (NS), 11; ex-smokers (ExS), 25; current smokers (CS), 9; COPD GOLD stage 1 (S1), 7; COPD S2, 37; COPD S3, 13. Cytokines were measured by protein microarray (see text and [23
] for details). Experiments were performed three times, with two replicates in each experiment, and the data averaged across the three experiments. The data are presented as scatter plots, with each point representing an individual subject’s serum sample, and the solid, short vertical lines show the median values for each cytokine in each group. The dotted vertical lines represent the median values of the NS group. The dashed vertical lines represent the 95th percentile of the NS group: individual cytokine concentrations higher than this are shown by black symbols and those below by grey symbols.