There were significantly more HDAC2 positive cells in COPD-ES compared to COPD-CS [median (range); COPD-ES, 2611.5 per mm2 (122 per mm2–4786.3 per mm2) versus COPD-CS, 1894.2 per mm2 (550.5 per mm2–2997.2 per mm2) p<0.05] (Figure 2 and 6); ie COPD-ES smokers were essentially normal. This evidence concerns the gene HDAC2 and chronic obstructive pulmonary disease.