HDAC2 and chronic obstructive pulmonary disease: In order to further address the potential confounder of changes in cellularity of the airway wall when interpreting HDAC2 expression in smokers and COPD, we performed both cross-sectional and longitudinal studies to test our hypothesis that the current literature is correct in terms of HDAC2 being down-regulated in the COPD airway, but that HDAC2 levels could be normalised by aggressive ICS therapy [8].