CD4 and chronic obstructive pulmonary disease: In summary, our current research identifies an imbalance of pro/anti-inflammatory CD4+ T subsets in patients with COPD, with increased percentages of Th17 cells (only in AECOPD) and Th1 cells and reduced percentages of Th2 cells (only in SCOPD) and Th10 cells, as well as a reduced quantity and impaired capacity of Tregs.