CD8A and chronic obstructive pulmonary disease: We observed biased decreased frequencies of CD8+ subpopulations in COPD patients (mean 42.77 vs. 64.36%, P < 0.01) consistent with previous results (25, 33), since CD4+ subset (mean 29.30 vs.13.12%) increased, and DN subset (mean 25.35 vs.19.06%) proportion was no difference between patients and healthy individuals (Figure 1D).