The findings indicate that COPD is causally related to CD25 + CD4 + T cell Absolute Count (Treg, odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.01–1.39, P-value < 0.05), CD8 on Effector Memory CD8 + T cell (CD8 + T cell, odds ratio [OR] = 0.81, 95% confidence interval [CI] = 0.68–0.96, P-value < 0.05), and CD4 + CD8dim T cell %lymphocyte (CD4 + T cell, odds ratio [OR] = 1.19, 95% confidence interval [CI] = 1.02–1.39, P-value < 0.05) (Fig. 2). This evidence concerns the gene CD8A and chronic obstructive pulmonary disease.