Although pro-inflammatory CD8+ T cell pool (mainly including CD8+ IFN-γ+Tc1, CD8+ IL-4+Tc2, and CD8+ IL-17+Tc17) and anti-inflammatory CD8+ T cell pool (mainly including CD8+ Foxp3+Treg, and CD8+ IL-10+Tc10) have been considered to be involved in COPD pathogenesis, existing studies regarding this association vary widely in their designs, population sizes and experimental methods. This evidence concerns the gene IL17A and chronic obstructive pulmonary disease.