In conclusion, we observed the accumulation of circulating MDSCs subsets, immunosuppressive Tregs and upregulation expression of the PD-1/PD-L1, not PD-L2, on these two cell populations in COPD patients and we speculated that PD-1/PD-L1 axis may be involved in MDSCs, especially M-MDSCs, induced Tregs expansion and activation at least partially in COPD patients. The gene discussed is PDCD1LG2; the disease is chronic obstructive pulmonary disease.