Abstract: Objective To explore the value of CD4+/CD8+, and helper T cells 17 (Th 17)/ regulatory T cells (Treg) in the evaluation of disease severity and prognosis in elderly patients with chronic obstructive pulmonary disease (COPD). 
Methods In total, 288 elderly patients with COPD (COPD group) and 70 healthy elderly undergoing physical examination (control group) were selected. CD4+, CD8+, Th17, Treg, CD4+/CD8+, Th17/Treg were compared between the COPD group and the control group and between patients with different disease severity in the COPD group. The COPD group was followed up for 6 months, the clinical data of patients with different prognosis were compared. Multivariate Logistic regression was used to analyze the influencing factors of the short-term adverse prognosis of elderly COPD patients. The receiver operating characteristic(ROC) curve was drawn to analyze the clinical value of CD4+/CD8+ Th17/Treg in predicting the short-term adverse prognosis of elderly COPD. 
Results The levels of CD4+, CD4+/CD8+ and Treg in peripheral blood of COPD group were lower than those of the control group (P＜0.01), while the levels of CD8+, Th17 and Th17/Treg in peripheral blood of COPD group were higher than those of the control group (P＜ 0.01). The levels of CD4+, CD4+/CD8+ and Treg in peripheral blood of grade Ⅲ  group were lower than those of grade Ⅰ, and Ⅱ groups, while the levels of CD8+, Th17 and Th 17/Treg in peripheral blood were higher than those of grade Ⅰ and Ⅱ groups; The levels of CD4+, CD4+/CD8+and Tregin peripheral blood of the grade Ⅱ group were lower than those of grade Ⅰ group, while the levels of CD8+, Th17 and Th17/Treg were higher than those of grade Ⅰ group (P＜0.05). Pearson correlation analysis showed that CD4+/CD8+ in COPD patients was negatively correlated with the disease grades (P＜0.05), and that Th17/Treg was positively correlated with the disease grade (P＜0.05). The levels of CD4+, CD4+/CD8+ and Treg in peripheral blood of the poor prognosis group was lower than those of the good prognosis group. The levels of CD8+, Th17, Th17/Treg, serum IL-6 and CRP were higher than those of the good prognosis group (P＜0.05). Multivariate Logistic regression analysis showed that CD4+/CD8+, Th17/Treg, IL-6, and CRP are the factors affecting the recent poor prognosis in elderly COPD patients. The ROC curve analysis showed that the areas under the ROC curve (AUC) of CD4+/CD8+ and Th17/Treg in predicting the short-term adverse prognosis of elderly COPD patients were 0.813 (95%CI: 0.730-0.896) and 0.852 (95%CI: 0.730-0.896), respectively. 
Conclusion CD4+/CD8+and Th17/Treg have high clinical values in the evaluation of the severity of disease and short-term prognosis of elderly COPD patients.

Key words: pulmonary disease, chronic obstructive, CD4/CD8 ratio, Th17 cells, T-lymphocytes, regulatory