Abstract: Objective To investigate the expression levels and clinical significance of PD-L1 and PD-1 in peripheral T-cell lymphoma.Methods Expression levels of PD-L1 and PD-1 in peripheral T-cell lymphoma tissues (test group, n=51) and lymph node optimum pathology (control group, n=20) were detected using immunohistochemistry. Correlations of PD-L1 and PD-1 expressions with clinical pathological parameters and prognosis were analyzed between two groups. Results The expression level of PD-L1 was significantly higher in test group than that in control group（74.51%vs35.00%，?2=9.662，P?0.05）.The expression level of PD-1 was significantly higher in test group than that in control group(66.67%vs 25.00%，?2=10.074，P?0.05).There were significant differences between PD-L1 and PD-1 expressions and peripheral LDH levels involved within test group. After two cycles of CHOP or ECHOP treatments,the response rate(RR) in PD-L1 negative group was higher than that in positive group（84.6%vs47.4%，?2=5.478, P?0.05）and the response rate (RR) in PD-1 negative group was higher than that in positive group（82.4% vs 44.1%，?2=6.755, P?0.05）. The media OS in PD-L1 in negative group was higher than that in positive group（29.8M vs 17.6M，P?0.05）and the media OS in PD-1 negative group was higher than that in positive group（29.8M vs 17.6M，P?0.05）.Conclusion：There was a high level expression of PD-L1 and PD-1 in peripheral T-cell lymphoma,which was closely related with elevated LDH in peripheral blood ,poor response rate and shorter OS. So they could be the factors of worse effect of chemotherapy and poor prognosis.

Key words: peripheral T-cell lymphoma, programmed death 1-ligad, programmed cell death factor-1, immunohistochemistry, Kaplan-Meiers estimate