OBJECTIVETo detect the expression levels of programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) in the peripheral blood of patients with oral squamous cell carcinoma (OSCC) and to discuss their biological and clinical significance.

METHODSPD-1/PD-L1 expression on the surface of T-lymphocytes and the counts of T-lymphocyte subpopulations of peripheral blood in 82 patients with OSCC (OSCC group) and 25 healthy controls (control group) were examined via flow cytometry. The expression levels of soluble PD-1 (sPD-1) and soluble PD-L1 (sPD-L1) in the serum were observed through enzyme-link immunology method. The data were tested and analyzed with SPSS 17.0 software.

RESULTSThe percentage of CD8+ T cells in the OSCC group was significantly higher than that in the control group (P<0.05), whereas the percentages of CD3+ and CD4+ T cells as well as CD4+/CD8+ ratio were significantly lower than those in the control group (P<0.05). The positive rates of PD-1 and PD-L1 in CD3+ and CD4+ T cells in OSCC peripheral blood were remarkably higher than those in the control group (P<0.01). Difference was not observed between the expression levels of sPD-1 in the serum of OSCC group and those in the control group (P>0.05), but the average of sPD-L1 was remarkably higher than that in the control group (P<0.05). sPD-L1 expression was related to clinical stage, tumor cell differentiation, and lymph node status (P<0.05) but not related to sex, age, tumor location, and tumor size.

CONCLUSIONT-lymphocyte subpopulations in the peripheral blood of patients with OSCC developed immunosuppression with different degrees. PD-1 and PD-L1 expression levels on the surface of CD3+ and CD4+ T cells significantly increased. Abnormal increase in sPD-L1 expression may be associated with OSCC development.