Objective  To investigate the expression and clinical significance of B7 family molecules and their receptor PD-1(programmed death-1) in human NK/T-cell lymphoma (NKTL).

  Methods  Real time fluorescence quantitative PCR (RQ-PCR) and Immunohistochemistry SP method were used to detect the expression levels of PD-1 and B7 family molecules (PD-L1 and PD-L2) in human NKTL cell lines (SNK-6 and YTS) and NKTL tissues.The correlation between these proteins and Clinical histopathological parameters and curative effect were analyzed subsequently.

  Results  The expression levels of PD-L1 and PD-L2 mRNA in SNK-6 and YTS were significantly higher than that in normal NK cells.. The expression of PD-L1 and PD-L2 proteins in human NKTL tissues (60.0%、63.3%) and curative effect were significantly increased compared with rhinitis tissues (22.2%、16.7%); furthermore, the mean count of PD-1+Tumor-infiltrating T lymphocytes(TIL) was inversely correlated with PD-L1 and PD-L2 protein expression levels in NKTL tissues.. The expression of PD-L1 and PD-L2 showed a positive correlation with clinical stage.. PD-L1 expression was also positively correlated with LDH, Ki-67 level and was negatively correlated with IPI score. However, there were no significant correlation between PD-L1 and PD-L2 with other Clinical histopathological parameters..-PD-L1 expression was negatively correlated with curative effect. However, there was no correlation between PD-L2 expression and curative effect.

  Conclusion  B7 family molecules and their receptor PD-1 are overexpressed in human NKTL and have greatly clinical significance.PD-L/PD-1 pathway may involved in the tumor immune escape in human NKTL, and it is expected to be a novel target for immunotherapy of human NKTL.