TLR9 expression is associated with PD-L1 expression and indicates a poor prognosis in patients with peripheral T-cell lymphomas

•Expression of TLR9 and PD-L1 in peripheral T-cell lymphomas (PTCL).•Correlation between TLR9 and PD-L1 expression and clinicopathological features.•TLR9 and PD-L1 expression on tumor cell indicates a poor prognosis in PTCL.•Univariate and multivariate analyses of prognostic factors in PTCL. Toll-like receptor9 (TLR9), a member of pattern recognition receptors, play an important role in tumor immunologic surveillance. However, the clinical impact of TLR9 and programmed cell death-ligand 1 (PD-L1) in peripheral T-cell lymphomas (PTCL) remains unclear. In this study, we examined the expression of TLR9 and PD-L1 by immunohistochemical staining in patients with PTCL, and evaluated the clinical significance between expression and clinicopathological features. We found that the rates of high expression of TLR9 and PD-L1 on tumor cells were 65.3% and 45.8% in PTCL, respectively. TLR9 expression was associated with PD-L1 expression in PTCL. Moreover, TLR9 expression was associated with gender, ECOG score, Ki-67 expression, while PD-L1 expression was associated with the number of extranodal involvement and platelet count. High expression of either TLR9 or PD-L1 indicated a poor survival rate for patients with PTCL. Multivariate analysis confirmed that high expression of TLR9 and PD-L1 were unfavorable prognostic factors for patients with PTCL. Thus, TLR9 and PD-L1 expression might be important on the point of prognostic markers in PTCL.