Evaluation of PD-1 and interleukin-10-receptor expression by T lymphocytes in malignant and benign pleural effusions

Abstract Background: PD-1 (programmed cell death protein-1)/PD-L1 (programmed cell death ligand-1) as well as IL-10 (interleukin-10)/IL-10R (interleukin-10 receptor) interactions play a major role in tumor immune evasion in various malignancies. Several studies investigated the expression of PD-1 on T lymphocytes in pleural effusions (PE) in patients with malignant diseases. However, results in malignant pleural effusions (MPE) compared to benign PE (BPE) are underreported. Methods: In this prospective study, 51 patients (median age 66 years, IQR 54–78, 47% male) with PE of malignant or benign origin were enrolled and divided into three groups according to the cytological results (group 1: MPE n = 24, 47%; group 2: BPE in malignant disease n = 22, 43%; group 3: BPE in benign disease n = 5, 10%). In the cytological samples, T cells were analyzed for the expression of PD-1 and IL-10R via flow cytometry. Results: In MPE, the proportion of PD-1 + T lymphocytes on CD4 + cells was significantly lower than in BPE (group 1 vs 3, p = 0.019). Moreover, a significantly lower expression of PD-1 + IL-10R + CD8+ (group 1 vs 2, p = 0.016; group 1 vs 3, p = 0.032) and a significantly higher expression of PD-1-IL-10R-CD8 + T lymphocytes (group1 vs 2, p = 0.045; group 1 vs 3, p = 0.032) were observed in MPE when compared to BPE. Conclusion: The frequency of T cells expressing PD-1 and IL-10R is significantly lower in MPE compared to BPE regardless of the underlying disease indicating a different microenvironment in PE driven by the presence of tumor cells. Our observation spotlights the possible involvement of PD-1 and IL-10R in MPE.