The aim of this study was to evaluate PD-1+ and IL-10R expression on CD4+, CD8+ T cells, and FOXp3 regulatory T lymphocytes in pleural effusions of malignant versus benign origin in order to describe the local microenvironment in pleural effusions that may differ in MPE and BPE and may have an impact on therapeutic decisions. Here, FOXP3 is linked to Pleural effusion.