In seven patients with paired malignant effusion and peripheral blood mononuclear cell (PBMC) samples, PD-L1 expression was significantly higher on CD3-positive T cells present in malignant effusions as compared with PBMCs (p = 0.016).
The low intensity of PD-L1 expression in immune cells is associated with the poor survival of patients with lung cancer with malignant pleural effusion.