Interleukin 22-producing CD4+ T cells in malignant pleural effusion

► The numbers of Th22 cells were increased in malignant pleural effusion when compared with those in blood. ► Each of IL-1β, IL-6 and TNF-α could promote the differentiation of Th22 cells from naïve CD4+ T cells. ► Th22 cells could be recruited into pleural space via CCL20-CCR6, CCL22-CCR4, or/and CCL27-CCR10 axes. ► IL-22 substantially and persistently promoted the proliferation and migratory activity of A549 cells. ► IL-22 could strongly facilitate intercellular adhesion of A549 cells to pleural mesothelial cell monolayers.