In comparison to peripheral blood, there was a significantly higher proportion of T helper cells 1 (Th1, p=0.0023), T helper cells 17 (Th17, p=0.0334) and memory effector cytotoxic T cells (CD3+CD8+CD45RO+CD62L-, p=0.0449) in pleural effusion and the same trend was observed for memory effector Th cells (CD3+CD4+CD45RO+CD62L-, p=0.0633) and double-negative T cells (CD3+CD4-CD8-) (p=0.1085). The gene discussed is CD8A; the disease is Pleural effusion.