BTLA and Pleural effusion: 1. Co-expression of BTLA and B7-H4 on myeloid dendritic cells DCs (mDCs) in peripheral blood and pleural effusions of pleural TB patients was significantly higher than in the control group.2. High expression of BTLA and B7-H4 promoted a high level of CD83 and HLA-DR, which had a negative regulatory effect on mDCs on anti-TB immunity.