Pleural fluid mononuclear cells (PFMCs) from tuberculous pleurisy can migrate in vitro in response to CXCL10

We recently reported that pleural fluid mononuclear cells (PFMCs) from tuberculous pleurisy stimulated with Bacillus Calmette-Guérin (BCG) or TB antigens produced high levels of cytokines. However, it was still unclear what mechanism of the PFMCs used to migrate into the pleural fluids in TB infection. In the present study, we found that CD3(+)CD4(+) and CD3(+)CD8(+) T cells from PFMCs expressed significantly high levels of CXCR3 compared to PBMCs. In addition, the levels of CXCL10 (the ligand for CXCR3) in pleural fluids were significantly higher than those in normal serum and cancerous fluids. After stimulation with BCG, PFMCs produced high levels of CXCL10. Importantly, the synthesis of CXCL10 was mainly dependent on the BCG-induced production of IFNs, because the neutralization of endogenous IFN-α or IFN-γ with mAbs significantly reduced the production of CXCL10 from BCG-stimulated PFMCs. In addition, the tubercular pleural fluid (TBPF) or exogenous CXCL10 induced the migration of PFMCs, indicating that IFN-α or IFN-γ modulated the immune response through the expression of CXCL10 to aid the recruitment and selective homing of activated/effector cells to the site of Mycobacterium tuberculosis (M.tb) infection. Taken together, the levels of CXCL10 in pleural fluids were high and BCG-stimulated PFMCs expressed high levels of CXCL10, and CXCL10 induced the migration of PFMCs into the pleural fluids in TB infection.