Increased pleural soluble fas ligand (sFasL) levels in tuberculosis pleurisy and its relation with T-helper type 1 cytokines.

Tuberculosis (TB) pleurisy is accepted to be the best model for evaluating the local protective cellular immune response to Mycobacterium tuberculosis (MTB) since it can be spontaneously self-cured. Therefore, we aimed to evaluate the involvement of cytokines and the soluble apoptosis-modulating factors sFas and sFasL in local protective cellular immunity to MTB. Pleural fluid samples were collected from 35 patients with TB pleurisy, 39 patients with malignant pleurisy, and 14 patients with non-TB nonmalignant (n-TB n-M) pleurisy and were evaluated for the levels of several cytokines, soluble Fas (sFas), and sFas ligand (sFasL) by using ELISA. The levels of IFN-gamma, IL-12p40, IL-18, IL-8, and sFasL in TB pleurisy were significantly higher in comparison to those in the malignant pleurisy and n-TB n-M pleurisy groups. In addition, pleural sFasL levels were increased and positively correlated with IFN-gamma and IL-18 levels in TB patients. In conclusion, this study demonstrates that Th1-type-specific cellular immunity is responsible for protective immunity in TB and suggests that Fas-mediated apoptosis may be at least a part of protective immunity to tuberculosis and could be regulated by type 1 T-cell response. IFN-gamma and sFasL levels can be used as diagnostic markers for differing TB pleurisy from other pleurisies.