Expression Profiles of Cytokine mRNAs in the Pleural Fluid Reveal Differences Among Tuberculosis, Malignancies, and Pneumonia-Exudative Pleural Effusions

Introduction Tuberculosis (TB) and malignant diseases are the most common causes of lymphocytic pleural effusion in adults. Serum and pleural fluid cytokine levels have been analyzed to help in the differential diagnosis, but with limited results. Purpose This study investigates transcription levels of selected cytokine genes in pleural effusion of patients under investigation for TB. Methods This was a prospective study that included adult patients under investigation for pleural effusion in Brazil. The expression of 19 cytokine genes was analyzed by RT-qPCR. Results The majority of cytokine-related genes expressed in pleural fluid of TB patients were similar in non-TB patients, except for RORA and RORC genes, which showed a statistically higher level in TB. All cytokines in the Th17 pattern were induced in TB patients' pleural fluid. Patients with malignant pleural effusion expressed higher levels of IFN-alpha 1, IFN-beta 1, TNF-alpha, IL-4 and IL-6, and suppression of TGF beta-1. Conclusion There is still a lot to understand about the cytokine roles in the pro- and anti-inflammatory environment of exudative pleural effusions. The data presented here showed an increased expression of Th17 pattern cytokines genes in TB patients that could be used as markers to differentiate tuberculous pleuritis from other common causes of exudative pleural effusion.