Evaluation of Th9 and Th22 cells within pleural effusions of tuberculosis and non-tuberculosis patients

<b>Background:</b> Mycobacterium Tuberculosis (Mtb) is the leading cause of death in worldwide. Tuberculous pleural effusion (TPE) is one of the most common forms of extrapulmonary TB. Patients with tuberculous or malignant pleural effusions (MPE) frequently have similar clinical manifestations and pleural fluid profile. <b>Objective:</b> In this pilot study we sought to characterize the immunophenotype of lymphocytes in the pleural effusions of TPE and non-TB patients as a tool for differential diagnosis. <b>Methods:</b> 30 patients with TPE, 30 patients with MPE, 14 patients with empyema and 14 patients with parapneumonic were enrolled between Dec 2018- Dec 2019 from the Masih Daneshvari Hospital, Tehran-Iran. 2 ml of PE was obtained from patients by paracentesis and cells were stained with CD4-FITC surface and intracellular staining with IL-9-PE and IL-22-PE performed for the detection of Th9 and Th22 cells respectively. 10000 events were evaluated by flow cytometery. <b>Results:</b> There were significant increases in the percentage of Th9 cells (63.5±2.6 vs 53.5±3.7%; p≤0.0306) and in Th22 cells (22.7±4.3%,vs 7.8±2.2; p≤0.0020) in patients with TPE compared with MPE. The percentage of Th9 cells was also significantly increased in pleural effusions of TPE patients compared with parapneumonia subjects (53.5±3.7 vs 24.0±3.8%; p≤0.0001). No other differences in Th9 or Th22 percentages between subject groups was seen. <b>Conclusion:</b> The current pilot study shows that the percentage of Th9 and Th22 cells was able to distinguish TPE from MPE. Additional studies are required to confirm these results and determine the functional consequences of these observations.