Role of TNF-a in host immune response in tuberculous pleuritis

Tumour Necrosis Factor (TNF)-a, a pro-inflammatory cytokine has a dual role in host immunity and immunopathology of tuberculosis and is considered to be pivotal for determining the clinical course of the disease, either beneficial or detrimental. The assessment of TNF-a in pleural tuberculosis will help us to understand its role in host defence mechanism against Mycobacterium tuberculosis (MTB) infection. In this study, TNF-a and IFN-g levels were measured in plasma and pleural fluid of both tuberculosis (TB) and non- TB patients and in the supernatants of blood and pleural fluid mononuclear cells (PBMCs and PFMCs) stimulated in vitro with PPD, culture filtrate and heatkilled (MTB). In addition, apoptosis induced by PPD and MTB was also studied. TNF-a and IFN-g were significantly elevated in pleural fluid than in plasma of pleural tuberculosis patients, suggesting the compartmentalization of Th1 cytokine-secreting cells at the site of disease. In vitro stimulation of PFMCs with PPD and MTB showed a significant increase in these cytokine levels and also enhanced apoptosis of these cells. This increase in TNF-a levels may contribute to the containment of infection by synergizing with IFN- g to activate infected macrophages or by the regulation of T-cell apoptosis