Elevated IP-10 and IL-6 from bronchoalveolar lavage cells are biomarkers of non-cavitary tuberculosis.

Background: Active TB disease can destroy lung parenchyma leading to cavities. Immune responses that predispose or protect individuals from lung damage during TB are poorly defined.
Objective: To sample lung immune cells and assay bronchoalveolar lavage (BAL) cell cytokine production.
Design: Enrolled subjects (n = 73) had bilateral infiltrates and underwent BAL.
Results: All had sputum culture demonstrating Mycobacterium tuberculosis and 22/73 (30%) had cavities on their chest radiograph. Those with cavities at presentation had a higher percentage of polymorphonuclear neutrophils (PMN) in BAL as well as lower inducible protein (IP) 10 (P < 0.01) and interleukin (IL) 6 (P = 0.013) in BAL cell supernatants compared to those without cavities. There was no correlation between cavities and other BAL or serum cytokines. IP-10 was negatively associated with BAL PMN. IP-10 and IL-6 expression above median reduces the odds of cavities by 79% and 78% in logistic regression models. IP-10 and IL-6 clustered with interferon-gamma and tumour necrosis factor-alpha in a principal component analysis, while IL-4 clustered with PMN.
Conclusion: Increasing IP-10 and IL-6 production by BAL cells is associated with non-cavitary TB in patients who present with radiographically advanced TB. IP-10 and IL-6 may reflect an effective T-helper 1 immune control pathway for TB, attenuating tuberculous lung destruction.