Increased release of interleukin-1β, interleukin-6, and tumor necrosis factor-α by bronchoalveolar cells lavaged from involved sites in pulmonary tuberculosis

Mycobocterium tuberculosis and its components have been shown to stimulate mononuclear phagocytes in vitro to release interleukin-1β (IL-1β), tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6). Animal models of tuberculosis (TB) also demonstrate the presence of cytokines in granulomas. We hypothesized that bronchoalveolar lavage (BAL) cells from patients with pulmonary TB would have increased spontaneous release of IL-1β, IL-6, and TNF-α and would have a concomitant alveolitis. We performed BAL on 26 patients with active TB and on six normal volunteers. BAL fluid from radiographically involved and uninvolved sites was evaluated separately for cell types and the spontaneous release of cytokines. The alveolar inflammation in involved sites was characterized by an increase in lymphocytes (miliary TB, 38 ± 10%; involved sites, 22 ± 4%; uninvolved sites, 13 ± 2%; normal, 5 ± 2%) and neutrophils (involved sites, 21 ± 7%; uninvolved sites, 3 ± 2%). There was a significant increase in the spontaneous release of IL-1β (501 ± 280 pg/ml), TNF-α (782 ± 165 pg/ml), and IL-6 (473 ± 157 pg/ml) from involved sites of TB patients that was 5- to 20-fold greater than uninvolved sites, normal controls, or miliary TB. Northern analysis revealed increased gene expression of IL-1β, TNF-α, and IL-6 from the involved sites from two patients with TB compared with two negative controls. We conclude that BAL cells, especially alveolar macrophages, are activated in the alveolar inflammation of active TB and spontaneously release increased quantities of IL-1β, IL-6, and TNF-α, and that these cytokines are likely to be involved in directing granuloma formation and control of M. tuberculosis infection.