Interleukin 6 is an autocrine growth factor for normal human pleural mesothelial cells.

Interleukin 6 (IL-6) is a multifunctional inflammatory cytokine whose abnormal production has been implicated in a variety of diseases. Our previous study demonstrated that exudative pleural effusions contain a large amount of IL-6, and the levels of IL-6 in pleural effusion have diagnostic and pathophysiologic values. Although IL-6 is produced by a variety of cells, the origin of IL-6 in pleural effusion has not been determined clearly. We hypothesized that pleural mesothelial cells (PMCs) are an important source of IL-6 in pleural diseases. In this study, we tried to demonstrate whether PMCs could produce IL-6 and to characterize the modulation of its production. PMCs were established from patients with nonmalignant pleural effusion. Immunoreactive IL-6 could be detected in cultured supernatants of all PMCs from five patients, and all IL-6 detected in the supernatants were biologically active. IL-6 production was augmented by the addition of interleukin 1 alpha (IL-1 alpha) in a dose-dependent manner an...