Increased Levels of Interleukin-18 in Patients with Pulmonary Sarcoidosis

Interleukin-18 (IL-18) has recently been identified as an interferon- γ (IFN- γ )-inducing factor, and it plays an important role in T helper 1 (Th1) response. We measured the serum levels of IL-18 and IFN- γ in 37 patients with pulmonary sarcoidosis and 25 healthy control subjects. We also measured the levels of IL-18 and IFN- γ in 10-fold concentrated bronchoalveolar lavage (BAL) fluids of 19 patients with pulmonary sarcoidosis and 9 healthy control subjects (all lifelong nonsmokers). The levels of serum IL-18 and IFN- γ were significantly increased in patients with sarcoidosis. The levels of BAL fluid IL-18 were significantly elevated in patients with sarcoidosis, however, the IFN- γ levels of the patients and control subjects were all below sensitivity. Serum IL-18 levels significantly correlated with serum IFN- γ levels and lysozyme activity. The patients positive for gallium-67 (67Ga) scan had significantly elevated serum IL-18 levels as compared with those of the negative patients. BAL fluid IL-18 ...