Down-regulatory Role of Alveolar Macrophages in IL-2-Stimulated Proliferation and Killer Induction of Lung Lymphocytes in Patients with Active Pulmonary Sarcoidosis

Abstract

Normal human alveolar macrophages (AM) were previously found to suppress the expression of lymphokine-activated killer (LAK) activity by blood lymphocytes in response to IL-2. The present study was undertaken to examine whether AM obtained by bronchoalveolar lavage (BAL) in the lungs of patients with pulmonary sarcoidosis affect the responses of lymphocytes in the blood and BAL fluid (BALF), assessed as the proliferative responses to IL-2 and LAK activity against Daudi cells. BALF lymphocytes of healthy donors did not generate LAK activity in response to IL-2. Lymphocytes purified from the blood and BALF of patients with active sarcoidosis proliferated and generated LAK activity in response to IL-2. A significant correlation was found in sarcoidosis patients between the percentage of lymphocytes in BALF and their LAK activity induced by IL-2. AM of sarcoidosis patients suppressed the responses of BAL lymphocytes to IL-2. These results suggest that AM may be important in down-regulating the local responsiveness of lymphocytes to IL-2 in the pathogenesis of pulmonary sarcoidosis.