ROLE OF LYSOSOMAL-ENZYMES RELEASED BY ALVEOLAR MACROPHAGES IN THE PATHOGENESIS OF THE ACUTE-PHASE OF HYPERSENSITIVITY PNEUMONITIS

HYDROLYTIC enzymes are the major constituents of alveolar macrophages (AM) and have been shown to be involved in many aspects of the inflamm atory pulmonary response. The aim of this study was to evaluate the ro le of lysosomal enzymes in the acute phase of hypersensitivity pneumon itis (HPs). An, experimental study on AM lysosomal enzymes of an HP-gu inea-pig model was performed. The results obtained both in vivo and in vitro suggest that intracellular enzymatic activity decrease is, at l east partly, due to release of lysosomal enzymes into the medium. A po sitive but slight correlation was found between extracellular lysosoma l activity and four parameters of lung lesion (lung index, bronchoalve olar fluid total (BALF) protein concentration, BALF LDH and BALF alkal ine phosphatase activities). Ah the above findings suggest that the AM release of lysosomal enzymes during HP Is a factor involved, although possibly not the only one, in the pulmonary lesions appearing in this disease.