DEGRADATION OF TUBERCULOPROTEINS BY CATHEPSIN D-TYPE PROTEINASE OF ALVEOLAR AND PERITONEAL MACROPHAGES OF MICE

Abstract

During the progress of tuberculous infection in mice, cathepsin activity of the lung homogenate increased to a considerable extent. With a view that this increase was due to the local accumulation of phagocytic cells, alveolar and peritoneal macrophages were harvested for examination of their proteinase activities. They were capable of digesting acid-denatured hemoglobin and less efficiently native tuberculoproteins. Alveolar macrophages appeared more active in this respect than peritoneal macrophages. The pH optimum lay between 3.0 and 4.0. The activity was inhibited with pepstatin, a specific pepsin inhibitor, suggesting the cathepsin D-type nature. The peptide fraction as degraded products of tuberculoproteins was still capable of eliciting skin reactions in sensitized guinea pigs, though the potency was lower. These data were compatible with our previous finding that the tuberculin-active peptides of low-molecular weights were separated from the infected mouse lung homogenate.