CD13/aminopeptidase N, a novel chemoattractant for T lymphocytes in pulmonary sarcoidosis

CD13/aminopeptidase N (E.C.3.4.11.2) is an ectoenzyme located in the outer membrane of a variety of cells. Because aminopeptidase expression was shown to be upregulated by a Th1-related cytokine, IFN-gamma, we examined here t he significance of CD13/aminopeptidase N in pulmonary sarcoidosis. The acti vity of aminopeptidase in bronchoalveolar lavage fluid (BALF) was significa ntly higher in patients with sarcoidosis than in normal volunteers (NV) and control patients (CP). The activity significantly correlated with lymphocy te percentages and the ratio of CD4+ to CD8+ T lymphocytes in the BALF, and was higher in patients with sarcoidosis with parenchymal involvement than in those without the involvement, CD13/aminopeptidase N protein, which has a molecular mass of approximately 150 kD, was detectable in alveolar macrop hages (AM) from patients with sarcoidosis at higher levels than in those fr om NV. CD13/aminopeptidase N induced in vitro chemotactic migration of huma n lymphocytes in a concentration range of 10(-5) to 10(-1) U/ml. The chemot actic activity was greater for CD4+ T lymphocytes than for CD8+ T lymphocyt es. The enzymatic activity of CD13/aminopeptidase N was responsible for the chemotactic activity because bestatin, an inhibitor of CD13/aminopeptidase N, abolished the chemotactic activity. Higher chemotactic activity for lym phocytes was detected in the BALF from patients with sarcoidosis than in th at from NV, and the activity was significantly decreased by treatment with bestatin. This study indicates that CD13/aminopeptidase N expressed in AM m ay have a role in T-lymphocyte involvement in the sarcoid lung and the path ogenesis of alveolitis in this disorder.