Current concepts of pulmonary sarcoidosis suggest that the alveolar macrophage plays a central role in the pathogenesis of the disease. To help define the population of alveolar macrophages in sarcoidosis, we compared the surface phenotype of alveolar macrophages from patients with sarcoidosis and from normal individuals by using monoclonal antibodies (63D3, OKM1, MΦP-9, MΦS-1, 61D3, and MΦS-39) that detect surface antigens on cells of monocyte/macrophage lineage. Although almost all blood monocytes expressed surface antigens detected by each of these antibodies, only a minority of normal alveolar macrophages expressed the same surface antigens (p < 0.05, each comparison). However, in sarcoidosis, the percentage of alveolar macrophages expressing these surface antigens was increased (p < 0.05, each comparison with normal alveolar macrophages). Several findings supported the conclusion that the increasd expression of these monocyte-linkage surface antigens on sarcoid alveolar macrophages resulted from increased recruitment of monocytes to the lung in sarcoidosis and not from abnormal 'activation' of alveolar macrophages. First, alveolar macrophages expressing these antigens had an immature morphology. Second, in vitro cultivation of blood monocytes and alveolar macrophages in the presence of immune and inflammatory mediators, including mediators known to be present in the lung in sarcoidosis, did not prevent the loss of expression of monocyte-lineage surface antigens from monocytes or induce reexpression of monocyte-lineage surface antigens on alveolar macrophages. Third, the expression of monocyte-lineage surface antigens was only increased on sarcoid macrophages from patients whose lower respiratory tract contained an increased number of T lymphocytes, cells known to release monocyte chemotactic factor in sarcoidosis. Consistent with the knowledge that corticosteroids usually suppress the alveolitis of active sarcoidosis, when the expression of alveolar macrophage surface antigens was evaluated before and during therapy, the percentage of alveolar macrophage expressing monocyte-lineage surface antigens returned to normal after 1 to 3 mo of therapy. These observations support the concept that the changes in the alveolar macrophage population in sarcoidosis are linked, at least in part, to increased recruitment of blood monocytes to the lung and suggest that the population of alveolar macrophages in sarcoidosis is relatively immature compared with the alveolar macrophages present in the normal lung.
|Number of pages||9|
|Journal||Journal of Immunology|
|Publication status||Published - 6 Mar 1985|
ASJC Scopus subject areas
- Immunology and Allergy