PROLIFERATING ALVEOLAR MACROPHAGES IN BAL AND LUNG-FUNCTION CHANGES IN INTERSTITIAL LUNG-DISEASE

In interstitial lung disease, the number of alveolar macrophages (AMs) can be increased. This may be caused by recruitment of precursor cell s from peripheral blood and/or local proliferation in the lung. We the refore analysed proliferation, by studying both the expression of the nuclear proliferation antigen, Ki67, and the deoxyribonucleic acid (DN A) content, using the Feulgen reaction followed by cytometry. The pati ents had interstitial lung disease, i.e. sarcoidosis (n=20), extrinsic allergic alveolitis (n=20), idiopathic lung fibrosis or lung involvem ent in collagen-vascular disease (n=19). In all patient groups there w as a significant increase in proliferating AMs compared to healthy con trols (4.2 versus 1.4% Feulgen, 2.1 versus 0.5% Ki67), with a signific ant correlation between these two parameters. A positive correlation w as also found in bronchoalveolar lavage (BAL) between numbers of lymph ocytes and proliferating cells in sarcoidosis and in fibrosis. In fibr osis, numbers of eosinophils and proliferating cells were also positiv ely correlated. Our main finding was, however, a positive correlation between numbers of proliferating cells (Feulgen) and lung function par ameters, especially vital capacity and oxygen tension (Po2) at rest, i n patients with sarcoidosis and lung fibrosis. By contrast, in extrins ic allergic alveolitis, no correlation could be observed between proli ferating cells and cell population or lung function. Our results sugge st that local proliferation of macrophages is an important element in interstitial lung disease.