Differences in expression of monocyte/macrophage surface antigens in peripheral blood and bronchoalveolar lavage cells in interstitial lung diseases.

The surface antigens of monocytic cells in bronchoalveolar lavage (BAL) fluid were analyzed in 10 patients with sarcoidosis, 8 patients with idiopathic pulmonary fibrosis (IPF), 9 patients with extrinsic allergic alveolitis (EAA), and 10 healthy volunteers, and compared with the surface antigens of peripheral blood monocytes (PBM) of the same individuals. The absolute numbers of alveolar macrophages (AM) were increased in all disease groups as were the numbers of small monocyte-like cells, indicating an increased influx of PBM into the alveoli, which was the most prominent in EAA patients. In all groups investigated, the percentages of PBM positive for the monoclonal antibodies (mAb) CD13, CD14, CD33, U26, and Max3 were higher than the percentages of BAL macrophages positive for these markers, while the Max24 marker was equally expressed. In all groups the percentages of AM positive for RFD9 and CD68 were higher than the percentages positive for PBM. The absolute numbers of CD13+ macrophages were increased in IPF and EAA patients, probably due to the increased influx of monocytic cells. The 3 mAb in the CD68 cluster (i.e., Ki-M6, Ki-M7, and Y2/131) demonstrated marked differences in expression on PBM as well as on AM. This is probably because CD68(Ki-M6) recognizes a different epitope than CD68(Ki-M7) and CD68(Y2/131). The latter 2 become increasingly expressed by AM and this is paralleled by an increased CD68(KiM6) expression. The expression of CD68, which is associated with the generation of oxygen radicals during the respiratory burst and increased chemiluminescence, tended to be elevated on PBM and AM of IPF patients, although with a broad range.