ALVEOLAR MACROPHAGE SURFACE CARBOHYDRATE EXPRESSION IS ALTERED IN INTERSTITIAL LUNG-DISEASE AS DETERMINED BY LECTIN-BINDING PROFILES

Cell-surface-associated glycoconjugates play important roles in cellul ar functions such as antigen presentation and cell adhesion, functions that may be modulated in patients with interstitial lung disease. Bec ause carbohydrate residues can be recognized by specific lectins, we d esigned our study to establish baseline data for bronchoalveolar-lavag e-derived cells from normal volunteers and to compare the lectin-bindi ng properties of these cells with cells recovered from patients presen ting with interstitial lung disease. Cells were obtained from patients with idiopathic pulmonary fibrosis (n = 10), patients with sarcoidosi s (n = 20), and patients receiving amiodarone without evidence of clin ical lung disease (n = 10) as well as from normal volunteers (n = 8). To determine the pattern of cell-surface glycoconjugate expression on alveolar macrophages (AM), we used a panel of 21 fluorochrome-coupled plant lectins and employed flow cytometry to determine their binding t o AM. The labeling profiles of AM were found to be highly reproducible for normal subjects. At the lectin concentrations used for this study , some lectins showed very little binding to AM and some displayed int ermediate binding, but the majority of the lectins labeled nearly all AM in samples. Fluorescence intensity varied characteristically for ce lls labeled with different lectins, providing further refinement and p ermitting discrimination beyond that provided by data restricted to pe rcent of labeling. AM from patients with interstitial lung disease sho wed increased binding for the plant-derived lectins PNA, UEA-l, BSL-l, VVL, and SJA compared with AM from normal subjects, being most augmen ted for AM from patients with idiopathic pulmonary fibrosis. Because p eripheral blood monocytes from normal subjects show a higher percentag e of labeling with PNA, UEA-l, SJA, and BSL-l than did AM, the increas ed expression of binding sites for these four lectins by AM from patie nts with interstitial lung disease may reflect the influx of immature blood monocytes and/or the emergence of a proinflammatory macrophage p henotype. This study demonstrated heterogeneous expression of surface carbohydrate residues by AM and blood monocytes from normal subjects a nd alterations in carbohydrate receptor expression in interstitial lun g disease. Lectin-binding properties may prove useful, therefore, in t he evaluation of mononuclear phagocyte populations in interstitial lun g disease, especially by the identification of functional subsets and/ or changed activation states.