Different expression of integrins by mononuclear phagocytes in peripheral blood and bronchoalveolar lavage fluid

Alveolar macrophages (AM) originate from blood monocytes and, during the ma turation process, undergo functional and morphological changes which are al so reflected in their phenotypic pattern. Among the macrophage membrane ant igens, adhesion molecules of the integrin family are particularly important for effector functions and cell-cell interactions. The aim of this study w as to analyse the membrane expression of selected integrins by AM recovered from bronchoalveolar lavage (BAL) as compared to their precursors, periphe ral blood monocytes (PBM). The cells were stained using a sensitive immunop eroxidase assay with 10 different monoclonal antibodies. The data showed a higher expression by AM than PBM of all but one of the studied adhesion mol ecules, The only exception was CD11b (Mac-l, CR3) which showed a higher exp ression in PBM than in AM. Several molecules, for example, CD49d (VLA-4), C D51 (vitronectin receptor), and CD54 (intercellular adhesion molecule-1, IC AM-1) were found to be upregulated by AM in patients with a lymphocytic pat tern of BAL. In contrast, the phenotype of PBM does not show any changes in these patients. In conclusion, we have demonstrated differences in the exp ression of integrins between AM and PBM which can be partially responsible for some of their functional differences.