RESUMO
BACKGROUND AND AIM OF THE WORK: The phenotype of human alveolar macrophages (AM) can be affected by the process of maturation/differentiation and by multiple factors from the local environment. The aim of our study was to assess the expression of selected phenotypic markers characteristic for subsets of mononuclear phagocytes in bronchoalveolar lavage fluid (BAL) and peripheral blood with special attention to calprotectin (27E10), a marker of acute inflammatory macrophages. METHODS: The expression of calprotectin and 13 other phenotypic markers was evaluated by an immunoperoxidase slide assay and computer image analysis. RESULTS: We consider calprotectin (27E10 antigen) to be a marker of freshly recruited, monocyte-like, mononuclear phagocytes, being expressed in 84 +/- 13% PBM and only 10 +/- 11% of AM, p < 0.001. Computer image analysis confirmed that calprotectin-positive mononuclear cells in peripheral blood and BAL are morphologically very similar in contrast to the much larger calprotectin-negative AM. On the other hand, 25F9 antigen, the transferrin receptor (CD71), KiM8 (CD68), RFD1 (marker of dendritic cells), RFD7 (marker of mature macrophages), RFD9 (marker of epithelioid cells and macrophages of germinal centers), and RM3/1 (macrophages of late phase inflammation) were restricted preferentially to mature AM. CONCLUSIONS: Our study demonstrates phenotypic differences between mononuclear phagocytes derived from BAL and their peripheral blood precursors, and indicates markers useful for assessing the stages of maturation/differentiation of these cells. The percentage of calprotectin (27E10) positive AM might represent a parameter for assessing mononuclear phagocyte influx from peripheral blood to the lung in the very early stage of inflammatory reactions.