Localization of surfactant protein A (SP-A) in alveolar macrophage subpopulations of normal and fibrotic rat lung |
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Authors: | M. Kasper G. Haroske D. Schuh M. Müller R. Koslowski K -W. Wenzel K. Sakai |
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Affiliation: | (1) Institute of Pathology, Technical University of Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany;(2) Institute of Physiological Chemistry, Technical University of Dresden, Fetscherstrasse 74, D-01307 Dresden, Germany;(3) Department of Nutrition, The University of Tokushima, School of Medicine, 770 Tokushima, Japan |
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Abstract: | The colocalization of surfactant protein A (SP-A) and the alveolar macrophage markers ED1 and RM-1, as well as various lectins of the N-acetyl-galactosamine group [Maclura pomifera lectin (MPA), Dolichos biflorus lectin (DBA), soybean agglutinin (SBA)] and of the mannose group [Canavalia ensiformis lectin (ConA), Galanthus nivalis lectin (GNA)] was studied in normal and fibrotic rat lung tissues. In normal tissue, SP-A was located preferentially in the alveolar macrophage subpopulation lacking specific binding sites for lectins of the N-acetylgalactosamine group (DBA and SBA), although 50% of MPA-binding macrophages contained SP-A. The ED1-positive cells were SP-A-negative, whereas SP-A uptake could be detected among the RM-1 immunoreactive as well as the ConA and GNA binding macrophages. In fibrotic lung tissue, however, a small number of .DBA and SBA binding macrophages contained SP-A and the percentage of GNA and ConA binding alveolar macrophages exhibiting SP-A immunoreactivity was reduced. Additionally, the number of ED1+/SP-A+ macrophages was found to be increased. Immunoelectron microscopy revealed accumulation of SP-A in the extracellular space. The differing SP-A content in different alveolar macrophage subpopulations suggests a more complex mechanism of uptake and degradation of surfactant proteins in normal and pathological conditions, which cannot simply be explained by the glycoconjugate pattern on the surface of alveolar macrophages. |
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