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National Institute of Environmental Health Sciences

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Your Environment. Your Health.

Publication Detail

Title: MARCO is the major binding receptor for unopsonized particles and bacteria on human alveolar macrophages.

Authors: Arredouani, Mohamed S; Palecanda, Aiyappa; Koziel, Henry; Huang, Yuh-Ching; Imrich, Amy; Sulahian, Timothy H; Ning, Yao Yu; Yang, Zhiping; Pikkarainen, Timo; Sankala, Marko; Vargas, Sara O; Takeya, Motohiro; Tryggvason, Karl; Kobzik, Lester

Published In J Immunol, (2005 Nov 01)

Abstract: Alveolar macrophages (AMs) avidly bind and ingest inhaled environmental particles and bacteria. To identify the particle binding receptor(s) on human AMs, we used functional screening of anti-human AM hybridomas and isolated a mAb, PLK-1, which inhibits AM binding of unopsonized particles (e.g., TiO2, latex beads; 63 +/- 5 and 67 +/- 4% inhibition, respectively, measured by flow cytometry; n = 11) and unopsonized bacteria ( approximately 84 and 41% inhibition of Escherichia coli and Staphylococcus aureus binding by mAb PLK-1, respectively). The PLK-1 Ag was identified as the human class A scavenger receptor (SR) MARCO (macrophage receptor with collagenous structure) by observing specific immunolabeling of COS cells transfected with human MARCO (but not SR-AI/II) cDNA and by immunoprecipitation by PLK-1 of a protein of appropriate molecular mass (approximately 70 kDa) from both normal human bronchoalveolar lavage cells (>90% AMs) and human MARCO-transfected COS cells. PLK-1 also specifically inhibited particle binding by COS cells, only after transfection with human MARCO cDNA. Immunostaining showed specific labeling of AMs within human lung tissue, bronchoalveolar lavage samples, as well as macrophages in other sites (e.g., lymph node and liver). Using COS transfectants with different truncated forms of MARCO, allowed epitope mapping for the PLK-1 Ab to MARCO domain V between amino acid residues 420 and 431. A panel of Abs to various SRs identified expression on AMs, but failed to inhibit TiO2 or S. aureus binding. The data support a dominant role for MARCO in the human AM defense against inhaled particles and pathogens.

PubMed ID: 16237101 Exiting the NIEHS site

MeSH Terms: No MeSH terms associated with this publication

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