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Infect Immun, June 1998, p. 2769-2777, Vol. 66, No. 6
Division of Infectious Diseases, Department
of Medicine, Department of Veterans Affairs Medical Center, and the
University of Iowa, Iowa City, Iowa 52242
Received 5 February 1998/Returned for modification 9 March
1998/Accepted 27 March 1998
The macrophage mannose receptor (MR) along with complement
receptors mediates phagocytosis of the M. tuberculosis
virulent strains Erdman and H37Rv. We have determined that the terminal mannosyl units of the M. tuberculosis surface lipoglycan,
lipoarabinomannan (LAM), from the Erdman strain serve as ligands for
the MR. The biology of the MR (receptor binding and trafficking) in
response to phagocytic stimuli is not well characterized. This study
analyzes the MR-dependent phagocytosis mediated by Erdman LAM presented on a 1-µm-diameter phagocytic particle. Erdman LAM microspheres exhibited a time- and dose-dependent rapid increase in attachment and
internalization by human monocyte-derived macrophages (MDMs). In
contrast, internalization of LAM microspheres by monocytes was minimal.
Microsphere internalization by MDMs was visualized and quantitated by
immunofluorescence and confocal and electron microscopy and resembled
conventional phagocytosis. Phagocytosis of LAM microspheres by MDMs was
energy, cytoskeleton, and calcium dependent and was mannan inhibitable.
Trypsin treatment of MDMs at 37°C, which depleted surface and
recycling intracellular pools of the MR, reduced the subsequent
attachment of LAM microspheres. Trypsin treatment at 4°C allowed for
subsequent recovery of LAM microsphere phagocytosis at 37°C by
recycled MRs. Pretreatment of MDMs with cycloheximide influenced LAM
microsphere phagocytosis to only a small extent, indicating that
MR-dependent phagocytosis of the microspheres was occurring primarily
by preformed recycled receptors. This study characterizes the
requirements for macrophage phagocytosis of a LAM-coated particle
mediated by the MR. This model will be useful in further
characterization of the intracellular pathway taken by phagocytic
particles coated with different LAM types in macrophages following
ingestion.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Characterization of Mannose Receptor-Dependent
Phagocytosis Mediated by Mycobacterium tuberculosis
Lipoarabinomannan
*
Corresponding author. Mailing address: Division of
Infectious Diseases, Department of Medicine, University of Iowa, 200 Hawkins Dr., SW54-GH, Iowa City, IA 52242. Phone: (319) 356-1387. Fax: (319) 356-4600.
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