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J. Exp. Med.,
Volume 189, Number 12, June 21, 1999 1961-1972
By

From the * Sir William Dunn School of Pathology, Oxford OX1 3RE, United Kingdom; and the The mannose receptor (MR) has established roles in macrophage (M
Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis,
Missouri 63110
) phagocytosis of microorganisms and endocytic clearance of host-derived glycoproteins, and has recently been implicated in antigen capture by dendritic cells (DCs) in vitro. MR is the founder member of a family of homologous proteins, and its recognition properties differ according to its tissue of origin.
Given this heterogeneity and our recent discovery of a soluble form of MR in mouse serum,
we studied the sites of synthesis of MR mRNA and expression of MR protein in normal mouse
tissues. We demonstrate that synthesis and expression occur at identical sites, and that mature
M
and endothelium are heterogeneous with respect to MR expression, additionally describing
MR on perivascular microglia and glomerular mesangial cells. However, MR was not detected
on DCs in situ, or on marginal zone or subcapsular sinus M
, both of which have MR-like
binding activities. We also compared expression of MR to the binding of a recombinant probe
containing the cysteine-rich domain of MR. We show that MR and its putative ligand(s) are
expressed at nonoverlapping sites within lymphoid organs, consistent with a transfer function
for soluble MR. Therefore, in addition to endocytic and phagocytic roles, MR may play an
important role in antigen recognition and transport within lymphoid organs.
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