The mannose receptor is expressed by subsets of APC in non-lymphoid organs.
BACKGROUND
The mannose receptor (MR) is an endocytic receptor of Mphi and endothelial cell subsets whose natural ligands include both self glycoproteins and microbial glycans. It is also expressed by immature cultured dendritic cells (DC), where it mediates high efficiency uptake of glycosylated antigens, yet its role in antigen handling in vivo is unknown. Knowledge of which APC subsets express MR will assist the design of experiments to address its immunological functions. Here the expression of MR by MHC class II positive APC in non-lymphoid organs of the mouse is described.


RESULTS
MR positive APC were identified in several peripheral organs: skin, liver, cardiac and skeletal muscle and tongue. MR positive cells in salivary gland, thyroid and pancreas coexpressed MHC class II and the myeloid markers macrosialin and sialoadhesin, but not the dendritic cell markers CD11c or DEC-205. MR and MHC class II colocalised in confocal microscope images, implying that antigen capture may be the primary role of MR in these cells. Distinct ligands of MR were found in salivary gland and pancreas tissue lysates that are candidate physiological ligands of MR positive APC in these organs.


CONCLUSIONS
The tissue and subcellular distribution of MR suggest it is appropriately located to serve as a high efficiency antigen uptake receptor of APC.
Linehan
Sheena A
SA
Sir William Dunn School of Pathology, South Parks Road, Oxford, OX1 3RE, UK. s.a.linehan@imperial.ac.uk
D000818:Animals; D000938:Antigen-Presenting Cells / Q000737:chemistry* / Q000276:immunology; D015703:Antigens, CD / Q000032:analysis; D015214:Antigens, Differentiation, Myelomonocytic / Q000032:analysis; D003713:Dendritic Cells / Q000737:chemistry / Q000276:immunology; D000949:Histocompatibility Antigens Class II / Q000032:analysis; D007371:Interferon-gamma / Q000172:deficiency / Q000235:genetics; D037181:Lectins, C-Type / Q000032:analysis*; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000032:analysis; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009928:Organ Specificity; D011956:Receptors, Cell Surface / Q000032:analysis*; D011971:Receptors, Immunologic / Q000032:analysis; D063267:Sialic Acid Binding Ig-like Lectin 1; D013347:Subcellular Fractions / Q000737:chemistry; D000097382:CD68 Molecule
D015703:Antigens, CD; D015214:Antigens, Differentiation, Myelomonocytic; D000949:Histocompatibility Antigens Class II; D007371:Interferon-gamma; D037181:Lectins, C-Type; D000090323:Mannose Receptor; D037241:Mannose-Binding Lectins; D008562:Membrane Glycoproteins; D011956:Receptors, Cell Surface; D011971:Receptors, Immunologic; D063267:Sialic Acid Binding Ig-like Lectin 1; C081026:CD68 protein, mouse; D000097382:CD68 Molecule; C571167:Siglec1 protein, mouse