C1qR(P), a myeloid cell receptor in blood, is predominantly expressed on endothelial cells in human tissue.
C1qR(P) is a type I cell surface glycoprotein that has been shown to enhance ingestion of suboptimally opsonized targets by phagocytes in vitro. In this study, we developed and characterized polyclonal antibodies to study the tissue distribution of this receptor targeted to either the N- or C-terminal portion of the molecule. C1qR(P) was detected in vascular endothelial cells and in a subset of pyramidal neurons in the brain, as well as neutrophils, but it was absent in most tissue macrophages. Analysis of in vitro differentiation of blood monocytes to dendritic cells demonstrated a down-regulation of the receptor as monocytes differentiate to dendritic cells, providing a possible explanation for the lack of reactivity of these cells in tissue. The predominant presence of C1qR(P) in endothelial cells, while compatible with a phagocytic role in host defense and/or clearance of cellular material, suggests other possible novel roles for this receptor.
Fonseca
M I
MI
Department of Molecular Biology and Biochemistry, University of California, Irvine, Irvine, CA 92697, USA. atenner@uci.edu
Carpenter
P M
PM
Park
M
M
Palmarini
G
G
Nelson
E L
EL
Tenner
A J
AJ
D000818:Animals; D016466:CHO Cells; D002196:Capillaries / Q000166:cytology; D002352:Carrier Proteins; D002454:Cell Differentiation; D006224:Cricetinae; D003412:Cricetulus; D003713:Dendritic Cells / Q000737:chemistry / Q000187:drug effects; D004730:Endothelium, Vascular / Q000737:chemistry* / Q000166:cytology; D005786:Gene Expression Regulation; D006801:Humans; D018960:Hyaluronan Receptors; D007124:Immunoenzyme Techniques; D008264:Macrophages / Q000737:chemistry; D017737:Macrophages, Peritoneal / Q000737:chemistry; D008562:Membrane Glycoproteins; D051379:Mice; D017628:Microglia / Q000737:chemistry; D024101:Mitochondrial Proteins; D009000:Monocytes / Q000737:chemistry / Q000166:cytology; D009206:Myocardium / Q000737:chemistry; D009363:Neoplasm Proteins / Q000032:analysis; D009419:Nerve Tissue Proteins / Q000032:analysis; D009504:Neutrophils / Q000737:chemistry; D017924:Nucleopolyhedroviruses / Q000235:genetics; D009928:Organ Specificity; D010587:Phagocytosis; D017966:Pyramidal Cells / Q000737:chemistry; D051381:Rats; D011951:Receptors, Complement / Q000032:analysis* / Q000235:genetics / Q000276:immunology / Q000502:physiology; D011993:Recombinant Fusion Proteins / Q000032:analysis; D018411:Spodoptera / Q000166:cytology; D014162:Transfection; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology; D020298:U937 Cells / Q000737:chemistry; D014471:Umbilical Veins / Q000166:cytology; D014781:Viscera / Q000737:chemistry
C087299:C1QBP protein, human; C490193:C1qbp protein, mouse; C490195:C1qbp protein, rat; D002352:Carrier Proteins; D018960:Hyaluronan Receptors; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D009419:Nerve Tissue Proteins; D011951:Receptors, Complement; D011993:Recombinant Fusion Proteins; D014409:Tumor Necrosis Factor-alpha; C032402:complement 1q receptor