title: Comparison of C1q-receptors on rat microglia and peritoneal macrophages.
abstract: A comparison of the expression and ligand specificity of the C1q (first complement component) receptor on rat microglia and peritoneal macrophages was made. This revealed that radiolabelled C1q was competed from the peritoneal macrophages with intact C1q, and additively displaced by calf-skin collagen and purified C1q globular heads, suggesting the presence of at least two receptors. This was in contrast to microglia, where radiolabelled C1q was displaced with intact C1q and to a modest degree with collagen, but not with globular heads. Taken together, this implies that under these conditions, peritoneal macrophages and microglia both express a C1q receptor which binds to the collagen-like region, and that peritoneal macrophages additionally express a molecule which binds to the globular head of C1q. Analysis of the ligand bound by these cells reflected the differences observed in the competitive binding experiments, with the novel identification of naturally-occurring peptides from the globular head of C1q bound to the peritoneal macrophages, but not the microglia.
authors.affiliation: Molecular Immunopathology Unit, MRC Centre, Cambridge, UK. mgw1001@medschl.cam.ac.uk
authors.forename: M G
authors.initials: MG
authors.lastname: Wing
authors.forename: D J
authors.initials: DJ
authors.lastname: Seilly
authors.forename: R S
authors.initials: RS
authors.lastname: Nicholas
authors.forename: S
authors.initials: S
authors.lastname: Rahman
authors.forename: J
authors.initials: J
authors.lastname: Zajicek
authors.forename: P J
authors.initials: PJ
authors.lastname: Lachmann
authors.forename: D A
authors.initials: DA
authors.lastname: Compston
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001667:Binding, Competitive / Q000276:immunology; D002352:Carrier Proteins; D003094:Collagen / Q000494:pharmacology; D017364:Collagenases / Q000235:genetics / Q000494:pharmacology; D015922:Complement C1q / Q000378:metabolism / Q000494:pharmacology; D004591:Electrophoresis, Polyacrylamide Gel; D006801:Humans; D018960:Hyaluronan Receptors; D017737:Macrophages, Peritoneal / Q000737:chemistry* / Q000276:immunology*; D008562:Membrane Glycoproteins; D017628:Microglia / Q000737:chemistry* / Q000276:immunology*; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D051381:Rats; D017208:Rats, Wistar; D011951:Receptors, Complement / Q000032:analysis* / Q000378:metabolism
chemical_list: C087299:C1QBP protein, human; C490195:C1qbp protein, rat; D002352:Carrier Proteins; D018960:Hyaluronan Receptors; D008562:Membrane Glycoproteins; D024101:Mitochondrial Proteins; D011951:Receptors, Complement; C032402:complement 1q receptor; D015922:Complement C1q; D003094:Collagen; D017364:Collagenases