title: Clearance of complement by human vascular endothelial cells: effects of hypoxia/reoxygenation and IL-1beta activation.
abstract: Antibody-mediated rejection is characterized by deposits of complement (C) C4 and C3 split products on endothelial cells (ECs). C3 split products are critical mechanistically and diagnostically because they are deposited in amplified quantities, bind covalently to ECs and act as ligands for leukocytes. This study was designed to determine whether cultured vascular human ECs could clear covalently bound C3 split products from their surface. An immunoglobulin M (IgM) antibody against beta(2)-microglobulin of major histocompatibility complex class I antigens was used to activate C in human serum. Some cells were exposed to hypoxia/reoxygenation and/or interleukin 1beta (IL-1beta) prior to incubation with antibody. C3b/iC3b and C3d deposition on the cell surface was measured by flow cytometry. Incubation with antibody followed by human serum caused a dose-dependent deposition of C3b/iC3b and C3d. Over half of deposited C3b/iC3b and one-third of C3d were cleared from the cell surface during a 3-7-h incubation period with human serum. Neither hypoxia/reoxygenation nor IL-1beta further increased the deposition of C3b/iC3b and C3d, and only slightly modulated their rates of clearance. In summary, human ECs rapidly clear iC3b and C3d from their surface. This finding may have important diagnostic and mechanistic implications to transplantation because C3d is used as a marker of antibody-mediated rejection.
authors.affiliation: Department of Biomedical Engineering, Johns Hopkins University School of Medicine, Baltimore, MD, USA.
authors.forename: Jered B
authors.initials: JB
authors.lastname: Haun
authors.forename: William M
authors.initials: WM
authors.lastname: Baldwin
authors.forename: B Rita
authors.initials: BR
authors.lastname: Alevriadou
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000494:pharmacology; D015687:Cell Hypoxia / Q000502:physiology*; D002462:Cell Membrane / Q000378:metabolism; D002478:Cells, Cultured; D003179:Complement C3b / Q000378:metabolism*; D015933:Complement C3d / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D042783:Endothelial Cells / Q000378:metabolism*; D006801:Humans; D007075:Immunoglobulin M / Q000276:immunology / Q000378:metabolism; D018799:Intercellular Adhesion Molecule-1 / Q000378:metabolism; D007375:Interleukin-1 / Q000494:pharmacology / Q000502:physiology*; D010100:Oxygen / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000494:pharmacology; D019010:Vascular Cell Adhesion Molecule-1 / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D007075:Immunoglobulin M; D007375:Interleukin-1; D011994:Recombinant Proteins; D019010:Vascular Cell Adhesion Molecule-1; D018799:Intercellular Adhesion Molecule-1; D003179:Complement C3b; D015933:Complement C3d; D010100:Oxygen