title: Enhanced uptake of blood coagulation factor VIII containing immune complexes by antigen presenting cells.
abstract: Essentials Anti-factor (F) VIII antibody formation is a major complication in the treatment of hemophilia A. We investigated uptake of FVIII and FVIII immune complex by bone marrow derived dendritic cells. Immune complex formation increased uptake of FVIII 3-4 fold in a Fcγ receptor dependent manner. FVIII immune complex binding to Fcγ receptors may modulate immune tolerance induction.
  
  
  
  Background A major complication in the treatment of hemophilia A is the development of inhibitory antibodies targeting coagulation factor VIII (FVIII). Eradication of these inhibitors can be established by immune tolerance induction (ITI), which consists of daily administration of high dosages of FVIII. FVIII immune complexes (FVIII-IC) could be formed following FVIII infusion in patients with pre-existing anti-FVIII antibodies. Objectives Here we studied endocytosis of FVIII-IC by bone marrow-derived dendritic cells (BMDCs). Methods BMDCs were pulsed with FVIII/FVIII-IC and uptake was assessed by flow cytometry and confocal imaging. Results BMDCs were able to efficiently internalize FVIII-IC in a dose-dependent manner, 3-4-fold more efficiently when compared with equimolar concentrations of non-complexed FVIII. Uptake of FVIII-IC, but not FVIII alone, could be inhibited with anti-Fcγ receptor (FcγR) antibody 2.4G2, indicating functional involvement of FcγR. No internalization of FVIII-IC was observed in BMDCs lacking FcγRI, FcγRIIb, FcγRIII and FcγRIV. Genetic ablation of FcγRIIb, FcγRIII or FcγRIV individually did not affect the ability of anti-FVIII IgG to promote the uptake of FVIII. BMDCs lacking FcγRI showed lower FVIII-IC uptake levels when compared with other single FcγR null BMDCs. Expression of the inhibitory FcγRIIb alone was sufficient to internalize FVIII-IC more efficiently than FVIII. Conclusions FcγR are critical in the internalization of FVIII-IC by BMDCs and multiple FcγR can contribute independently to this process. Our findings provide a basis for future studies to address whether the outcome of ITI is dependent on the interplay between FVIII-IC and inhibitory and activating FcγR.
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: R B
authors.initials: RB
authors.lastname: Hartholt
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Wroblewska
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Herczenik
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: I
authors.initials: I
authors.lastname: Peyron
authors.affiliation: Department of Immunopathology, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Ten Brinke
authors.affiliation: Department of Immunopathology, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Rispens
authors.affiliation: Department of Hematopoiesis, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: M A
authors.initials: MA
authors.lastname: Nolte
authors.affiliation: Department of Hematopoiesis, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Slot
authors.affiliation: Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: J W
authors.initials: JW
authors.lastname: Claassens
authors.affiliation: Chair of Genetics, Department of Biology, University of Erlangen-Nuremberg, Erlangen, Germany.
authors.forename: F
authors.initials: F
authors.lastname: Nimmerjahn
authors.affiliation: Department of Human Genetics, Leiden University Medical Center, Leiden, the Netherlands.
authors.forename: J S
authors.initials: JS
authors.lastname: Verbeek
authors.affiliation: Department of Plasma Proteins, Sanquin-AMC Landsteiner Laboratory, Amsterdam, the Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Voorberg
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000008:administration & dosage; D000936:Antigen-Antibody Complex / Q000276:immunology; D000938:Antigen-Presenting Cells / Q000276:immunology / Q000378:metabolism*; D001777:Blood Coagulation; D001854:Bone Marrow Cells / Q000378:metabolism; D003713:Dendritic Cells / Q000378:metabolism; D004705:Endocytosis; D005169:Factor VIII / Q000276:immunology / Q000378:metabolism*; D006467:Hemophilia A / Q000276:immunology / Q000628:therapy*; D006801:Humans; D007108:Immune Tolerance; D007074:Immunoglobulin G / Q000737:chemistry; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018613:Microscopy, Confocal; D008968:Molecular Conformation; D051381:Rats; D017452:Receptors, IgG / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D000936:Antigen-Antibody Complex; D007074:Immunoglobulin G; D017452:Receptors, IgG; D011994:Recombinant Proteins; C427184:recombinant factor VIII SQ; C078147:F8 protein, human; D005169:Factor VIII
keywords: Fc gamma receptors; endocytosis; factor VIII; hemophilia A; immune complex