1. Deletion or inhibition of Fc gamma receptor 2B (CD32) prevents FVIII-specific activation of memory B cells in vitro
- Author
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Sonja Werwitzke, Marcus von Hornung, Julia Kutzschbach, Arne Trummer, Arnold Ganser, Andreas Tiede, Katy Kalippke, and Nadine Vollack
- Subjects
0301 basic medicine ,congenital, hereditary, and neonatal diseases and abnormalities ,Adoptive cell transfer ,CD32 ,medicine.drug_class ,animal diseases ,B-cell receptor ,B-Lymphocyte Subsets ,Dose-Response Relationship, Immunologic ,Antibodies, Heterophile ,Apoptosis ,Antigen-Antibody Complex ,Hemophilia A ,Lymphocyte Activation ,Monoclonal antibody ,Immune tolerance ,Mice ,03 medical and health sciences ,0302 clinical medicine ,Immune system ,Bone Marrow ,hemic and lymphatic diseases ,medicine ,Animals ,Cells, Cultured ,B cell ,Mice, Knockout ,Factor VIII ,biology ,Receptors, IgG ,Antibodies, Monoclonal ,Hematology ,Adoptive Transfer ,Antibodies, Neutralizing ,Molecular biology ,Recombinant Proteins ,Disease Models, Animal ,030104 developmental biology ,medicine.anatomical_structure ,Immunology ,biology.protein ,Leukocyte Common Antigens ,Antibody ,Immunologic Memory ,Spleen ,030215 immunology - Abstract
SummaryDevelopment of inhibitory antibodies against factor VIII (FVIII) is a severe complication of replacement therapy in haemophilia A. Patients with inhibitors are treated with high FVIII doses in the context of immune tolerance therapy (ITT). Data from haemophilia A mouse model suggest that high FVIII concentrations prevent the formation of antibody secreting cells (ASCs) from memory B cells (MBCs) by inducing apoptosis. Fc gamma receptor 2B (CD32) is an important regulator of B cell function, mediating inhibitory signals after cross-linking with the B cell receptor. Here, the role of CD32 in the regulation of FVIII-specific MBCs was investigated using F8-/- and F8-/-CD32-/- knockout mice and monoclonal antibodies (mAbs). The initial immune response was similar between F8-/- and F8-/-CD32-/- mice, including concentration of anti-FVIII antibodies and number of FVIII-specific ASCs in spleen and bone marrow. In contrast, formation of ASCs from MBCs upon rhFVIII re-stimulation in vitro was abolished in F8-/-CD32-/- mice, whereas FVIII/anti-FVIII immune complexes significantly enhanced ASC formation in F8-/- mice. Inhibition of CD32 by mAbs or F(ab)2 fragments prevented ASC formation in a dose-dependent manner. Transfer of B cell-depleted splenocytes using CD45R (B220) depletion from CD32-competent mice did not restore ASC formation in F8-/-CD32-/- cells confirming that CD32 is required on B cells. We conclude that CD32 is a crucial regulator of FVIII-specific B cells and is required for the differentiation of MBCs into ASCs. Inhibition of CD32 could potentially improve the efficacy of FVIII in the context of ITT.
- Published
- 2015
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