Recombinant Factor VIII Fc Inhibits B Cell Activation via Engagement of the FcγRIIB Receptor. 2020

Maria T Georgescu, and Paul C Moorehead, and Tongyao Liu, and Jennifer Dumont, and David W Scott, and Christine Hough, and David Lillicrap
Clinical and Molecular Hemostasis Research Group, Department of Pathology and Molecular Medicine, Queen's University, Kingston, ON, Canada.

The development of neutralizing antibodies (inhibitors) against factor VIII (FVIII) is a major complication of hemophilia A treatment. The sole clinical therapy to restore FVIII tolerance in patients with inhibitors remains immune tolerance induction (ITI) which is expensive, difficult to administer and not always successful. Although not fully understood, the mechanism of ITI is thought to rely on inhibition of FVIII-specific B cells (1). Its efficacy might therefore be improved through more aggressive B cell suppression. FcγRIIB is an inhibitory Fc receptor that down-regulates B cell signaling when cross-linked with the B cell receptor (BCR). We sought to investigate if recombinant FVIII Fc (rFVIIIFc), an Fc fusion molecule composed of FVIII and the Fc region of immunoglobulin G1 (IgG1) (2), is able to inhibit B cell activation more readily than FVIII. rFVIIIFc was able to bind FVIII-exposed and naïve B cells from hemophilia A mice as well as a FVIII-specific murine B cell hybridoma line (413 cells). An anti-FcγRIIB antibody and FVIII inhibited binding, suggesting that rFVIIIFc is able to interact with both FcγRIIB and the BCR. Furthermore, incubation of B cells from FVIII-exposed mice and 413 cells with rFVIIIFc resulted in increased phosphorylation of SH-2 containing inositol 5-phosphatase (SHIP) when compared to FVIII. B cells from FVIII-exposed hemophilia A mice also exhibited decreased extracellular signal-regulated kinase (ERK) phosphorylation when exposed to rFVIIIFc. These differences were absent in B cells from naïve, non-FVIII exposed hemophilic mice suggesting an antigen-dependent effect. Finally, rFVIIIFc was able to inhibit B cell calcium flux induced by anti-Ig F(ab)2. Our results therefore indicate that rFVIIIFc is able to crosslink FcγRIIB and the BCR of FVIII-specific B cells, causing inhibitory signaling in these cells.

UI MeSH Term Description Entries
D007141 Immunoglobulin Fc Fragments Crystallizable fragments composed of the carboxy-terminal halves of both IMMUNOGLOBULIN HEAVY CHAINS linked to each other by disulfide bonds. Fc fragments contain the carboxy-terminal parts of the heavy chain constant regions that are responsible for the effector functions of an immunoglobulin (COMPLEMENT fixation, binding to the cell membrane via FC RECEPTORS, and placental transport). This fragment can be obtained by digestion of immunoglobulins with the proteolytic enzyme PAPAIN. Fc Fragment,Fc Fragments,Fc Immunoglobulin,Fc Immunoglobulins,Ig Fc Fragments,Immunoglobulin Fc Fragment,Immunoglobulins, Fc,Immunoglobulins, Fc Fragment,Fc Fragment Immunoglobulins,Fc Fragment, Immunoglobulin,Fc Fragments, Ig,Fc Fragments, Immunoglobulin,Fragment Immunoglobulins, Fc,Fragment, Fc,Fragments, Ig Fc,Immunoglobulin, Fc
D008213 Lymphocyte Activation Morphologic alteration of small B LYMPHOCYTES or T LYMPHOCYTES in culture into large blast-like cells able to synthesize DNA and RNA and to divide mitotically. It is induced by INTERLEUKINS; MITOGENS such as PHYTOHEMAGGLUTININS, and by specific ANTIGENS. It may also occur in vivo as in GRAFT REJECTION. Blast Transformation,Blastogenesis,Lymphoblast Transformation,Lymphocyte Stimulation,Lymphocyte Transformation,Transformation, Blast,Transformation, Lymphoblast,Transformation, Lymphocyte,Activation, Lymphocyte,Stimulation, Lymphocyte
D011961 Receptors, Fc Molecules found on the surface of some, but not all, B-lymphocytes, T-lymphocytes, and macrophages, which recognize and combine with the Fc (crystallizable) portion of immunoglobulin molecules. Fc Receptors,Fc Receptor,Receptor, Fc
D011993 Recombinant Fusion Proteins Recombinant proteins produced by the GENETIC TRANSLATION of fused genes formed by the combination of NUCLEIC ACID REGULATORY SEQUENCES of one or more genes with the protein coding sequences of one or more genes. Fusion Proteins, Recombinant,Recombinant Chimeric Protein,Recombinant Fusion Protein,Recombinant Hybrid Protein,Chimeric Proteins, Recombinant,Hybrid Proteins, Recombinant,Recombinant Chimeric Proteins,Recombinant Hybrid Proteins,Chimeric Protein, Recombinant,Fusion Protein, Recombinant,Hybrid Protein, Recombinant,Protein, Recombinant Chimeric,Protein, Recombinant Fusion,Protein, Recombinant Hybrid,Proteins, Recombinant Chimeric,Proteins, Recombinant Fusion,Proteins, Recombinant Hybrid
D005169 Factor VIII Factor VIII of blood coagulation. Antihemophilic factor that is part of the factor VIII/von Willebrand factor complex. Factor VIII is produced in the liver and acts in the intrinsic pathway of blood coagulation. It serves as a cofactor in factor X activation and this action is markedly enhanced by small amounts of thrombin. Coagulation Factor VIII,Factor VIII Clotting Antigen,Factor VIII Coagulant Antigen,Factor VIII Procoagulant Activity,Thromboplastinogen,Blood Coagulation Factor VIII,F VIII-C,Factor 8,Factor 8 C,Factor Eight,Factor VIIIC,Hyate-C,Hyatt-C,F VIII C,Hyate C,HyateC,Hyatt C,HyattC
D006467 Hemophilia A The classic hemophilia resulting from a deficiency of factor VIII. It is an inherited disorder of blood coagulation characterized by a permanent tendency to hemorrhage. Factor VIII Deficiency,Hemophilia,Autosomal Hemophilia A,Classic Hemophilia,Deficiency, Factor VIII,Factor 8 Deficiency, Congenital,Factor VIII Deficiency, Congenital,Haemophilia,Hemophilia A, Congenital,Hemophilia, Classic,As, Autosomal Hemophilia,Autosomal Hemophilia As,Classic Hemophilias,Congenital Hemophilia A,Congenital Hemophilia As,Hemophilia A, Autosomal,Hemophilia As,Hemophilia As, Autosomal,Hemophilia As, Congenital,Hemophilias, Classic
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D001402 B-Lymphocytes Lymphoid cells concerned with humoral immunity. They are short-lived cells resembling bursa-derived lymphocytes of birds in their production of immunoglobulin upon appropriate stimulation. B-Cells, Lymphocyte,B-Lymphocyte,Bursa-Dependent Lymphocytes,B Cells, Lymphocyte,B Lymphocyte,B Lymphocytes,B-Cell, Lymphocyte,Bursa Dependent Lymphocytes,Bursa-Dependent Lymphocyte,Lymphocyte B-Cell,Lymphocyte B-Cells,Lymphocyte, Bursa-Dependent,Lymphocytes, Bursa-Dependent
D017452 Receptors, IgG Specific molecular sites on the surface of various cells, including B-lymphocytes and macrophages, that combine with IMMUNOGLOBULIN Gs. Three subclasses exist: Fc gamma RI (the CD64 antigen, a low affinity receptor), Fc gamma RII (the CD32 antigen, a high affinity receptor), and Fc gamma RIII (the CD16 antigen, a low affinity receptor). Antigens, CD16,Antigens, CD32,Antigens, CD64,CD16 Antigens,CD32 Antigens,CD64 Antigen,CD64 Antigens,Fc Gamma Receptor,Fc Receptors, gamma,Fc gamma Receptors,IgG Receptor,IgG Receptors,Leu-11 Antigen,Receptors, Fc gamma,gamma Fc Receptor,gamma Fc Receptors,CD 16 Antigens,CD 32 Antigens,CD 64 Antigens,CDw32 Antigens,Fc gamma RI,Fc gamma RII,Fc gamma RIII,Immunoglobulin G Receptor,Leu-11 Antigens,Antigen, CD64,Antigen, Leu-11,Antigens, CD 16,Antigens, CD 32,Antigens, CD 64,Antigens, CDw32,Antigens, Leu-11,Fc Receptor, gamma,Gamma Receptor, Fc,Leu 11 Antigen,Leu 11 Antigens,Receptor, Fc Gamma,Receptor, IgG,Receptor, Immunoglobulin G,Receptor, gamma Fc,Receptors, gamma Fc,gamma RI, Fc,gamma RII, Fc,gamma RIII, Fc,gamma Receptors, Fc
D051379 Mice The common name for the genus Mus. Mice, House,Mus,Mus musculus,Mice, Laboratory,Mouse,Mouse, House,Mouse, Laboratory,Mouse, Swiss,Mus domesticus,Mus musculus domesticus,Swiss Mice,House Mice,House Mouse,Laboratory Mice,Laboratory Mouse,Mice, Swiss,Swiss Mouse,domesticus, Mus musculus

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