Deletion or Inhibition of Fc Gamma Receptor IIb (CD32) Prevents the Memory B Cell Response to Factor VIII in a Hemophilia A Mouse Model

Abstract Abstract 204 The formation of inhibitory antibodies to factor VIII (FVIII) is the foremost complication of replacement therapy in hemophilia A. Patients with inhibitors are treated with very high doses of FVIII, over prolonged periods of time, to induce immune tolerance. Studies in a hemophilia A mouse model demonstrated that very high doses of FVIII can induce apoptosis in FVIII-specific memory B cells and prevent their differentiation into antibody-secreting cells. The Fc gamma receptor IIb (FcgRIIb) is expressed on B cells and mediates inhibitory signals after crosslinking with the B cell receptor. Here, we studied the potential role of this receptor in the regulation of memory B cell response to FVIII. FVIII knockout mice (B6;129S4-F8tm2Kaz/J) were crossed with FcgRIIb knockout mice (B6;129S4-Fcgr2btm1Ttk/J). Comparing F8−/− mice and F8−/−/FcgR2b−/− double knockout mice, the initial anti-FVIII antibody formation was similar after intravenous exposure to 4 weekly doses of 80 or 400 IU/kg. Similar numbers of FVIII-specific antibody-secreting cells were detected in the spleen and bone marrow by ELISPOT. As previously shown, in vitro re-stimulation of memory B cells from spleens of immunized F8−/− mice at doses of 1 to 200 ng/ml induced their differentiation into antibody-secreting cells. Higher doses of 400 to 800 ng/ml prevented differentiation. In F8−/−/FcgR2b−/− double knockout mice, however, formation of antibody-secreting cells was completely inhibited across all FVIII doses tested. Addition of B220-depleted splenocytes from F8−/− mice did not restore memory B cell function in F8−/−/FcgR2b−/− double knockout mice, indicating that the observed effect was not due to dysfunction of follicular dendritic cells or other antigen-presenting cells. Inhibition of FcgRIIb using a monoclonal antibody prevented the FVIII-specific memory B cell response in splenocytes from immunized F8−/− mice. Staining with propidium iodide, annexin V, or anti-caspase 3 indicated increased rates of apoptosis when FcgRIIb was blocked during re-stimulation. In summary, FcgRIIb plays a crucial role for the differentiation of FVIII-specific splenic memory B cells into antibody-secreting cells. Inhibition of FcgRIIb appears to sensitize B cells for apoptosis during re-stimulation with FVIII. This mechanism could potentially facilitate the eradication of FVIII-specific memory B cells during ITI. Disclosures: No relevant conflicts of interest to declare.

Download Full-text

SARS-CoV-2 spike-specific memory B cells express higher levels of T-bet and FcRL5 after non-severe COVID-19 as compared to severe disease

PLoS ONE ◽

10.1371/journal.pone.0261656 ◽

2021 ◽

Vol 16 (12) ◽

pp. e0261656

Author(s):

Raphael A. Reyes ◽

Kathleen Clarke ◽

S. Jake Gonzales ◽

Angelene M. Cantwell ◽

Rolando Garza ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Symptom Onset ◽

Cell Response ◽

Severe Disease ◽

Memory B Cells ◽

Memory B Cell ◽

Specific Memory ◽

Specific Igg ◽

B Cell Response

SARS-CoV-2 infection elicits a robust B cell response, resulting in the generation of long-lived plasma cells and memory B cells. Here, we aimed to determine the effect of COVID-19 severity on the memory B cell response and characterize changes in the memory B cell compartment between recovery and five months post-symptom onset. Using high-parameter spectral flow cytometry, we analyzed the phenotype of memory B cells with reactivity against the SARS-CoV-2 spike protein or the spike receptor binding domain (RBD) in recovered individuals who had been hospitalized with non-severe (n = 8) or severe (n = 5) COVID-19. One month after symptom onset, a substantial proportion of spike-specific IgG+ B cells showed an activated phenotype. In individuals who experienced non-severe disease, spike-specific IgG+ B cells showed increased expression of markers associated with durable B cell memory, including T-bet and FcRL5, as compared to individuals who experienced severe disease. While the frequency of T-bet+ spike-specific IgG+ B cells differed between the two groups, these cells predominantly showed an activated switched memory B cell phenotype in both groups. Five months post-symptom onset, the majority of spike-specific memory B cells had a resting phenotype and the percentage of spike-specific T-bet+ IgG+ memory B cells decreased to baseline levels. Collectively, our results highlight subtle differences in the B cells response after non-severe and severe COVID-19 and suggest that the memory B cell response elicited during non-severe COVID-19 may be of higher quality than the response after severe disease.

Download Full-text

Inhibition of Factor VIII-Specific Memory B Cell Responses by Supra-Physiological Concentrations of Factor VIII.

Blood ◽

10.1182/blood.v104.11.38.38 ◽

2004 ◽

Vol 104 (11) ◽

pp. 38-38

Author(s):

Christina Hausl ◽

Rafi U. Ahmad ◽

Maria Sasgary ◽

Christopher B. Doering ◽

Pete S. Lollar ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

Factor Viii ◽

B Cell ◽

Immune Tolerance ◽

Hemophilia A ◽

Memory B Cells ◽

Memory B Cell ◽

Specific Memory ◽

Stimulation Of

Abstract Inhibitory antibodies against factor VIII (FVIII) are the major complication experienced by hemophilia A patients treated with FVIII products. The most effective therapy to eradicate these antibodies is elevated doses of FVIII over a prolonged period. Despite clinical practice in using such protocols, nothing is known about the immunological mechanisms that cause the down-modulation of FVIII-specific immune responses and the induction of long-lasting immune tolerance against FVIII. Understanding the underlying mechanisms, however, would facilitate designing new therapeutic strategies. The re-stimulation of FVIII-specific memory responses after each dose of FVIII is probably the most important event in the maintenance of FVIII inhibitors in patients. Therefore, the eradication of these memory responses should be an essential step in the down-modulation of inhibitory antibodies and the induction of immune tolerance. We used a murine model of hemophilia A to answer the question whether FVIII-specific memory responses are sensitive to increasing doses of FVIII. In particular, we were interested in the differential effects of FVIII on memory-B-cell and memory-T-cell responses. For the analysis of FVIII-specific memory responses, we re-stimulated FVIII-specific memory B- and T-cells obtained from spleens of hemophilic mice treated with four doses of human FVIII or eight doses of murine FVIII as described (Sasgary et al.: Thromb Haemost2002; 87:266–72; Hausl et al.: Blood2004; 104:115–22). Our results show dose-dependent effects of FVIII on the re-stimulation of FVIII-specific memory B cells in vitro. Physiological concentrations of FVIII below 100 ng/ml re-stimulate memory B cells and induce their differentiation into anti-FVIII antibody-secreting plasma cells. Supra-physiological concentrations above 100 ng/ml, however, inhibit memory-B-cell re-stimulation. The inhibition of memory-B-cell re-stimulation is irreversible and seems to be due to an induction of apoptosis that is at least partly mediated by Fas-dependent mechanisms. Furthermore, the inhibition appears to be initiated by triggering the B-cell receptor (BCR) without the requirement of an excessive cross-linking of the BCR. The activation of FVIII-specific T cells is not affected by increasing doses of FVIII. We conclude that the induction of apoptosis in FVIII-specific memory B cells might be the first step in the induction of immune tolerance in hemophilia A patients with FVIII inhibitors who receive high doses of FVIII. The eradication of memory B cells would prevent their differentiation into antibody-secreting plasma cells and, moreover, might lead to a deficiency of effective antigen-presenting cells required for the re-stimulation of FVIII-specific memory T cells. The induction of regulatory T cells rather than effector T cells could be the consequence of this deficiency.

Download Full-text

SARS-CoV-2 spike-specific memory B cells express markers of durable immunity after non-severe COVID-19 but not after severe disease

10.1101/2021.09.24.461732 ◽

2021 ◽

Author(s):

Raphael Reyes ◽

Kathleen Clarke ◽

S. Jake Gonzales ◽

Angelene M. Cantwell ◽

Rolando Garza ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Symptom Onset ◽

Cell Response ◽

Severe Disease ◽

Memory B Cells ◽

Memory B Cell ◽

Specific Memory ◽

Specific Igg ◽

B Cell Response

SARS-CoV-2 infection elicits a robust B cell response, resulting in the generation of long-lived plasma cells and memory B cells. Here, we aimed to determine the effect of COVID-19 severity on the memory B cell response and characterize changes in the memory B cell compartment between recovery and five months post-symptom onset. Using high-parameter spectral flow cytometry, we analyzed the phenotype of memory B cells with reactivity against the SARS-CoV-2 spike protein or the spike receptor binding domain (RBD) in recovered individuals who had been hospitalized with non-severe (n=8) or severe (n=5) COVID-19. One month after symptom onset, a substantial proportion of spike-specific IgG+ B cells showed an activated phenotype. In individuals who experienced non-severe disease, spike-specific IgG+ B cells showed increased expression of markers associated with durable B cell memory, including T-bet, FcRL5, and CD11c, which was not observed after severe disease. Five months post-symptom onset, the majority of spike-specific memory B cells had a resting phenotype and the percentage of spike-specific T-bet+ IgG+ memory B cells decreased to baseline levels. Collectively, our results suggest that the memory B cell response elicited during non-severe COVID-19 may be of higher quality than the response after severe disease.

Download Full-text

Agonist for Toll-Like Receptor (TLR) 9 Amplifies as Well as Inhibits the Differentiation of FVIII-Specific Memory B Cells into Antibody-Producing Plasma Cells in Vitro and in Vivo.

Blood ◽

10.1182/blood.v112.11.3382.3382 ◽

2008 ◽

Vol 112 (11) ◽

pp. 3382-3382

Author(s):

Peter Allacher ◽

Christina Hausl ◽

Aniko Ginta Pordes ◽

Rafi Uddin Ahmad ◽

Hartmut J Ehrlich ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Memory B Cells ◽

Memory B Cell ◽

Cpg Dna ◽

Cell Responses ◽

Specific Memory ◽

B Cell Responses

Abstract Memory B cells are essential for maintaining long-term antibody responses. They can persist for years even in the absence of antigen and are rapidly re-stimulated to differentiate into antibody-producing plasma cells when they encounter their specific antigen. Previously we demonstrated that ligands for TLR 7 and 9 amplify the differentiation of FVIII-specific memory B cells into anti-FVIII antibody-producing plasma cells at low concentrations of FVIII and prevent the inhibition of memory-B-cell differentiation at high concentrations of FVIII. The modulation of FVIII-specific memory-B-cell responses by agonists for TLR is highly relevant for the design of new immunotherapeutic approaches in patients with FVIII inhibitors because TLR are activated by a range of different viral and bacterial components. Specifically, TLR 7 is triggered by single-stranded RNA derived from viruses and TLR 9 is triggered by bacterial DNA containing unmethylated CpG motifs. We further explored the modulation of FVIII-specific memory-B-cell responses by agonists for TLRs by studying a broad range of concentrations of CpG DNA, a ligand for TLR 9, both in vitro and in vivo using the murine E17 model of hemophilia A. We used CpG-DNA in concentrations ranging from 0.1 to 10,000 ng/ml to study the modulation of FVIII-specific memory-B-cell responses in vitro and verified the specificity of the effects observed by including a blocking agent for TLR 9 and GpC-DNA, a non-stimulating negative control for CpG DNA. Furthermore, we used doses of CpG DNA ranging from 10 to 50,000 ng per dose to study the modulation of FVIII-specific memory-B-cell responses in vivo. E17 hemophilic mice were treated with a single intravenous dose of 200 ng FVIII to stimulate the generation of FVIII-specific memory B cells and were subsequently treated with another dose of FVIII that was given together with CpG DNA. We analyzed titers of anti-FVIII antibodies in the circulation of these mice one week after the second dose of FVIII. Previously we had shown that a single dose of 200 ng FVIII, given intravenously to E17 hemophilic mice, stimulates the formation of FVIII-specific memory B cells but is not sufficient to induce anti-FVIII antibodies that would be detectable in the circulation. Our results demonstrate a biphasic effect of CpG DNA on the re-stimulation of FVIII-specific memory B cells and their differentiation into antibody-producing plasma cells. Both in vitro and in vivo studies show that CpG DNA at high doses inhibits the re-stimulation and differentiation of FVIII-specific memory B cells. However, CpG DNA at low doses amplifies these processes. Amplification and inhibition of memory-B-cell responses are due to specific interactions of CpG DNA with TLR 9. Both effects are blocked by addition of a blocking agent for TLR 9 in vitro. We conclude that triggering of TLR 9 by bacterial DNA has a substantial influence on FVIII-specific memory-B-cell responses. The consequence of TLR 9 triggering can be inhibitory or stimulatory, depending on the actual concentration of the bacterial DNA. Our findings demonstrate the potential modulatory effects of bacterial infections on the regulation of FVIII inhibitor development.

Download Full-text

Memory persistence and differentiation into antibody-secreting cells accompanied by positive selection in longitudinal BCR repertoires

10.1101/2021.12.30.474135 ◽

2022 ◽

Author(s):

Artem I. Mikelov ◽

Evgeniia I. Alekseeva ◽

Ekaterina A. Komech ◽

Dmitriy B. Staroverov ◽

Maria A. Turchaninova ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Peripheral Blood ◽

Plasma Cells ◽

Inflammatory Diseases ◽

Affinity Maturation ◽

Memory B Cells ◽

Immune Memory ◽

Memory B Cell ◽

Antibody Secreting Cells

B-cell mediated immune memory holds both plasticity and conservatism to respond to new challenges and repeated infections. Here, we analyze the dynamics of immunoglobulin heavy chain (IGH) repertoires of memory B cells, plasmablasts and plasma cells sampled several times during one year from peripheral blood of volunteers without severe inflammatory diseases. We reveal a high degree of clonal persistence in individual memory B-cell subsets with inter-individual convergence in memory and antibody-secreting cells (ASCs). Clonotypes in ASCs demonstrate clonal relatedness to memory B cells and are transient in peripheral blood. Two clusters of expanded clonal lineages displayed different prevalence of memory B cells, isotypes, and persistence. Phylogenetic analysis revealed signs of reactivation of persisting memory B cell-enriched clonal lineages, accompanied by new rounds of affinity maturation during proliferation to ASCs. Negative selection contributes to both, persisting and reactivated lineages, saving functionality and specificity of BCRs to protect from the current and future pathogens.

Download Full-text

Single-Cell Analysis of FVIII-Specific Memory B Cells in Murine Hemophilia A.

Blood ◽

10.1182/blood.v110.11.1157.1157 ◽

2007 ◽

Vol 110 (11) ◽

pp. 1157-1157 ◽

Cited By ~ 1

Author(s):

Christina Hausl ◽

Rafi U. Ahmad ◽

Bernhard Baumgartner ◽

Hans Peter Schwarz ◽

Hartmut Ehrlich ◽

...

Keyword(s):

T Cells ◽

B Cells ◽

B Cell ◽

Single Cell ◽

Cd4 T Cells ◽

Single Cell Analysis ◽

Memory B Cells ◽

Cell Analysis ◽

Memory B Cell ◽

Specific Memory

Abstract The elimination of FVIII-specific memory B cells is an essential step in the design of new therapeutic strategies for the induction of immune tolerance in hemophilia A with FVIII inhibitors. Using a mouse model of hemophilia A we recently reported that low dose FVIII stimulates the differentiation of FVIII-specific memory B cells into antibody-secreting plasma cells whereas high dose FVIII inhibits this process. The inhibition of memory-B-cell re-stimulation is irreversible and seems to be due to an induction of apoptosis. Further understanding of the complex interactions that lead to either re-stimulation and differentiation of memory B cells or inhibition and eradication of these cells requires appropriate technologies for single-cell analysis and functional studies. We established a new technology for single-cell analysis and cell sorting of FVIII-specific murine memory B cells. A combination of magnetic bead separation and multi-color flow cytometry enabled us to analyze and purify FVIII-specific memory B cells obtained from hemophilic mice treated with FVIII. In a first step, we depleted undesirable cell populations (IgM+, IgD+, CD11c+, F4/80+, Gr1+ and CD49b+ cells) from total spleen cells by magnetic bead separation. In a second step, we used multicolor flow cytometry to exclude CD4+ T cells and analyze the FVIII-specific memory B cell compartment. This compartment was specified by staining the specific B-cell receptor with FVIII and anti-IgG antibodies. Frequencies of cells in this compartment ranged from 0.1–0.5% of total spleen cells in animals treated with 4 intravenous doses of FVIII, given at weekly intervals. We could not detect any FVIII-specific memory B cells in naïve mice. By means of single cell sorting we isolated FVIII-specific memory B cells for further functional studies. We were able to cultivate FVIII-specific memory B cells in microwell cultures in vitro and differentiate them into antibody-secreting plasma cells. The re-stimulation and differentiation of single-cell sorted memory B cells was strictly dependent on the presence of activated CD4+ T cells. CD4+ T cells obtained from naïve mice did not support the memory response. Furthermore, the re-stimulation and differentiation of memory B cells in the presence of activated CD4+ T cells did not require additional dendritic cells for antigen presentation. Obviously, memory B cells provide sufficient antigen presentation to CD4+ T cells to enable them to trigger the memory response. Our approach for single-cell analysis and purification of FVIII-specific memory B cells provides a new tool for tracking memory B cell populations in vivo and for directly analyzing the regulation of memory B cell function. It opens the field for future studies which should elucidate signals and molecules involved in activation or inhibition and eradication of FVIII-specific memory B cells. These activities will eventually lead to the identification of targets for the design of new treatment strategies for patients with FVIII inhibitors.

Download Full-text

Serotype-Specific and Age-Dependent Generation of Pneumococcal Polysaccharide-Specific Memory B-Cell and Antibody Responses to Immunization with a Pneumococcal Conjugate Vaccine

Clinical and Vaccine Immunology ◽

10.1128/cvi.00336-07 ◽

2007 ◽

Vol 15 (2) ◽

pp. 182-193 ◽

Cited By ~ 38

Author(s):

Elizabeth A. Clutterbuck ◽

Sarah Oh ◽

Mainga Hamaluba ◽

Sharon Westcar ◽

Peter C. L. Beverley ◽

...

Keyword(s):

B Cells ◽

B Cell ◽

Conjugate Vaccine ◽

Pneumococcal Conjugate Vaccine ◽

Plasma Cells ◽

Memory B Cells ◽

Antibody Responses ◽

Memory B Cell ◽

Cell Responses ◽

Specific Memory

ABSTRACT Glycoconjugate vaccines have dramatically reduced the incidence of encapsulated bacterial diseases in toddlers under 2 years of age, but vaccine-induced antibody levels in this age group wane rapidly. We immunized adults and 12-month-old toddlers with heptavalent pneumococcal conjugate vaccine to determine differences in B-cell and antibody responses. The adults and 12-month-old toddlers received a pneumococcal conjugate vaccine. The toddlers received a second dose at 14 months of age. The frequencies of diphtheria toxoid and serotype 4, 14, and 23F polysaccharide-specific plasma cells and memory B cells were determined by enzyme-linked immunospot assay. The toddlers had no preexisting polysaccharide-specific memory B cells or serum immunoglobulin G (IgG) antibody but had good diphtheria toxoid-specific memory responses. The frequencies of plasma cells and memory B cells increased by day 7 (P < 0.0001) in the adults and the toddlers following a single dose of conjugate, but the polysaccharide responses were significantly lower in the toddlers than in the adults (P = 0.009 to <0.001). IgM dominated the toddler antibody responses, and class switching to the IgG was serotype dependent. A second dose of vaccine enhanced the antibody and memory B-cell responses in the toddlers but not the ex vivo plasma cell responses. Two doses of pneumococcal conjugate vaccine are required in toddlers to generate memory B-cell frequencies and antibody class switching for each pneumococcal polysaccharide equivalent to that seen in adults.

Download Full-text

New markers for murine memory B cells that define mutated and unmutated subsets

Journal of Experimental Medicine ◽

10.1084/jem.20062571 ◽

2007 ◽

Vol 204 (9) ◽

pp. 2103-2114 ◽

Cited By ~ 173

Author(s):

Shannon M. Anderson ◽

Mary M. Tomayko ◽

Anupama Ahuja ◽

Ann M. Haberman ◽

Mark J. Shlomchik

Keyword(s):

B Cells ◽

B Cell ◽

Cell Subset ◽

Memory B Cells ◽

Memory Cells ◽

Pulse Label ◽

Memory B Cell ◽

Specific Memory ◽

V Region ◽

Different Origins

The study of murine memory B cells has been limited by small cell numbers and the lack of a definitive marker. We have addressed some of these difficulties with hapten-specific transgenic (Tg) mouse models that yield relatively large numbers of antigen-specific memory B cells upon immunization. Using these models, along with a 5-bromo-2′-deoxyuridine (BrdU) pulse-label strategy, we compared memory cells to their naive precursors in a comprehensive flow cytometric survey, thus revealing several new murine memory B cell markers. Most interestingly, memory cells were phenotypically heterogeneous. Particularly surprising was the finding of an unmutated memory B cell subset identified by the expression of CD80 and CD35. We confirmed these findings in an analogous V region knock-in mouse and/or in non-Tg mice. There also was anatomic heterogeneity, with BrdU+ memory cells residing not just in the marginal zone, as had been thought, but also in splenic follicles. These studies impact the current understanding of murine memory B cells by identifying new phenotypes and by challenging assumptions about the location and V region mutation status of memory cells. The apparent heterogeneity in the memory compartment implies either different origins and/or different functions, which we discuss.

Download Full-text

Toll-Like Receptor Triggering Modulates Factor VIII-Specific Immune Memory in Murine Hemophilia A with Factor VIII Inhibitors.

Blood ◽

10.1182/blood.v106.11.214.214 ◽

2005 ◽

Vol 106 (11) ◽

pp. 214-214 ◽

Cited By ~ 5

Author(s):

Peter Allacher ◽

Christina Hausl ◽

Rafi U. Ahmad ◽

Hans Peter Schwarz ◽

Peter L. Turecek ◽

...

Keyword(s):

B Cells ◽

Factor Viii ◽

B Cell ◽

Hemophilia A ◽

Memory B Cells ◽

Immune Memory ◽

Low Doses ◽

Specific Memory ◽

High Doses ◽

Stimulation Of

Abstract The development of inhibitory antibodies against factor VIII (FVIII) is the major complication in the treatment of hemophilia A patients with FVIII products. Immune Tolerance Induction (ITI) therapy using long-term application of high doses of FVIII has evolved as an effective therapy to eradicate the antibodies and induce long-lasting immune tolerance. It is a common observation that infections, particularly central venous catheter infections during ITI cause a rise in anti-FVIII antibody titers that can prolong the course of ITI or possibly even lead to failure of ITI. Based on this observation, we asked the question whether microbial components derived from viruses or bacteria modulate the re-stimulation of FVIII-specific immune memory and disturb the recently described inhibition of memory-B-cell-re-stimulation by high doses of FVIII (Hausl et al.: Blood2005; in press). Microbial components are recognized by toll-like receptors (TLRs) that serve as an important link between innate and adaptive immunity. TLRs can discriminate various microbial components such as lipopeptides derived from bacteria or zymosan derived from yeast (recognized by TLR1/2 or TLR2/6), double-stranded RNA derived from viruses (recognized by TLR3), lipopolysaccharide (LPS) derived from gram-negative bacteria (recognized by TLR4), flagellin derived from bacterial flagella (recognized by TLR5), single-stranded RNA derived from viruses (recognized by TLR7/8) or bacterial DNA containing the unmethylated CpG motif (recognized by TLR9). We analyzed the re-stimulation of FVIII-specific memory-B cells using a murine model of hemophilia A as described previously (Hausl et al.: Blood2004; 104:115–22; Hausl et al.: Blood2005, in press). The following TLR ligands were tested: zymosan for TLR2 (0.1–10,000 ng/ml), poly I:C for TLR3 (1.0–50,000 ng/ml), LPS for TLR4 (0.1–10,000 ng/ml), Flagellin for TLR5 (0.01–1,000 ng/ml), Loxoribine for TLR7 (1.0–50,000 ng/ml) and CpG oligonucleotides for TLR9 (0.1–10,000 ng/ml). Our results indicate that none of the TLR ligands at the concentrations tested induced a significant re-stimulation of FVIII-specific memory B cells in the complete absence of either FVIII or T cells. However, ligands for TLR3, TLR4, TLR7 and TLR9 were able to disturb the inhibition of memory-B-cell-re-stimulation by high doses of FVIII and amplified the re-stimulation induced by low doses of FVIII substantially. We conclude that triggering of TLRs by microbial components that are present during infections amplify the re-stimulation of FVIII-specific memory B-cells induced by low doses of FVIII and disturb the inhibition induced by high doses of FVIII.

Download Full-text