IgG Overproduction Research Articles

GPR55 in B cells limits atherosclerosis development and regulates plasma cell maturation

Dissecting the pathways regulating the adaptive immune response in atherosclerosis is of particular therapeutic interest. Here we report that the lipid G-protein-coupled receptor GPR55 is highly expressed by splenic plasma cells (PCs), upregulated in mouse spleens during atherogenesis and human unstable or ruptured compared to stable plaques. Gpr55-deficient mice developed larger atherosclerotic plaques with increased necrotic core size compared to their corresponding controls. Lack of GPR55 hyperactivated B cells, disturbed PC maturation and resulted in IgG overproduction. B-cell-specific Gpr55 depletion or adoptive transfer of Gpr55-deficient B cells was sufficient to promote plaque development and elevated IgG titers. In vitro, the endogenous GPR55 ligand lysophsophatidylinositol (LPI) enhanced PC proliferation, whereas GPR55 antagonism blocked PC maturation and increased their mitochondrial content. Collectively, these discoveries provide previously undefined evidence for GPR55 in B cells as a key modulator of the adaptive immune response in atherosclerosis.

Elevated expression of BAFF receptor, BR3, on monocytes correlates with B cell activation and clinical features of patients with primary Sj\xf6gren\u2019s syndrome

BackgroundWe reported that the production of BAFF (B cell-activating factor) and IL-6, both of which are involved in survival and differentiation of B cells, is dysregulated in monocytes of patients with primary Sjögren’s syndrome (pSS). In this study, we investigate the relationship between possible aberrations of pSS monocytes and clinical features of pSS patients and the contribution of monocytes to B cell activation, a mechanism involved in the pathogenesis of pSS.MethodsExpression of BAFF-receptor (BR3) on peripheral monocytes from patients with pSS (n = 67) and healthy controls (HC: n = 37) was analyzed by FACS. Peripheral monocytes were stimulated with BAFF, and IL-6 production by the cells was measured by ELISA. Peripheral B cells were cultured with BAFF-stimulated monocytes in the presence or absence of anti-IL-6 receptor antibody, and IgG production by the cells was measured by ELISA. Patients’ serological data were collected from their clinical records. Patients’ disease activity was quantified based on their EULAR Sjögren’s syndrome disease activity index (ESSDAI) scores.ResultsThe proportion of peripheral BR3-positive monocytes (BR3+/CD14+) was significantly increased in pSS patients compared to HC. Moreover, IL-6 production by BAFF-stimulated monocytes was remarkably higher than HC and was significantly correlated with BR3+/CD14+ ratios of patients. In addition, BR3 expression on pSS monocytes was elevated in anti-Ro/SSA and/or anti-La/SSB positive compared to negative patients. Remarkably, BR3 expression on peripheral monocytes was positively and significantly correlated with patients’ serum IgG and IgM levels and ESSDAI scores. Moreover, the amount of IgG produced by B cells was markedly higher in pSS patients compared to HC when the cells were co-cultured with BAFF-stimulated autologous monocytes in vitro. Notably, addition of anti-IL-6 receptor antibody into the co-culture system led to inhibition of IgG production by B cells.ConclusionsOur data suggest that elevated BR3 expression in monocytes is associated with clinical features in pSS patients and that enhanced production of IL-6 by BAFF-stimulated monocytes plays a part in the overproduction of IgG by B cells in pSS. These results suggest that BAFF signaling pathways through BR3 in monocytes are possible therapeutic targets for pSS.

Telbivudine on IgG-associated hypergammaglobulinemia and TGF-β1 hyperactivity in hepatitis B virus-related liver cirrhosis.

As debate rumbles on about whether anti-hepatitis B virus (HBV) nucleos(t)ide analogue treatments modulate host immune system during end-stage liver diseases, we studied effects of two potent anti-HBV agents, telbivudine or entecavir, on humoral immune activities including cytokine secretion, immunoglobulin production, and IgG-Fc agalactosylation, which is known to induce proinflammatory responses, in liver cirrhosis. Serum IgG-Fc N-glycan structures in patients with HBV-related liver cirrhosis, who had received either telbivudine treatment or entecavir treatment for at least 48 weeks were analyzed using liquid chromatography tandem-mass spectrometry. Levels of cytokines and each immunoglobulin isotype were measured using enzyme-linked immunosorbent assays. Results showed that 48 weeks of entecavir treatment caused HBV DNA loss, alanine aminotransferase normalization, and an amelioration of hypergammaglobulinemia in cirrhotic patients; however, telbivudine treatment, though possessing similar efficacies on HBV suppression and an improvement in liver inflammation to entecavir treatment, did not mitigate IgG-related hypergammaglobulinemia. Levels of IgG and transforming growth factor (TGF)-β1 in sera of the cirrhotic patients before and during treatment were positively correlated. In vitro assays revealed that telbivudine treatment induced TGF-β1 expression in human macrophagic cells. Moreover, recombinant TGF-β1 treatment stimulated cell proliferation and IgG overproduction in human IgG-producing B cell lines. Finally, we found that telbivudine treatment enhanced the proportion of serum IgG-Fc agalactosylation in cirrhotic patients, which was associated with enhanced levels of TGF-β1 and IgG. In conclusion, telbivudine therapy was associated with TGF-β1 hyperactivity, IgG-related hypergammaglobulinemia, and IgG-Fc agalactosylation in HBV-related liver cirrhosis.

OP0281 ELEVATED EXPRESSION OF BAFF-RECEPTOR IN PERIPHERAL MONOCYTES PROMOTES B CELL ACTIVATION AND CORRELATES WITH CLINICAL MANIFESTATIONS OF PRIMARY SJÖGREN'S SYNDROME

Background Primary Sjogren’s syndrome (pSS) is an idiopathic autoimmune disease whose major clinical manifestations are xerostomia and keratoconjunctive sicca, and is often accompanied with hypergammaglobulinemia. Several lines of evidence suggest that a focal lymphocytic infiltrate of the exocrine glands is responsible for lesion formation, IgG production and subsequent dysfunction of the glands. It is well known that B cell activating factor (BAFF) and its receptor, BR3, are deeply involved in the pathogenesis of pSS, and hence BAFF and BR3 are promising targets to treat the disease. We have reported that the abnormally elevated expression of BR3 in monocytes is associated with overproduction of inflammatory cytokines, such as IL-6, by monocytes of pSS patients. Our in vitro experiments suggest that BAFF-stimulated monocytes contribute to IgG overproduction by pSS B cells. We also found that the population of a specific subset of B cells overexpressing BR3 was abnormally increased in pSS patients and that the proportion of the subset was positively and significantly correlated with serum levels of autoantibodies and total IgG as well as ESSDAI, one of the indicators of disease activity of pSS. Our results collectively suggest that the elevated expression of BR3 in pSS monocytes results in B cell activation and subsequent overproduction of IgG. However, the relationship between the abnormalities of peripheral cells and clinical manifestations of pSS has not been fully understood. Objectives To elucidate possible roles of abnormal monocytes in the development of clinical manifestations of pSS. Methods The expression level of BR3 in peripheral monocytes of patients with pSS (n = 65) and healthy controls (HC: n = 38) was analyzed by FACS. Peripheral B cells were cultured with BAFF-stimulated monocytes in the presence or absence of an anti-IL-6 receptor antibody, and the proportion of CD38highIgDlow cells among CD19+ cells, and IgG production were analyzed by FACS and ELISA, respectively. The serological data and focus scores by lip biopsy of the patients were collected by clinical records. Results FACS analysis revealed that the expression level of BR3 in pSS monocytes was significantly higher than that of HC (p Conclusion Our data strongly suggest that accelerated signal transduction through a BAFF-BR3 axis in monocytes is involved in the pathogenesis of pSS and associates with clinical manifestations of the disease. These results also suggest that BAFF and the BAFF signaling pathways through BR3 are the possible therapeutic targets for pSS. Disclosure of Interests Keiko Yoshimoto: None declared, Katsuya Suzuki: None declared, Yumi Ikeda: None declared, Eriko Takei: None declared, Tsutomu Takeuchi Grant/research support from: Astellas Pharma Inc, Chugai Pharmaceutical Co, Ltd., Daiichi Sankyo Co., Ltd., Takeda Pharmaceutical Co., Ltd., AbbVie GK, Asahikasei Pharma Corp., Mitsubishi Tanabe Pharma Co., Pfizer Japan Inc., Eisai Co., Ltd., AYUMI Pharmaceutical Corporation, Nipponkayaku Co. Ltd., Novartis Pharma K.K., Grant/research support from: AbbVie, Asahi Kasei, Astellas, AstraZeneca, AYUMI, Bristol-Myers Squibb, Chugai, Daiichi Sankyo, Eisai, Eli Lilly Japan, Janssen, Mitsubishi Tanabe, Nippon Kayaku, Novartis, Pfizer Japan Inc, Taiho, Taisho Toyama, Takeda, Teijin, Grant/research support from: Astellas Pharma Inc., Bristol Myers Squibb, Chugai Pharmaceutical Co., Ltd., Mitsubishi Tanabe Pharma Co., Pfizer Japan Inc., Santen Pharmaceutical Co., Ltd., Takeda Pharmaceutical Co., Ltd., Teijin Pharma Ltd., AbbVie GK, Asahi Kasei Pharma Corp., Taisho Toyama Pharmaceutical Co., Ltd., SymBio Pharmaceuticals Ltd., Janssen Pharmaceutical K.K., Celltrion Inc., Nipponkayaku Co. Ltd., and UCB Japan, Consultant for: Astra Zeneca K.K., Eli Lilly Japan K.K., Novartis Pharma K.K., Mitsubishi Tanabe Pharma Co., Abbivie GK, Nipponkayaku Co.Ltd, Janssen Pharmaceutical K.K., Astellas Pharma Inc., Taiho Pharmaceutical Co. Ltd., Chugai Pharmaceutical Co. Ltd., Taisho Toyama Pharmaceutical Co. Ltd., GlaxoSmithKline K.K., UCB Japan Co. Ltd., Consultant for: AbbVie, Asahi Kasei, Astellas, AstraZeneca, AYUMI, Bristol-Myers Squibb, Chugai, Daiichi Sankyo, Eisai, Eli Lilly Japan, Janssen, Mitsubishi Tanabe, Nippon Kayaku, Novartis, Pfizer Japan Inc, Taiho, Taisho Toyama, Takeda, Teijin, Consultant for: Astra Zeneca K.K., Eli Lilly Japan K.K., Novartis Pharma K.K., Mitsubishi Tanabe Pharma Co., Asahi Kasei Medical K.K., AbbVie GK, Daiichi Sankyo Co., Ltd., Bristol Myers Squibb, and Nipponkayaku Co. Ltd., Speakers bureau: Astellas Pharma Inc., Bristol Myers Squibb, Chugai Pharmaceutical Co., Ltd., Mitsubishi Tanabe Pharma Co., Pfizer Japan Inc., Santen Pharmaceutical Co., Ltd., Takeda Pharmaceutical Co., Ltd., Teijin Pharma Ltd., AbbVie GK, Asahi Kasei Pharma Corp., Taisho Toyama Pharmaceutical Co., Ltd., SymBio Pharmaceuticals Ltd., Janssen Pharmaceutical K.K., Celltrion Inc., Nipponkayaku Co. Ltd., and UCB Japan, Speakers bureau: AbbVie, Asahi Kasei, Astellas, AstraZeneca, AYUMI, Bristol-Myers Squibb, Chugai, Daiichi Sankyo, Eisai, Eli Lilly Japan, Janssen, Mitsubishi Tanabe, Nippon Kayaku, Novartis, Pfizer Japan Inc, Taiho, Taisho Toyama, Takeda, Teijin, Speakers bureau: AbbVie GK., Bristol–Myers K.K., Chugai Pharmaceutical Co. Ltd., Mitsubishi Tanabe Pharma Co., Pfizer Japan Inc., Astellas Pharma Inc, Diaichi Sankyo Co. Ltd., Eisai Co. Ltd., Sanofi K.K., Teijin Pharma Ltd., Takeda Pharmaceutical Co. Ltd., Novartis Pharma K.K.

A Low molecular weight BAFF receptor antagonist inhibits differentiation of human peripheral B cells into plasma blasts/plasma cells in vitro.

Abstract Backgrounds and Purpose We have demonstrated that the elevated expression of BAFF receptor (BR3) on monocytes is involved in the overproduction of IgG by B cells in patients with primary Sjögren’s syndrome (pSS) which is often accompanied with hypergammaglobulinemia. We discovered a low molecular weight compound, BIK13, which inhibits binding of BAFF to BR3, by our original high-throughput screening system. We found that BIK-13 suppressed IL-6 production by BAFF-stimulated pSS monocytes. In this study, we investigated inhibitory effects of BIK-13 on B cell functions. Methods PBMCs were cultured with a B cell-stimulants cocktail, such as anti-IgM and CD40 antibodies, human IL-21 and human BAFF, in the presence of BIK-13. B cell-differentiation was monitored through analysis of the expression levels of CD19/CD38/IgD and activation-induced cytidine deaminase (AID) by FACS and qPCR, respectively. The amounts of IL-6 and IgG produced in vitro by the cells were measured by ELISA. Results Increased production of IgG and IL-6 by PBMC upon stimulation with B cell-stimulants was suppressed by BIK13 in a dose dependent manner. FACS analysis indicated that differentiation of B cells into plasma blasts and/or plasma cells was inhibited by BIK-13. In addition, the expression level of AID was also suppressed by the compound, suggesting that the IgG class switching was impaired. Conclusion These data collectively suggest that BIK-13 suppresses the B cell functions and may provide a novel therapeutic possibility to treat autoimmune diseases such as pSS.

Increased proportion of a CD38highIgD+ B cell subset in peripheral blood is associated with clinical and immunological features in patients with primary Sjögren's syndrome

We investigated the correlation between the increased proportion of peripheral B cell subsets and clinical and immunological features in primary Sjögren's syndrome (pSS). We found that the proportion of CD19+ B cells was significantly increased in pSS as compared with HC and was correlated with serum IgG levels. Moreover, in vitro IgG production by CD19+ B cells was significantly increased in pSS and was positively and significantly correlated with serum IgG levels. FACS analysis revealed that the proportions of peripherally CD38highIgD+ B cells and CD38highIgD− B cells were significantly increased in pSS. In addition, the proportion of CD38highIgD+ B cells positively correlated with ESSDAI scores and serum levels of IgG, anti-Ro/SSA and anti-La/SSB antibodies while that of CD38highIgD− B cells showed no correlation with these parameters. Our data suggest that increased proportion of CD38highIgD+ B cells in pSS is involved in IgG overproduction including autoantibodies, and correlates with disease progression.

THU0533 Baff-Induced IL-6 Signaling Plays A Pivotal Role in Interactions between Monocytes and B Cells That Accelerate Igg Overproduction in Patients with Primary SjÖGren's Syndrome

BackgroundWe have found that B cell activating factor (BAFF) robustly increased IL-6 production by peripheral monocytes from the patients with primary Sjögren's syndrome (pSS), and that the expression level of...

BAFF induces IL-6 production by monocytes through a BAFF receptor and promotes IgG production by B cells in patients with primary Sjögren's syndrome. (CCR3P.210)

Abstract Backgrounds and Objectives: We have found that the elevated expression of BAFF receptor (BR3) on monocytes is involved in activation of monocytes to promote IL-6 production in patients with primary Sjögren's syndrome (pSS). In addition, it is well known that pSS is often accompanied by hypergammaglobulinemia (HγG). In our present study, we investigated the possible involvement of monocytes in the development of HγG. Methods: Peripheral monocytes were cultured in vitro with or without peripheral B cells and stimulated with soluble BAFF (sBAFF). The amounts of IL-6 and IgG in the culture supernatants were measured by ELISA. FACS analysis of whole blood samples was employed to analyze the expression of BR3. Results: The serum level of IgG and the proportion of BR3-positive monocytes (BR3+/CD14+) were elevated in pSS patients as compared to those in normal individuals. Remarkably, the BR3+/CD14+ ratio was positively and significantly correlated with the serum IgG level. In addition, the ratio was positively and significantly correlated with the amount of IL-6 produced by pSS monocytes stimulated with sBAFF. Stimulation of co-culture of B cells and monocytes with sBAFF drastically enhanced IgG production by B cells. Conclusions: Our data collectively suggest that the abnormal expression of BR3 on monocytes is responsible for the overproduction of IgG by B cells in pSS patients.

IgG4‐related disease with hypergammaglobulinemic hyperviscosity and retinopathy

Immunoglobulin G4-related disease (IgG4-RD) is a recently described entity with protean manifestations. We describe a novel case of IgG4-RD with hypergammaglobulinemic hyperviscosity responsive to fludarabine and rituximab. A 33-year-old Asian man developed bilateral lacrimal gland and submandibular salivary gland swelling with cervical lymphadenopathy. Biopsies of the affected tissues revealed reactive follicular hyperplasia. Seven years later, he presented with bilateral retinal hemorrhages due to hyperviscosity syndrome from profound polyclonal increase in IgG, including marked IgG4 elevation. Despite plasmapheresis, overproduction of IgG continued and he was refractory to systemic steroids, azathioprine, interferon alpha, and cyclophosphamide. IgG4-RD was suspected following a myocardial infarction and detection of aneurysmal coronary arteries indicating large vessel vasculitis. Review of the cervical lymph node and lacrimal gland biopsies with immunohistochemical staining for IgG4-positive plasma cells confirmed IgG4-RD. B-cell depletion with rituximab produced a partial response, but clinical symptoms and elevated protein levels persisted. Fludarabine was added to rituximab to suppress T-cell activity, and this resulted in an excellent clinical and biochemical response. Combination therapy with fludarabine and rituximab in IgG4-RD has not previously been reported and can be considered in patients with severe refractory disease.

Mercury exposure, malaria, and serum antinuclear/antinucleolar antibodies in amazon populations in Brazil: a cross-sectional study

BackgroundMercury is an immunotoxic metal that induces autoimmune disease in rodents. Highly susceptible mouse strains such as SJL/N, A.SW, B10.S (H-2s) develop multiple autoimmune manifestations after exposure to inorganic mercury, including lymphoproliferation, elevated levels of autoantibodies, overproduction of IgG and IgE, and circulating immune complexes in kidney and vasculature. A few studies have examined relationships between mercury exposures and adverse immunological reactions in humans, but there is little evidence of mercury-associated autoimmunity in humans.MethodsTo test the immunotoxic effects of mercury in humans, we studied communities in Amazonian Brazil with well-characterized exposures to mercury. Information was collected on diet, mercury exposures, demographic data, and medical history. Antinuclear and antinucleolar autoantibodies (ANA and ANoA) were measured by indirect immunofluorescence. Anti-fibrillarin autoantibodies (AFA) were measured by immunoblotting.ResultsIn a gold mining site, there was a high prevalence of ANA and ANoA: 40.8% with detectable ANoA at ≥1:10 serum dilution, and 54.1% with detectable ANA (of which 15% had also detectable ANoA). In a riverine town, where the population is exposed to methylmercury by fish consumption, both prevalence and levels of autoantibodies were lower: 18% with detectable ANoA and 10.7% with detectable ANA. In a reference site with lower mercury exposures, both prevalence and levels of autoantibodies were much lower: only 2.0% detectable ANoA, and only 7.1% with detectable ANA. In the gold mining population, we also examined serum for AFA in those subjects with detectable ANoA (≥1:10). There was no evidence for mercury induction of this autoantibody.ConclusionsThis is the first study to report immunologic changes, indicative of autoimmune dysfunction in persons exposed to mercury, which may also reflect interactions with infectious disease and other factors.

Evidence of immunosuppression in the genetically epilepsy-prone rat

Immune system function was examined in the genetically epilepsy prone (GEPR-9) rat and non-epileptic Sprague-Dawley control rats. Significant decreases in direct and indirect plaque-forming cell responses were observed in GEPR-9 rats immunized with sheep erythrocytes. Serum levels of IgM were also decreased in non-immunized GEPR-9 rats, providing additional evidence of immunosuppression. However, total serum levels of IgG were three-fold greater in GEPR-9 rats compared to control. These results suggest that the nature of the immune system deficit in the GEPR-9 is complex and may involve an active T-cell population stimulating an overproduction of IgG leading to a diminished capacity to respond to new antigen challenges. This immunological defect may underlie the enhanced susceptibility of GEPR-9 rats to infectious agents. The specific cause of this immune dysfunction is not known. Possible etiological factors include a breakdown in the communication between cells within the immune system or an alteration of neuroendocrine modulation of immune responses.

Inherited hyperactivation of L-arginine synthesis in γ+B lymphocytes of systemic autoimmune MRL mice

The hyperactivation of B lymphocytes of MRL mice, which are an animal model for human systemic lupus erythematosus (SLE), is characterized as the preferential propagation of gamma + B lymphocytes and IgG overproduction followed by aging. Little is known about the molecular mechanisms, although the involvement of cytokines has been extensively investigated. Here we now show that gamma-committed B lymphocytes selectively exhibit a highly elevated L-citrulline metabolism while mu or alpha-committed B lymphocytes show a normal level in autoimmune MRL mice. L-Arginine proportionally supports the lymphocyte proliferation and antibody production in a concentration-dependent fashion (approximately 100 microM). However, normal murine lymphocytes show an extremely low activity of citrulline metabolism, which converts L-citrulline to L-arginine. Thus, these results suggest that the overexpression of elevated citrulline metabolism is associated with gamma chain expression, and this elevation may enable gamma-committed B lymphocytes to preferentially propagate and overproduce IgG compared with mu or alpha-committed B lymphocytes.

The role of plasma proteins in chronic expansion of plasma volume in tropical splenomegally syndrome II. The metabolism of 131I-Labelled IgG

Metabolic studies using 181I-labelled outologous IgG have been performed in 14 adult New Guineans suffering from tropical splenomegaly syndrome, each of whom had at least Grade III splenomegaly. Synthesis rates were elevated in all subjects and despite shortened half-lives, marked increases in both intravascular and extravascular IgG pools were observed in most subjects. There was a significant positive correlation between synthesis rate and plasma volume, indicating that in this disease overproduction of IgG is in part responsible for the expansion of plasma volume which is commonly seen.