IgG-producing Plasma Cells Research Articles

Single-cell RNA sequencing of submandibular gland reveals collagen type XV-positive fibroblasts as a disease-characterizing cell population of IgG4-related disease

ObjectivesIgG4-related disease (IgG4-RD) is a systemic autoimmune disease with an unknown etiology, affecting single/multiple organ(s). Pathological findings include the infiltration of IgG4-producing plasma cells, obliterative phlebitis, and storiform fibrosis. Although immunological studies have shed light on the dysregulation of lymphocytes in IgG4-RD pathogenesis, the role of non-immune cells remains unclear. This study aimed to investigate the demographics and characteristics of non-immune cells in IgG4-RD and explore potential biomarkers derived from non-immune cells in the sera.MethodsWe conducted single-cell RNA sequence (scRNA-seq) on non-immune cells isolated from submandibular glands of IgG4-RD patients. We focused on fibroblasts expressing collagen type XV and confirmed the presence of those fibroblasts using immunohistochemistry. Additionally, we measured the levels of collagen type XV in the sera of IgG4-RD patients.ResultsThe scRNA-seq analysis revealed several distinct clusters consisting of fibroblasts, endothelial cells, ductal cells, and muscle cells. Differential gene expression analysis showed upregulation of COL15A1 in IgG4-RD fibroblasts compared to control subjects. Notably, COL15A1-positive fibroblasts exhibited a distinct transcriptome compared to COL15A1-negative counterparts. Immunohistochemical analysis confirmed a significant presence of collagen type XV-positive fibroblasts in IgG4-RD patients. Furthermore, immune-suppressive therapy in active IgG4-RD patients resulted in decreased serum levels of collagen type XV.ConclusionsOur findings suggest that collagen type XV-producing fibroblasts may represent a disease-characterizing non-immune cell population in IgG4-RD and hold potential as a disease-monitoring marker.

Abstract SY16-02: Generation of B cell immunity in tertiary lymphoid structures supports response to immunotherapy

Abstract SY16-02: Generation of B cell immunity in tertiary lymphoid structures supports response to immunotherapy

Reply to: Comments on: Differential IgG4-Producing Plasma Cell Infiltration in Non- and Post-Transplant Plasma Cell Hepatitis.

Reply to: Comments on: Differential IgG4-Producing Plasma Cell Infiltration in Non- and Post-Transplant Plasma Cell Hepatitis.

IgG4-Related Disease Presenting as Hypertrophic Pachymeningitis

IgG4-related disease (IgG4-RD) is a multi-organ, immune-mediated inflammatory condition of unknown etiology characterized by infiltration of tissues by IgG4 producing plasma cells. IgG4-related disease (IgG4-RD) can ideally affect any organs, but the involvement of the central nervous system (CNS) is a rare entity. We present a case of a 67-year-old male who presented with diplopia with imaging showing hypertrophic pachymeningitis (HPM) and was diagnosed with IgG4-RD of the CNS based on histopathology report.

Immunoglobulin G4-related Disease: A New Systemic Disease Emerging in Japan.

Immunoglobulin G4-related disease (IgG4-RD) is a fibro-inflammatory disease characterized by organ enlargement and elevated serum IgG4 levels. In 2003, IgG4-RD was proposed as a distinct form of IgG4-related systemic disease based on a histopathological study involving patients with autoimmune pancreatitis. IgG4-RD occurs mainly in older men and can affect almost any organ simultaneously or metachronously. Pathophysiologically, IgG4-RD occurs when an autoantigen triggers an immune response characterized by Th2 predominance with increased production of cytokines, such as interleukin 4 (IL-4), IL-5, IL-10, IL-13, and tumor growth factor-β (TGF-β), in the affected organ. IL-10 and TGF-β produced by the increased number of regulatory T cells induce a switch from B cells to IgG4-producing plasma cells and fibrosis, respectively. The characteristic histological features consist of dense infiltration of lymphocytes and IgG4-positive plasma cells, storiform fibrosis, and obliterative phlebitis. IgG4-RD is diagnosed based on a combination of clinical, serological, radiological, and histopathological findings. Differentiating IgG4-RD from malignant tumors or similar inflammatory diseases in the affected organs is important. The 2019 America College of Rheumatology/European League against Rheumatism classification criteria for IgG4-RD have high diagnostic sensitivity and specificity. IgG4-RD generally responds well to treatment with steroids, and a swift response is reassuring and provides further diagnostic confirmation. However, relapses are common during tapering or after cessation of steroids. In Japan, low-dose steroid maintenance therapy is usually given to prevent a relapse. B-cell depletion with rituximab is effective in patients resistant to or dependent on steroids. Most patients with IgG4-RD who receive steroid therapy show good short-term clinical, morphological, and functional outcomes. However, long-term outcomes, such as relapse, fibrosis development, and associated malignancies, have not been clearly defined. Therefore, novel treatment strategies, including rituximab, need to be tested in international randomized controlled clinical trials.

Role of Memory B Cells in Antibody Mediated Rejection: A Proof of Concept

<h3>Introduction</h3> Antibody mediated rejection (AMR) diagnosis, monitoring and treatment is exclusively based on circulating donor specific antibodies (DSA). However, DSA often fails to predict and diagnose AMR, since it does not represent the whole HLA-specific memory B cell (mBc) repertoire. Central and peripheral donor (HLA)-sp B-cell responses may offer a new diagnostic and therapeutic target. <h3>Case Report</h3> 44 years old female affected from an advanced Chagasic cardiomyopathy refractory to therapy was listed for heart transplant with a PRA of 67% in 03/2019. She was transplanted in 11/2019, with a negative CDC-XM. Induction was based on basiliximab and tacrolimus-based triple therapy with Mycophenolate mofetil and steroids. Despite a negative CDC-XM, 5 C3q-fixing DSA were detected (A3, DR1, DR7, DPB1, DQ2 and DQ5). Post-op was uneventful and biventricular function was preserved at day 7. The 14-day endomyocardial biopsy showed acute cellular rejection G2R and p(AMR)1 i+ with persistent DSAs. High doses of esteroids, IVIG and plasmapheresis were started. The SAB assay on day 25 showed persistent detection of all DSA, although with lower MFI levels. To characterize B-cell immune response, we used a novel HLA-specific B-cell FluorSpot assay. Bone marrow aspirate and peripheral blood demonstrated high frequencies of donor(HLA)-sp IgG-producing plasma cells and circulating donor-specific mBc, respectively, against different donor(HLA)-Ag specificities <b>(figure 1)</b>. Given patient's favorable evolution, with two main immune compartments showing anti-donor B-cell activation requiring a combined immunosuppressive therapy, no additional treatment was started. At 12 months of follow-up the patient remains clinically stable with negative ACR/pAMR EMB. <h3>Summary</h3> Our data highlights the need of a more accurate evaluation of the anti-donor humoral immune response leading to DSA production in order to refine current immune-risk stratification and ultimately help decision-making regarding the type of rescue immunosuppressive therapy.

Muscarinic Acetylcholine Receptors Modulate Interleukin-6 Production and Immunoglobulin Class Switching in Daudi Cells.

B cells express muscarinic and nicotinic acetylcholine receptors (mAChRs and nAChRs, respectively). Following immunization with ovalbumin, serum immunoglobulin G (IgG) and interleukin (IL)-6 levels were lower in M1 and M5 mAChR double-deficient mice and higher in α7 nAChR-deficient mice than in wild-type mice. This suggests mAChRs participate in the cytokine production involved in B cell differentiation into plasma cells, which induces immunoglobulin class switching from IgM to IgG. However, because these results were obtained with conventional knockout mice, in which all cells in the body were affected, the specific roles of these receptors expressed in B cells remains unclear. In the present study, Daudi B lymphoblast cells were used to investigate the specific roles of mAChRs and nAChR in B cells. Stimulating Daudi cells using Pansorbin cells (heat-killed, formalin-fixed Staphylococcus aureus coated with protein A) upregulated expression of M1-M4 mAChRs and the α4 nAChR subunit. Under these conditions, mAChRs, but not nAChRs, mediated immunoglobulin class switching to IgG. This effect was blocked by scopolamine, a non-selective mAChR antagonist, and 4-diphenylacetoxy-N-methyl-piperidine methiodide (4-DAMP), a Gq/11-coupled M1, M3, M5 antagonist. In addition, IL-6 secretion was further enhanced following mAChR activation. Thus, Gq/11-coupled mAChRs expressed in B cells thus appear to contribute to IL-6 production and B cell maturation into IgG-producing plasma cells.

Intranasal immunization with outer membrane vesicle pertussis vaccine confers broad protection through mucosal IgA and Th17 responses

A vaccine based on outer membrane vesicles of pertussis (omvPV) is protective in a mouse-challenge model and induces a broad antibody and mixed Th1/Th2/Th17 response against multiple antigens following subcutaneous immunization. However, this route did not result in mucosal immunity and did not prevent nasopharyngeal colonization. In this study, we explored the potential of intranasal immunization with omvPV. Only intranasal immunization induced strong mucosal immune responses that encompasses enhanced pulmonary and nasal IgA antibody levels, mainly directed against Vag8 and LPS. Furthermore, high numbers of IgA- and IgG-producing plasma cells were detected as well as lung-resident IgA memory B-cells. Finally, only intranasal immunization induced pulmonary Th1/Th17-related cytokine responses. The magnitude and type of systemic immunity was comparable between both routes and included high systemic IgG antibody levels, strong IgG-producing plasma cell responses, memory B-cells residing in the spleen and systemic Th1/Th2/Th17-related cytokine responses. Importantly, only intranasal immunization prevented colonization in both the lungs and the nasal cavity. In conclusion, intranasal omvPV immunization induces mucosal IgA and Th17-mediated responses without influencing the systemic immunity profile. These responses resulted in prevention of Bordetella pertussis colonization in the respiratory tract, including the nasal cavity, thereby potentially preventing transmission.

P038 A single-cell transcriptomics approach reveals high-resolution cellular signatures in Crohn’s disease

Abstract Background Single-cell RNA sequencing (sc-RNAseq) provides high-resolution analysis of individual cells and cell clusters within complex tissues like the intestinal mucosa. No study to date has applied this novel technology to understand the complexity of intestinal inflammation in Crohn’s disease (CD) patients. Our aim is to identify the cellular subsets present in healthy and inflamed colon, and to describe how individual subsets are regulated in active CD. Methods Colon biopsies from a healthy control (HC) and two patients with endoscopically active colonic CD were collected and processed by enzymatic digestion and cell sorting to discard dead cells. Single-cell suspensions were processed by droplet-based protocol 10× chromium system followed by library preparation and sequencing. Sequencing data were aligned and quantified using Cell Ranger. Downstream analysis was performed using the R package Seurat. Results scRNA-seq analysis identified 14 transcriptionally different cell subsets in the healthy colon, including diverse types of T cells, plasma cells, mesenchymal cells, epithelial cells and myeloid populations, as well as a subset of MHCII+ CD20+ B cells. Overall, the number of transcriptionally differentiated cellular subsets was greater (16 and 17 subsets per sample) in the two CD colonic samples revealing higher cellular heterogeneity in active CD. In particular, in the HC we identified three T-cell subsets including a CD4+, CD8+ and a smaller subset of intraepithelial lymphocytes. In contrast, samples from CD patients presented four to six clearly differentiated T-cell clusters depending on the patient, with a marked enrichment of cytotoxicity genes (GZMA, GZMB, NKG7, CCL5 and AOAH) and T-regulatory genes (FOXP3, CTLA4, BATF and IL2RA). In addition, the HC sample presented three differentiated subsets of antibody-secreting plasma cells with predominant IgA and IgM production. In contrast, a clear expansion of IgG-producing plasma cells was observed in both CD patients. Moreover, the profiles of specific subsets significantly changed revealing transcriptional regulation within the individual subsets. Specifically, macrophages within the HC mucosa expressed the M2 markers CD163 and CD209 together with a whole signature of 163 additional genes, while in CD, they lost expression of these markers and upregulated CXCL8 and IL1B which were co-expressed with 268 additional genes common to macrophage populations in both CD patients. Conclusion We show that sc-RNAseq can be applied to study at a high cellular resolution human intestinal biopsies. Understanding the transcriptomic profile of the CD-related subsets will help dissect disease pathophysiology and provide knowledge for therapeutic targets.

Plasma Cell Polarization to the Immunoglobulin G Phenotype in Hepatocellular Carcinomas Involves Epigenetic Alterations and Promotes Hepatoma Progression in Mice

Little is known about the composition and generation of plasma cell subsets in patients with hepatocellular carcinoma (HCC) and how these associate with outcomes. We investigated whether, or how, plasma cells differentiate and function in patients with HCC and mice with liver tumors. We analyzed subset composition and distribution of plasma cells in HCC samples from 342 patients who underwent curative resection at the Cancer Center of Sun Yat-sen University in China; samples of non-tumor liver tissue were used as controls. We associated plasma cell profiles with patient outcomes. Tissue-derived leukocytes were analyzed by flow cytometry and real-time polymerase chain reaction. The ability of macrophages to regulate plasma cell differentiation was determined in exvivo cultures of cells from human HCC tissues. C57BL/6 and BALB/c mice were given injections of Hepa1-6 cells, which formed hepatomas, or H22 cells, which formed ascitic hepatomas. Gene expression patterns were analyzed in human HCC, mouse hepatoma, and non-tumor tissues by real-time polymerase chain reaction. Mice with hepatomas were given injections of GSK126 (an inhibitor of histone H3 lysine 27 methyltransferase [EZH2]) and 5-AZA-dC (an inhibitor of DNA methyltransferases); tumor tissues were analyzed by immunofluorescence and immunohistochemistry for the presence of immune cells and cytokines. B cells isolated from HCCs had somatic hypermutations and class-switch recombinations to the IgG phenotype that were not observed in non-tumor tissues. Increased level of plasma cells correlated with poor outcomes of patients. Activated CD4+ T cells from HCCs stimulated C-X-C motif chemokine 10 (CXCL10) production by macrophages. CXCL10 bound CXC chemokine receptor 3 on B cells and signaled via extracellular signal-regulated kinase to cause them to become IgG-producing plasma cells. IgG activated Fc receptors on macrophages and induced them to produce interleukin 6, interleukin 10, and C-C motif chemokine ligand 20 (CCL20). In mice with hepatomas, depletion of B cells prevented generation of these macrophage, increased the anti-tumor T cell response, and reduced growth of hepatomas. However, these effects were lost after injection of CXC chemokine receptor 3-positive plasma cells. Human HCC and mouse hepatoma tissues had increased expression of DNA methyltransferase 1 and EZH2 compared with non-tumor tissues. Injection of mice with GSK126 and 5-AZA-dC induced expression of CXCL10 by tumor cells and caused plasma cell polarization, suppression ofthe anti-tumor T cell response, and hepatoma growth. Human HCC tissues contain B cells with class-switch recombinations to the IgG phenotype. Activated CD4+ T cells from HCCs stimulate CXCL10 production by macrophages; CXCL10 binds CXC chemokine receptor 3 on B cells and causes them to become IgG-producing plasma cells. IgG activates Fc receptor in macrophages to produce cytokines that reduce the anti-tumor immune response. In mice with hepatomas, depletion of B cells prevented generation of these macrophages, increased the anti-tumor T cell response, and reduced growth of hepatomas. This pathway involves increased expression of DNA methyltransferase 1 and EZH2 by HCC and hepatoma cells.

Follicular B Cells Promote Atherosclerosis via T Cell-Mediated Differentiation Into Plasma Cells and Secreting Pathogenic Immunoglobulin G.

B cells promote or protect development of atherosclerosis. In this study, we examined the role of MHCII (major histocompatibility II), CD40 (cluster of differentiation 40), and Blimp-1 (B-lymphocyte-induced maturation protein) expression by follicular B (FO B) cells in development of atherosclerosis together with the effects of IgG purified from atherosclerotic mice. Using mixed chimeric Ldlr-/- mice whose B cells are deficient in MHCII or CD40, we demonstrate that these molecules are critical for the proatherogenic actions of FO B cells. During development of atherosclerosis, these deficiencies affected T-B cell interactions, germinal center B cells, plasma cells, and IgG. As FO B cells differentiating into plasma cells require Blimp-1, we also assessed its role in the development of atherosclerosis. Blimp-1-deficient B cells greatly attenuated atherosclerosis and immunoglobulin-including IgG production, preventing IgG accumulation in atherosclerotic lesions; Blimp-1 deletion also attenuated lesion proinflammatory cytokines, apoptotic cell numbers, and necrotic core. To determine the importance of IgG for atherosclerosis, we purified IgG from atherosclerotic mice. Their transfer but not IgG from nonatherosclerotic mice into Ldlr-/- mice whose B cells are Blimp-1-deficient increased atherosclerosis; transfer was associated with IgG accumulating in atherosclerotic lesions, increased lesion inflammatory cytokines, apoptotic cell numbers, and necrotic core size. The mechanism by which FO B cells promote atherosclerosis is highly dependent on their expression of MHCII, CD40, and Blimp-1. FO B cell differentiation into IgG-producing plasma cells also is critical for their proatherogenic actions. Targeting B-T cell interactions and pathogenic IgG may provide novel therapeutic strategies to prevent atherosclerosis and its adverse cardiovascular complications.

IgG4-related disease: why is it so important?

IgG4-related disease (IgG4-RD) is a recently defined systemic inflammatory and fibrous condition of unknown etiology and multiple clinical presentations. Characteristic features include elevated serum IgG4 levels in approximately 70% of patients; diffuse lymphoplasmocytic infiltrates rich in IgG4(+) cells; a “storiform” fibrosis pattern; and obliterative phlebitis affecting various organs. The disease responds well to corticosteroid treatment, with a second-line therapy involving B-cell-directed immunosuppressive biologic agents. Despite intense studies, the pathogenesis of IgG4-RD remains unclear. The inflammatory infiltrates present in affected tissues contain also multiple polyclonal T and B cells, plasma cells, and – often – eosinophils. Cytokines secreted by type 2 helper T-cells and regulatory T-cells are known to cause B-cell differentiation into IgG4-producing plasma cells. On the other hand, large numbers of IgG4(+) plasma cells can be observed in nonspecific chronic inflammatory conditions, areas adjacent to neoplastic lesions with an inflammatory response, and in autoimmune inflammatory infiltrates. Thus, the fundamental question about the role of IgG4(+) cells in the pathogenesis of inflammation, tissue damage, and fibrosis in IgG4-RD still remains unanswered: does IgG4 stimulate or rather – which is more consistent with its natural properties – play a regulatory function in the inflammatory process?

Immunoglobulin G; structure and functional implications of different subclass modifications in initiation and resolution of allergy.

IgE and not IgG is usually associated with allergy. IgE lodged on mast cells in skin or gut and basophils in the blood allows for the prolonged duration of allergy through the persistent expression of high affinity IgE receptors. However, many allergic reactions are not dependent on IgE and are generated in the absence of allergen specific and even total IgE. Instead, IgG plasma cells are involved in induction of, and for much of the pathogenesis of, allergic diseases. The pattern of IgG producing plasma cells in atopic children and the tendency for direct or further class switching to IgE are the principle factors responsible for long‐lasting sensitization of mast cells in allergic children. Indirect class switching from IgG producing plasma cells has been shown to be the predominant pathway for production of IgE while a Th2 microenvironment, genetic predisposition, and the concentration and nature of allergens together act on IgG plasma cells in the atopic tendency to undergo further immunoglobulin gene recombination. The seminal involvement of IgG in allergy is further indicated by the principal role of IgG4 in the natural resolution of allergy and as the favourable immunological response to immunotherapy. This paper will look at allergy through the role of different antibodies than IgE and give current knowledge of the nature and role of IgG antibodies in the start, maintenance and resolution of allergy.

Molecular and cellular signatures underlying superior immunity against Bordetella pertussis upon pulmonary vaccination

Mucosal immunity is often required for protection against respiratory pathogens but the underlying cellular and molecular mechanisms of induction remain poorly understood. Here, systems vaccinology was used to identify immune signatures after pulmonary or subcutaneous immunization of mice with pertussis outer membrane vesicles. Pulmonary immunization led to improved protection, exclusively induced mucosal immunoglobulin A (IgA) and T helper type 17 (Th17) responses, and in addition evoked elevated systemic immunoglobulin G (IgG) antibody levels, IgG-producing plasma cells, memory B cells, and Th17 cells. These adaptive responses were preceded by unique local expression of genes of the innate immune response related to Th17 (e.g., Rorc) and IgA responses (e.g., Pigr) in addition to local and systemic secretion of Th1/Th17-promoting cytokines. This comprehensive systems approach identifies the effect of the administration route on the development of mucosal immunity, its importance in protection against Bordetella pertussis, and reveals potential molecular correlates of vaccine immunity to this reemerging pathogen.

Human Basophils Modulate Plasma Cell Differentiation and Maturation

Basophils represent <1% of circulating leukocytes. They play a crucial role during allergy and helminth-induced Th2 responses. However, recent data also suggest a contribution to the pathogenesis of autoimmune diseases. Basophils from patients with systemic lupus erythematosus show an activated phenotype, correlating to disease activity. Furthermore, murine basophils or their mediators enhance memory responses and plasma cell (PC) survival, suggesting that they directly modulate the function of B cells. This is highly relevant with respect to human allergy and autoimmunity because a possible modulation of B cell differentiation by basophils could point to new therapeutic targets. Therefore, the interaction between human B cells and basophils and the mechanism underlying this interaction were investigated in detail. Using two different methods to induce PC differentiation, we found that human basophils enhance B cell proliferation, class switching, differentiation into PC, maturation of PC, and production of Igs, especially IgG. Basophil supernatants enhanced the expression of the B cell markers CD23 and CD40, which are important for B cell differentiation into IgG-producing PC. This was mainly IL-4 dependent. IL-3 amplified the number of PC in vitro, and acted synergistically with basophils in enhancing Ab production. Thus, human basophils modulate B cell differentiation into Ab-producing PC. Their contribution as modulators and effectors during allergy and autoimmunity should be considered when designing new therapeutic options.

간세포암종으로 오인된 면역글로불린 G4-연관 염증 가성종양

Immunoglobulin G4-related disease is a recently recognized entity characterized by a massforming or regional lesion that contains an extensive infiltration of IgG4-producing plasma cells with dense fibrosis. Immunoglobulin G4-related disease can affect any organ system, but solitary hepatic lesion of Immunoglobulin G4-related disease is very rare. This entity mimics primary malignant hepatic tumor, such as hepatocellular carcinoma or intrahepatic cholangiocarcinoma. We experienced a case of hepatic IgG4-related inflammatory pseudotumor in a 50-year-old woman, mimicking hepatocellular carcinoma.

Epstein-Barr virus in the enlarged salivary tissues of patients with IgG4-related disease.

Immunoglobulin G4-related disease (IgG4-RD) is a recently recognized disease entity characterized by high-serum IgG4 concentration and IgG4-producing plasma cell production with fibrotic or sclerotic changes in affected organs. We aimed to clarify the roles of Epstein-Barr virus (EBV) in patients with IgG4-RDs. A retrospective clinical study at the Yamagata University School of Medicine, Yamagata, Japan. The patient group consisted of four males and four females with an average age of 62 years (range: 48-73). Expression of IgG4, latent member protein 1, EBV nuclear antigens-2, and EBV-encoded RNA in affected salivary glands from patients with IgG4-RD was examined by using immunohistochemistry and in situ hybridization. The copy number of EBV DNA in the salivary glands was also investigated by real-time polymerase chain reaction. All patients had hard masses in the salivary or lacrimal glands, or both, bilaterally. Serum concentrations of IgG4 were elevated in all cases (mean 589.1, range 129-1750), and IgG4-positive plasmacytes were observed in the involved salivary glands. Four patients developed potentially life-threatening systemic involvement after initial salivary gland swelling. EBV-associated molecules (EBNA and EBER) were overexpressed in the affected salivary glands. The copy number of EBV DNA was significantly higher in patients with potentially life-threatening systemic involvement than in patients without systemic involvement (P < 0.05). These results suggest that the copy number of EBV DNA could be useful as diagnostic findings in IgG4-RD to predict potentially life-threatening systemic involvement. 4.

Silica Triggers Inflammation and Ectopic Lymphoid Neogenesis in the Lungs in Parallel with Accelerated Onset of Systemic Autoimmunity and Glomerulonephritis in the Lupus-Prone NZBWF1 Mouse.

Genetic predisposition and environmental factors influence the development of human autoimmune disease. Occupational exposure to crystalline silica (cSiO2) has been etiologically linked to increased incidence of autoimmunity, including systemic lupus erythematosus (SLE), but the underlying mechanisms are poorly understood. The purpose of this study was to test the hypothesis that early repeated short-term cSiO2 exposure will modulate both latency and severity of autoimmunity in the lupus-prone female NZBWF1 mouse. Weekly intranasal exposure to cSiO2 (0.25 and 1.0 mg) for 4 wk beginning at 9 wk of age both reduced latency and increased intensity of glomerulonephritis. cSiO2 elicited robust inflammatory responses in the lungs as evidenced by extensive perivascular and peribronchial lymphoplasmacytic infiltration consisting of IgG-producing plasma cells, and CD45R+ and CD3+ lymphocytes that were highly suggestive of ectopic lymphoid tissue (ELT). In addition, there were elevated concentrations of immunoglobulins and the cytokines MCP-1, TNF-α and IL-6 in bronchoalveolar lavage fluid. cSiO2-associated kidney and lung effects paralleled dose-dependent elevations of autoantibodies and proinflammatory cytokines in plasma. Taken together, cSiO2-induced pulmonary inflammation and ectopic lymphoid neogenesis in the NZBWF1 mouse corresponded closely to systemic inflammatory and autoimmune responses as well as the early initiation of pathological outcomes in the kidney. These findings suggest that following airway exposure to crystalline silica, in mice genetically prone to SLE, the lung serves as a platform for triggering systemic autoimmunity and glomerulonephritis.

THU0408 Anti-Lactoferrin Autoantibodies Contribute to the Pathogenesis of Igg4-Related Disease by Inducing Neutrophil Extracellular TRAP Formation

BackgroundIgG4-related disease (IgG4-RD) is a newly recognized fibroinflammatory condition characterized by infiltration of IgG4-positive plasma cells into the pancreas, biliary tracts, or salivary glands. In addition to helper type 2...

(209) - IL-6 Blockage by Anti-Interleukin-6 Receptor Antibody Suppresses Plasma Cells during Development of Alloantibody Responses

We previously reported that IL-6 blockage by anti-IL6R antibody (mMR16-1) resulted in attenuation of donor-specific antibody (DSA) responses in a mouse model of allo-sensitization. However, the mechanism(s) responsible for antibody suppression is poorly understood. We recently conducted series of studies by examining the peripheral T and B cells to explore the DSA suppression mechanism. C57BL/6 mice were sensitized with skin allografts from a HLA.A2 transgenic mouse, and treated with intraperitoneal injections of mMR16-1 or control antibody. Alloantibody responses were monitored weekly by measurement of serum anti-HLA.A2 antibodies. Cellular kinetics of B subsets, including B1a (CD5+ B220+), B1b (CD11b+CD5-B220+) and follicular B2 (CD5-CD11b-B220+) cells were analyzed in FACS. IgG producing plasma cells were quantitated in an ELISpot assay. mMR16-1 significantly reduced DSA IgM (treated vs. control, MFI: 12.7+2.3 vs. 22.9+3.2 at Day 14, p=0.00022), and IgG (MFI: 99.41+35.31 vs. 300.6+53.04 at Day 28, p=6.621E-05) responses. FACS analysis of the splenic B cells showed that there was a transient reduction of B1a cells at the early responses (p<0.01 vs. control) in the treatment group while no significant difference was found in the B2 cell population between the treatment and control mice. IgG ELISpot assay demonstrated a significant reduction in IgG generating plasma cells in the spleens of the treatment mice (p<0.01 vs. control). Immune fluorescent microscopy showed that the IgG-secreting plasma cells were CD138+ localized in the marginal zones of the splenic lymphoid nodes. The data indicate that anti-IL6R antibody may affect the final stage of B cell maturation into plasma cells, or suppression of antibody forming plasma cells during the development of de novo alloantibody responses. Thus, one of the mechanisms by which mMR16-1 attenuates alloantibody responses is consistent with a blockage of a described IL-6 activity as a B/plasma cell growth factor.