Increased Autoantibody Production Research Articles

Abstract 42: Fecal Microbiota Transplantation Decreases Autoantibody Production and Lowers Blood Pressure in an Experimental Model of Autoimmune Disease

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disorder that disproportionately affects women. It is characterized by a breach of immunological self-tolerance and the expansion of autoreactive T and B lymphocytes, leading to the production of autoantibodies. Autoantibody production leads to downstream chronic inflammation resulting in high rates of hypertension, renal injury, and cardiovascular disease. Gut dysbiosis is associated with many autoimmune diseases, including SLE. In the present study, we hypothesized that gut dysbiosis in SLE may play a role in the development of immune system dysfunction and hypertension in an experimental model of SLE, and that fecal microbiota transplantation (FMT) with microbes from control mice may improve these parameters. To test this hypothesis, we treated 26-week-old female control (NZW, n=10) and SLE (NZBWF1, n=9) mice with broad spectrum antibiotics in drinking water for one week to deplete the existing microbiota. Subsequently, mice were given 0.1 mL of fecal microbes from either control or SLE mice via oral gavage two times per week for four weeks in the following groups (n=9-10 mice/group): Control-vehicle, Control-SLE microbes, SLE-vehicle, SLE-Control microbes. Changes in the gut microbiome after FMT were assessed by metagenomic sequencing of fecal pellets from all four groups. Mean arterial pressure (MAP, mmHg) was higher in SLE mice compared to control mice (Control: 112±3 vs. SLE: 140±2 mmHg, p<0.0001). SLE mice that received FMT with control microbes had lower blood pressure (SLE-FMT: 126±4 mmHg, p=0.03). While there were no changes in circulating and splenic B cell percentages, SLE mice had significantly higher percentages of CD11b + CD11c + autoimmune-associated B cells compared to control mice (Control: 0.41±0.04% vs. SLE: 1.2±0.1%, p=0.0006), which were significantly decreased in SLE-FMT mice (SLE-FMT: 0.76±0.1%, p=0.02). Circulating autoantibodies were also measured at the conclusion of the study. Anti-dsDNA IgG was elevated in SLE mice compared to control (Control: 149±38 vs. SLE: 527±114 kU/mL, p=0.02), and were significantly lower in SLE mice treated with control microbes (SLE-Control microbes: 126±4 mmHg, p=0.03). These data suggest that gut microbiota present in NZBWF1 mice contribute to the accumulation of activated B cells and increased autoantibody production, which are known pathogenic factors in the development of hypertension in SLE.

Mitochondrial aberrations in systemic lupus erythematosus pathogenesis: Insights and therapeutic implications

AbstractSystemic lupus erythematosus (SLE), a chronic autoimmune disease, is marked by impaired immune tolerance and heightened activity in both innate and adaptive immune systems. Hallmarks of SLE include elevated type I interferons and autoantibody production, though the exact causes of SLE remain elusive despite advances in research techniques. Crucial to SLE research is understanding its pathogenesis and developing effective diagnostic and therapeutic methods. Recent studies have highlighted a significant link between mitochondrial abnormalities and SLE's development and progression. Mitochondrial dysfunction plays a key role in SLE pathogenesis through various mechanisms such as mitochondrial DNA mutations, oxidative stress, immune metabolic reprogramming, and cellular death. These factors collectively contribute to the loss of self‐tolerance, increased autoantibody production, and impaired clearance of immune complexes, leading to their deposition. This triggers sustained inflammatory responses and damages multiple organs. This review focuses on the diagnostic and therapeutic approaches related to mitochondrial abnormalities in SLE. Targeting mitochondrial pathways presents a promising strategy for treating SLE, potentially improving prognosis and quality of life for those affected. Future research should further investigate the role of mitochondria in the onset and progression of SLE, providing new avenues for understanding and managing this complex disease.

Adaptive immunity and atherosclerosis: aging at its crossroads.

Adaptive immunity plays a profound role in atherosclerosis pathogenesis by regulating antigen-specific responses, inflammatory signaling and antibody production. However, as we age, our immune system undergoes a gradual functional decline, a phenomenon termed "immunosenescence". This decline is characterized by a reduction in proliferative naïve B- and T cells, decreased B- and T cell receptor repertoire and a pro-inflammatory senescence associated secretory profile. Furthermore, aging affects germinal center responses and deteriorates secondary lymphoid organ function and structure, leading to impaired T-B cell dynamics and increased autoantibody production. In this review, we will dissect the impact of aging on adaptive immunity and the role played by age-associated B- and T cells in atherosclerosis pathogenesis, emphasizing the need for interventions that target age-related immune dysfunction to reduce cardiovascular disease risk.

Myocardial injury causes changes in the transcriptional and regulatory landscape of adaptive immune cells in the heart

Abstract Background Ischaemic heart disease is a leading cause of heart failure (HF) and despite advanced therapeutic options, morbidity and mortality rates remain high. Acute inflammation after myocardial infarction (MI) has been thoroughly studied in recent years and persistent immune-mediated damage has been suggested as a factor contributing to the development of HF. T and B cells are critical mediators of adaptive immune responses after MI, however a thorough analysis of their transcriptomic phenotypes in the heart at baseline and over time after injury are missing. Purpose Here, we aim to understand the transcriptional activity of B and T cells in the post-MI heart, in order to characterize their role in maintaining post-MI autoreactivity. Methods We obtained single cell RNA sequencing data of mouse and human hearts from Forte et al (2020), Martini et al (2019) and Litviňuková et al (2020) and performed differential expression analysis, gene regulatory inferences and trajectory-based differential expression analysis. Results Myocardial T cells subclustered into CD8+, CD4+, CD20+ and NK lineages with naïve, memory and effector functions (Fig. 1). The B cell population was divided into immature, plasma, memory, collagen-producing and B1 cell subgroups (Fig. 2). At baseline, despite a striking presence of effector populations, both B and T cells are governed by homeostatic and tolerance-promoting transcription factors (Deaf1, Ikzf1 and Nr1h3 for T cells and Spi-B as well as Bcl11 for B cells). Post-MI, the activity of transcription factors concerned with differentiation and proliferation increased. T cells express transcripts for proinflammatory chemokines and cytokines (Ccr7, Ccl5, Ifng and Tnf) as well as granzymes and perforin up until 28 days post-MI (Gzma and Prf1). Surprisingly, B cells upregulate collagen transcript levels 5-7 days post-MI (Col1a, Col5a, and Col4a) and regulon analysis supports that B cells increase the activity of transcription factors necessary for collagen production (Ets-1 and Krox20). Both B and T cells remain persistently activated post MI. 28 days post-MI T cells have increased activity of proinflammatory (Nfkb1) and cytokine producing (Crem and Rel) transcription factors, whereas B cells have increase maturation (Nfkb1), autoantibody production (Stat3 and Rel) and memory (Stat5b) transcription factor activity. Conclusion Collectively, our data shows that there are effector immune cell populations present at baseline, which are governed by homeostatic transcription factors. Post-MI, effector transcription factors are upregulated in both T cells and B cells, which promote proliferation, differentiation, cytokine production and in the case of B cells, collagen production. Even after resolution of acute inflammation, both the T and B cell population do not return fully to baseline but remain at a state of persistent activation, as effector transcription factors remain upregulated.

P23 Curing the nail

Abstract Introduction Ultraviolet light is a well known trigger for inducing cutaneous flares in people who are predisposed or have been diagnosed with cutaneous lupus, it may have far reaching implications, triggering organ threatening disease Ultraviolet light could be from various sources including the sun, light bulbs and drying lamps used in nail salons to “cure the nails”. Curing the nails is a term used in the manicure world where UVA type 2 light is used to facilitate complete and quick drying of the nail polish: these type of UV light have been implicated in the pathogenesis of lupus. Case description This is the case of a 41 year old lady of African descent diagnosed with discoid lupus at the age of 33. Symptoms include hair loss, hypopigmented lesions on her ear, urticarial rash, fatigue, joint stiffness. Prior history of pregnancy loss at 14 weeks noted, and her sister also suffers from lupus. On examination she was found to have scarring alopecia with hyperkeratotic erythematous lesions at the periungual area with acrylic nails. Blood work showed lymphopenia, positive ANA, positive dsDNA by ELISA, RO+, positive anti smith antibody, normal complements and no evidence of kidney involvement. She was treated with topical therapy and then escalated in turns to hydroxychloroquine, mycophenolate mofetil, azathioprine, rituximab and methotrexate. She had developed a rash on hydroxychloroquine leading to it's discontinuation. The periungual lesions were resistant to all of the above treatment including intralesional steroid. She had recurrent flares of the lesions which resulted in episodes of infection, pus drainage, and treatment with antibiotics. Nifedipine was introduced but did not ameliorate symptoms A causal link was eventually made between her exposure to UV light at the nail salon and the periungual lesion. She was advised to discontinue using the UV light and possibly resort to traditional nail polish and air drying. The periungual lesions significantly improved on cessation of using the UV lights. Discussion Gel/acrylic manicures are becoming increasingly popular as they are more aesthetically pleasing and long lasting compared to traditional nail polish which uses air drying method, however we should be aware of the risk of ultraviolet (UV) light exposure which is used to dry the nails. UV light stimulates keratinocytes to express more small nuclear ribonucleoproteins thereby secreting IL-1,1L-6, IL-3, GM-CSF which lead to tissue damage and increased autoantibody production, this can result in development of cutaneous lupus, worsening of cutaneous lupus or in some cases can precipitate organ threatening systemic lupus. As clinicians we should be aware of the risks and educate our patients on the implication to their disease, they should be encouraged not to use this method of manicure but rather resort to the traditional nail polish which uses air drying technique rather than UV light. Other options may include applying sun protection cream to the fingers before manicure or the use of UV protective gloves, these measures though may not provide adequate coverage to the periungual area. We should be aware and educate our patients on avoidance of other sources of UV light including avoidance of fluorescent light, tanning beds, surgical lamps and measures to reduce exposure. Key learning points Consider other sources of UV light exposure in patients with hard to treat skin disease. It is critical that we educate our patients on the possible side effects of UV exposure and counsel on strategies to minimise exposure

A 72-year-old man with nonhealing facial erosions and bullae

A 72-year-old man with nonhealing facial erosions and bullae

Human SLE variant NCF1-R90H promotes kidney damage and murine lupus through enhanced Tfh2 responses induced by defective efferocytosis of macrophages

ObjectivesWe previously identified a hypomorphic variant, p.Arg90His (p.R90H) of neutrophil cytosolic factor 1 (NCF1, a regulatory subunit of phagocyte nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 complex), as an putative...

Mechanisms Driving Immune-Related Adverse Events in Cancer Patients Treated with Immune Checkpoint Inhibitors.

In the past decade, immune checkpoint inhibitors (ICIs) have revolutionized the field of cancer treatment. With the continuing rise in the number of cancer patients eligible for ICIs, a corresponding rise in immune-related adverse events (irAEs) is occurring. IrAEs are inflammatory reactions against normal, healthy tissue that occur due to ICI-induced activation of the immune system. Although the exact immune pathogenesis driving irAE development remains unknown, we review the main proposed mechanisms, highlighting how they may inform irAE prediction and treatment. IrAEs are common and diverse, varying in incidence, timing, and severity. The possible mechanisms driving irAEs include (1) activation of cytotoxic T cells; (2) activation of B cells and increased autoantibody production; (3) direct molecular mimicry and off-target toxicity; (4) activation of intracellular signaling and pro-inflammatory cytokine production; and (5) environmental modifiers of immune system activation, including composition of the host gut microbiome. These mechanisms may help identify predictive biomarkers and targeted treatment strategies. IrAEs are driven by multiple components of the immune system. More research is needed to understand their immunopathogenesis so that clinicians across all specialties may more effectively monitor and manage these increasingly common conditions.

CGAS-STING Pathway Does Not Promote Autoimmunity in Murine Models of SLE.

Detection of DNA is an important determinant of host-defense but also a driver of autoinflammatory and autoimmune diseases. Failure to degrade self-DNA in DNAseII or III(TREX1)-deficient mice results in activation of the cGAS-STING pathway. Deficiency of cGAS or STING in these models ameliorates disease manifestations. However, the contribution of the cGAS-STING pathway, relative to endosomal TLRs, in systemic lupus erythematosus (SLE) is controversial. In fact, STING deficiency failed to rescue, and actually exacerbated, disease manifestations in Fas-deficient SLE-prone mice. We have now extended these observations to a chronic model of SLE induced by the i.p. injection of TMPD (pristane). We found that both cGAS- and STING-deficiency not only failed to rescue mice from TMPD-induced SLE, but resulted in increased autoantibody production and higher proteinuria levels compared to cGAS STING sufficient mice. Further, we generated cGASKOFaslpr mice on a pure MRL/Faslpr background using Crispr/Cas9 and found slightly exacerbated, and not attenuated, disease. We hypothesized that the cGAS-STING pathway constrains TLR activation, and thereby limits autoimmune manifestations in these two models. Consistent with this premise, mice lacking cGAS and Unc93B1 or STING and Unc93B1 developed minimal systemic autoimmunity as compared to cGAS or STING single knock out animals. Nevertheless, TMPD-driven lupus in B6 mice was abrogated upon AAV-delivery of DNAse I, implicating a DNA trigger. Overall, this study demonstrated that the cGAS-STING pathway does not promote systemic autoimmunity in murine models of SLE. These data have important implications for cGAS-STING-directed therapies being developed for the treatment of systemic autoimmunity.

Lupus susceptibility gene Pbx1 promotes atherosclerosis via dysfunctional T cells in a mouse model

Abstract The incidence of atherosclerosis is higher among patients with systemic lupus erythematosus (SLE). An imbalance between regulatory T cells (Treg) and follicular helper T cells (Tfh) occurs in the development and progression in both diseases. However, the mechanisms by which lupus T cells may aggravate atherosclerosis remain unclear. Pre-B-cell leukemia transcription factor 1 isoform d (Pbx1-d) is a lupus susceptibility gene and transgenic (Tg) Pbx1-d in CD4+ T cells expands Tfh and impairs Treg. Here, we investigated the role of CD4-Pbx1-d-Tg T cells in the low-density lipoprotein receptor-deficient (Ldlr−/−) mice, an experimental model for atherosclerosis. Pbx1-d T cells exacerbated atherosclerosis in Ldlr−/− mice as compared to B6 T cells. The enhanced atherosclerosis was associated with increased body weight, increased autoantibody production, reduced Treg in the aorta, as well as increased splenic Tfh frequency and impaired Treg cell suppressive markers. Dyslipidemia inhibited the differentiation and function of Treg cells in vitro. Moreover, Pbx1-d Treg cells were less suppressive than B6 control Treg cells in dyslipidemia conditions. Thus, our results showed that Pbx1-d-Tg T cells exacerbate atherosclerosis due to the dysregulated Treg and Tfh cells, briging autoimmunity and cardiovascular pathology.

Sex-mediated elevation of the specialized pro-resolving lipid mediator levels in a Sjögren's syndrome mouse model.

Our previous results showed that the specialized pro-resolving mediator (SPM) Resolvin D1 (RvD1) promotes resolution of inflammation in salivary glands in non-obese diabetic (NOD)/ShiLtJ, a mouse model for Sjögren's syndrome (SS). Additionally, mice lacking the RvD1 receptor ALX/FPR2 show defective innate and adaptive immune responses in salivary glands. Particularly, ALX/FPR2 KO mice exhibit exacerbated inflammation in their salivary glands in response to systemic LPS treatment. Moreover, female ALX/FPR2 KO mice show increased autoantibody production and loss of salivary gland function with age. Together, these studies suggest that an underlying SPM dysregulation could be contributing to SS progression. Therefore, we investigated whether SPM production is altered in NOD/ShiLtJ using metabololipidomics and enzyme-linked immunosorbent assay (ELISA). Our results demonstrate that SPM levels were broadly elevated in plasma collected from NOD/ShiLtJ female mice after disease onset, whereas these drastic changes did not occur in male mice. Moreover, gene expression of enzymes involved in SPM biosynthesis were altered in submandibular glands (SMG) from NOD/ShiLtJ female mice after disease onset, with 5-LOX and 12/15-LOX being downregulated and upregulated, respectively. Despite this dysregulation, the abundances of the SPM products of these enzymes (ie, RvD1 and RvD2) were unaltered in freshly isolated SMG cells suggesting that other cell populations (eg, lymphocytes) may be responsible for the overabundance of SPMs that we observed. The elevation of SPMs noted here appeared to be sex mediated, meaning that it was observed only in one sex (females). Given that SS primarily affects females (roughly 90% of diagnosed cases), these results may provide some insights into the mechanisms underlying the observed sexual dimorphism.

Coordination between innate immune cells, type I IFNs and IRF5 drives SLE pathogenesis

Systemic lupus erythematosus (SLE) is a complex autoimmune disease which affects multiple organs. The type I interferon (IFN) gene signature and circulating autoantibodies are hallmarks of SLE. Plasmacytoid dendritic cells (pDCs) are considered the main producers of type I IFN and production is modulated by multiple other immune cell types. In SLE, essentially every immune cell type is dysregulated and aberrant deregulation is thought to be due, in part, to direct or indirect exposure to IFN. Genetic variants within or around the transcription factor interferon regulatory factor 5 (IRF5) associate with SLE risk. Elevated IFNα activity was detected in the sera of SLE patients carrying IRF5 risk polymorphisms who were positive for either anti-RNA binding protein (anti-RBP) or anti-double-stranded DNA (anti-dsDNA) autoantibodies. Neutrophils are also an important source of type I IFNs and are found in abundance in human blood. Neutrophil extracellular traps (NETs) are considered a potential source of antigenic trigger in SLE that can lead to type I IFN gene induction, as well as increased autoantibody production. In this review, we will focus on immune cell types that produce type I IFNs and/or are affected by type I IFN in SLE. In addition, we will discuss potential inducers of endogenous type I IFN production in SLE. Last, we will postulate how the different immune cell populations may be affected by an IRF5-SLE risk haplotype.

Estrogen receptor \u03b1 in T cells suppresses follicular helper T cell responses and prevents autoimmunity

Estrogen receptor alpha (ERα) is a sex hormone nuclear receptor that regulates various physiological events, including the immune response. Although there have been some recent studies on ERα regarding subsets of T cells, such as Th1, Th2, Th17, and Treg cells, its role in follicular helper T (TFH) cells has not yet been elucidated. To determine whether ERα controls TFH response and antibody production, we generated T cell-specific ERα knockout (KO) mice by utilizing the CD4-Cre/ERα flox system (CD4-ERα KO) and then analyzed their phenotype. At approximately 1 year of age, CD4-ERα KO mice spontaneously showed mild autoimmunity with increased autoantibody production and CD4+CD44+CXCR5+Bcl-6+ TFH cells in the mesenteric lymph nodes and spleen. We next immunized 6–8-week-old CD4-ERα KO mice with sheep red blood cells (SRBCs), which resulted in an increased proportion of TFH cells and germinal center (GC) responses. In addition, 17β-estradiol (E2) treatment decreased TFH responses in wild-type mice and suppressed the mRNA expression of Bcl-6 and IL-21. Finally, we confirmed that the production of high-affinity antigen-specific antibodies and isotype class switching induced by NP-conjugated ovalbumin immunization were elevated in CD4-ERα KO mice under sufficient estrogen conditions. These results collectively demonstrate that the female sex hormone receptor ERα inhibits the TFH cell response and GC reaction to control autoantibody production, which was related to estrogen signaling and autoimmunity.

P2RX7 Deletion in T Cells Promotes Autoimmune Arthritis by Unleashing the Tfh Cell Response.

Rheumatoid arthritis (RA) is an autoimmune disease that affects ~1% of the world's population. B cells and autoantibodies play an important role in the pathogenesis of RA. The P2RX7 receptor is an ATP-gated cation channel and its activation results in the release of pro-inflammatory molecules. Thus, antagonists of P2RX7 have been considered to have potential as novel anti-inflammatory therapies. Although originally identified for its role in innate immunity, P2RX7 has recently been found to negatively control Peyer's patches (PP) T follicular helper cells (Tfh), which specialize in helping B cells, under homeostatic conditions. We have previously demonstrated that PP Tfh cells are required for the augmentation of autoimmune arthritis mediated by gut commensal segmented filamentous bacteria (SFB). Thus, we hypothesized that P2RX7 is required to control autoimmune disease by keeping the Tfh cell response in check. To test our hypothesis, we analyzed the impact of P2RX7 deficiency in vivo using both the original K/BxN autoimmune arthritis model and T cell transfers in the K/BxN system. We also examined the impact of P2RX7 ablation on autoimmune development in the presence of the gut microbiota SFB. Our data illustrate that contrary to exerting an anti-inflammatory effect, P2RX7 deficiency actually enhances autoimmune arthritis. Interestingly, SFB colonization can negate the difference in disease severity between WT and P2RX7-deficient mice. We further demonstrated that P2RX7 ablation in the absence of SFB caused reduced apoptotic Tfh cells and enhanced the Tfh response, leading to an increase in autoantibody production. It has been shown that activation of TIGIT, a well-known T cell exhaustion marker, up-regulates anti-apoptotic molecules and promotes T cell survival. We demonstrated that the reduced apoptotic phenotype of P2rx7−/− Tfh cells is associated with their increased expression of TIGIT. This suggested that while P2RX7 was regulating the Tfh population by promoting cell death, TIGIT may have been opposing P2RX7 by inhibiting cell death. Together, these results demonstrated that systemic administration of general P2RX7 antagonists may have detrimental effects in autoimmune therapies, especially in Tfh cell-dependent autoimmune diseases, and cell-specific targeting of P2RX7 should be considered in order to achieve efficacy for P2RX7-related therapy.

Interleukin-25 Axis Is Involved in the Pathogenesis of Human Primary and Experimental Murine Sjögren's Syndrome.

To investigate the role of the interleukin-25 (IL-25)/IL-17 receptor B (IL-17RB) axis in experimental Sjögren's syndrome (SS) and in patients with primary SS and primary SS-associated lymphoma. Expression of IL-25, IL-17RB, IL-17B, and tumor necrosis factor receptor-associated factor 6 (TRAF6) was analyzed on minor salivary gland (SG) samples from patients with primary SS and on parotid gland samples from patients with primary SS-associated B cell non-Hodgkin's lymphoma (NHL). IL-17RB expression and the frequencies of natural group 2 innate lymphoid cells (ILC2s), inflammatory ILC2s, and M2-polarized macrophages were assessed by flow cytometry in SG mononuclear cells and peripheral blood mononuclear cells (PBMCs). Tissue distribution of ILC2s was studied by confocal microscopy. The role of recombinant IL-25 and of rituximab in modulating IL-25 expression was investigated in in vitro studies. IL-25/IL-17RB and TRAF6 expression and the role of IL-25 inhibition were also studied in the experimental murine model of SS. Activation of the IL-25/IL-17RB/TRAF6 axis correlated with the focus score and was observed in patients with primary SS and in patients with primary SS-associated NHL. A significant increase in the frequency of inflammatory ILC2s was observed both in SG mononuclear cells and in PBMCs. IL-25 stimulation of isolated SG mononuclear cells and PBMCs from patients and controls resulted both in inflammatory ILC2 expansion and in increased autoantibody production. Rituximab modulated expression of inflammatory ILC2s and IL-25 in primary SS. SG protein-immunized mice developed overt SS symptoms with increased IL-25 expression and increased frequency of CD4+IL-17RB+TRAF6+ cells. IL-25 neutralization attenuated disease progression and tissue pathology in mice with experimental SS. IL-25 may promote the inflammatory state in primary SS and may be a potential target for novel disease-modifying therapeutic strategies in patients with primary SS.

Atherogenic dyslipidemia promotes autoimmune follicular helper T cell responses via IL-27.

The incidence of atherosclerosis is higher among patients with systemic lupus erythematosus (SLE); however, the mechanism by which an atherogenic environment affects autoimmunity remains unclear. We found that reconstitution of atherosclerosis-prone Apoe-/- and Ldlr-/- mice with bone marrow from lupus-prone BXD2 mice resulted in increased autoantibody production and glomerulonephritis. This enhanced disease was associated with an increase in CXCR3+ follicular helper T cells (TFH cells). TFH cells isolated from Apoe-/- mice had higher expression of genes associated with inflammatory responses and SLE and were more potent in inducing production of the immunoglobulin IgG2c. Mechanistically, the atherogenic environment induced the cytokine IL-27 from dendritic cells in a Toll-like receptor 4 (TLR4)-dependent manner, which in turn triggered the differentiation of CXCR3+ TFH cells while inhibiting the differentiation of follicular regulatory T cells. Blockade of IL-27 signals diminished the increased TFH cell responses in atherogenic mice. Thus, atherogenic dyslipidemia augments autoimmune TFH cell responses and subsequent IgG2c production in a TLR4- and IL-27-dependent manner.

Siglec genes confer resistance to systemic lupus erythematosus in humans and mice

A recent meta-analysis revealed the contribution of the SIGLEC6 locus to the risk of developing systemic lupus erythematosus (SLE). However, no specific Siglec (sialic acid-binding immunoglobulin-like lectin) genes (Siglecs) have been implicated in the pathogenesis of SLE. Here, we performed in silico analysis of the function of three major protective alleles in the locus and found that these alleles were expression quantitative trait loci that enhanced expression of the adjacent SIGLEC12 gene. These data suggest that SIGLEC12 may protect against the development of SLE in Asian populations. Consistent with human genetic data, we identified two missense mutations in lupus-prone B6.NZMSle1/Sle2/Sle3 (Sle1–3) mice in Siglece, which is the murine Siglec with the greatest homology to human SIGLEC12. Since the mutations resulted in reduced binding of Siglec E to splenic cells, we evaluated whether Siglece−/− mice had SLE phenotypes. We found that Siglece−/− mice showed increased autoantibody production, glomerular immune complex deposition and severe renal pathology reminiscent of human SLE nephropathy. Our data demonstrate that the Siglec genes confer resistance to SLE in mice and humans.

Adoptive transfer of autoimmune splenic dendritic cells to lupus-prone mice triggers a B lymphocyte humoral response

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by increased autoantibody production that leads to multiple tissue injuries. Dendritic cells (DCs) are important orchestrators of immune responses and key components in fine-tuning the balance between tolerance and immunity. However, their role in autoimmune disorders such as SLE remains uncertain. We analyzed the contribution of DCs in triggering SLE by adoptively transferring splenic DCs from aged autoimmune [NZB×NZW]F1 (BWF1) mice to young healthy BWF1 mice. We observed that the transfer of DCs from autoimmune mice to pre-autoimmune mice induced high autoantibody titers in the serum of recipient mice. Moreover, autoimmune DCs from aged BWF1 mice were crucial for the expansion and differentiation of plasmablasts and CD5+ B cells or B1-like cells in the peripheral blood, and spleen of recipient BWF1 mice, a phenomenon that is observed in autoimmune BWF1 mice. On the other hand, DCs from aged BWF1 mice participated in the expansion and differentiation of DCs and IFN-γ-producing T cells. These results reveal that DCs from autoimmune BWF1 mice exhibit functional and phenotypic characteristics that allow them to trigger B cell hyperactivation, as well as DC and T cell expansion and differentiation, thereby promoting an exacerbated humoral response in lupus-prone mice.

TACI-dependent APRIL signaling maintains autoreactive B cells in a mouse model of systemic lupus erythematosus.

Autoantibodies contribute to the development of systemic lupus erythematosus (SLE). APRIL (a proliferation-inducing ligand), a member of the TNF superfamily, regulates plasma-cell survival and binds to TACI (transmembrane activator CAML interactor) and BCMA (B-cell maturation antigen). We previously showed that APRIL blockade delayed disease onset in lupus-prone mice. In order to evaluate the role of APRIL receptors in the development of SLE, APRIL, TACI, BCMA, or double TACI.BCMA null mutations were introduced into the Nba2.Yaa (Y-linked autoimmune acceleration) spontaneous lupus mouse model. Mortality as a consequence of glomerulonephritis (GN) was reduced in Nba2.APRIL-/- .Yaa, Nba2.TACI-/- .Yaa and double-KO mice compared with Nba2.Yaa mice and correlated with lower levels of circulating antibodies, while splenic populations remained unchanged. In contrast, the appearance of symptoms was accelerated in BCMA-deficient mice, in which TACI signaling was increased. Finally, lupus-prone mice deficient for the APRIL-TACI axis produced less pathogenic antibodies and developed less GN. Disease reduction was attributed to impaired T-independent type 2 responses when the APRIL-TACI signaling axis was disrupted. Collectively, our results have identified and confirmed APRIL as a new target involved in B-cell activation, in the maintenance of plasma cell survival and subsequent increased autoantibody production that sustains lupus development in mice.

Basophil Activation-Dependent Autoantibody and Interleukin-17 Production Exacerbate Systemic Lupus Erythematosus.

Autoantibody and inflammatory cytokines play crucial roles in the development of systemic lupus erythematosus (SLE); however, the regulation of their production warrants further investigation. This study aimed to investigate the role of basophil activation in the development of SLE based on studies in patients with SLE and spontaneous lupus-prone MRL-lpr/lpr mice. The phenotypes of peripheral basophils and the production of autoantibody and interleukin (IL)-17 in patients with SLE were determined by flow cytometry and enzyme-linked immunosorbent assay, and also their correlations were investigated by statistical analysis. Thereafter, the effect of basophils on autoantibody production by B cells and Th17 differentiation in SLE were evaluated in vitro. Finally, the effect of basophil depletion on the development of autoimmune disorders in spontaneous lupus-prone MRL-lpr/lpr mice was examined. The decreased numbers and an increased activation of peripheral basophils were found to be correlated with increased autoantibody production and disease activity in patients with SLE. Correspondingly, in vitro coculture studies showed that basophils obtained from patients with SLE promoted autoantibody production by SLE B cells and promoted Th17 differentiation from SLE naïve CD4+ T cells. The decrease of peripheral basophils in patients with SLE might be due to their migration to lymph nodes post their activation mediated by (autoreactive) IgE as supported by their increased CD62L and CCR7 expressions and accumulation in the lymph nodes of MRL-lpr/lpr mice. Furthermore, an increased activation of peripheral basophils was identified in MRL-lpr/lpr mice. Importantly, basophil-depleted MRL-lpr/lpr mice exhibited an extended life span, improved renal function, and lower serum levels of autoantibodies and IL-17, while basophil-adoptive-transferred mice exhibited the opposite results. These finding suggest that basophil activation-dependent autoantibody and IL-17 production may constitute a critical pathogenic mechanism in SLE.