Production Of Antinuclear Antibodies Research Articles

An Animal Model Using Metallic Ions to Produce Autoimmune Nephritis.

Autoimmune nephritis triggered by metallic ions was assessed in a Long-Evans rat model. The parameters evaluated included antinuclear autoantibody production, kidney damage mediated by immune complexes detected by immunofluorescence, and renal function tested by retention of nitrogen waste products and proteinuria. To accomplish our goal, the animals were treated with the following ionic metals: HgCl2, CuSO4, AgNO3, and Pb(NO3)2. A group without ionic metals was used as the control. The results of the present investigation demonstrated that metallic ions triggered antinuclear antibody production in 60% of animals, some of them with anti-DNA specificity. Furthermore, all animals treated with heavy metals developed toxic glomerulonephritis with immune complex deposition along the mesangium and membranes. These phenomena were accompanied by proteinuria and increased concentrations of urea. Based on these results, we conclude that metallic ions may induce experimental autoimmune nephritis.

Pathogenic effects of maternal antinuclear antibodies during pregnancy in women with lupus

Lupus is an autoimmune disease that primarily affects young women of childbearing age. Fertility rates in lupus patients depend on various factors, including disease activity, nephritis, and the presence of antiphospholipid antibodies; however, after lupus patients become pregnant, different factors may affect the course of pregnancy, such as the production of autoantibodies, pre-existing renal disease, and eclampsia, among others. The placenta is a temporary hemochorial organ that prevents immunological conflict due to exposure to alloantigens at the maternal-fetal interface; placental regulatory T cells play a major role in maternal-fetal tolerance. Typically, significant amounts of maternal IgG class antibodies cross the placenta and enter the fetal circulation. This transition depends on the distribution of Fc receptors along the syncytiotrophoblast. The production of antinuclear antibodies (ANA) is a hallmark of lupus, and these autoantibodies can form immune complexes that are typically trapped in the placenta during gestation. However, the entry of ANA into the fetal circulation depends on the IgG-ANA concentration and the FcR placental density. Maternal antinuclear antibodies with anti-Ro or anti-La specificity might be pathogenic to the fetus if transfused by the placental pathway and could induce neonatal pathologies, such as neonatal lupus and congenital heart block. Here, we review the experimental and clinical data supporting a pathogenic role for maternal autoantibodies transmitted to the fetus

Association between antinuclear antibodies and the HLA class II locus and heterogeneous characteristics of staining patterns: the Nagahama study.

While antinuclear antibodies (ANAs) are observed in healthy populations as well as in patients with autoimmune diseases such as systemic lupus erythematosus (SLE), the detailed genetic background of ANAs has remained unclear. We undertook this study to identify the genetic determinants of ANAs in the general population in order to elucidate the underlying mechanisms of ANA production and to distinguish disease susceptibility genes from ANA production genes. A total of 9,575 Japanese volunteers were registered, and their ANA levels were quantified using indirect immunofluorescence to analyze correlates of ANA positivity. Genetic studies were performed using 7,148 of the 9,575 subjects. We performed a genome-wide association study using 3,185 subjects genotyped for 303,506 single-nucleotide polymorphisms (SNPs), followed by a replication study of 3,963 subjects. HLA-DRB1 and HLA-DQB1 alleles were imputed, and associations between ANA positivity and the SNPs or the HLA alleles associated with SLE were analyzed. Female sex and old age were associated with ANA positivity, except for the nucleolar pattern. The T allele of rs2395185 in the HLA locus, which was in moderate linkage disequilibrium with HLA-DRB1*0405, was significantly associated with ANA positivity (P = 1.3 × 10(-11) ). The T allele of rs2395185 displayed increasing effects on the frequency of speckled and homogeneous patterns (P = 7.5 × 10(-12) and P = 2.2 × 10(-11) , respectively) but decreasing effects on the frequency of the nucleolar pattern (P = 0.0045). The 7 SNPs and 4 HLA-DRB1 alleles associated with SLE did not display strong associations with ANA positivity. SNP rs2395185 linked with HLA-DRB1*0405 is a genetic determinant of ANA production in the Japanese population. Overlapping of loci for susceptibility to SLE and to ANA positivity was limited. The nucleolar pattern showed different associations from other staining patterns, both with correlates of ANA positivity and with the HLA locus.

Disease Activity in Systemic Lupus Erythematosus Correlates With Expression of the Transcription Factor AT‐Rich–Interactive Domain 3A

ObjectiveSystemic lupus erythematosus (SLE) is a complex and multifactorial autoimmune disease with striking clinical, immunologic, and genetic heterogeneity, despite nearly ubiquitous antinuclear antibody (ANA) production. Multiple gene polymorphisms have been associated with the disease, but these individually account for only a very small percentage of overall SLE risk. In earlier studies, constitutive expression of the DNA‐binding protein AT‐rich–interactive domain 3A (ARID3a) in transgenic mouse B lymphocyte lineage cells led to spontaneous ANA production and preferential development of B cells associated with production of polyreactive antibodies. Therefore, we undertook this study to determine whether ARID3a was overexpressed in B lymphocytes of SLE patients and whether ARID3a expression was associated with disease severity.MethodsA cross‐section of SLE patients, rheumatoid arthritis patients, and age‐ and sex‐matched controls was analyzed longitudinally for lupus disease activity, numbers of ARID3a+ peripheral blood mononuclear B cells from multiple B cell subsets, and immunoglobulin and cytokine levels.ResultsFifty of 115 SLE patients (43%) had dramatically increased numbers of ARID3a+ B cells compared to healthy controls. ARID3a was not expressed in naive B cells of healthy controls, but was abundant in these precursors of antibody‐secreting cells in SLE patients. Total numbers of ARID3a+ B cells correlated with increased disease activity as defined by SLE Disease Activity Index scores in individuals assessed at 3 time points.ConclusionThese findings identify B cell anomalies in SLE that allow stratification of patient samples based on ARID3a expression and implicate ARID3a as a potential marker of CD19+ B lymphocytes correlated with disease activity.

Restored immunosuppressive effect of mesenchymal stem cells on B cells after olfactory 1/early B cell factor-associated zinc-finger protein down-regulation in patients with systemic lupus erythematosus.

To evaluate whether olfactory 1/early B cell factor-associated zinc-finger protein (OAZ), a candidate lupus susceptibility gene involved in antinuclear antibody (ANA) production, plays a role in the regulation of B cells by mesenchymal stem cells (MSCs). MSCs derived from the bone marrow of patients with systemic lupus erythematosus (SLE) and healthy control subjects were expanded and incubated with small interfering RNAs specific for OAZ or a nontargeting sequence. Knockdown of messenger RNA levels of OAZ and its downstream genes was measured using real-time polymerase chain reaction, and protein levels of chemokine/cytokine and immunoglobulins were determined by enzyme-linked immunosorbent assay or Western blotting. The effects of modulating the OAZ levels in MSCs, by either silencing or overexpression, on B cell proliferation and terminal differentiation were assessed by coculturing MSCs with mouse spleen cells. OAZ gene expression was highly enriched in MSCs compared with peripheral blood leukocytes and was increased in patients with SLE compared with control subjects. After the silencing of OAZ expression, SLE MSCs could regain the ability to inhibit B cell proliferation and terminal differentiation, as indicated by decreased percentages of bromodeoxyuridine-positive cells and CD138+ cells as well as decreased levels of IgG, IgM, and ANAs. The level of CCL2 was increased after OAZ knockdown, while anti-CCL2 antibodies completely counteracted the effect of OAZ silencing. Umbilical cord-derived normal MSCs that overexpressed OAZ had a diminished ability to inhibit B cell proliferation and terminal differentiation. OAZ down-regulation could restore the impaired function of SLE MSCs in the immune regulation of B cells, contributing to a reduction in ANA levels. OAZ might represent a new target for therapy in patients with SLE.

The development of autoimmune features in aging mice is closely associated with alterations of the peripheral CD4⁺ T-cell compartment.

Some signs of potential autoimmunity, such as the appearance of antinuclear antibodies (ANAs) become prevalent with age. In most cases, elderly people with ANAs remain healthy. Here, we investigated whether the same holds true for inbred strains of mice. Indeed, we show that most mice of the C57BL/6 (B6) strain spontaneously produced IgG ANA at 8-12 months of age, showed IgM deposition in kidneys and lymphocyte infiltrates in submandibular salivary glands. Despite all of this, the mice remained healthy. ANA production is likely CD4(+) T-cell dependent, since old (40-50 weeks of age) B6 mice deficient for MHC class II do not produce IgG ANAs. BM chimeras showed that ANA production was not determined by age-related changes in radiosensitive, hematopoietic progenitor cells, and that the CD4(+) T cells that promote ANA production were radioresistant. Thymectomy of B6 mice at 5 weeks of age led to premature alterations in T-cell homeostasis and ANA production, by 15 weeks of age, similar to that in old mice. Our findings suggest that a disturbed T-cell homeostasis may drive the onset of some autoimmune features.

THU0058 Intestinal Microbiota Plays A Critical Role in the Production of Antinuclear Antibodies in Lymphopenia-Induced Autoimmunity

BackgroundProduction of antinuclear autoantibodies (ANAs) is one of the major characteristics of the systemic autoimmune diseases, such as systemic lupus erythematosus (SLE), but the mechanisms of their production are not...

Tight skin 2 mice exhibit a novel time line of events leading to increased extracellular matrix deposition and dermal fibrosis

The tight skin 2 (Tsk2) mouse model of systemic sclerosis (SSc) has many features of the human disease including tight skin, fibrosis, extracellular matrix abnormalities, and reported antinuclear antibodies (ANA). Here we report that Tsk2/+ mice develop excess dermal fibrosis with age, as skin is not significantly fibrotic until 10weeks, a full eight weeks after the development of the physical tight skin phenotype. Concomitantly with the tight skin phenotype at two weeks of age, Tsk2/+ mice demonstrate increased levels of total transforming growth factor beta 1 (TGF-β1) and excessive accumulation of dermal elastic fibers. The increase in elastic fibers is not responsible for tight skin, however, because Tsk2/+ mice genetically engineered to lack skin elastic fibers nevertheless have tight skin and fibrosis. Finally, about two months after the first measurable increases of total collagen, a portion of Tsk2/+ mice produce ANAs, but at a similar level to wild-type littermates. The timeline of disease development in the Tsk2/+ mouse shows that fibrosis is progressive, with elastic fiber alterations and TGF-β1 over-production occurring at least two months before bona fide fibrosis, that is not dependent on ANA production.

Lupus nephritis with positive myeloperoxidase/proteinase 3-antineutrophil cytoplasmic autoantibody that developed after 17 years of propylthiouracil therapy

Dear Editor, Propylthiouracil (PTU) is a thiouracil-derived drug used to treat hyperthyroidism. A number of adverse effects have been reported in association with this drug, including fever, agranulocytosis, skin rash, and vasculitis. Increasing evidence has recently suggested that PTU can induce autoimmune syndromes with the production of antinuclear antibodies or antineutrophil cytoplasmic autoantibody (ANCA) in patients with Graves’ disease. We herein report a patient who developed lupus nephritis with positive myeloperoxidase (MPO)/proteinase 3 (PR3)-ANCA after taking PTU for 17 years. A 51-year-old man with a history of Graves’ disease, treated with PTU at 50 mg/day for approximately 17 years, presented to another institution with persistent high fever, polyarthralgia, and foot edema and was subsequently referred to our hospital. Upon presentation, he had thrombocytopenia (platelet count, PLT: 3.8 9 10/lL), leukocytopenia (WBC: 2.9 9 10/lL with 47 % neutrophils), microhematuria ([100 red blood cells per highpower field), proteinuria (1.01 g/day, peak value 4.26 g/ day), and an elevated serum creatinine level (1.42 mg/dL, peak value 5.66 mg/dL; Fig. 1). Thyroid function tests were within the normal range. Serological examinations showed a high titer of antinuclear antibodies (1:320, speckled pattern), positive MPO-ANCA (140.0 U/mL), positive PR3-ANCA (19.5 U/mL), positive double-stranded DNA antibody (Ds-DNA IgG Ab: 19.1 IU/mL), positive single-stranded DNA antibody (Ss-DNA IgG Ab: 140.0 IU/mL), and hypocomplementemia (C3: 41.7 mg/dL, C4: 7.1 mg/dL, and CH50: 13.9 U/mL). Renal biopsy showed mesangial proliferative glomerulonephritis, and immunofluorescence revealed positive staining for IgG, IgM, C3, and C1q. The pathological finding of a crescentic lesion indicating ANCA-associated renal vasculitis was not seen. Based on these findings, ANCA-positive lupus nephritis (WHO class II) was diagnosed. PTU treatment was discontinued, and he was effectively treated with plasmapheresis and hemodialysis combined with two pulses of cyclophosphamide and three pulses of methylprednisolone, prednisolone, and intravenous immunoglobulin therapy. After 3 months, his thrombocytopenia, proteinuria, and MPO/PR3-ANCA titer were significantly improved (Fig. 1). Potassium iodide and radioiodine therapy was administered to treat Graves’ disease. At the current time point of 2-years follow-up with low-dose prednisolone, his serum creatinine level is 1.28 mg/dL with no proteinuria and microhematuria. MPO-ANCA is 12.5 IU/mL (normal range is \3.5 IU/ml) without any remarkable findings of vasculitis, and Ds-DNA/Ss-DNA IgG Ab and complement titers are within the normal range. While the renal biopsy showed lupus nephritis, this patient had overlapping clinical and laboratory findings of lupus and vasculitis. In a previous study, ANCA was detected in 37.3 % of patients with idiopathic systemic lupus erythematosus, and patients with this condition are almost always positive for MPO-ANCA [1]. In addition, MPO-ANCA is found in a similar proportion of patients with PTU-induced lupus and patients with vasculitis; however, PR3-ANCA is detected only in patients with PTU-induced vasculitis [2]. In the present case, the regular long-term use of PTU and overlapping clinical findings of lupus and vasculitis with positive PR3-ANCA highly indicated that this patient developed an autoimmune T. Taguchi (&) S. Nakayama S. Fujimoto Y. Terada Department of Endocrinology, Metabolism and Nephrology, Kochi Medical School, Kochi University, Kohasu, Oko-cho, Nankoku 783-8505, Japan e-mail: ttagu27k@axel.ocn.ne.jp

Interleukin‐6 Trans‐Signaling Exacerbates Inflammation and Renal Pathology in Lupus‐Prone Mice

Systemic lupus erythematosus (SLE) is a heterogeneous autoimmune disease that is characterized by the production of antinuclear antibodies (ANAs) and leads to immune complex deposition in the kidneys and nephritis. Lyn tyrosine kinase is a regulator of antibody-mediated autoimmune disease, as evidenced by studies in gene-targeted mice and as suggested in genome-wide association studies in SLE. Like SLE patients, Lyn-deficient mice have increased levels of interleukin-6 (IL-6). Deletion of IL-6 from Lyn-deficient mice abrogates levels of inflammation, pathogenic autoantibodies, and nephritis. The purpose of this study was to assess the role of IL-6 trans-signaling in autoimmune disease by overexpressing soluble gp130Fc (sgp130Fc) in a mouse model. The effect of overexpression of sgp130Fc on immune cell phenotypes was determined by flow cytometry in young and aged mice with lupus, and ANAs were measured by enzyme-linked immunosorbent assay. Glomerulonephritis was assessed by histopathologic analysis, by measuring the glomerular area and the blood urea nitrogen concentration, and by immunohistochemistry. Immunofluorescence defined renal immune complex and complement deposition. The acute-phase response was determined by quantitative real-time polymerase chain reaction. In contrast to removing IL-6, impaired IL-6 trans-signaling had little effect on many immune cell abnormalities in Lyn-/- mice. Pathogenic ANAs and kidney deposition of immune complexes were also unaltered by sgp130Fc. However, sgp130Fc overexpression led to diminished macrophage expansion, reduced glomerular leukocyte infiltration, reduced complement fixation, significantly attenuated glomerulonephritis, and improved renal function in Lyn-deficient mice. Our results reveal key roles of leukocytes, complement, and the innate immune system in mediating glomerulonephritis, and they implicate IL-6 trans-signaling in this process. We suggest that targeting this pathway may be an effective adjunct to B cell depletion in SLE treatment.

HRES-1/Rab4-mediated depletion of Drp1 impairs mitochondrial homeostasis and represents a target for treatment in SLE

ObjectiveAccumulation of mitochondria underlies T-cell dysfunction in systemic lupus erythematosus (SLE). Mitochondrial turnover involves endosomal traffic regulated by HRES-1/Rab4, a small GTPase that is overexpressed in lupus T cells. Therefore,...

Treatment of SLE: bridging the gap from clinical trials to the clinic - a meeting report

Treatment of SLE: bridging the gap from clinical trials to the clinic - a meeting report

SAT0244 Correlation between circulating TFH cells and disease activity as well as autoantibody production in chinese patients with systemic lupus erythematosus

BackgroundPreviously we have shown that interleukin-21 (IL-21) level was tightly associated with anti-nuclear antibody (ANA) production in cultured peripheral blood mononuclear cells (PBMCs) from patients with systemic lupus erythematosus (SLE)...

AB0224 Oaz regulate B-cell functions through the inhibition of CCL2 expression in mesenchymal stem cells

BackgroundMesenchymal stem cells (MSCs) had been indicated to exert suppressive effects on B-cell proliferation and differentiation through released humoral factor(s) yet to be defined, which is impaired in patients with...

Immunodeficiency and autoimmunity in H2-O deficient mice (P5016)

Abstract HLA-DO/H2-O is a highly conserved non-polymorphic MHC class II-like molecule whose physiological function remains unknown. The cell maturation-dependent DO expression in B-lymphocytes and DCs suggests a role H2-O in promoting presentation of exogenous Ag by attenuating presentation of endogenous self-peptides. We report herein that H2-O-/- mice spontaneously develop high titers of IgG2a/c antinuclear antibodies (ANA) with specificity for dsDNA, ssDNA, and histones. Reconstitution of RAG1-/- mice with T and B cells from H2-O-/- or WT mice demonstrated that production of ANAs requires participation of CD4+ T cells from H2-O-/- mice. Bone marrow chimeras demonstrated that loss of H2-O expression in thymic epithelial cells did not induce ANAs, and that lack of H2-O expression in bone marrow-derived cells was sufficient to induce the autoimmune phenotype. Despite production of high titers of autoantibodies, H2-O-/- mice exhibit a delayed generation of humoral immunity to model antigens (OVA and KLH), affecting all major T-dependent Ig classes including IgG2a/c. Consistently, presentation of all the natural Ag epitopes by H2-O-/- APC was inefficient as compared to WT APC. Thus, H2-O promotes immunity towards exogenous Ag while preventing autoimmunity. We propose that H2-O, through spatially and temporally inhibiting H2-M, enhances presentation of exogenous antigen by preventing nascent/newly-synthesized class II molecules from forming stable complexes with endogenous self-peptides.

Identification of a lupus-susceptibility locus leading to impaired clearance of apoptotic debris on New Zealand Black chromosome 13

Systemic lupus erythematosus is a chronic multi-organ autoimmune disease marked mainly by the production of anti-nuclear antibodies. Nuclear antigens become accessible to the immune system following apoptosis and defective clearance of apoptotic debris has been shown in several knockout mouse models to promote lupus. However, genetic loci associated with defective clearance are not well defined in spontaneously arising lupus models. We previously showed that introgression of the chromosome 13 interval from lupus-prone New Zealand Black (NZB) mice onto a non-autoimmune B6 genetic background (B6.NZBc13) recapitulated many of the NZB autoimmune phenotypes. Here, we show that B6.NZBc13 mice have impaired clearance of apoptotic debris by peritoneal and tingible-body macrophages and have narrowed down the chromosomal interval of this defect using subcongenic mice with truncated NZB chromosome 13 intervals. This chromosomal region (81–94 Mb) is sufficient to produce polyclonal B and T cell activation, and expansion of dendritic cells. To fully recapitulate the autoimmune phenotypes seen in B6.NZBc13 mice, at least one additional locus located in the centromeric portion of the interval is required. Thus, we have identified a novel lupus susceptibility locus on NZB chromosome 13 that is associated with impaired clearance of apoptotic debris.

Ly9 (CD229) Cell-Surface Receptor is Crucial for the Development of Spontaneous Autoantibody Production to Nuclear Antigens

The Signaling Lymphocyte Activation Molecule Family (SLAMF) genes, which encode cell-surface receptors that modulate innate and adaptive immune responses, lay within a genomic region of human and mouse chromosome 1 that confers a predisposition for the development of systemic lupus erythematosus (SLE). Herein, we demonstrate that the SLAMF member Ly9 arises as a novel receptor contributing to the reinforcement of tolerance. Specifically, Ly9-deficient mice spontaneously developed features of systemic autoimmunity such as the production of anti-nuclear antibodies (ANA), -dsDNA, and -nucleosome autoantibodies, independently of genetic background [(B6.129) or (BALB/c.129)]. In aged (10- to 12-month-old) Ly9−/− mice key cell subsets implicated in autoimmunity were expanded, e.g., T follicular helper (Tfh) as well as germinal center (GC) B cells. More importantly, in vitro functional experiments showed that Ly9 acts as an inhibitory receptor of IFN-γ producing CD4+ T cells. Taken together, our findings reveal that the Ly9 receptor triggers cell intrinsic safeguarding mechanisms to prevent a breach of tolerance, emerging as a new non-redundant inhibitory cell-surface receptor capable of disabling autoantibody responses.

Role of peroxynitrite-modified biomolecules in the etiopathogenesis of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic inflammatory autoimmune disease characterized by autoantibodies directed against various biomolecules. The initial immunogens that drive the development of SLE are unknown, but characteristics of the immune response in SLE suggest that it is an antigen-driven response, and a chromatin antigen could be one of the immunogens for the production of antinuclear antibodies (ANA) in SLE. Other factors implicated in the pathogenesis of SLE include nitrogen-free radicals such as nitric oxide and peroxynitrite. The free radical-mediated damage to proteins results in the modification of amino acid residues, cross-linking of side chains and fragmentation. The tyrosine residues in proteins are susceptible to attack by various reactive nitrogen intermediates, including peroxynitrite to form 3-nitrotyrosine (3-NT). The presence of nitrated proteins in vivo indicates that peptides derived from the proteolytic degradation of modified proteins could serve as neoantigens. Histones are highly conserved proteins that are rich in basic amino acids lysine and arginine. Autoantibodies against histones and anti-DNA antibodies are present in SLE. The anti-DNA autoantibodies coexist with anti-histone autoantibodies and may react with chromatin-associated histones and histone complexes. Elevated levels of reactive nitrogen species (RNS) in SLE patients suggest a possible role in the pathogenesis of the disease. The alteration of proteins resulting from photomodification or peroxynitrite could lead to the development of antibodies. Therefore, the modified proteins or photoadducts could have important implications in autoimmunity, and understanding the pathophysiology of peroxynitrite-modified biomolecules could lead to a better understanding of autoimmune phenomenon in SLE.

P099 Myd88 gene knockout inhibits the development of lupus-like disease in NZB/W F1 mice

The New Zealand Black (NZB) × New Zealand White (NZW) F1 hybrid female mice (NZB/WF1) develop a disease closely resembling human systemic lupus erythematosus (SLE), characterized by the production of antinuclear antibodies, severe glomerulonephritis and early mortality. Recently, innate immune responses have been reported to play an important role in the development of autoimmune disease. In this study we investigated the role of Myd88 protein (an important regulator of innate immune signaling pathways) in the pathogenesis of lupus-like disease in Myd88 knockout NZB/W F1 mice. The Myd88-deficient mice were backcrossed separately in the NZB and NZW backgroud. Heterozygous NZB as well as NZW of F10 backcross generation were intercrossed to achieve Myd88 -/- NZB/W F1 mice (KO) and Myd88 +/+ NZB/W F1 mice (WT). WT and Myd88 KO mice were compared for serum concentrations of anti-dsDNAantibody, biochemical markers of active disease (BUN, Cr, Alb, TP, T-CHO, protein urea), histological analysis of kidney pathology and mortality. Compared with WT mice, Myd88 KO mice featured significantly reduced serum concentrations of anti-dsDNAantibody, reduced levels of biochemical markers of active disease, reduced kidney pathology and reduced mortality. Our result indicates that innate immunity participates in the pathogenesis of lupus prone mice and Myd88 is its important regulator.

P154 PPAR-gamma is a negative feedback regulator of IRF7-dependent TLR/MYD88 signaling for type-I interferon (IFN) production and a crucial suppressor of type-I IFN responses in murine lupus

Introduction Anti-viral immune responses involve the robust production of type-I interferon (IFN-α/β) in plasmacytoid dendritic cells (pDCs). This occurs through the virus-activated MyD88-independent pathway, or the TLR7, 9/MyD88 pathways, and is completely dependent on the transcription factor IRF7 [1] . How type-I IFN is negatively regulated with respect to IRF7 remains unknown.Here we report that peroxisome proliferator-activated receptor gamma (PPAR-γ) is a negative-feedback regulator of IRF7-dependent TLR signaling for type-I IFN production. Methods WT and PPAR-γ (+/−) mice were used for in vitro stimulation of pDCs with TLR agonists, or i.v delivery of TLR agonists. Levels of type-I IFN in culture supernatants were assessed by ELISA. Interactions between IRF7 and PPAR-γ were studied by FLAG-IRF7 immunoprecipitation and Western blot analysis for PPAR-γ. Pristane (0.5 ml) was injected into WT and PPAR-γ (+/−) C57BL/6 to develop lupus-like disease, or control PBS. Interferon responses in mice were assessed by RT-PCR and ELISAs for autoantibodies. Results Through TLR7, 9/MyD88 signaling in pDCs, type-I IFN induces the expression of PPAR-γ, which binds to the DNA-binding domain of IRF7, inhibiting IRF7 activation of type-I IFN genes. A critical role in vivo was confirmed in PPAR-γ (+/−) mice, which displayed enhanced TLR9-type-I IFN induction, compared to WT mice. Using the pristane-induced lupus model (TLR7/MyD88-type-IFN-dependent [2] ), disease in PPAR-γ (+/−) mice correlated with enhanced type-I IFN production/signaling, type-I IFN-dependent anti-nuclear antibody production and poor survival, compared to in WT mice. Pioglitazone (a PPAR-γ agonist) treatment inhibits murine lupus through a potent inhibitory effect on type-I IFN signaling. Conclusion Thus, the role of PPAR-γ in murine lupus, as a key regulator of type-I IFN production, provides a compelling argument for the therapeutic application of PPAR-γ agonists in human lupus, which is considered to be IFN-α-driven [3] , [4] , [5] .