Cleaved Form of Osteopontin in Urine as a Clinical Marker of Lupus Nephritis.

We assessed the utility of two forms of osteopontin (OPN), OPN full and its cleaved form (OPN N-half), in plasma and urine as markers of disease activity in lupus nephritis (LN). Samples were collected from patients with systemic lupus erythematosus (SLE) (LN: N = 29, non-LN: N = 27), IgA nephropathy (IgAN) (N = 14), minimal change nephrotic syndrome (MCNS) (N = 5), diabetic nephropathy (DN) (N = 14) and healthy volunteers (HC) (N = 17). While there was no significant difference in urine OPN full concentration between groups, urine OPN N-half concentration was significantly higher in patients with LN than HC (p < 0.05). Moreover, urine OPN N-half was higher in LN patients with overt proteinuria (urine protein/creatinine ratio: P/C > 0.5) than LN patients with minimal proteinuria (P/C < 0.5, p < 0.0001), and also higher than in DN patients with overt proteinuria (P/C > 0.5, p < 0.01). Urine thrombin activity correlated with urine OPN N-half concentration (p < 0.0001), but not with urine OPN full concentration. These results suggest that urine OPN N-half concentration reflects renal inflammation. Thus, urine OPN N-half may be a novel disease activity marker for LN.

Methotrexate-associated EBV-positive vasculitis in the skin: a report of two cases simulating rheumatoid vasculitis.

Rheumatoid vasculitis (RV) is one of the most serious extra-articular complications of rheumatoid arthritis (RA), generally treated with a high dose of immunosuppressive drugs. Recently, we encountered two cases of ulcerative vasculitis in methotrexate (MTX)-prescribed RA patients, which simulated RV; however, Epstein-Barr virus (EBV)-encoded RNA in situ hybridization on their skin biopsies revealed many EBV-positive lymphocytes (over 50 cells/high-power field) within the vessel walls and perivascular stroma, which led us to the diagnosis of EBV-related vasculitis instead of RV. Subsequently, both ulcers regressed after the discontinuation of MTX and no recurrence was noted during the follow-up period. To prevent unnecessary treatment, EBV-positive vasculitis should be added in the differential diagnosis of lymphocytic vasculitis observed in MTX-administered RA patients.

Screening for IgG4-type anti-nuclear antibodies in IgG4-related disease.

BACKGROUND: Immunoglobulin (Ig) G4-related disease (IgG4-RD) is characterized by elevated serum IgG4 and infiltration of IgG4(+) plasma cells into multiple organs. It is not known whether serum IgG4 is autoreactive in IgG4-RD. METHODS: We measured anti-nuclear antibody (ANA) in 19 IgG4-RD cases, determined IgG subclasses of the ANA, and compared them with those of other systemic autoimmune diseases (systemic lupus erythematosus, Sjögren's syndrome, systemic sclerosis, and polymyositis), using subclass-based ANA test (indirect immunofluorescence). RESULTS: 58 % of IgG4-RD cases were ANA-positive (cut-off: 1:40). Whereas their subclass of ANA was predominantly IgG2, we observed no IgG4-type ANA. In systemic autoimmune diseases, subclasses of ANA were mostly IgG1, 2, or 3, but IgG4-type ANA was very rarely detected. We also found several patients in whose serum ANA patterns differed among IgG subclasses, probably due to the difference of corresponding autoantigens. CONCLUSIONS: Although IgG4 is highly elevated in sera of IgG4-RD patients, their ANA do not include IgG4 subclass. These results offer new insight into the role of IgG4 and the pathogenesis of IgG4-RD, implying that each IgG subclass tends to cover its own spectrum of antigens, and IgG4 is not preferentially used to make ANA.

Sustainable Efficacy of Switching From Intravenous to Subcutaneous Tocilizumab Monotherapy in Patients With Rheumatoid Arthritis.

OBJECTIVE: To evaluate the efficacy and safety of switching from intravenous (IV) tocilizumab (TCZ) to subcutaneous (SC) TCZ monotherapy in rheumatoid arthritis patients. METHODS: Patients who had completed 24 weeks of TCZ-SC (162 mg/2 weeks) or TCZ-IV (8 mg/kg/4 weeks) monotherapy in the double-blind period of the MUSASHI study were enrolled in an 84-week open-label extension period. All received TCZ-SC (162 mg/2 weeks) monotherapy. Effects of the IV to SC switch were evaluated at week 36 (12 weeks after switching). RESULTS: Overall, 319 patients received ≥1 dose of TCZ-SC during the open-label extension period; 160 switched from TCZ-IV to TCZ-SC (TCZ IV/SC) and 159 continued TCZ-SC (TCZ SC/SC). Disease Activity Score in 28 joints using the erythrocyte sedimentation rate clinical remission rates were 62.5% (100 of 160) for TCZ IV/SC and 50.0% (79 of 158) for TCZ SC/SC at week 24, and were maintained at 62.5% (100 of 160) and 57.0% (90 of 158), respectively, at week 36. In the TCZ IV/SC group, 9% of patients (9 of 100) who had achieved remission at week 24 could not maintain remission at week 36. In TCZ IV/SC patients weighing ≥70 kg, the percentage with a sufficient serum TCZ concentration (≥1 µg/ml) decreased from 90.9% (10 of 11) at week 24 to 45.5% (5 of 11) at week 36. Overall safety profiles were similar in TCZ IV/SC and TCZ SC/SC except for mild injection site reactions in TCZ IV/SC. CONCLUSION: Efficacy is adequately maintained in most patients switching from TCZ-IV (8 mg/kg/4 weeks) to TCZ-SC (162 mg/2 weeks) monotherapy. Patients receiving TCZ-IV can switch to TCZ-SC without serious safety concerns. Clinical efficacy may be reduced after switching in some patients with high body weight.

Successful treatment with tocilizumab in a case of intralymphatic histiocytosis associated with rheumatoid arthritis.

A 75-year-old woman with rheumatoid arthritis (RA) presented with long-term painful erythema on the right upper arm and left elbow. The patient was diagnosed with intralymphatic histiocytosis (ILH) based on the biopsy findings. Because the patient was unresponsive to single-agent treatment with methotrexate, infliximab and etanercept, we switched to tocilizumab (TCZ) treatment, which induced remission of the ILH. Our case suggests that TCZ may be a treatment option for ILH in patients with RA.

A clinical, pathological, and genetic characterization of methotrexate-associated lymphoproliferative disorders.

OBJECTIVE: Methotrexate-associated lymphoproliferative disorders (MTX-LPD) often regress spontaneously during MTX withdrawal, but the prognostic factors remain unclear. The aim of our study was to clarify the clinical, histological, and genetic factors that predict outcomes in patients with MTX-LPD. METHODS: Patients with MTX-LPD diagnosed between 2000 and 2012 were analyzed retrospectively regarding their clinical course, site of biopsy, histological typing, Epstein-Barr virus (EBV) in situ hybridization and immunostaining, and HLA type. RESULTS: Twenty-one patients, including 20 with rheumatoid arthritis (RA) and 1 with polymyositis, were analyzed. The mean dose of MTX was 6.1 mg/week and the mean duration of treatment was 71.1 months. Clinically, 5 patients were diagnosed with EBV-positive mucocutaneous ulcer (EBVMCU) and had polymorphic histological findings. The proportion of those patients successfully treated solely by withdrawal of MTX was significantly greater than that of those without EBVMCU (75% vs 7.7%, p = 0.015). The HLA-B15:11 haplotype was more frequent in patients with EBV+ RA with MTX-LPD than in healthy Japanese controls (p = 0.0079, Bonferroni's method). EBV latency classification and HLA typing were not associated with the prognosis of MTX-LPD in our cohort. CONCLUSION: Our data demonstrate that patients in the EBVMCU, a specific clinical subgroup of MTX-LPD, had a better clinical outcome when MTX was withdrawn than did other patients with MTX-LPD.

Two susceptibility loci to Takayasu arteritis reveal a synergistic role of the IL12B and HLA-B regions in a Japanese population.

Takayasu arteritis (TAK) is an autoimmune systemic vasculitis of unknown etiology. Although previous studies have revealed that HLA-B*52:01 has an effect on TAK susceptibility, no other genetic determinants have been established so far. Here, we performed genome scanning of 167 TAK cases and 663 healthy controls via Illumina Infinium Human Exome BeadChip arrays, followed by a replication study consisting of 212 TAK cases and 1,322 controls. As a result, we found that the IL12B region on chromosome 5 (rs6871626, overall p = 1.7 × 10(-13), OR = 1.75, 95% CI 1.42-2.16) and the MLX region on chromosome 17 (rs665268, overall p = 5.2 × 10(-7), OR = 1.50, 95% CI 1.28-1.76) as well as the HLA-B region (rs9263739, a proxy of HLA-B*52:01, overall p = 2.8 × 10(-21), OR = 2.44, 95% CI 2.03-2.93) exhibited significant associations. A significant synergistic effect of rs6871626 and rs9263739 was found with a relative excess risk of 3.45, attributable proportion of 0.58, and synergy index of 3.24 (p ≤ 0.00028) in addition to a suggestive synergistic effect between rs665268 and rs926379 (p ≤ 0.027). We also found that rs6871626 showed a significant association with clinical manifestations of TAK, including increased risk and severity of aortic regurgitation, a representative severe complication of TAK. Detection of these susceptibility loci will provide new insights to the basic mechanisms of TAK pathogenesis. Our findings indicate that IL12B plays a fundamental role on the pathophysiology of TAK in combination with HLA-B(∗)52:01 and that common autoimmune mechanisms underlie the pathology of TAK and other autoimmune disorders such as psoriasis and inflammatory bowel diseases in which IL12B is involved as a genetic predisposing factor.

Association of Takayasu arteritis with HLA-B 67:01 and two amino acids in HLA-B protein.

OBJECTIVE: Takayasu arteritis (TAK) is a rare autoimmune arteritis that affects large arteries. Although the association between TAK and HLA-B 52:01 is established, the other susceptibility HLA-B alleles are not fully known. We performed genetic association studies to determine independent HLA-B susceptibility alleles other than HLA-B 52:01 and to identify important amino acids of HLA-B protein in TAK susceptibility. METHODS: One hundred patients with TAK and 1000 unrelated healthy controls were genotyped for HLA-B alleles in the first set, followed by a replication set containing 73 patients with TAK and 1000 controls to compare the frequencies of HLA-B alleles. Step-up logistic regression analysis was performed to identify susceptibility amino acids of HLA-B protein. RESULTS: Strong associations of susceptibility to TAK with HLA-B 52:01 and HLA-B 67:01 were observed (P = 1.0 × 10(-16) and 9.5 × 10(-6), respectively). An independent susceptibility effect of HLA-B 67:01 from HLA-B 52:01 was also detected (P = 1.8 × 10(-7)). Amino acid residues of histidine at position 171 and phenylalanine at position 67, both of which are located in antigen binding grooves of the HLA-B protein, were associated with TAK susceptibility (P ≤ 3.8 × 10(-5)) with a significant difference from other amino acid variations (ΔAIC ≥ 9.65). CONCLUSION: HLA-B 67:01 is associated with TAK independently from HLA-B 52:01. Two amino acids in HLA-B protein are strongly associated with TAK susceptibility.

Neutrophils are essential as a source of IL-17 in the effector phase of arthritis.

OBJECTIVE: Th17 has been shown to have a pivotal role in the development of arthritis. However, the role of IL-17 in the T cell-independent effector phase has not fully been examined. We investigated whether IL-17 is involved in the effector phase of arthritis by using K/BxN serum-induced arthritis model. METHODS: K/BxN serum was transferred into IL-17 knockout (KO) mice, SCID mice and their control mice, and arthritis was evaluated over time. In order to clarify the source of IL-17 in the effector phase, neutrophils or CD4+ T cells collected from IL-17 KO or control mice were injected into IL-17 KO recipient mice together with K/BxN serum. To examine if neutrophils secrete IL-17 upon stimulation, neutrophils were stimulated with immune complex in vitro and IL-17 in the supernatant was measured by ELISA. RESULTS: K/BxN serum-induced arthritis was much less severe in IL-17 KO mice than in WT mice. Since K/BxN serum-transferred SCID mice developed severe arthritis with high serum IL-17 concentration, we speculated neutrophils are the responsible player as an IL-17 source. When wild type (WT) but not IL-17 KO neutrophils were co-injected with K/BxN serum into IL-17 KO mice, arthritis was exacerbated, whereas co-injection of WT CD4+ T cells had no effect. In vitro, stimulation of neutrophils with immune complex caused IL-17 secretion. CONCLUSIONS: Neutrophils are essential as a source of IL-17 in the effector phase of arthritis. The trigger of secreting IL-17 from neutrophils may be immune complex.

Three groups in the 28 joints for rheumatoid arthritis synovitis--analysis using more than 17,000 assessments in the KURAMA database.

Rheumatoid arthritis (RA) is a joint-destructive autoimmune disease. Three composite indices evaluating the same 28 joints are commonly used for the evaluation of RA activity. However, the relationship between, and the frequency of, the joint involvements are still not fully understood. Here, we obtained and analyzed 17,311 assessments for 28 joints in 1,314 patients with RA from 2005 to 2011 from electronic clinical chart templates stored in the KURAMA (Kyoto University Rheumatoid Arthritis Management Alliance) database. Affected rates for swelling and tenderness were assessed for each of the 28 joints and compared between two different sets of RA patients. Correlations of joint symptoms were analyzed for swellings and tenderness using kappa coefficient and eigen vectors by principal component analysis. As a result, we found that joint affected rates greatly varied from joint to joint both for tenderness and swelling for the two sets. Right wrist joint is the most affected joint of the 28 joints. Tenderness and swellings are well correlated in the same joints except for the shoulder joints. Patients with RA tended to demonstrate right-dominant joint involvement and joint destruction. We also found that RA synovitis could be classified into three categories of joints in the correlation analyses: large joints with wrist joints, PIP joints, and MCP joints. Clustering analysis based on distribution of synovitis revealed that patients with RA could be classified into six subgroups. We confirmed the symmetric joint involvement in RA. Our results suggested that RA synovitis can be classified into subgroups and that several different mechanisms may underlie the pathophysiology in RA synovitis.

A case of Behçet's disease developing after poststreptococcal acute glomerulonephritis.

We report a case of a 73-year-old Japanese male patient who developed Behçet's disease (BD) after poststreptococcal acute glomerulonephritis. Three months after the initial presentation, acneiform eruption and oral and genital ulcers appeared. Treatment with oral prednisolone (20 mg/day) resulted in the remarkable disappearance of these symptoms. These findings support the hypothesis that Streptococcus pyogenes may be an etiologic factor of BD.

Serum BAFF and APRIL levels in patients with IgG4-related disease and their clinical significance.

INTRODUCTION: B cell-activating factor of the tumor necrosis factor family (BAFF) and a proliferation-inducing ligand (APRIL) play a crucial role in B cell development, survival, and antibody production. Here we analyzed the serum levels of BAFF and APRIL and their respective clinical associations in patients with an immunoglobulin (Ig) G4-related disease (IgG4-RD). METHODS: We measured serum levels of BAFF and APRIL in patients with IgG4-RD, primary Sjögren's syndrome (pSS), and healthy individuals. Serum BAFF and APRIL levels in IgG4-RD were assessed for correlations with serological parameters, including Ig, particularly IgG4, and the number of affected organs. Serum BAFF and APRIL levels in IgG4-RD were monitored during glucocorticoid (GC) therapy. RESULTS: Serum BAFF and APRIL levels in patients with IgG4-RD were significantly higher (P < 0.01) than in healthy individuals. The BAFF levels of patients with IgG4-RD were comparable to those of patients with pSS. Although clinical parameters, such as serum IgG4 and the number of affected organs, were not correlated with the levels of BAFF, serum APRIL levels were inversely correlated with serum IgG4 levels (r = -0.626, P < 0.05). While serum BAFF levels decreased following GC therapy, serum APRIL levels increased during follow-up. CONCLUSION: These results indicate that BAFF and APRIL might be useful markers for predicting disease activity in IgG4-RD. Further studies are needed to elucidate the role of BAFF and APRIL in the pathogenesis of IgG4-RD.

NEFA/nucleobindin-2 is a target autoantigen of the anti-Wa antibody and is associated with transfer RNA.

OBJECTIVES: The anti-Wa antibody found in systemic sclerosis patients reacts with a transfer RNA (tRNA)-associated 48-kDa protein and immunoprecipitates several tRNAs. We investigated the Wa antigen and its binding to tRNA species. METHODS: We performed molecular cloning of the Wa antigen and made its recombinant protein. To investigate Wa antigen distribution in the cell, we performed an indirect immunofluorescence study. To determine the Wa-bound tRNA species, we performed a reverse transcription (RT)-polymerase chain reaction (PCR) using the RNAs immunoprecipitated by anti-Wa antibody as templates, and synthetic primers of mammalian tRNA sequences. To clarify the tissue expression of Wa antigen, we performed quantitative and semi-quantitative PCR of the cDNA. RESULTS: We demonstrated that the Wa antigen was identical to NEFA (DNA binding/EF-hand/acidic amino acid rich region), otherwise known as nucleobindin-2. A full-length and an alternative splice variant cDNA lacking exon 11 were isolated by cloning NEFA cDNA. Anti-Wa-positive sera stained both the nucleus and cytoplasm of HEp-2 cells. RT-PCR suggested that Wa binds at least six tRNA species. In human tissues, NEFA is expressed predominantly in exocrine glands. CONCLUSIONS: We have demonstrated that the Wa antigen is NEFA or nucleobindin-2, which binds specific tRNA species, and is distributed in specific human tissues.

Follistatin-related protein/follistatin-like 1 evokes an innate immune response via CD14 and toll-like receptor 4.

Follistatin-related protein (FRP)/follistatin-like 1 (FSTL1) has multi-specific binding nature especially with TGF-ß superfamily proteins, and thereby modulates organ development. However, its function in immune systems remains unclear. Previously, we reported FRP interacts with CD14, which is known to mediate toll-like receptor 4 (TLR4) signaling. Here, we investigated whether FRP activates TLR4 signaling. Recombinant FRP induced interleukin 6 or interleukin 8 production from target cells in a CD14- and TLR4-dependent manner. Moreover, similar to lipopolysaccharide (LPS), FRP induced tolerance to the second LPS stimulation. FRP has the function of evoking innate immune responses as one of the endogenous TLR4 agonists.

Serum IgG levels demonstrate seasonal change in connective tissue diseases: a large-scale, 4-year analysis in Japanese.

Hypergammaglobulinemia is often found in patients with autoimmune diseases, such as systemic lupus erythematosus (SLE), and its level may correlate with disease activity. However, it is unclear whether immunoglobulin G (IgG) displays seasonal changes. We analyzed the seasonal change in serum IgG by assessing 450 patients with connective tissue disease. The serum IgG levels in summer were compared with those in winter from 2006 to 2009. Independent samples from 355 patients were analyzed to confirm results in the first set. The differences in the IgG levels between the two seasons were analyzed in each disease and compared with disease activity. 488 patients without connective tissue disease were analyzed as reference instead of healthy people as control. We found that connective tissue disease patients tended to show higher levels of serum IgG in summer than in winter every year from 2006 to 2009, whereas patients without connective tissue disease did not demonstrate such a tendency. We observed this seasonal tendency in each disease. Seasonal changes weakly correlated with those of anti-DNA antibody in SLE patients and those of disease activity score in rheumatoid arthritis (RA) patients. Serum IgG levels of patients with connective tissue diseases display seasonal variations. Biological and clinical significance of these variations should be elucidated.

[B cell abnormality in systemic lupus erythematosus].

B cells play central roles in pathogenesis of SLE through autoantibody production, autoantigen-presentation, cytokine production and activation of cognate T cells. Recently, a specific subset of B cells, which exerts immunoregulatory properties via IL-10 production was identified, and dysfunction of these B cells might involved in the pathogenesis of SLE. Currently, various therapies targeting B cells, such as B cell-depletive therapy and B cell regulation molecules seems promising, however, their efficacy and safety in the treatment of SLE should be carefully verified in the future. Because the pathogenesis varies in each patients with SLE, the advent of new era in which therapies can be selected based on an individual immune abnormality is waiting.

Correlation of antinuclear antibody and anti-double-stranded DNA antibody with clinical response to infliximab in patients with rheumatoid arthritis: a retrospective clinical study.

INTRODUCTION: The induction of antinuclear antibodies (ANAs) or anti-double-stranded (ds) -DNA antibodies (Abs) after infliximab (IFX) therapy in rheumatoid arthritis (RA) is a well-known phenomenon, but the correlation of such Abs with the clinical response to IFX has not yet been determined. The aims of this retrospective observational study were to examine the prevalence of positive ANA and anti-ds-DNA Abs before and after IFX therapy in patients with RA and to investigate whether an increased titer of such Abs is associated with the clinical efficacy of IFX. METHODS: One hundred eleven RA patients who had received IFX were studied. ANA (indirect immunofluorescence with HEp-2 cells) and anti-ds-DNA Abs (Farr assay) results were examined before and after IFX therapy. RESULTS: The overall clinical response assessed by EULAR response criteria was as follows: good response in 55%, including remission in 38%; moderate response in 18%; and no response (NOR) in 27%. The positivity of ANA (≥ 1:160) and anti-ds-DNA Abs significantly increased from 25% to 40% (P = 0.03) and from 3% to 26% (P < 0.001) after IFX, respectively. EULAR response differed significantly according to the ANA titer before IFX (P = 0.001), and the efficacy of IFX became worse as the ANA titer before starting IFX increased. Furthermore, the differences in the clinical response of the ANA titer before IFX ≤ 1:80 and ≥ 1:160 were significant (good, moderate, and no response were 66%, 9%, and 25% in ≤ 1:80 group versus 26%, 33%, 41% in ≥ 1:160 group, respectively; P < 0.001). In 13 patients whose ANA had increased after IFX, 10 showed NOR, only one showed a good response, and none reached remission. These clinical responses were significantly different from ANA no-change patients. In 21 patients with positive anti-ds-DNA Abs after IFX, 16 showed NOR, only two showed a good response, and none reached remission. CONCLUSIONS: The present study suggests that the ANA titer before starting IFX predicts the clinical response to IFX. The increased titers of ANA or anti-ds-DNA Abs after IFX may be useful markers of NOR.

Overexpression of a minimal domain of calpastatin suppresses IL-6 production and Th17 development via reduced NF-κB and increased STAT5 signals.

Calpain, a calcium-dependent cysteine protease, is reportedly involved in the pathophysiology of autoimmune diseases such as rheumatoid arthritis (RA). In addition, autoantibodies against calpastatin, a natural and specific inhibitor of calpain, are widely observed in RA. We previously reported that E-64-d, a membrane-permeable cysteine protease inhibitor, is effective in treating experimental arthritis. However, the exact role of the calpastatin-calpain balance in primary inflammatory cells remains unclear. Here we investigated the effect of calpain-specific inhibition by overexpressing a minimal functional domain of calpastatin in primary helper T (Th) cells, primary fibroblasts from RA patients, and fibroblast cell lines. We found that the calpastatin-calpain balance varied during Th1, Th2, and Th17 development, and that overexpression of a minimal domain of calpastatin (by retroviral gene transduction) or the inhibition of calpain by E-64-d suppressed the production of IL-6 and IL-17 by Th cells and the production of IL-6 by fibroblasts. These suppressions were associated with reductions in RORγt expression and STAT3 phosphorylation. Furthermore, inhibiting calpain by silencing its small regulatory subunit (CPNS) suppressed Th17 development. We also confirmed that overexpressing a minimal domain of calpastatin suppressed IL-6 by reducing NF-κB signaling via the stabilization of IκBα, without affecting the upstream signal. Moreover, our findings indicated that calpastatin overexpression suppressed IL-17 production by Th cells by up-regulating the STAT5 signal. Finally, overexpression of a minimal domain of calpastatin suppressed IL-6 production efficiently in primary fibroblasts derived from the RA synovium. These findings suggest that inhibiting calpain by overexpressing a minimal domain of calpastatin could coordinately suppress proinflammatory activities, not only those of Th cells but also of synovial fibroblasts. Thus, this strategy may prove viable as a candidate treatment for inflammatory diseases such as RA.

[IgG4-related tubulointerstitial nephritis presented with multiple renal nodular lesions].

A 66-year-old man presented with multiple bilateral renal nodular lesions demonstrated by enhanced computed tomographic scan. He had a history of autoimmune pancreatitis and renal cell carcinoma, which had been treated with partial nephrectomy. We performed renal biopsy under ultrasound guidance. Pathological examination revealed plasma cell infiltration to the renal interstitium. Serum IgG4 level was high and we diagnosed as IgG4-related tubulointerstitial nephritis. After one month of oral steroid therapy the multiple nodular lesions disappeared.

Antigen is required for maturation and activation of pathogenic anti-DNA antibodies and systemic inflammation.

Systemic lupus erythematosus is an autoimmune disease characterized by autoantibodies and systemic inflammation that results in part from dendritic cell activation by nucleic acid containing immune complexes. There are many mouse models of lupus, some spontaneous and some induced. We have been interested in an induced model in which estrogen is the trigger for development of a lupus-like serology. The R4A transgenic mouse expresses a transgene-encoded H chain of an anti-DNA Ab. This mouse maintains normal B cell tolerance with deletion of high-affinity DNA-reactive B cells and maturation to immunocompetence of B cells making nonglomerulotropic, low-affinity DNA-reactive Abs. When this mouse is given estradiol, normal tolerance mechanisms are altered; high-affinity DNA-reactive B cells mature to a marginal zone phenotype, and the mice are induced to make high titers of anti-DNA Abs. We now show that estradiol administration also leads to systemic inflammation with increased B cell-activating factor and IFN levels and induction of an IFN signature. DNA must be accessible to B cells for both the production of high-affinity anti-DNA Abs and the generation of the proinflammatory milieu. When DNase is delivered to the mice at the same time as estradiol, there is no evidence for an abrogation of tolerance, no increased B cell-activating factor and IFN, and no IFN signature. Thus, the presence of autoantigen is required for positive selection of autoreactive B cells and for the subsequent positive feedback loop that occurs secondary to dendritic cell activation by DNA-containing immune complexes.