High serum IFN-alpha activity is a heritable risk factor for systemic lupus erythematosus

Potential role of IFNα in adult lupus

Patients with lupus have a continuous production of IFNα and display an increased expression of IFNα-regulated genes. The reason for the ongoing IFNα synthesis in these patients seems to be an activation of plasmacytoid dendritic cells (pDCs) by immune complexes (ICs), consisting of autoantibodies in combination with DNA-containing or RNA-containing autoantigens. The mechanisms behind the activation of pDCs by such ICs have to some extent been elucidated during the last years. Thus, interferogenic ICs are internalized via the FcγRIIa expressed on pDCs, reach the endosomes and stimulate Toll-like receptor (TLR) 7 or 9, which subsequently leads to IFNα gene transcription. Variants of genes involved in both the IFNα synthesis and response have been linked to an increased risk to develop lupus. Among these genes are interferon regulatory factor 5 (IRF5), which is involved in TLR signaling, and the signal transducer and activator of transcription 4 (STAT4) that interacts with the type I interferon receptor. Produced IFNα may at least partially be responsible for several of the observed alterations in the immune system of lupus patients and contribute to the autoimmune disease process, which will be discussed in the present review. How produced IFNα can contribute to some clinical manifestations will briefly be described, as well as the possible consequences of this knowledge in clinical practice for disease monitoring and therapy.

Genetic associations in type I interferon related pathways with autoimmunity

Type I interferons play an outstanding role in innate and adaptive immunity by enhancing functions of dendritic cells, inducing differentiation of monocytes, promoting immunoglobulin class switching in B cells and stimulating effector functions of T cells. The increased production of IFNα/β by plasmacytoid dendritic cells could be responsible for not only efficient antiviral defence, but it also may be a pathological factor in the development of various autoimmune disorders. The first evidence of a genetic link between type I interferons and autoimmune diseases was the observation that elevated IFNα activity is frequently detected in the sera of patients with systemic lupus erythematosus, and that this trait shows high heritability and familial aggregation in their first-degree healthy relatives. To date, a number of genes involved in interferon signalling have been associated with various autoimmune diseases. Patients with systemic lupus erythematosus, Sjögren's syndrome, dermatomyositis, psoriasis, and a fraction of patients with rheumatoid arthritis display a specific expression pattern of interferon-dependent genes in their leukocytes, termed the interferon signature. Here, in an attempt to understand the role of type I interferons in the pathogenesis of autoimmunity, we review the recent advances in the genetics of autoimmune diseases focusing on the association of genes involved in type I interferon pathways.

Clinically validated approaches to the treatment of autoimmune diseases

IMPORTANCE OF THE FIELD

Autoimmune diseases are pathological conditions in which "self-tolerance" has been broken, and an immune response has been mounted against the body's own tissues. More than seventy autoimmune diseases have been described, some of which are systemic and others of which are organ-specific. Although many of these diseases are rare, the collective prevalence of autoimmune diseases in the United States alone is between 5 and 8%, and is increasing.

AREAS COVERED IN THIS REVIEW

Herein, we review the exciting advances made during the past decade (1999 - 2009) in the development of clinically-validated agents for the treatment of autoimmune disease. We focus on five of the most prevalent conditions: rheumatoid arthritis, psoriasis, multiple sclerosis, Crohn's disease, and systemic lupus erythematosus. The discussion is largely restricted to agents - both small molecules and macromolecules - that have advanced through randomized, controlled clinical trials.

WHAT THE READER WILL GAIN

An overview of the pathogenesis of each disease is provided, along with a description of the therapies. Results from pivotal clinical trials are tabulated for four of the disease areas. We also provide summaries of experiences with both failed clinical trials and side effects observed during the course of clinical investigations. We conclude the review with thoughts on current challenges in the field and the prospect for future innovations.

TAKE HOME MESSAGE

During the past decade, some of the largest advances in the treatment of autoimmune disease have arisen from highly potent and selective macromolecule-based therapies (e.g. antibodies, recombinant proteins and fusion proteins). Together, these clinical experiences have provided insight into the critical mechanisms in autoimmune pathogenesis, including inflammatory cytokine release, T-cell migration and co-stimulation, and B-cell function.

Genetic variants and disease-associated factors contribute to enhanced interferon regulatory factor 5 expression in blood cells of patients with systemic lupus erythematosus

OBJECTIVE

Genetic variants of the interferon (IFN) regulatory factor 5 gene (IRF5) are associated with susceptibility to systemic lupus erythematosus (SLE). The contribution of these variants to IRF-5 expression in primary blood cells of SLE patients has not been addressed, nor has the role of type I IFNs. The aim of this study was to determine the association between increased IRF-5 expression and the IRF5 risk haplotype in SLE patients.

METHODS

IRF-5 transcript and protein levels in 44 Swedish patients with SLE and 16 healthy controls were measured by quantitative real-time polymerase chain reaction, minigene assay, and flow cytometry. Single-nucleotide polymorphisms rs2004640, rs10954213, and rs10488631 and the CGGGG insertion/deletion were genotyped in these patients. Genotypes of these polymorphisms defined both a common risk haplotype and a common protective haplotype.

RESULTS

IRF-5 expression and alternative splicing were significantly up-regulated in SLE patients compared with healthy donors. Enhanced transcript and protein levels were associated with the risk haplotype of IRF5; rs10488631 displayed the only significant independent association that correlated with increased transcription from the noncoding first exon 1C. Minigene experiments demonstrated an important role for rs2004640 and the CGGGG insertion/deletion, along with type I IFNs, in regulating IRF5 expression.

CONCLUSION

This study provides the first formal proof that IRF-5 expression and alternative splicing are significantly up-regulated in primary blood cells of patients with SLE. Furthermore, the risk haplotype is associated with enhanced IRF-5 transcript and protein expression in patients with SLE.

Genetic variation at the IRF7/PHRF1 locus is associated with autoantibody profile and serum interferon-alpha activity in lupus patients

OBJECTIVE

Interferon-alpha (IFNalpha) is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variation near IRF7 is implicated in SLE susceptibility. SLE-associated autoantibodies can stimulate IFNalpha production through the Toll-like receptor/IRF7 pathway. This study was undertaken to determine whether variants of IRF7 act as risk factors for SLE by increasing IFNalpha production and whether autoantibodies are important to this phenomenon.

METHODS

We studied 492 patients with SLE (236 African American, 162 European American, and 94 Hispanic American subjects). Serum levels of IFNalpha were measured using a reporter cell assay, and single-nucleotide polymorphisms (SNPs) in the IRF7/PHRF1 locus were genotyped.

RESULTS

In a joint analysis of European American and Hispanic American subjects, the rs702966 C allele was associated with the presence of anti-double-stranded DNA (anti-dsDNA) antibodies (odds ratio [OR] 1.83, P = 0.0069). The rs702966 CC genotype was only associated with higher serum levels of IFNalpha in European American and Hispanic American patients with anti-dsDNA antibodies (joint analysis P = 4.1 x 10(-5) in anti-dsDNA-positive patients and P = 0.99 in anti-dsDNA-negative patients). In African American subjects, anti-Sm antibodies were associated with the rs4963128 SNP near IRF7 (OR 1.95, P = 0.0017). The rs4963128 CT and TT genotypes were associated with higher serum levels of IFNalpha only in African American patients with anti-Sm antibodies (P = 0.0012). In African American patients lacking anti-Sm antibodies, an effect of anti-dsDNA-rs702966 C allele interaction on serum levels of IFNalpha was observed, similar to the other patient groups (overall joint analysis P = 1.0 x 10(-6)). In European American and Hispanic American patients, the IRF5 SLE risk haplotype showed an additive effect with the rs702966 C allele on IFNalpha level in anti-dsDNA-positive patients.

CONCLUSION

Our findings indicate that IRF7/PHRF1 variants in combination with SLE-associated autoantibodies result in higher serum levels of IFNalpha, providing a biologic relevance for this locus at the protein level in human SLE in vivo.

Association of the response to tumor necrosis factor antagonists with plasma type I interferon activity and interferon-beta/alpha ratios in rheumatoid arthritis patients: a post hoc analysis of a predominantly Hispanic cohort

OBJECTIVE

Despite the substantial clinical efficacy of tumor necrosis factor alpha (TNFalpha) antagonist therapy in patients with rheumatoid arthritis (RA), some patients respond poorly to such agents. Since an interferon (IFN) signature is variably expressed among RA patients, we investigated whether plasma type I IFN activity might predict the response to TNF antagonist therapy.

METHODS

RA patients (n = 35), the majority of whom were Hispanic, from a single center were evaluated before and after initiation of TNF antagonist therapy. As controls, 12 RA patients from the same center who were not treated with a TNF antagonist were studied. Plasma type I IFN activity was measured using a reporter cell assay, and disease status was assessed using the Disease Activity Score in 28 joints (DAS28). Levels of interleukin-1 receptor antagonist (IL-1Ra) were determined in baseline plasma samples using a commercial enzyme-linked immunosorbent assay. The clinical response was classified according to the European League Against Rheumatism criteria for improvement in RA.

RESULTS

Plasma type I IFN activity at baseline was significantly associated with clinical response (odds ratio 1.36 [95% confidence interval 1.05-1.76], P = 0.020), with high baseline IFN activity associated with a good response. Changes in DAS28 scores were greater among patients with a baseline plasma IFNbeta/alpha ratio >0.8 (indicating elevated plasma IFNbeta levels). Consistent with the capacity of IFNbeta to induce IL-1Ra, elevated baseline IL-1Ra levels were associated with better therapeutic outcomes (odds ratio 1.82 [95% confidence interval 1.1-3.29], P = 0.027).

CONCLUSION

The plasma type I IFN activity, the IFNbeta/alpha ratio, and the IL-1Ra level were predictive of the therapeutic response in TNF antagonist-treated RA patients, indicating that these parameters might define clinically meaningful subgroups of RA patients with distinct responses to therapeutic agents.

Genetic regulation of serum cytokines in systemic lupus erythematosus

Genetic association studies in systemic lupus erythematosus (SLE) have been extremely successful in recent years, identifying several loci associated with disease susceptibility. Much work remains to integrate these loci into the functional pathogenic pathways that characterize the disease. Our working hypothesis is that many genetic variations linked to SLE and autoimmunity mediate the risk of disease by altering cytokine profiles or responses to cytokine signaling. Genetic polymorphisms that affect cytokine signaling could alter thresholds for immune responses, resulting in proinflammatory presentation of self-antigens and the subsequent misdirection of adaptive immunity against self, which is observed in autoimmune disease. SLE is clinically heterogeneous and genetically complex, and we expect that individual genes and cytokine patterns will be more or less important to different disease manifestations and subgroups of patients. Defining these genotype-cytokine-phenotype relationships will increase our understanding of both initial disease pathogenesis as well as subsequent response/nonresponse to various therapies. In this review, we summarize some recent work in the area of SLE cytokine genetics and describe the implications for SLE, autoimmunity, and immune system homeostasis, which are revealed by these investigations.

Association of IRF5 polymorphisms with activation of the interferon alpha pathway

OBJECTIVE

The genetic association of interferon regulatory factor 5 (IRF5) with systemic lupus erythematosus (SLE) susceptibility has been convincingly established. To gain understanding of the effect of IRF5 variation in individuals without SLE, a study was undertaken to examine whether such genetic variation predisposes to activation of the interferon alpha (IFNalpha) pathway.

METHODS

Using a computer simulated approach, 14 single nucleotide polymorphisms (SNPs) and haplotypes of IRF5 were tested for association with mRNA expression levels of IRF5, IFNalpha and IFN-inducible genes and chemokines in lymphoblastoid cell lines (LCLs) from individuals of European (CEU), Han Chinese (CHB), Japanese (JPT) and Yoruba Nigerian (YRI) backgrounds. IFN-inducible gene expression was assessed in LCLs from children with SLE in the presence and absence of IFNalpha stimulation.

RESULTS

The major alleles of IRF5 rs13242262 and rs2280714 were associated with increased IRF5 mRNA expression levels in the CEU, CHB+JPT and YRI samples. The minor allele of IRF5 rs10488631 was associated with increased IRF5, IFNalpha and IFN-inducible chemokine expression in CEU (p(c)=0.0005, 0.01 and 0.04, respectively). A haplotype containing these risk alleles of rs13242262, rs10488631 and rs2280714 was associated with increased IRF5, IFNalpha and IFN-inducible chemokine expression in CEU LCLs. In vitro studies showed specific activation of IFN-inducible genes in LCLs by IFNalpha.

CONCLUSIONS

SNPs of IRF5 in healthy individuals of a number of ethnic groups were associated with increased mRNA expression of IRF5. In European-derived individuals, an IRF5 haplotype was associated with increased IRF5, IFNalpha and IFN-inducible chemokine expression. Identifying individuals genetically predisposed to increased IFN-inducible gene and chemokine expression may allow early detection of risk for SLE.

Overexpression of interferon-activated gene 202 (Ifi202) correlates with the progression of autoimmune glomerulonephritis associated with the MRL chromosome 1

B6.MRLc1(82-100) congenic mice carrying the telomeric region of lupus-prone MRL chromosome 1 develop autoimmune glomerulonephritis (GN). The GN susceptibility locus of B6.MRLc1(82-100) contains the interferon activated gene 200 (Ifi200) family, which consists of Ifi202, 203, 204, and 205. Recently, Ifi202 was suggested as a candidate gene for murine lupus. In this study, we assessed the association between Ifi200 family and GN in several disease models. We compared the expression of Ifi200 family members in 24 organs between the C57BL/6 and B6.MRLc1(82-100). The expressions of Ifi200 family members differed between strains, and the most dramatic differences appeared in Ifi202 expression. Briefly, in the blood, immune organs, lungs, and testes mRNA expression was higher in B6.MRLc1(82-100) mice. In the kidney and immune organs, only Ifi202 expression increased with the development of GN in B6.MRLc1(82-100), and significant differences from C57BL/6 were observed even before disease onset. Ifi202 expression in the kidneys of BXSB, NZB/WF1, and MRL/lpr was also significantly high in the early- and late-disease stages. Furthermore, laser microdissection-reverse-transcriptase-polymerase chain reaction analysis confirmed the high Ifi202 expression in all areas of B6.MRLc1(82-100) kidneys. In conclusion, in the Ifi200 family, Ifi202 expressions in the kidney and immune organs significantly increased with GN progression.

The impact of vitamin D on dendritic cell function in patients with systemic lupus erythematosus

Background

Excessive activity of dendritic cells (DCs) is postulated as a central disease mechanism in Systemic Lupus Erythematosus (SLE). Vitamin D is known to reduce responsiveness of healthy donor DCs to the stimulatory effects of Type I IFN. As vitamin D deficiency is reportedly common in SLE, we hypothesized that vitamin D might play a regulatory role in the IFNα amplification loop in SLE. Our goals were to investigate the relationship between vitamin D levels and disease activity in SLE patients and to investigate the effects of vitamin D on DC activation and expression of IFNα-regulated genes in vitro.

Methodology/Principal Findings

In this study, 25-OH vitamin D (25-D) levels were measured in 198 consecutively recruited SLE patients. Respectively, 29.3% and 11.8% of African American and Hispanic SLE patient had 25-D levels <10 ng/ml. The degree of vitamin D deficiency correlated inversely with disease activity; R = −.234, p = .002. In 19 SLE patients stratified by 25-D levels, there were no differences between circulating DC number and phenotype. Monocyte-derived DCs (MDDCs) of SLE patients were normally responsive to the regulatory effects of vitamin D in vitro as evidenced by decreased activation in response to LPS stimulation in the presence of 1,25-D. Additionally, vitamin D conditioning reduced expression of IFNα-regulated genes by healthy donor and SLE MDDCs in response to factors in activating SLE plasma.

Conclusions/Significance

We report on severe 25-D deficiency in a substantial percentage of SLE patients tested and demonstrate an inverse correlation with disease activity. Our results suggest that vitamin D supplementation will contribute to restoring immune homeostasis in SLE patients through its inhibitory effects on DC maturation and activation. We are encouraged to support the importance of adequate vitamin D supplementation and the need for a clinical trial to assess whether vitamin D supplementation affects IFNα activity in vivo and, most importantly, improves clinical outcome.

Interferon-alpha: a therapeutic target in systemic lupus erythematosus

The long history of elevated interferon (IFN)-alpha in association with disease activity in patients who have systemic lupus erythematosus (SLE) has assumed high significance in the past decade, with accumulating data strongly supporting broad activation of the type I IFN pathway in cells of patients who have lupus, and association of IFN pathway activation with significant clinical manifestations of SLE and increased disease activity based on validated measures. In addition, a convincing association of IFN pathway activation with the presence of autoantibodies specific for RNA-binding proteins has contributed to delineation of an important role for Toll-like receptor activation by RNA-containing immune complexes in amplifying innate immune system activation and IFN pathway activation. Although the primary triggers of SLE and the IFN pathway remain undefined, rapid progress in lupus genetics is helping define lupus-associated genetic variants with a functional relationship to IFN production or response in patients. Together, the explosion of data and understanding related to the IFN pathway in SLE have readied the lupus community for translation of those insights to improved patient care. Patience will be needed to allow collection of clinical data and biologic specimens across multiple clinical centers required to support testing of IFN activity, IFN-inducible gene expression and chemokine gene products as candidate biomarkers. Meanwhile, promising clinical trials are moving forward to test the safety and efficacy of monoclonal antibody inhibitors of IFN-alpha. Other therapeutic approaches to target the IFN pathway may follow close behind.

IFN regulatory factor 5 is required for disease development in the FcgammaRIIB-/-Yaa and FcgammaRIIB-/- mouse models of systemic lupus erythematosus

Polymorphisms in the transcription factor IFN regulatory factor 5 (IRF5) are strongly associated in human genetic studies with an increased risk of developing the autoimmune disease systemic lupus erythematosus. However, the biological role of IRF5 in lupus pathogenesis has not previously been tested in an animal model. In this study, we show that IRF5 is absolutely required for disease development in the FcgammaRIIB(-/-)Yaa and FcgammaRIIB(-/-) lupus models. In contrast to IRF5-sufficient FcgammaRIIB(-/-)Yaa mice, IRF5-deficient FcgammaRIIB(-/-)Yaa mice do not develop lupus manifestations and have a phenotype comparable to wild-type mice. Strikingly, full expression of IRF5 is required for the development of autoimmunity, as IRF5 heterozygotes had dramatically reduced disease. One effect of IRF5 is to induce the production of the type I IFN, IFN-alpha, a cytokine implicated in lupus pathogenesis. To address the mechanism by which IRF5 promotes disease, we evaluated FcgammaRIIB(-/-)Yaa mice lacking the type I IFN receptor subunit 1. Unlike the IRF5-deficient and IRF5-heterozygous FcgammaRIIB(-/-)Yaa mice, type I IFN receptor subunit 1-deficient FcgammaRIIB(-/-)Yaa mice maintained a substantial level of residual disease. Furthermore, in FcgammaRIIB(-/-) mice lacking Yaa, IRF5-deficiency also markedly reduced disease manifestations, indicating that the beneficial effects of IRF5 deficiency in FcgammaRIIB(-/-)Yaa mice are not due only to inhibition of the enhanced TLR7 signaling associated with the Yaa mutation. Overall, we demonstrate that IRF5 plays an essential role in lupus pathogenesis in murine models and that this is mediated through pathways beyond that of type I IFN production.

Interferon-inducible IFI16, a negative regulator of cell growth, down-regulates expression of human telomerase reverse transcriptase (hTERT) gene

Background

Increased levels of interferon (IFN)-inducible IFI16 protein (encoded by the IFI16 gene located at 1q22) in human normal prostate epithelial cells and diploid fibroblasts (HDFs) are associated with the onset of cellular senescence. However, the molecular mechanisms by which the IFI16 protein contributes to cellular senescence-associated cell growth arrest remain to be elucidated. Here, we report that increased levels of IFI16 protein in normal HDFs and in HeLa cells negatively regulate the expression of human telomerase reverse transcriptase (hTERT) gene.

Methodology/Principal Findings

We optimized conditions for real-time PCR, immunoblotting, and telomere repeat amplification protocol (TRAP) assays to detect relatively low levels of hTERT mRNA, protein, and telomerase activity that are found in HDFs. Using the optimized conditions, we report that treatment of HDFs with inhibitors of cell cycle progression, such as aphidicolin or CGK1026, which resulted in reduced steady-state levels of IFI16 mRNA and protein, was associated with increases in hTERT mRNA and protein levels and telomerase activity. In contrast, knockdown of IFI16 expression in cells increased the expression of c-Myc, a positive regulator of hTERT expression. Additionally, over-expression of IFI16 protein in cells inhibited the c-Myc-mediated stimulation of the activity of hTERT-luc-reporter and reduced the steady-state levels of c-Myc and hTERT.

Conclusions/Significance

These data demonstrated that increased levels of IFI16 protein in HDFs down-regulate the expression of hTERT gene. Our observations will serve basis to understand how increased cellular levels of the IFI16 protein may contribute to certain aging-dependent diseases.

Longitudinal expression of type I interferon responsive genes in systemic lupus erythematosus

Cross-sectional studies of patients with systemic lupus erythematosus (SLE) have demonstrated an association between activation of type I interferon (IFN) pathway and disease activity. This study examined longitudinal changes in IFN-regulated gene expression in peripheral blood using microarrays. A cross-section of 66 patients from the Autoimmune Biomarkers Collaborative Network SLE archive was evaluated. We also examined paired samples from a 15 patient subset collected during a period of low disease activity (Baseline) and at a subsequent flare event, and baseline scores of 29 patients who maintained low disease activity. IFN response (IFNr) scores were calculated from three IFN-regulated genes. Overall, higher IFNr scores were associated with increased disease activity. However, IFNr scores were not significantly different between the paired Baseline and Flare samples. An extended longitudinal analysis in 11 patients indicated little change in IFNr scores over time, even during dynamic disease activity. In patients with low disease activity, IFNr scores were not different between patients who experienced a subsequent flare and those who maintained low disease activity. In summary, although higher IFNr scores were associated with greater disease activity, IFNr scores of individual patients did not correlate with changes in disease severity or flare risk.

A genomic approach to human autoimmune diseases

The past decade has seen an explosion in the use of DNA-based microarrays. These techniques permit assessment of RNA abundance on a genome-wide scale. Medical applications emerged in the field of cancer, with studies of both solid tumors and hematological malignancies leading to the development of tests that are now used to personalize therapeutic options. Microarrays have also been used to analyze the blood transcriptome in a wide range of diseases. In human autoimmune diseases, these studies are showing potential for identifying therapeutic targets as well as biomarkers for diagnosis, assessment of disease activity, and response to treatment. More quantitative and sensitive high-throughput RNA profiling methods are starting to be available and will be necessary for transcriptome analyses to become routine tests in the clinical setting. We expect this to crystallize within the coming decade, as these methods become part of the personalized medicine armamentarium.

Type I interferon and lupus

PURPOSE OF REVIEW

Patients with lupus have signs of an ongoing production of type I interferons (IFNs) that are of importance both for the etiopathogenesis and the clinical manifestations. In this review, we summarize the latest information concerning the type I IFN system in lupus.

RECENT FINDINGS

Activated plasmacytoid dendritic cells are responsible for the IFNalpha production in lupus and can be found in target organs such as glomeruli. The plasmacytoid dendritic cells are triggered by interferogenic immune complexes, and produced IFNalpha activates the immune system and impairs T-regulatory cell function. Autoantibodies, which can form interferogenic immune complexes, are not only present in serum of lupus patients but also in the cerebrospinal fluid of patients with neuropsychiatric manifestations. There is a strong association between risk to develop lupus and gene variants connected to the production and effects of type I IFN. Risk variants can not only cause either increased serum IFNalpha activity or sensitivity but also a more severe disease phenotype. Administration of monoclonal anti-IFNalpha antibodies to lupus patients downregulates several proinflammatory pathways and reduces disease activity.

SUMMARY

Increasing evidence indicates that the activated type I IFN system in lupus is critical in the etiopathogenesis of the disease and is an important therapeutic target.

Developments in the clinical understanding of lupus

Advances in genetics and new understanding of the molecular pathways that mediate innate and adaptive immune system activation, along with renewed focus on the role of the complement system as a mediator of inflammation, have stimulated elaboration of a scheme that might explain key mechanisms in the pathogenesis of systemic lupus erythematosus. Clinical observations identifying important comorbidities in patients with lupus have been a recent focus of research linking immune mechanisms with clinical manifestations of disease. While these advances have identified rational and promising targets for therapy, so far the therapeutic trials of new biologic agents have not met their potential. Nonetheless, progress in understanding the underlying immunopathogenesis of lupus and its impact on clinical disease has accelerated the pace of clinical research to improve the outcomes of patients with systemic lupus erythematosus.

Genetic complementation results in augmented autoantibody responses to lupus-associated antigens

Lupus-prone female New Zealand Mixed (NZM)2328 mice develop high titers of anti-nuclear and anti-dsDNA autoantibodies. Despite high expression of type I IFNs, these mice do not develop autoantibodies to the small nuclear ribonucleoprotein (snRNP) complex. Thus, additional genetic factors must regulate the generation of anti-snRNP autoantibodies. In contrast, despite much lower expression of type 1 IFNs, the diabetes-prone NOD mice spontaneously make anti-snRNP autoantibodies, albeit at a low incidence. To determine whether combination of high type I IFN response of NZM mice with appropriate susceptibility genes of NOD mice would result in anti-snRNP Ab response, cohorts of (NZM2328 x NOD)F(1) mice were generated and characterized for development of autoimmunity. In comparison with parental strains, the PBMCs from F(1) mice showed intermediate expression of type I IFN-responsive genes and augmented expression of IL-6 transcripts. TLR7 expression was similar in all strains. The F(1) mice had very high incidence and titer of anti-snRNP autoantibodies, anti-nuclear Abs, and anti-dsDNA autoantibodies. The levels of anti-snRNP autoantibody correlated with the expression levels of type I IFN-responsive genes. None of the F(1) mice developed diabetes, and only female mice developed severe renal disease. Our data demonstrate that only in presence of appropriate susceptibility genes, anti-snRNP autoantibodies are induced and type I IFNs amplify this response. A synergy between IL-6 and type I IFNs might be critical for amplifying overall autoantibody responses in systemic lupus erythematosus. In NZM/NOD F(1) mouse, genetic complementation between NZM and NOD genes leads to expression of phenotypes similar to those seen in certain lupus patients.

Age- and gender-specific modulation of serum osteopontin and interferon-alpha by osteopontin genotype in systemic lupus erythematosus

Osteopontin (OPN) is a multifunctional cytokine involved in long bone remodeling and immune system signaling. Additionally, OPN is critical for interferon-alpha (IFN-alpha) production in murine plasmacytoid dendritic cells. We have previously shown that IFN-alpha is a heritable risk factor for systemic lupus erythematosus (SLE). Genetic variants of OPN have been associated with SLE susceptibility, and one study suggests that this association is particular to men. In this study, the 3' UTR SLE-risk variant of OPN (rs9138C) was associated with higher serum OPN and IFN-alpha in men (P=0.0062 and P=0.0087, respectively). In women, the association between rs9138 C and higher serum OPN and IFN-alpha was restricted to younger subjects, and risk allele carriers showed a strong age-related genetic effect of rs9138 genotype on both serum OPN and IFN-alpha (P<0.0001). In African-American subjects, the 5' region single nucleotide polymorphisms, rs11730582 and rs28357094, were associated with anti-RNP antibodies (odds ratio (OR)=2.9, P=0.0038 and OR=3.9, P=0.021, respectively). Thus, we demonstrate two distinct genetic influences of OPN on serum protein traits in SLE patients, which correspond to previously reported SLE-risk variants. This study provides a biologic relevance for OPN variants at the protein level, and suggests an influence of this gene on the IFN-alpha pathway in SLE.

Elevated serum interferon-alpha activity in juvenile dermatomyositis: associations with disease activity at diagnosis and after thirty-six months of therapy

OBJECTIVE

Interferon-alpha (IFNalpha) has been implicated in the pathogenesis of juvenile dermatomyositis (DM). The aim of this study was to examine serum IFNalpha activity in a cohort of children with juvenile DM to determine relationships between IFNalpha and indicators of disease activity and severity.

METHODS

Thirty-nine children with definite/probable juvenile DM were included in the study. Serum samples were obtained at the time of diagnosis from 18 untreated patients with juvenile DM. Second samples from 11 of these patients were obtained at 24 months, while they were receiving treatment, and third samples were obtained from 7 of these patients at 36 months. The remaining 21 children were studied 36 months after their initial diagnosis. Serum IFNalpha activity was measured using a functional reporter cell assay.

RESULTS

Patients with juvenile DM had higher serum IFNalpha activity than both pediatric and adult healthy control subjects. In untreated patients, serum IFNalpha activity was positively correlated with serum muscle enzyme levels (P<0.05 for creatine kinase, aspartate aminotransferase, and aldolase) and inversely correlated with the duration of untreated disease (P=0.017). The tumor necrosis factor alpha -308A allele was associated with higher serum IFNalpha levels only in untreated patients (P=0.030). At 36 months, serum IFNalpha levels were inversely correlated with muscle enzyme levels in those patients still requiring therapy and with the skin Disease Activity Score in those patients who had completed therapy (P=0.002).

CONCLUSION

Serum IFNalpha activity was associated with higher serum levels of muscle-derived enzymes and a shorter duration of untreated disease in patients with newly diagnosed juvenile DM and was inversely correlated with measures of chronic disease activity at 36 months postdiagnosis. These data suggest that IFNalpha could play a role in disease initiation in juvenile DM.

Endosomal Toll-like receptors in autoimmunity: mechanisms for clinical diversity

The endosomal Toll-like receptors (TLR3, TLR7 and TLR9) have been implicated in the pathogenesis of autoimmune diseases. Their signaling pathways show remarkable similarities and yet the outcomes following activation of each of these TLRs lead to clinically distinct autoimmune disease phenotypes. This review discusses how differences may arise at a molecular and cellular level to account for this diversity of responses. Understanding the roles of individual TLR pathways and the relationships between them and non-TLR innate immune pathways in the pathogenesis of diseases such as systemic lupus erythematosis highlights potential treatment targets for this spectrum of autoimmune diseases.

Genetic susceptibility to SLE: new insights from fine mapping and genome-wide association studies

Genome-wide association studies and fine mapping of candidate regions have rapidly advanced our understanding of the genetic basis of systemic lupus erythematosus (SLE). More than 20 robust associations have now been identified and confirmed, providing insights at the molecular level that refine our understanding of the involvement of host immune response processes. In addition, genes with unknown roles in SLE pathophysiology have been identified. These findings may provide new routes towards improved clinical management of this complex disease.

High-density genotyping of STAT4 reveals multiple haplotypic associations with systemic lupus erythematosus in different racial groups

OBJECTIVE

Systemic lupus erythematosus (SLE) is the prototypical systemic autoimmune disorder, with complex etiology and a strong genetic component. Recently, gene products involved in the interferon pathway have been under intense investigation in terms of the pathogenesis of SLE. STAT-1 and STAT-4 are transcription factors that play key roles in the interferon and Th1 signaling pathways, making them attractive candidates for involvement in SLE susceptibility.

METHODS

Fifty-six single-nucleotide polymorphisms (SNPs) across STAT1 and STAT4 on chromosome 2 were genotyped using the Illumina platform, as part of an extensive association study in a large collection of 9,923 lupus patients and control subjects from different racial groups. DNA samples were obtained from the peripheral blood of patients with SLE and control subjects. Principal components analyses and population-based case-control association analyses were performed, and the P values, false discovery rate q values, and odds ratios with 95% confidence intervals were calculated.

RESULTS

We observed strong genetic associations with SLE and multiple SNPs located within STAT4 in different ethnic groups (Fisher's combined P = 7.02 x 10(-25)). In addition to strongly confirming the previously reported association in the third intronic region of this gene, we identified additional haplotypic association across STAT4 and, in particular, a common risk haplotype that is found in multiple racial groups. In contrast, only a relatively weak suggestive association was observed with STAT1, probably due to its proximity to STAT4.

CONCLUSION

Our findings indicate that STAT4 is likely to be a crucial component in SLE pathogenesis in multiple racial groups. Knowledge of the functional effects of this association, when they are revealed, might improve our understanding of the disease and provide new therapeutic targets.

Cytokines in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by the production of autoantibodies that can form immune complexes and deposit in tissues, causing inflammation and organ damage. There is evidence that interferons and some interleukins can have an active role in the pathogenesis of SLE and can contribute significantly to the immune imbalance in the disease, whereas the role of some cytokines (such as TNF) is still debated. This review discusses the activity of several cytokines in SLE, their effects on the immune cells in relation to the disease pathogenesis, and the promise and limitations of cytokine-based therapies in clinical trials for lupus patients.

Management of hepatitis B reactivation in patients with lupus nephritis

Hepatitis B is endemic in many Asian countries and immunosuppression may precipitate hepatitic flare. There is little data on the treatment of hepatitis B in patients with systemic lupus erythematosus. We monitored serial transaminase and HBV DNA levels in our HBsAg-positive patients with a history of lupus nephritis and instituted anti-viral treatment in patients who showed virological reactivation. This retrospective pilot study reports the data with this pre-emptive management strategy. Amongst 228 patients with lupus nephritis, eight (3.51%) were HBsAg-positive and five had received Lamivudine treatment for hepatitis B. In two patients the virological flares were preceded by lupus flares that necessitated an increase in immunosuppressive treatment. Median HBV DNA level was 1.9 x 10(7) copies/mL (range 1.2 x 10(4)-1.0 x 10(9) copies/mL) at baseline, and it decreased by 2-5 logs after treatment. Four patients had abnormal transaminase levels at baseline, with mean alanine aminotransferase at 125.0 +/- 67.4 U/L, and all achieved normalisation after 3-24 months (median 13 months) of treatment. Discontinuation of Lamivudine treatment was attempted in three patients after 9-15 months. In one patient treatment was recommenced because of virological flare. For the remaining two patients in whom treatment was not interrupted, one showed sustained viral suppression and one developed drug resistance. All antiviral treatments were well-tolerated. These results indicate the importance of serial monitoring of HBV DNA and transaminase levels, and prompt anti-viral therapy, in the management of HBsAg-positive lupus patients. Also, it may be feasible to discontinue treatment in stable patients to avoid the selection of drug-resistant variants.

Recent advances in the genetics of autoimmune disease

Extraordinary technical advances in the field of human genetics over the past few years have catalyzed an explosion of new information about the genetics of human autoimmunity. In particular, the ability to scan the entire genome for common polymorphisms that associate with disease has led to the identification of numerous new risk genes involved in autoimmune phenotypes. Several themes are emerging. Autoimmune disorders have a complex genetic basis; multiple genes contribute to disease risk, each with generally modest effects independently. In addition, it is now clear that common genes underlie multiple autoimmune disorders. There is also heterogeneity among subphenotypes within a disease and across major racial groups. The current crop of genetic associations are only the start of a complete catalog of genetic factors for autoimmunity, and it remains unclear to what extent common variation versus multiple rare variants contribute to disease susceptibility. The current review focuses on recent discoveries within functionally related groups of genes that provide clues to novel pathways of pathogenesis for human autoimmunity.

Cutting edge: autoimmune disease risk variant of STAT4 confers increased sensitivity to IFN-alpha in lupus patients in vivo

Increased IFN-alpha signaling is a primary pathogenic factor in systemic lupus erythematosus (SLE). STAT4 is a transcription factor that is activated by IFN-alpha signaling, and genetic variation of STAT4 has been associated with risk of SLE and rheumatoid arthritis. We measured serum IFN-alpha activity and simultaneous IFN-alpha-induced gene expression in PBMC in a large SLE cohort. The risk variant of STAT4 (T allele; rs7574865) was simultaneously associated with both lower serum IFN-alpha activity and greater IFN-alpha-induced gene expression in PBMC in SLE patients in vivo. Regression analyses confirmed that the risk allele of STAT4 was associated with increased sensitivity to IFN-alpha signaling. The IFN regulatory factor 5 SLE risk genotype was associated with higher serum IFN-alpha activity; however, STAT4 showed dominant influence on the sensitivity of PBMC to serum IFN-alpha. These data provide biologic relevance for the risk variant of STAT4 in the IFN-alpha pathway in vivo.

A high incidence of disease flares in an open pilot study of infliximab in patients with refractory inflammatory myopathies

OBJECTIVE

To investigate the effect of the tumour necrosis factor (TNF) blocking agent infliximab in patients with treatment-resistant inflammatory myopathies.

METHODS

A total of 13 patients with refractory polymyositis (PM), dermatomyositis (DM), or inclusion body myositis (IBM) were treated with 4 infliximab infusions (5 mg/kg body weight) over 14 weeks. Outcome measures included myositis disease activity score with improvement defined according to The International Myositis Assessment and Clinical Studies Group (IMACS), and MRI. Repeated muscles biopsies were investigated for cellular infiltrates, major histocompatibility complex (MHC) class I and II, TNF, interleukin (IL)1alpha, IL6, high mobility group box chromosomal protein 1 (HMGB-1), interferon gamma (IFNgamma), myxovirus resistance protein A (MxA) and membrane attack complex (MAC) expression. Type I IFN activity was analysed in sera.

RESULTS

Nine patients completed the study. Three patients discontinued due to adverse events and one due to a discovered malignancy. Three of the completers improved by >or=20% in three or more variables of the disease activity core set, four were unchanged and two worsened >or=30%. No patient improved in muscle strength by manual muscle test. At baseline, two completers had signs of muscle inflammation by MRI, and five at follow-up. T lymphocytes, macrophages, cytokine expression and MAC deposition in muscle biopsies were still evident after treatment. Type I IFN activity was increased after treatment.

CONCLUSIONS

Infliximab treatment was not effective in refractory inflammatory myopathies. In view of radiological and clinical worsening, and activation of the type I IFN system in several cases, infliximab is not an alternative treatment in patients with treatment-resistant myositis.

Interferon autoantibodies associated with AIRE deficiency decrease the expression of IFN-stimulated genes

Neutralizing autoantibodies to type I, but not type II, interferons (IFNs) are found at high titers in almost every patient with autoimmune polyendocrinopathy candidiasis ectodermal dystrophy (APECED), a disease caused by AIRE gene mutations that lead to defects in thymic T-cell selection. Combining genome-wide expression array with real time RT-PCR assays, we here demonstrate that antibodies against IFN-alpha cause highly significant down-regulation of interferon-stimulated gene expression in cells from APECED patients' blood by blocking their highly dilute endogenous IFNs. This down-regulation was lost progressively as these APECED cells matured in cultures without neutralizing autoantibodies. Most interestingly, a rare APECED patient with autoantibodies to IFN-omega but not IFN-alpha showed a marked increase in expression of the same interferon-stimulated genes. We also report unexpected increases in serum CXCL10 levels in APECED. Our results argue that the breakdown of tolerance to IFNs in AIRE deficiency is associated with impaired responses to them in thymus, and highlight APECED as another autoimmune disease with associated dysregulation of IFN activity.

The PTPN22 C1858T polymorphism is associated with skewing of cytokine profiles toward high interferon-alpha activity and low tumor necrosis factor alpha levels in patients with lupus

OBJECTIVE

The C1858T polymorphism in PTPN22 has been associated with the risk of systemic lupus erythematosus (SLE) as well as multiple other autoimmune diseases. We have previously shown that high serum interferon-alpha (IFNalpha) activity is a heritable risk factor for SLE. The aim of this study was to determine whether the PTPN22 risk variant may shift serum cytokine profiles to higher IFNalpha activity, resulting in risk of disease.

METHODS

IFNalpha was measured in 143 patients with SLE, using a functional reporter cell assay, and tumor necrosis factor alpha (TNFalpha) was measured by enzyme-linked immunosorbent assay. The rs2476601 single-nucleotide polymorphism in PTPN22 (C1858T) was genotyped in the same patients. Patients were grouped, using a clustering algorithm, into 4 cytokine groups (IFNalpha predominant, IFNalpha and TNFalpha correlated, TNFalpha predominant, and both IFNalpha and TNFalpha low).

RESULTS

SLE patients carrying the risk allele of PTPN22 had higher serum IFNalpha activity than patients lacking the risk allele (P = 0.027). TNFalpha levels were lower in carriers of the risk allele (P = 0.030), and the risk allele was more common in patients in the IFNalpha-predominant and IFNalpha and TNFalpha-correlated groups as compared with patients in the TNFalpha-predominant and both IFNalpha and TNFalpha-low groups (P = 0.001). Twenty-five percent of male patients carried the risk allele, compared with 10% of female patients (P = 0.024); however, cytokine skewing was similar in both sexes.

CONCLUSION

The autoimmune disease risk allele of PTPN22 is associated with skewing of serum cytokine profiles toward higher IFNalpha activity and lower TNFalpha levels in vivo in patients with SLE. This serum cytokine pattern may be relevant in other autoimmune diseases associated with the PTPN22 risk allele.

Hypothetical review: thymic aberrations and type-I interferons; attempts to deduce autoimmunizing mechanisms from unexpected clues in monogenic and paraneoplastic syndromes

In sporadic autoimmune disorders, dendritic cells are increasingly being incriminated as agents provocateurs. However, the mechanisms and any 'danger signals' that induce them to autoimmunize remain enigmatic. Here, we focus on unexpected clues from two prototypic/ highly informative autoimmune syndromes, acquired thymoma-associated myasthenia gravis and the monogenic autoimmune polyendocrine syndrome type-1 (APS1), caused by mutations in the AutoImmune Regulator (AIRE). Both involve the thymus, and in both we find early, persistent, highly prevalent and high-titre neutralizing autoantibodies against type-I interferons, regardless of the exact AIRE genotype or the characteristically variable clinical phenotype in APS1. Thus these key innate<-->adaptive immune intermediaries are now implicated in APS1 and paraneoplastic myasthenia as well as in systemic lupus erythematosus and other sporadic autoimmune disorders. The currently accepted notion that autoimmunization proceeds automatically (by 'default') does not explain how, when or where autoimmune responses are initiated against which targets in APS1, or whether exogenous or internal danger signals are involved, or predict whether the primary auto-immunogenic targets are AIRE-dependent. As the parallels between these syndromes must hold novel clues to these puzzles, they demand explanations. To unify these and other findings, we propose that autoimmunization occurs centrally in aberrant thymic environments rendered 'dangerous' by AIRE-deficiency (possibly by excess undegraded nucleic acids/dead cell debris). The ensuing autoreactivity focuses early on the locally abundant type I interferons and then on other peripheral tissue autoantigens that are still expressed despite the absence of AIRE. These ideas raise numerous questions that others may already have the materials to address.

Interferon-inducible Ifi200-family genes in systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is the prototype of complex autoimmune diseases. Studies have suggested that genetic, hormonal, and environmental factors contribute to the development of the disease. Interestingly, several recent studies involving SLE patients and mouse models of the disease have suggested a role for interferon (IFN)-stimulated genes (ISGs) in the development of SLE. One family of ISGs is the Ifi200-family, which includes mouse (Ifi202a, Ifi202b, Ifi203, Ifi204, and Ifi205) and human (IFI16, MNDA, AIM2, and IFIX) genes. The mouse genes cluster between serum amyloid P-component (Apcs) and alpha-spectrin (Spna-1) genes on chromosome 1 and the human genes cluster in syntenic region 1q23. The Ifi200-family genes encode structurally and functionally related proteins (the p200-family proteins). Increased expression of certain p200-family proteins in cells is associated with inhibition of cell proliferation, modulation of apoptosis, and cell differentiation. Our studies involving generation of B6.Nba2 congenic mice, coupled with gene expression analyses, identified the Ifi202 as a candidate lupus-susceptibility gene. Importantly, recent studies using different mouse models of SLE have suggested that increased expression of Ifi202 gene (encoding p202 protein) in immune cells contributes to lupus susceptibility. Consistent with a functional role for the p202 protein in lupus susceptibility, increased levels of IFI16 protein in human SLE patients are associated with the diseases. This review summarizes recent findings concerning the regulation and role of p200-family proteins in the development of SLE.

Association of the IRF5 risk haplotype with high serum interferon-alpha activity in systemic lupus erythematosus patients

OBJECTIVE

A haplotype of the interferon regulatory factor 5 (IRF5) gene has been associated with the risk of developing systemic lupus erythematosus (SLE), and our previous studies have demonstrated that high levels of serum interferon-alpha (IFNalpha) activity are a heritable risk factor for SLE. The aim of this study was to determine whether the IRF5 SLE risk haplotype mediates the risk of SLE by predisposing patients to the development of high levels of serum IFNalpha activity.

METHODS

IFNalpha levels in 199 SLE patients of European and Hispanic ancestry were measured with a sensitive functional reporter cell assay. The rs2004640, rs3807306, rs10488631, and rs2280714 single-nucleotide polymorphisms (SNPs) in IRF5 were genotyped in these patients. Haplotypes were categorized as SLE risk, neutral, or protective based on published data.

RESULTS

SLE patients with risk/risk and risk/neutral IRF5 genotypes had higher serum IFNalpha activity than did those with protective/protective and neutral/protective genotypes (P = 0.025). This differential effect of IRF5 genotype on serum IFNalpha levels was driven largely by SLE patients who were positive for either anti-RNA binding protein (anti-RBP) or anti-double-stranded DNA (anti-dsDNA) autoantibodies (P = 0.012 for risk/risk or risk/neutral versus protective/protective or neutral/protective). The rs3807306 genotype was independently associated with high serum IFNalpha in this autoantibody group. We found no difference in IFNalpha activity according to IRF5 genotype in patients lacking either type of autoantibody or in patients positive for both classes of autoantibody.

CONCLUSION

The IRF5 SLE risk haplotype is associated with higher serum IFNalpha activity in SLE patients, and this effect is most prominent in patients positive for either anti-RBP or anti-dsDNA autoantibodies. This study demonstrates the biologic relevance of the SLE risk haplotype of IRF5 at the protein level.

Age- and sex-related patterns of serum interferon-alpha activity in lupus families

OBJECTIVE

Interferon-alpha (IFNalpha) levels are elevated in many patients with systemic lupus erythematosus (SLE) and may play a primary role in its pathogenesis. The purpose of this study was to determine whether serum IFNalpha activity in SLE patients and their healthy first-degree relatives is highest in early adulthood, when the incidence of SLE is greatest.

METHODS

Serum samples from 315 SLE patients, 359 healthy first-degree relatives, and 141 healthy unrelated donors were measured for IFNalpha activity using a functional reporter cell assay. IFNalpha activity was analyzed in relation to age, and subgroups with high levels of IFNalpha activity were identified within the large data sets using a Mann-Whitney sliding window segmentation algorithm. The significance of each subgrouping was ranked by Kruskal-Wallis testing.

RESULTS

Age was inversely correlated with IFNalpha activity in female SLE patients (r = -0.20, P = 0.001) as well as their healthy female first-degree relatives (r = -0.16, P = 0.02). In male patients and their healthy male first-degree relatives, there was no significant overall correlation between age and serum IFNalpha activity. The segmentation algorithm revealed significantly increased IFNalpha activity between the ages of 12 and 22 years in female SLE patients and between the ages of 16 and 29 years in male SLE patients. Both male and female healthy first-degree relatives had significantly decreased IFNalpha activity after the age of 50 years.

CONCLUSION

Serum IFNalpha activity is higher in younger individuals in the SLE family cohorts, and this tendency is accentuated in affected individuals. This age-related pattern of IFNalpha activity may contribute to the increased incidence of SLE in early adulthood, and interestingly, males and females had similar age-related patterns of IFNalpha activity.

Defective T-cell ERK signaling induces interferon-regulated gene expression and overexpression of methylation-sensitive genes similar to lupus patients

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by the production of autoantibodies against a host of nuclear antigens. The pathogenesis of lupus is incompletely understood. Environmental factors may play a role via altering DNA methylation, a mechanism regulating gene expression. In lupus, genes including CD11a and CD70 are overexpressed in T cells as a result of promoter hypomethylation. T-cell DNA methyltransferase expression is regulated in part by the extracellular signal-regulated kinase (ERK) signaling pathway. In this study, we investigate the effects of decreased ERK pathway signaling in T cells using transgenic animals. We generated a transgenic mouse that inducibly expresses a dominant-negative MEK in T cells in the presence of doxycycline. We show that decreased ERK pathway signaling in T cells results in decreased expression of DNA methyltransferase 1 and overexpression of the methylation-sensitive genes CD11a and CD70, similar to T cells in human lupus. Our transgenic animal model also develops anti-dsDNA antibodies. Interestingly, microarray expression assays revealed overexpression of several interferon-regulated genes in the spleen similar to peripheral blood cells of lupus patients. This model supports the contention that ERK pathway signaling defects in T cells contribute to the development of autoimmunity.

Serum type I interferon activity is dependent on maternal diagnosis in anti-SSA/Ro-positive mothers of children with neonatal lupus

OBJECTIVE

The type I interferon (IFN) pathway is activated in many patients with systemic lupus erythematosus (SLE), and high serum levels of IFN are associated with anti-SSA/Ro autoantibodies. To investigate the clinical features associated with type I IFN production in vivo, we compared serum IFN activity in individuals with anti-SSA/Ro antibodies who were asymptomatic with that in individuals with clinical manifestations of SLE or Sjögren's syndrome (SS).

METHODS

Antibody-positive sera from 84 mothers of children with manifestations of neonatal lupus were studied for type I IFN activity, using a functional reporter cell assay. Maternal health status was characterized as asymptomatic, SS, SLE, pauci-SLE, or pauci-SS, based on a screening questionnaire, telephone interview, and review of medical records. The prefix "pauci-" indicates symptoms insufficient for a formal classification of the disease.

RESULTS

Only 4% of asymptomatic mothers had high serum type I IFN activity, compared with 73% with pauci-SLE (P = 5.7 x 10(-5)), 35% with SLE (P = 0.011), and 32% of patients with SS (P = 0.032). One of the 4 patients with pauci-SS had high levels of IFN. The majority of patients for whom longitudinal data were available had stable type I IFN activity over time, and changes in IFN activity were not clearly accompanied by changes in the clinical diagnosis.

CONCLUSION

Patients with SLE, patients with pauci-SLE, and patients with SS are more likely to have high serum IFN activity than asymptomatic individuals with SSA/Ro autoantibodies, suggesting that these autoantibodies are insufficient for activation of the type I IFN pathway, and that disease-specific factors are important for type I IFN generation in vivo.