Delineating the genetic basis of systemic lupus erythematosus

Sle1ab Mediates the Aberrant Activation of STAT3 and Ras-ERK Signaling Pathways in B Lymphocytes

The Sle1ab genomic interval on murine chromosome 1 mediates the loss of immune tolerance to chromatin resulting in antinuclear Abs (ANA) production in the lupus-prone NZM2410 mouse. Global gene expression analysis was used to identify the molecular pathways that are dysregulated at the initiation of B lymphocyte autoimmunity in B6.Sle1ab mice. This analysis identified that STAT3 and ras-ERK signaling pathways are aberrantly activated in Sle1ab B lymphocytes, consistent with increased production of IL-6 by splenic B lymphocytes and monocytes in B6.Sle1ab mice. In vitro treatment of splenic mononuclear cells isolated from ANA-positive Sle1ab mice with anti-IL-6 Ab or AG490, an inhibitor of STAT3 signaling pathway, suppressed ANA production in short-term culture, indicating that this pathway was essential to the production of autoantibodies. In vivo treatment of ANA-positive B6.Sle1ab mice with the ras pathway inhibitor, perillyl alcohol, suppressed the increase of ANA. These findings identify IL-6 as a early key cytokine in Sle1ab-mediated disease development and indicate that the STAT3 and ras-ERK signaling pathways are potential therapeutic targets for treating systemic lupus erythematosus.

Association of extensive polymorphisms in the SLAM/CD2 gene cluster with murine lupus

Susceptibility to autoimmunity in B6.Sle1b mice is associated with extensive polymorphisms between two divergent haplotypes of the SLAM/CD2 family of genes. The B6.Sle1b-derived SLAM/CD2 family haplotype is found in many other laboratory mouse strains but only causes autoimmunity in the context of the C57Bl/6 (B6) genome. Phenotypic analyses have revealed variations in the structure and expression of several members of the SLAM/CD2 family in T and B lymphocytes from B6.Sle1b mice. T lymphocytes from B6.Sle1b mice have modified signaling responses to stimulation at 4-6 weeks of age. While autoimmunity may be mediated by a combination of genes in the SLAM/CD2 family cluster, the strongest candidate is Ly108, a specific isoform of which is constitutively upregulated in B6.Sle1b lymphocytes.

Altered expression of the T cell receptor-CD3 complex in systemic lupus erythematosus

SLE T cells may play a key role in autoantibody production in SLE B cells. In addition, accumulating evidence has shown that SLE T cells participate in the attack on target cells or tissues through the overproduction of pro-inflammatory cytokines or an increase in cell-to-cell adhesion. Thus, the functional abnormality of SLE T cells appears to be pivotal to an understanding of SLE pathogenesis. Accumulating evidence suggests that potential defects may reside in the proximal signal transduction around the TCR-CD3 complex. We have demonstrated that the expression of TCR zeta chain is significantly decreased in peripheral blood T cells from SLE patients. To explore the mechanism of defective expression of TCR zeta chain, we examined mRNA of TCR zeta, and found that two alternatively spliced variants such as exon 7 (-) and short 3'-UTR are detected in SLE. We review the possible role of the TCR zeta defects in autoimmunity and discuss how the splicing variants lead to downregulated protein expression of TCR zeta chain.

T-helper cell intrinsic defects in lupus that break peripheral tolerance to nuclear autoantigens

Special populations of T helper cells drive B cells to produce IgG class switched, pathogenic autoantibodies in lupus. The major source of antigenic determinants (epitopes) that trigger interactions between lupus T and B cells is nucleosomes of apoptotic cells. These epitopes can be used for antigen-specific therapy of lupus. Secondly, the autoimmune T cells of lupus are sustained because they resist anergy and activation-induced programmed cell death by markedly upregulating cyclooxygenase (COX) 2 along with the antiapoptotic molecule c-FLIP. Only certain COX-2 inhibitors block pathogenic anti-DNA autoantibody production in lupus by causing death of autoimmune T helper cells. Hence COX-2 inhibitors may work independently of their ability to block the enzymatic function of COX-2, and structural peculiarities of these select inhibitors may lead to better drug discovery and design.

Genetic origin of lupus in NZB/SWR hybrids: Lessons from an intercross study

OBJECTIVE

(SWR x NZB)F(1) (or SNF(1)) hybrid mice succumb to lupus nephritis. A previous analysis of SNF(1) x NZB backcross mice revealed the existence of 4 SWR loci (H2 on chromosome 17, Swrl-1 on chromosome 1, Swrl-2 on chromosome 14, and Swrl-3 on chromosome 18) and 2 NZB loci (Nba1 and Lbw2/Sbw2, both on chromosome 4). A second study focusing on SNF(1) x SWR backcross offspring uncovered 5 suggestive loci for antinuclear antibody formation, consisting of 3 dominant NZB contributions (Nba4 on chromosome 5, Lbw4 on chromosome 6, and Nba5 on chromosome 7) and 2 recessive SWR contributions (Swrl-1 on chromosome 1 and Swrl-4 on chromosome 10). The present intercross study was executed to replicate the earlier findings, using an independent panel of (SWR x NZB)F(2) offspring.

METHODS

A panel of (NZB x SWR)F(2) hybrids were phenotyped (for renal disease, early mortality, and a variety of autoantibodies) and genotyped (using 95 microsatellite primers positioned across all 19 autosomes and the X chromosome). Linkage analysis was conducted using the derived phenotype and genotype data, with the interval-mapping program MapManager.

RESULTS

Four suggestive loci were mapped: Swrl-5 on chromosome 1 (peak at 106 cM), linked to hypergammaglobulinemia; an NZB locus on chromosome 5 (Nba4; peak at 15 cM), linked to IgG anti-single-stranded DNA (anti-ssDNA) antibodies, IgG anti-doubled-stranded DNA (anti-dsDNA) antibodies, and glomerulonephritis; an NZB locus on chromosome 13 (Nba6; peak at 28 cM), linked to IgG anti-dsDNA antibodies; and an SWR locus on chromosome 14 (Swrl-2; peak at 30 cM), linked to IgG anti-ssDNA antibodies. Eight additional loci revealed linkage at P < 0.01, of which 7 co-mapped with lupus susceptibility loci previously identified in other models.

CONCLUSION

Considering all 3 mapping studies together, lupus in SWR/NZB hybrids appears to be the epistatic end product of several distinct loci, of which 3 SWR-derived loci (Swrl-1, Swrl-2, and Swrl-3) and 5 NZB-derived loci (Nba1, Nba3, Nba4, Nba5, and Lbw4) have been independently confirmed. The immunologic functions and molecular identities of these loci await elucidation.

Rituximab improves peripheral B cell abnormalities in human systemic lupus erythematosus

OBJECTIVE

B lymphocyte depletion has recently emerged as a promising approach to the treatment of systemic lupus erythematosus (SLE). As part of a phase I/II dose-ranging trial of rituximab in the treatment of SLE, we evaluated the fate of discrete B cell subsets in the setting of selective depletion by anti-CD20 monoclonal antibody and during the B cell recovery phase.

METHODS

B cell depletion and phenotype were examined by flow cytometry of peripheral blood mononuclear cells for CD19, CD20, CD27, IgD, and CD38 expression. Changes in autoreactive B lymphocytes and plasma cells were assessed by determination of serum autoantibody levels (anti-double-stranded DNA and VH4.34) and by direct monitoring of a unique autoreactive B cell population bearing surface antibodies whose heavy chain is encoded by the VH4.34 gene segment.

RESULTS

Compared with normal controls, SLE patients displayed several abnormalities in peripheral B cell homeostasis at baseline, including naive lymphopenia, expansion of a CD27-,IgD- (double negative) population, and expansion of circulating plasmablasts. Remarkably, these abnormalities resolved after effective B cell depletion with rituximab and immune reconstitution. The frequency of autoreactive VH4.34 memory B cells also decreased 1 year posttreatment, despite the presence of low levels of residual memory B cells at the point of maximal B cell depletion and persistently elevated serum autoantibody titers in most patients.

CONCLUSION

This study is the first to show evidence that in SLE, specific B cell depletion therapy with rituximab dramatically improves abnormalities in B cell homeostasis and tolerance that are characteristic of this disease. The persistence of elevated autoantibody titers may reflect the presence of low levels of residual autoreactive memory B cells and/or long-lived autoreactive plasma cells.

The Ro 60 kDa autoantigen: insights into cellular function and role in autoimmunity

An RNA-binding protein, the Ro 60 kDa autoantigen, is a major target of the immune response in patients suffering from two systemic rheumatic diseases, systemic lupus erythematosus and Sjogren's syndrome. In lupus patients, anti-Ro antibodies are associated with photosensitive skin lesions and with neonatal lupus, a syndrome in which mothers with anti-Ro antibodies give birth to children with photosensitive skin lesions and a cardiac conduction defect, third degree heart block. In vertebrate cells, the Ro protein binds small RNAs of unknown function known as Y RNAs. Although the cellular function of Ro has long been mysterious, recent studies have implicated Ro in two distinct processes: small RNA quality control and the enhancement of cell survival following exposure to ultraviolet irradiation. Most interestingly, mice lacking the Ro protein develop an autoimmune syndrome that shares some features with systemic lupus erythematosus in patients, suggesting that the normal function of Ro may be important for the prevention of this autoimmune disease. In this review, we summarize recent progress towards understanding the role of the Ro 60 kDa protein and discuss whether the cellular function of Ro could be related to certain manifestations of lupus in patients.

The inhibitory Fcgamma receptor modulates autoimmunity by limiting the accumulation of immunoglobulin G+ anti-DNA plasma cells

Deletion of the gene encoding the Fc immunoglobulin G receptor IIB (FcgammaRIIB) results in a fulminant, lupus-like disease in C57BL/6 but not BALB/c mice. Here we have investigated this strain-specific, epistatic loss of tolerance using gene-targeted immunoglobulin variable heavy-chain (V(H)) alleles 3H9 or 56R, which encode DNA-specific heavy chains, expressed on the C57BL/6 or BALB/c background. The combination of C57BL/6 and V(H) 56R (B6.56R) resulted in a loss of tolerance; hybridoma and single-cell analysis indicated an FcgammaRIIB-independent difference in immunoglobulin light-chain usage, consistent with an alteration in receptor editing. FcgammaRIIB deficiency resulted in an increase in immunoglobulin G (IgG) antibodies to DNA in the serum, an increased frequency of anti-DNA-reactive IgG(+) B cells with a plasma cell phenotype and immune complex deposition in the glomeruli and renal disease in B6.56R mice. Thus, FcgammaRIIB provides a distal peripheral checkpoint to limit the accumulation of autoreactive plasma cells, thereby maintaining tolerance.

Aberrant B1?cell migration into the thymus results in activation of CD4 T?cells through its potent antigen-presenting activity in the development of murine lupus

B1 cells have different origin and function from conventional B (B2) cells and are considered to be involved in autoantibody production in the development of autoimmune disease. We found that B1 cells preferentially accumulated in the target organs including thymus in aged BWF1 mice, a murine model for systemic lupus erythematosus, and that B lymphocyte chemoattractant (BLC/CXCL13) expression was increased in the thymus before the onset of lupus nephritis, while stromal cell-derived factor-1 (SDF-1/CXCL12) and secondary lymphoid tissue chemokine (SLC/CCL21) expression remained unchanged. Adhesion molecules such as peripheral node addressin (PNAd), ICAM-1, and VCAM-1 were also expressed on endothelial cells in the enlarged thymic perivascular space (PVS) in aged BWF1 mice. BLC protein and PNAd were co-localized on these high-endothelial-venules-like vessels in enlarged PVS. B1 cells expressed higher level of costimulatory molecules and showed a potent antigen-presenting activity in allogeneic mixed lymphocyte reaction comparable to splenic dendritic cells. Interestingly, B1 cells stimulated proliferation of autologous thymic CD4 T cells in the presence of IL-2. These results indicate that aberrant B1 cell trafficking into the thymus due to ectopic high expression of BLC may result in an activation of self-reactive T cells in the development of murine lupus.

A new CD21low B cell population in the peripheral blood of patients with SLE

A hallmark of systemic lupus erythematosus (SLE) is the production of autoantibodies. Recent reports suggest an abnormal peripheral blood B cell homeostasis in SLE patients without being conclusive. We analyzed by four color flow-cytometry peripheral blood B cell subpopulations of SLE patients, healthy donors, and patients with other systemic autoimmune diseases. IgM memory but not switched memory B cells of SLE patients were significantly decreased compared to healthy donors, whereas transitional B cells, characterized by CD19+IgMhiIgD+CD24hiCD38hi, were significantly expanded in SLE patients but also found in other autoimmune disorders. The population of plasmablasts (CD19loCD21loCD27++CD38++) was increased in active disease. Most interestingly, B cells in autoimmune disorders contain a so far uncharacterized subpopulation with an activated phenotype (CD19hiCD21loCD38loCD86int). None of the identified subpopulations was associated with current or previous therapy and therefore may represent different aspects of the disturbed B cell homeostasis in patients with SLE.

Decreased Expression of the Ets Family Transcription Factor Fli-1 Markedly Prolongs Survival and Significantly Reduces Renal Disease in MRL/lpr Mice

Increased Fli-1 mRNA is present in PBLs from systemic lupus erythematosus patients, and transgenic overexpression of Fli-1 in normal mice leads to a lupus-like disease. We report in this study that MRL/lpr mice, an animal model of systemic lupus erythematosus, have increased splenic expression of Fli-1 protein compared with BALB/c mice. Using mice with targeted gene disruption, we examined the effect of reduced Fli-1 expression on disease development in MRL/lpr mice. Complete knockout of Fli-1 is lethal in utero. Fli-1 protein expression in heterozygous MRL/lpr (Fli-1(+/-)) mice was reduced by 50% compared with wild-type MRL/lpr (Fli-1(+/+)) mice. Fli-1(+/-) MRL/lpr mice had significantly decreased serum levels of total IgG and anti-dsDNA Abs as disease progressed. Fli-1(+/-) MRL/lpr mice had significantly increased splenic CD8(+) and naive T cells compared with Fli-1(+/+) MRL/lpr mice. Both in vivo and in vitro production of MCP-1 were significantly decreased in Fli-1(+/-) MRL/lpr mice. The Fli-1(+/-) mice had markedly decreased proteinuria and significantly lower pathologic renal scores. At 48 wk of age, survival was significantly increased in the Fli-1(+/-) MRL/lpr mice, as 100% of Fli-1(+/-) MRL/lpr mice were alive, in contrast to only 27% of Fli-1(+/+) mice. These findings indicate that Fli-1 expression is important in lupus-like disease development, and that modulation of Fli-1 expression profoundly decreases renal disease and improves survival in MRL/lpr mice.

CD72 polymorphisms associated with alternative splicing modify susceptibility to human systemic lupus erythematosus through epistatic interaction with FCGR2B

We previously reported association of FCGR2B-Ile232Thr with systemic lupus erythematosus (SLE) in three Asian populations. Because polymorphism of CD72, another inhibitory receptor of B cells, was associated with murine SLE, we identified human CD72 polymorphisms, tested their association with SLE and examined genetic interaction with FCGR2B in the Japanese (160 SLE, 277 controls), Thais (87 SLE, 187 controls) and Caucasians (94 families containing SLE members). Four polymorphisms and six rare variations were detected. The former constituted two major haplotypes that contained one or two repeats of 13 nucleotides in intron 8 (designated as *1 and *2, respectively). Although association with susceptibility to SLE was not detected, the *1 allele was significantly associated with nephritis among the Japanese patients (P=0.024). RT-PCR identified a novel alternatively spliced (AS) transcript that was expressed at the protein level in COS-7 transfectants. The ratio of AS/common isoforms was strikingly increased in individuals with *2/*2 genotype when compared with *1/*1 (P=0.000038) or *1/*2 (P=0.0085) genotypes. Using the two Asian cohorts, significant association of FCGR2B-232Thr/Thr with SLE was observed only in the presence of CD72-*1/*1 genotype (OR 4.63, 95% CI 1.47-14.6, P=0.009 versus FCGR2B-232Ile/Ile plus CD72-*2/*2). Minigene assays demonstrated that the 13-nucleotide repeat and 4 bp deletion within the same haplotype of intron 8 could regulate alternative splicing. The AS isoform lacks exon 8, and is deduced to contain 49 amino acid changes in the membrane-distal portion of the extracellular domain, where considerable amino acid changes are known in CD72(c) allele associated with murine SLE. These results indicated that the presence of CD72-*2 allele decreases risk for human SLE conferred by FCGR2B-232Thr, possibly by increasing the AS isoform of CD72.

HLA-DRB1 and -DQB1 alleles and gene polymorphisms of selected cytokines in systemic lupus erythematosus

OBJECTIVE

The objective of this study was to evaluate the genetic profiles of selected cytokines (transforming growth factor beta 1, tumor necrosis factor alpha, interleukin-6, interferon gamma, and interleukin-10) in systemic lupus erythematosus and the contributions of human leukocyte antigen (HLA)-DRB1 and -DQB1 alleles to susceptibility for this disease.

PATIENTS AND METHODS

The study was carried out in 24 SLE patients and 36 healthy controls (from Upper Silesia) using polymerase chain reaction methods. All persons were of Caucasoid origin. Standard association analysis was used to compare the HLA alleles and frequency of cytokine gene polymorphisms between these groups.

RESULTS

Only the frequency of HLA-DRB1*07 allele was higher in SLE patients than controls (odds ratio 2.92, 95% confidence interval 1.16-7.33), but the difference did not reach statistical significance when Bonferroni's adjustment procedure was performed. No other significant associations were noted between class II alleles (DR1-DR6, DR8-DR10, DQ1-DQ4) and SLE. The frequency of the interleukin-6 GG and GC genotypes was significantly higher in SLE patients than in controls, and a significantly higher percentage of the G vs C alleles between patients and controls was revealed (odds ratio 2.53, 95% confidence interval 1.37-4.65, chi-squared test 8.16, P < 0.05). The most significant association of increased frequency of the G allele with SLE was more commonly noted in HLA-DRB1*07-positive patients (odds ratio 10.29, 95% confidence interval 5.34-19.83, P < 0.001). These data indicate that this combination could contribute toward determining the susceptibility to SLE, but its possible significance will require confirmation by further studies.

Potential mechanisms of interferon-alpha induced autoimmunity

The type I interferons (IFN) are cytokines encoded by a multigene family comprising 13 closely related IFN-A genes, and a single IFN-B gene. These factors are rapidly induced upon viral infection, and have pleiotropic effects. Historically, the induction of a cell-autonomous state of antiviral resistance, the inhibition of cell growth, and the regulation of apoptosis were appreciated first. More recently, it became generally accepted that they can regulate immune effector functions. This latter feature led them to be reconsidered as signals linking innate and adaptive immunity, and potentially orchestrating autoimmunity associated with viral infection and IFN-alpha therapy. Common to almost all autoimmune diseases is their polygenic inheritance, incomplete penetrance, and evidence for the role of environmental factors, particularly viral infection. In addition, they are characterized by increased numbers of circulating autoreactive T- and B-cells. Endogenously produced or therapeutically applied IFN-alpha can tilt the usually tightly controlled balance towards activation of these autoreactive cells via a vast array of mechanisms. The genetic susceptibility factors determine which type of autoimmunity will develop. IFN-alpha induces numerous target genes in antigen presenting cells (APC), such that APC are stimulated and enhance humoral autoimmunity, promote isotype switching, and potently activate autoreactive T cells. Moreover, IFN-alpha can synergistically amplify T cell autoreactivity by directly promoting T cell activation and keeping activated T cells alive. In essence, type I IFNs may constitute one example of genes that have been conserved because they confer dominant disease resistance, but at the same time they can trigger autoimmunity in genetically susceptible individuals.

Inhibition of lupus by genetic alteration of the interferon-alpha/beta receptor

Type I interferons (IFN-alphabeta) are immunoregulatory cytokines that promote both innate and adaptive immune responses. Although they have been implicated in human SLE, recent studies in mice have helped solidify this connection. By using lupus-prone mice with knockout of the IFN-alphabeta receptor, we and others have documented that lack of IFN-alphabeta leads to a marked reduction in disease manifestations, including autoantibody production, target organ damage and mortality. Furthermore, IFN-alphabeta was found to potentially contribute to several levels of disease pathogenesis. These included the differentiation and activation of dendritic cells, the activation and proliferation of T cells, T cell survival and the activation and survival of autoantibody-producing B cells. These findings strongly support the targeting of IFN-alphabeta in SLE and suggest that definition of the specific pathways critical for disease induction will be important for optimal intervention.

Association analyses of DNA methyltransferase-1 (DNMT1) polymorphisms with systemic lupus erythematosus

The etiology of systemic lupus erythematosus (SLE) is very complex, and genetic factors appear to play a significant role in susceptibility to SLE, in determining the disease expression, and in the autoantibody profiles of individuals with SLE. DNA methyltransferase-1 (DNMT1) is a major enzyme that determines genomic methylation patterns and both maintains methyltransferase and exhibits de novo DNA methylation activity in vivo. In order to clarify the association of DNMT1 polymorphisms with SLE, we scrutinized the genetic polymorphisms in exons and their boundaries of DNMT1, including the -1,500 bp promoter region, by direct sequencing in 24 Korean individuals. Twenty-nine sequence variants were identified: two in 5'UTR, six in exons, and 21 in introns. Eight of these polymorphisms were selected for a larger-scale genotyping (n=680) by considering their allele frequencies, haplotype-tagging status, and linkage disequilibrium coefficiencies (LDs) among polymorphisms. The associations between DNMT1 polymorphisms and the clinical profiles of SLE were analyzed. No significant associations with the risk of SLE were detected. However, further analyses of association with autoantibody production among SLE patients revealed that one nonsynonymous SNP, +14463G>C (V120L) in exon 4, was weakly associated with an increased risk of anti-La antibody production (P=0.04), although the significance could not be retained after correction of multiple tests. The DNMT1 variations and haplotypes clarified in this study would provide valuable information for future genetic studies of other autoimmune diseases.

Effective treatment of a mouse model of Sjögren's syndrome with eyedrop administration of anti-CD4 monoclonal antibody

OBJECTIVE

To determine whether eyedrop administration of an anti-CD4 monoclonal antibody (mAb) is effective in the treatment of Sjögren's syndrome (SS) using a mouse model of the disease.

METHODS

The anti-CD4 mAb was administered daily into the eyes of mice with SS from ages 4 to 8 weeks or ages 10 to 12 weeks. During treatment, tear volume was monitored and after final treatment, histologic features of the lacrimal and salivary glands, the phenotypes and function of T cells, and serum titers of anti-alpha-fodrin antibody were examined.

RESULTS

Eyedrop administration of anti-CD4 mAb before the onset of SS prevented the autoimmune pathology seen in the lacrimal glands but not that in the salivary glands. Furthermore, eyedrop administration of anti-CD4 mAb after the development of SS inhibited mononuclear cell infiltration and the destruction of parenchyma only in the lacrimal glands. Eyedrop administration of anti-CD4 mAb suppressed the local activation of CD4+ T cells rather than deleting CD4+ T cells, which reduced the expansion of pathologic CD4+ T cells against alpha-fodrin.

CONCLUSION

These results demonstrate the remarkable efficacy of anti-CD4 mAb eyedrops in the treatment of SS eye symptoms, which illustrates a new antibody-based therapeutic strategy for patients with eye problems caused by SS as well as other diseases.

Exploring the genetic basis of disease using RNA interference

Cancer and autoimmunity are polygenic diseases. In order to better understand the mechanisms of disease development and progression it is essential to uncover which genes are involved. Much has been learned from population studies in human patients by searching for polymorphic genetic loci associated with disease. In addition, animal models of tumor development, as well as models for various autoimmune conditions such as multiple sclerosis and Type I diabetes, have helped determine genetic loci that contribute to disease susceptibility. However, characterization of the exact genes involved is often difficult and requires lengthy and technically demanding genetic manipulations. The generation of knockout animals is the method of choice to probe single genes. However, this is not possible in all species or even in all inbred strains within a species. The recent discovery of a new post-transcriptional gene silencing pathway termed RNA interference, which is mediated by short fragments of double-stranded RNA (short-interfering RNA), has opened up new avenues for genetic manipulation of experimental animals. This review will consider how silencing genes by RNA interference within the context of experimental disease models promises to become a powerful new tool for the genetic analysis of cancer and autoimmunity. Advances in RNA interference technology now permit the relatively rapid generation of transgenic animals in a wide range of species with complex genetic backgrounds that were previously inaccessible to genetic manipulation. This novel approach should help refine the characterization of disease-associated genes, either by silencing specific candidates or even by screening a larger number of genes in vivo within a comparatively short time frame.

Deficiency of the cyclin kinase inhibitor p21(WAF-1/CIP-1) promotes apoptosis of activated/memory T cells and inhibits spontaneous systemic autoimmunity

A characteristic feature of systemic lupus erythematosus is the accumulation of activated/memory T and B cells. These G₀/G₁-arrested cells express high levels of cyclin-dependent kinase inhibitors such as p21, are resistant to proliferation and apoptosis, and produce large amounts of proinflammatory cytokines. Herein, we show that ablation of p21 in lupus-prone mice allows these cells to reenter the cell cycle and undergo apoptosis, leading to autoimmune disease reduction. Absence of p21 resulted in enhanced Fas/FasL-mediated activation-induced T cell death, increased activation of procaspases 8 and 3, and loss of mitochondrial transmembrane potential. Increased apoptosis was also associated with p53 up-regulation and a modest shift in the ratio of Bax/Bcl-2 toward the proapoptotic Bax. Proliferation and apoptosis of B cells were also increased in p21^−/− lupus mice. Thus, modulation of the cell cycle pathway may be a novel approach to reduce apoptosis-resistant pathogenic lymphocytes and to ameliorate systemic autoimmunity.

Genetic models for the clearance of apoptotic cells

The immunogenic potential of nuclear antigens exposed during apoptosis, together with considerable animal data suggesting that impaired apoptotic clearance can result in systemic lupus erythematosus (SLE)-like autoimmunity, has lent support to the idea that self-immunization with apoptotic debris is a key driving mechanism in lupus. The multiple roles of complement receptors, diverse scavenger receptors, and intermediate proteins that bind to and opsonize apoptotic cells indicate a complex web of interactions leading to the clearance of apoptotic debris. Disturbances in parts of this system may lead to lupus or to lupus exacerbations. Therapy directed toward augmenting clearance and decreasing concomitant inflammation may lead to improved management of SLE.

Genetic association of the R620W polymorphism of protein tyrosine phosphatase PTPN22 with human SLE

We genotyped 525 independent North American white individuals with systemic lupus erythematosus (SLE) for the PTPN22 R620W polymorphism and compared the results with data generated from 1,961 white control individuals. The R620W SNP was associated with SLE (genotypic P=.00009), with estimated minor (T) allele frequencies of 12.67% in SLE cases and 8.64% in controls. A single copy of the T allele (W620) increases risk of SLE (odds ratio [OR]=1.37; 95% confidence interval [CI] 1.07-1.75), and two copies of the allele more than double this risk (OR=4.37; 95% CI 1.98-9.65). Together with recent evidence showing association of this SNP with type 1 diabetes and rheumatoid arthritis, these data provide compelling evidence that PTPN22 plays a fundamental role in regulating the immune system and the development of autoimmunity.

Update on pediatric systemic lupus erythematosus

PURPOSE OF REVIEW

The purpose of this review is to provide an update on the clinical manifestations of SLE in children. Emerging clues on the pathogenesis of the disease based on recent human studies conducted both in children and adults, will also be summarized.

RECENT FINDINGS

Pediatric Rheumatologists caring for children with SLE face many challenges. As the life expectancy of these patients improves, new recognized complications such as accelerated atherosclerosis and hypertension emerge as major causes of morbidity. However, few longitudinal studies describing the long term outcome of these children, including the impact of disease and treatment on their physical and psychological development are available. Few prospective interventional studies have been carried out to assess the efficacy of established and novel treatments in the pediatric population. Recently, basic studies aimed at understanding the immune alterations underlying this disease have been performed in children. These studies indicate an important role for interferon-alpha (IFN-alpha) in the pathogenesis of this disease and reveal an overall striking homogeneity of leukocyte gene expression profiles in children and adults with SLE. The contribution of novel gene polymorphisms to disease susceptibility and the sequential breakdown of tolerance to nuclear antigens that precedes clinical manifestations in patients with SLE are among the recent studies that are helping us understand the complex SLE puzzle.

SUMMARY

SLE continues to cause significant morbidity in the pediatric age group. A better recognition of the age-specific manifestations and long-term complications of this disease is required to improve its outcome. Understanding its unique pathogenesis will hopefully lead to the development of better, more targeted and less toxic therapies.

Current advances in the human lupus genetics

Genetic predisposition has been firmly established as a key element in susceptibility to systemic lupus erythematosus (SLE). During the past three decades, association studies have assessed many genes for potential roles in predisposing to SLE. These studies have identified a few risk factors including hereditary deficiency of complement components, major histocompatibility complex class II alleles, and allelic variants for the Fc portion of IgG (FCGR) genes. In recent years, a few groups have completed linkage analyses in data sets from families containing multiple members affected with SLE. Results from these initial genome scans are encouraging; approximately eight chromosomal regions have been identified exhibiting evidence for significant linkage to SLE and have been confirmed using independent cohorts (1q23, 1q25-31, 1q41-42, 2q35-37, 4p16-15.2, 6p11-21, 12q24, and 16q12), suggesting the high likelihood of the presence of one or multiple SLE susceptibility genes at each locus. Another approach of linkage analyses conditioned on pedigrees where one affected member manifesting a particular clinical condition has also identified many chromosomal regions linked to SLE. Within several established susceptibility loci, evidence for association of positional candidate genes is emerging. Within 2q35-37, an intronic single nucleotide polymorphism (SNP) of the positional candidate gene program cell death 1 gene has been associated with SLE susceptibility. The SLE-associated SNP affects a transcription factor, RUNX1, binding site. Recently, SNPs of novel positional candidate genes that influence RUNX1 binding motifs have also been associated with other autoimmune diseases, suggesting the possibility of a common theme shared among susceptibility genes for autoimmune diseases. In the coming years, susceptibility genes responsible for the observed linkage will be identified, and will lead to further delineating genetic pathways involved in susceptibility to SLE.

The candidate gene approach: have murine models informed the study of human SLE?

Genome wide linkage studies in human SLE have identified seven highly significant loci linked to SLE, and more than 20 other loci showing suggestive linkage to disease. However, pin-pointing the susceptibility alleles in candidate genes within these linkage regions is challenging, due the genetic heterogeneity, racial differences and environmental influences on disease aetiology. Utilization of murine models of spontaneous lupus nephritis provide a complementary approach, which may then identify candidate genes for analysis in human cases. This review highlights the utility of cross-species approach to identify and characterize the effect of given candidate genes in lupus. The examples described in this review demonstrate the importance of bringing together both genetic and functional information in human and mouse studies.

Common DNase I polymorphism associated with autoantibody production among systemic lupus erythematosus patients

DNase I could be the most important nuclease for the removal of DNA from nuclear antigens at sites of high cell turnover, and thus may also prevent systemic lupus erythematosus (SLE). Sixteen SNPs were identified by direct DNA sequencing, among which six were selected for genotyping in a larger investigation on the basis of linkage disequilibria among SNPs, their frequency, location and haplotype tagging status. Genetic associations of polymorphisms in DNase I with the risk of SLE and the production of common autoantibodies were examined in a Korean population (350 SLE patients and 330 controls). Although no significant associations with the risk of SLE were found, logistic regression analyses revealed that one non-synonymous SNPs in exon 8, +2373A>G(Gln244Arg), was significantly associated with an increased risk of the production of anti-RNP and anti-dsDNA antibodies among SLE patients. The frequency of the homozygous minor allele (Arg/Arg) was much higher in patients who had the anti-RNP antibody (31.3%) than in patients who did not have this antibody (14.4%) (P=0.0006, OR=2.86). In addition, the A/T mutation in exon 2 of DNase reported in two Japanese SLE patients was not present in SLE patients (n=350) or controls (n=330) in our Korean population, which combined with the results of previous reports strongly suggests that the mutation is not present in three major ethnic groups: Caucasian, African and Asian.

Spontaneous autoimmunity in 129 and C57BL/6 mice-implications for autoimmunity described in gene-targeted mice

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disorder in which complex genetic factors play an important role. Several strains of gene-targeted mice have been reported to develop SLE, implicating the null genes in the causation of disease. However, hybrid strains between 129 and C57BL/6 mice, widely used in the generation of gene-targeted mice, develop spontaneous autoimmunity. Furthermore, the genetic background markedly influences the autoimmune phenotype of SLE in gene-targeted mice. This suggests an important role in the expression of autoimmunity of as-yet-uncharacterised background genes originating from these parental mouse strains. Using genome-wide linkage analysis, we identified several susceptibility loci, derived from 129 and C57BL/6 mice, mapped in the lupus-prone hybrid (129 × C57BL/6) model. By creating a C57BL/6 congenic strain carrying a 129-derived Chromosome 1 segment, we found that this 129 interval was sufficient to mediate the loss of tolerance to nuclear antigens, which had previously been attributed to a disrupted gene. These results demonstrate important epistatic modifiers of autoimmunity in 129 and C57BL/6 mouse strains, widely used in gene targeting. These background gene influences may account for some, or even all, of the autoimmune traits described in some gene-targeted models of SLE.

Several strains of gene-targeted mice develop systemic lupus erythematosus (SLE). Analysis of these strains demonstrates that the genetic background profoundly influences the development of autoimmunity

Association of the CT60 marker of the CTLA4 gene with systemic lupus erythematosus

OBJECTIVE

To investigate the possible association of the CT60A/G marker with systemic lupus erythematosus (SLE) in Spanish patients, and to identify the possible CTLA4 haplotype responsible for the association, taking into account other polymorphisms described at positions -1722T/C, -319C/T, +49A/G, and the microsatellite (AT)(n) in the 3'-untranslated region (3'-UTR) of the CTLA4 gene.

METHODS

Genotyping of CT60 was performed in 395 patients with SLE and 293 healthy controls using polymerase chain reaction (PCR)-restriction fragment length polymorphism analysis. Genotyping of the rest of the dimorphisms has been previously reported. Genotyping of microsatellite polymorphism (AT)(n) in the 3'-UTR was performed using PCR with a fluorescence-labeled primer.

RESULTS

With regard to CT60A/G, the frequency of the AA genotype was significantly decreased among the SLE patients (18.7% versus 28.3% in the control group; P = 0.003, corrected P [P(corr)] = 0.009, odds ratio [OR] = 0.58, 95% confidence interval [95% CI] 0.40-0.85). In other words, the frequency of individuals bearing the G phenotype was increased in the patient group compared with the control group (81.2% versus 71.7%; P = 0.003, P(corr) = 0.006, OR = 1.71, 95% CI 1.18-2.49). The distribution of allele frequency was also significantly different between patients and controls (P = 0.01, P(corr) = 0.02, OR [for allele G] = 1.32, 95% CI 1.06-1.65). After combining the data on the different polymorphisms, 2 neutral haplotypes were found: +49A;(AT)(7);CT60A and +49G;(AT)(8-19);CT60G. In addition, a susceptibility haplotype was found: +49A;(AT)(>19);CT60G.

CONCLUSION

The 3'-UTR of the CTLA4 gene is involved in susceptibility to SLE.

Genetic interactions between susceptibility loci reveal epistatic pathogenic networks in murine lupus

Interactions between Sle1 and other susceptibility loci were required for disease development in the NZM2410 model of lupus. Sle1 corresponds to at least three subloci, Sle1a, Sle1b, and Sle1c, each of which independently causes loss of tolerance to chromatin, but displays a distinctive immune profile. We have used congenic strains to analyze the interactions between the Sle1 subloci and other lupus susceptibility loci using Y autoimmunity accelerator (Yaa) and Faslpr as sensitizing mutations. Sle1 coexpressed with either one of these single susceptibility alleles resulted in a highly penetrant nephritis, splenomegaly, production of nephrophilic antibodies, and increased expression of B- and T-cell activation markers. Here, we show that only Sle1b interacted with Yaa to produce these phenotypes, suggesting that Sle1b and Yaa belong to the same functional pathway. Interactions between the three Sle1 loci and lpr resulted in lymphocyte activation and lupus nephritis, but a significant mortality was observed only for the Sle1a.lpr combination. This suggests a major role for the FAS pathway in keeping in check the loss of tolerance mediated by the Sle1 loci, especially for Sle1a. Our results illustrate the complexity of interactions between susceptibility loci in polygenic diseases such as lupus and may explain the clinical heterogeneity of the disease.

Quantitative trait loci in Chromosomes 3, 8, and 9 regulate antibody production against Salmonella flagellar antigensin the mouse

Two mouse lines were produced by bidirectional selection according to the high (HIII) or low (LIII) antibody responsiveness against Salmonella flagellar antigens (Selection III). In the present work we conducted a genomewide scan to map the quantitative trait loci (QTL) involved in the antibody response regulation in these selected mice. HIII and LIII genomes were screened with microsatellite markers and those found polymorphic between the lines (146) were used for linkage analysis in F2 (HIII x LIII) intercross. Simple interval mapping analysis was performed using Mapmanager QTX software. Three highly significant QTL linked to antibody production against Salmonella flagellar antigens have been demonstrated in Chromosomes 3, 8, and 9. HIII and LIII lines differ in the resistance to several diseases, therefore, the relevance of these QTL with the genetic factors involved in infections, autoimmunity, and neoplastic disease progression is discussed.

Lupus Glomerulonephritis Revisited 2004: Autoimmunity and End-Organ Damage

Histopathology of the kidney and clinical presentation are critical factors in the diagnosis of immune-mediated glomerulonephritis (GN). The histological manifestations of glomerular injury are shared by multiple underlying mechanisms. Work from our laboratory and from other investigators shows that antinuclear, antihistone or anti-dsDNA antibodies are neither required nor sufficient for development of lupus GN. In addition, antibody to dsDNA can be generated by mechanisms other than loss of tolerance to chromatin. Genetic analyses demonstrate that although there is some interaction between autoantibody production and renal disease, the phenotypes are regulated by distinct genetic intervals. Furthermore, renal failure is not an essential outcome of the immune-complex deposition and proliferative lupus GN. These data are also supported by published studies from systemic lupus erythematosus (SLE) patients. The immune regulation of lupus GN is distinct from other organ-specific diseases and not influenced by CD25(+) or NK1.1(+) regulatory T cells. Thus, fatal GN may depend upon a kidney-reactive T-cell response that, in turn, may be regulated by gender and intrinsic end-organ factors. The data discussed in this review call for a re-evaluation of the current paradigms for pathogenesis of SLE. An interactive model separating autoimmunity from end-organ susceptibility for the pathogenesis of SLE is proposed.

The stimulation of Toll-like receptors by nuclear antigens: a link between apoptosis and autoimmunity

As immunologists have long understood, effective responses to foreign antigens require adjuvants. It is now apparent that the initiation of autoimmune disease is comparably facilitated by adjuvant activity. In the case of antinuclear antibodies, it seems that DNA itself can serve as an endogenous adjuvant. Similar to many of the microbial adjuvants, mammalian DNA mediates its effect through a Toll-like receptor--in this case, TLR9.

New loci from New Zealand Black and New Zealand White mice on chromosomes 4 and 12 contribute to lupus-like disease in the context of BALB/c

New Zealand Black (NZB) and New Zealand White (NZW) mice are genetically predisposed to a lupus-like autoimmune syndrome. To further define the loci linked to disease traits in NZB and NZW mice in the context of the BALB/c genetic background, linkage analyses were conducted in two crosses: (NZW x BALB/c.H2(z))F(1) x NZB and (NZB x BALB/c)F(2). Novel loci linked to autoantibody production and glomerulonephritis, present in both NZB and NZW mice, were identified on proximal chromosomes 12 and 4. The chromosome 12 locus showed the strongest linkage to anti-nuclear Ab production. Additionally, a number of other novel loci linked to lupus traits derived from both the New Zealand and non-autoimmune BALB/c genomes were identified. Furthermore, we confirm the linkage of disease to a number of previously described lupus-associated loci, demonstrating that they are relatively background independent. These data provide a number of additional candidate gene regions in murine lupus, and highlight the powerful effect the non-autoimmune background strain has in influencing the genetic loci linked to disease.

A novel locus regulates both retroviral glycoprotein 70 and anti-glycoprotein 70 antibody production in New Zealand mice when crossed with BALB/c

Lupus-prone New Zealand Black and New Zealand White mice produce high serum levels of the endogenous retroviral envelope protein gp70 and develop an Ab response to this autoantigen as part of their autoimmune disease. Linkage analysis of two crosses involving New Zealand and BALB/c mice mapped these traits to a group of overlapping loci, including a novel locus on proximal chromosome 12. This locus was linked with serum gp70 and the autoimmune response against it. The linkage of serum gp70 levels to a previously described locus on distal chromosome 4 was also confirmed. Sequence analysis of a candidate gene on distal chromosome 4, Fv1, provided support that this gene may be associated with the control of serum gp70 levels in both New Zealand Black and New Zealand White mice. Linkage data and statistical analysis confirmed a close correlation between gp70 Ag and anti-gp70 Ab levels, and together gave support to the concept that a threshold level of gp70 is required for the production of anti-gp70 Abs. Serum levels of anti-gp70 Abs were closely correlated with the presence of renal disease, more so than anti-dsDNA Abs. Understanding the genetic basis of this complex autoantigen-autoantibody system will provide insight into the pathogenesis of lupus in mice, which may have implications for human disease.

Association between IFNA genotype and the risk of systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is characterized by multisystem inflammation and production of autoantibodies, which can generate immune complexes and may cause tissue damage through the recognition of an autoantigen. Although many factors have been proposed, such as genetic factors, environmental factors, hormonal action, viruses, and dysregulation of cytokine production, the cause of this disease is not well understood. It has been reported that the levels of interferon (IFN)-alpha in the sera of some SLE patients are elevated and that IFN-alpha induces maturation of monocytes into highly active antigen-presenting dendritic cells (DCs). We analyzed the association between IFN-alpha genotype and the risk of SLE to clarify whether IFN-alpha plays a central role in susceptibility to SLE. The results showed that no IFN-alpha genotype was significantly associated with the risk of SLE.

Haematopoietic stem cell transplantation for autoimmune disorders: the American perspective

The hypothesis that haematopoietic stem cell transplantation (HSCT) might be useful in treating refractory autoimmune diseases (AID) was suggested by studies in animal models and by the improvement of concurrent autoimmune diseases in patients who had undergone transplantation for haematological disorders. This concept has now been tested in a substantial number of phase I/II clinical trials of autologous HSCT. These early results are promising, even in patients who have failed on multiple standard therapies for AID. Transplantation-related toxicity has decreased with growing experience in the application of this procedure, better patient selection and the modification of treatment protocols. Randomized trials currently under way or under consideration should clarify the role of HSCT in patients with autoimmune disorders.

Characterization of heterogeneity in the molecular pathogenesis of lupus nephritis from transcriptional profiles of laser-captured glomeruli

The molecular pathogenesis of focal/diffuse proliferative lupus glomerulonephritis was studied by cDNA microarray analysis of gene expression in glomeruli from clinical biopsies. Transcriptional phenotyping of glomeruli isolated by laser-capture microscopy revealed considerable kidney-to-kidney heterogeneity in increased transcript expression, resulting in four main gene clusters that identified the presence of B cells, several myelomonocytic lineages, fibroblast and epithelial cell proliferation, matrix alterations, and expression of type I IFN-inducible genes. Glomerulus-to-glomerulus variation within a kidney was less marked. The myeloid lineage transcripts, characteristic of those found in isolated activated macrophages and myeloid dendritic cells, were widely distributed in all biopsy samples. One major subgroup of the samples expressed fibrosis-related genes that correlated with pathological evidence of glomerulosclerosis; however, decreased expression of TGF-beta1 argued against its role in lupus renal fibrosis. Expression of type I IFN-inducible transcripts by a second subset of samples was associated with reduced expression of fibrosis-related genes and milder pathological features. This pattern of gene expression resembled that exhibited by activated NK cells. A large gene cluster with decreased expression found in all samples included ion channels and transcription factors, indicating a loss-of-function response to the glomerular injury.

Mechanisms of natural tolerance in the intestine: implications for inflammatory bowel disease

Tolerance, the regulated inability to respond to a specific immunologic stimulant, is a physiological event important to normal immune function. Just as loss of tolerance to self-proteins results in autoimmune diseases, we assert that loss of tolerance to commensal flora in the intestinal lumen leads to inflammatory bowel disease (IBD). Mechanisms through which the mucosal immune system establishes and remains hyporesponsive toward the presence of food proteins and commensal flora, which we define as natural tolerance, are discussed. In addition to the contributions by commensal flora, the innate host defense and the adaptive immune systems promote natural tolerance to sustain normal mucosal homeostasis. Understanding the molecular and cellular events that mediate natural tolerance will lead to more advanced insights into IBD pathogenesis and improved therapeutic options.

Autoimmunity through cytokine-induced dendritic cell activation

We propose a model where autoimmunity can be viewed as a dynamic system driven by opposite vectors IFN-alpha/beta and TNF. These cytokines drive differentiation of distinct types of DCs, TNF-DCs, or IFN-DCs, which present different antigens leading to distinct autoimmune responses. When balanced, both cytokines synergize in protective immunity. When one of the cytokines prevails, autoimmunity occurs, Type I interferons (IFN-alpha/beta) playing a major role in systemic lupus erythematosus (SLE) and TNF playing a major role in rheumatoid arthritis. This model complements the Type 1/Type 2 paradigm. Therefore, immunity can be viewed as a dynamic system driven by two sets of opposite vectors: IFN-alpha/beta/TNF and IFN-gamma/IL-4.

The centromeric region of chromosome 7 from MRL mice (Lmb3) is an epistatic modifier of Fas for autoimmune disease expression

Lupus is a prototypic systemic autoimmune disease that has a significant genetic component in its etiology. Several genome-wide screens have identified multiple loci that contribute to disease susceptibility in lupus-prone mice, including the Fas-deficient MRL/Fas(lpr) strain, with each locus contributing in a threshold liability manner. The centromeric region of chromosome 7 was identified as a lupus susceptibility locus in MRL/Fas(lpr) mice as Lmb3. This locus was backcrossed onto the resistant C57BL/6 (B6) background, in the presence or absence of Fas, resulting in the generation of B6.MRLc7 congenic animals. Detailed analysis of these animals showed that Lmb3 enhances and accelerates several characteristics of lupus, including autoantibody production, kidney disease, and T cell activation, as well as accumulation of CD4(-)CD8(-) double-negative T cells, the latter a feature of Fas-deficient mice. These effects appeared to be dependent on the interaction between Lmb3 and Fas deficiency, as Lmb3 on the B6/+(Fas-lpr) background did not augment any of the lupus traits measured. These findings confirm the role of Lmb3 in lupus susceptibility, as a modifier of Fas(lpr) phenotype, and illustrate the importance of epistatic interaction between genetic loci in the etiology of lupus. Furthermore, they suggest that the genetic lesion(s) in MRLc7 is probably different from those in NZMc7 (Sle3/5), despite a significant overlap of these two intervals.

CD38 polymorphisms in Spanish patients with systemic lupus erythematosus

The ADP-ribosyl cyclase/cyclic ADP-ribose hydrolase (CD38) gene is a positional and functional candidate gene for the susceptibility to systemic lupus erythematosus (SLE) because CD38 gene maps in the described SLE risk region 4p15 and CD38 molecule is a leukocyte activation antigen and ectoenzyme involved in numerous immune functions. The aim of this study was to investigate the possible association of the polymorphisms located at positions 182 of intron 1 (C/G) and 418 (C/T, located in exon 3) of the CD38 gene with the susceptibility and clinical features of SLE. Genotyping of 276 Spanish patients with SLE and 194 controls was performed by polymerase chain reaction amplification-refractory mutation system techniques. No association between the polymorphisms studied and the susceptibility to SLE was found. However, when patients were stratified according to their clinical manifestations, a significant increase of CC individuals and a significant decrease of CG individuals among patients with discoid rash (67.9% vs. 53.1% in controls p = 0.02, pc > 0.05, odds ratio [OR] = 1.87, 95% confidence interval [95% CI] 1.05-3.35; and 23.5% vs. 40.2% in controls, p = 0.008, pc = 0.024, OR = 0.46 95% CI 0.24-0.85) were found. Logistic regression analysis identified CC genotype as an independent risk factor for discoid rash among patients with SLE (p = 0.01, OR = 2.23, 95% CI 1.19-4.18). In conclusion, a slight contribution of the polymorphism located in intron 1 of the CD38 gene in the clinical features of SLE could be postulated.

CTLA4 polymorphism in Spanish patients with systemic lupus erythematosus

The cytotoxic T-lymphocyte antigen 4 (CTLA4, CD152) gene is a positional and functional candidate gene to susceptibility to systemic lupus erythematosus (SLE) because CTLA4 gene maps in the described SLE risk region 2q33 and CTLA4 molecule has an inhibitory effect on T-cell activation. Several polymorphisms have been described in CTLA4 gene, among them, a T/C change at position -1722, a C/T transition at position -319, and another A/G transition at position +49. The aim of this study was to investigate the possible association of these polymorphisms with the susceptibility to SLE in 276 Spanish autochthonous patients using a healthy control group composed of 194 ethnically matched volunteer bone marrow donors. Genotyping of these CTLA4 positions was performed in SLE patients and controls using a polymerase chain reaction amplification refractory mutation system. The genotypic frequencies were in Hardy-Weinberg equilibrium in all patients. No differences in the distribution of the genotype frequencies between patients and controls were found in any case. Our results from the Spanish autochthonous population differ from those found in the Korean population regarding the involvement of the polymorphism located at -1722 in the susceptibility to SLE.

A Promoter Haplotype of the Immunoreceptor Tyrosine-Based Inhibitory Motif-Bearing FcγRIIb Alters Receptor Expression and Associates with Autoimmunity. I. RegulatoryFCGR2BPolymorphisms and Their Association with Systemic Lupus Erythematosus

FcgammaRIIb, the immunoreceptor tyrosine-based inhibitory motif-containing receptor for IgG (Mendelian Inheritance in Man no. 604590), plays an important role in maintaining the homeostasis of immune responses. We have identified 10 novel single-nucleotide polymorphisms in the promoter region of human FCGR2B gene and characterized two functionally distinct haplotypes in its proximal promoter. In luciferase reporter assays, the less frequent promoter haplotype leads to increased expression of the reporter gene in both B lymphoid and myeloid cell lines under constitutive and stimulated conditions. Four independent genome-wide scans support linkage of the human FcgammaR region to the systemic lupus erythematosus (SLE; Online Mendelian Inheritance in Man no. 152700) phenotype. Our case-control study in 600 Caucasians indicates a significant association of the less frequent FCGR2B promoter haplotype with the SLE phenotype (odds ratio = 1.65; p = 0.0054). The FCGR2B haplotype has no linkage disequilibrium with previously identified FCGR2A and FCGR3A polymorphisms, and after adjustment for FCGR2A and FCGR3A, FCGR2B showed a persistent association with SLE (odds ratio = 1.72; p = 0.0083). These results suggest that an expression variant of FCGR2B is a risk factor for human lupus and implicate FCGR2B in disease pathogenesis.

Interleukin-6 Induces Expression of Ifi202, an Interferon-inducible Candidate Gene for Lupus Susceptibility

Systemic lupus erythematosus (SLE) is a prototype autoimmune disease. In human SLE patients, as well as in mouse models of SLE, the development of disease is associated with increased levels of pro-inflammatory cytokines, such as interleukin-6 (IL-6). However, IL-6 target genes contributing to the development of disease remain to be identified. Our previous studies of one mouse model of SLE identified an interferon-inducible gene, Ifi202, as a major contributor to the disease. We now report that IL-6 induces expression of the Ifi202 gene. We found that IL-6 treatment of mouse splenocytes increased levels of Ifi202 mRNA and p202 protein. Furthermore, IL-6 treatment of NIH 3T3 cells or expression of a constitutively active form of STAT3, a known mediator of IL-6 signaling, stimulated the activity of a 202-luc-reporter through a potential STAT3 DNA-binding site (the 202-SBS) present in the 5'-regulatory region of the Ifi202 gene. Moreover, treatment of cells with IL-6 stimulated binding of the transcription factor STAT3 to an oligonucleotide containing the 202-SBS in gel-mobility shift assays and to the 5'-regulatory region of the Ifi202 gene in chromatin immunoprecipitation assays. Importantly, site-directed mutagenesis of 202-SBS or expression of a dominant negative form of STAT3 significantly reduced constitutive as well as IL-6-stimulated activity of the 202-luc-reporter. Together, our observations support the idea that IL-6 stimulates transcription of the Ifi202 gene through STAT3 activation and predict that increased levels of IL-6 in lupus contribute to up-regulation of p202.

Studies of murine systemic autoimmunity

Systemic autoimmunity is an important clinical problem, offering a window into fundamental questions of self-nonself tolerance. We have used cellular immunology, serology, and immunopathology to approach several spontaneous mouse models. Although much remains to be done, a picture is emerging of pathological antigen-driven immune responses to self nuclear antigens, highly dependent on multiple genes, and susceptible to abnormalities of apoptosis.

Human lupus T cells resist inactivation and escape death by upregulating COX-2

Autoimmune T-helper cells drive pathogenic autoantibody production in systemic lupus erythematosus (SLE), but the mechanisms maintaining those T cells are unknown. Autoreactive T cells are normally eliminated by functional inactivation (anergy) and activation-induced cell death (AICD) or apoptosis through death receptor (Fas) signaling. However, mutations in the genes encoding Fas and its ligand (FasL) are rare in classical SLE. By gene microarray profiling, validated by functional and biochemical studies, we establish here that activated T cells of lupus patients resist anergy and apoptosis by markedly upregulating and sustaining cyclooxygenase-2 (COX-2) expression. Inhibition of COX-2 caused apoptosis of the anergy-resistant lupus T cells by augmenting Fas signaling and markedly decreasing the survival molecule c-FLIP (cellular homolog of viral FLICE inhibitory protein). Studies with COX-2 inhibitors and Cox-2-deficient mice confirmed that this COX-2/FLIP antiapoptosis program is used selectively by anergy-resistant lupus T cells, and not by cancer cells or other autoimmune T cells. Notably, the gene encoding COX-2 is located in a lupus-susceptibility region on chromosome 1. We also found that only some COX-2 inhibitors were able to suppress the production of pathogenic autoantibodies to DNA by causing autoimmune T-cell apoptosis, an effect that was independent of prostaglandin E(2) (PGE(2)). These findings could be useful in the design of lupus therapies.