Systemic Lupus Erythematosus Families Research Articles

Cytotoxic CD161-CD8+ TEMRA cells contribute to the pathogenesis of systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a prototypical autoimmune disease affecting multiple organs and tissues with high cellular heterogeneity. CD8+ T cell activity is involved in the SLE pathogenesis. However, the cellular heterogeneity and the underlying mechanisms of CD8+ T cells in SLE remain to be identified. Single-cell RNA sequencing (scRNA-seq) of PBMCs from a SLE family pedigree (including 3HCs and 2 SLE patients) was performed to identify the SLE-associated CD8+ T cell subsets. Flow cytometry analysis of a SLE cohort (including 23HCs and 33 SLE patients), qPCR analysis of another SLE cohort (including 30HCs and 25 SLE patients) and public scRNA-seq datasets of autoimmune diseases were employed to validate the finding. Whole-exome sequencing (WES) of this SLE family pedigree was used to investigate the genetic basis in dysregulation of CD8+ T cell subsets identified in this study. Co-culture experiments were performed to analyze the activity of CD8+ T cells. We elucidated the cellular heterogeneity of SLE and identified a new highly cytotoxic CD8+ T cell subset, CD161-CD8+ TEMRA cell subpopulation, which was remarkably increased in SLE patients. Meanwhile, we discovered a close correlation between mutation of DTHD1 and the abnormal accumulation of CD161-CD8+ TEMRA cells in SLE. DTHD1 interacted with MYD88 to suppress its activity in T cells and DTHD1 mutation promoted MYD88-dependent pathway and subsequently increased the proliferation and cytotoxicity of CD161-CD8+ TEMRA cells. Furthermore, the differentially expressed genes in CD161-CD8+ TEMRA cells displayed a strong out-of-sample prediction for case-control status of SLE. This study identified DTHD1-associated expansion of CD161-CD8+ TEMRA cell subpopulation is critical for SLE. Our study highlights genetic association and cellular heterogeneity of SLE pathogenesis and provides a mechanistical insight into the diagnosis and treatment of SLE. Stated in the Acknowledgements section of the manuscript.

IKBKE and BANK1 Polymorphisms and Clinical Characteristics in Chinese Women with Systemic Lupus Erythematosus

ABSTRACT Background Defects in apoptotic cell clearance is a pathogenic factor in systemic lupus erythematosus (SLE). This study screened potential pathogenic single nucleotide polymorphisms (SNPs) related to anti-apoptosis from an SLE family and explored their contribution to SLE susceptibility in Chinese women. Methods Four SNPs (IKBKE rs15672, BANK1 rs12640056, BANK1 rs6842661, and NFKBIA rs1957106) with potential SLE susceptibility were analyzed for clinical characteristics between 567 patients with SLE and 345 healthy control subjects. Results IKBKE rs15672 G/A and BANK1 rs12640056C/T polymorphisms were associated with SLE susceptibility (rs15672 A vs G, P = 0.028, OR = 1.25, 95% CI = 1.02–1.52; rs12640056 T vs C, P = 0.015, OR = 0.78, 95% CI = 0.64–0.95, respectively). In addition, patients with AA+GA genotypes of IKBKE rs15672 had higher positive rates of anti-SSB antibodies (q = 0.008) and lower positive rates of anti-RIB antibodies (q = 0.024) than those with the GG genotype. There were no significant differences in BANK1 rs12640056 between different genotypes and clinical characteristics. Conclusion IKBKE rs15672 G/A and BANK1 rs12640056C/T polymorphisms are associated with susceptibility to SLE in Chinese women. This highlights the important role of these two SNPs in this disease and suggests that multiple genes from these pathways are candidates for functional studies and therapeutic targets.

Identification and functional analysis of a novel phospholipase D2 gene mutation associated with familial systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a kind of autoimmune inflammatory connective tissue disease which seriously endangers human health. Genetic factors play a key role in the pathogenesis of SLE. This study aims to investigate a novel phospholipase D2 (PLD2) mutation associated with familial SLE, and further explore the underlying mechanism of the mutation in SLE. The blood samples from a SLE patient, the patient's parents, and 147 normal controls were collected and DNA was extracted. Whole genome high-throughput sequencing was performed in the patient and her parents and the results were further analyzed by various bioinformatics methods. The wild type (wt), mutant type (mu), and negative control PLD2 plasmids were further constructed and transfected into 293 cells. The expression level of HRAS protein in 293 cells was detected by Western blotting. In this SLE family, the female SLE patient and her mother, 1 in generation II and 1 in generation III had typical clinical manifestations of SLE, and all of them had lupus nephritis at early stage. The genetic characteristics are consistent with autosomal dominant inheritance. A novel PLD2 heterozygous mutation (c.2722C>T) was found in the patient and her mother, but not in her father and other normal controls. Compared with wtPLD2 plasmid and negative control PLD2 plasmid, the expression of HRAS in 293 cells transfected with muPLD2 plasmid was significantly up-regulated (both P<0.05). PLD2 c.2722C>T mutation may be one of the pathogeny of SLE in this family.

The psychological effects of systemic lupus erythematosus: the imitator of aging

Objectives: To assess the psychological effects of systemic lupus erythematosus (SLE), including perception of aging, in a cohort of participants who were either diagnosed with SLE or had an affected family member. Methods: Over a period of 1 year, we conducted once-monthly face-to-face interviews with 12 participants. The participants were from 4 related families and include 7 females and 5 males. Three participants had a confirmed diagnosis of SLE. Spouses were also included in this study to assess transitivity of the psychological signs of SLE. Responses to structured interview questions were analyzed to assess the perception of aging. Results: The major complaints in participants diagnosed with SLE were pain and psychological stress. Nephrotic syndrome, urinary tract infection, weight disorders and increased need for psychosocial support were common in the participants’ medical history. Qualitative analysis of questionnaires completed by participants with SLE revealed a correlation of “feeling old” with the non-resolution of health complaints. Family members who did not have SLE also reported “feeling old”. Complaints of stress, anxiety, nervousness and lack of enjoyment of life were common in those who were diagnosed with SLE, as well as those who were not. All spouses reported experiencing digestive disorders, hemorrhoids as well as various phobias, regardless of whether their partners had a confirmed SLE diagnosis. Conclusions: In this study, we found that participants with SLE or those who had a close family member with SLE displayed psychological signs of aging. All participants had a predisposition to anxiety, while spouses developed various phobias. Statement of novelty: We show that individuals with SLE and close family members have an increased self-perception of aging.

Germline genetic patterns underlying familial rheumatoid arthritis, systemic lupus erythematosus and primary Sjögren’s syndrome highlight T cell-initiated autoimmunity

ObjectivesFamilial aggregation of primary Sjögren’s syndrome (pSS), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA) and co-aggregation of these autoimmune diseases (ADs) (also called familial autoimmunity) is well recognised. However, the...

Periodontal Tissue Condition on Systemic Lupus Erythematosus Patients: A Clinical Study

Objective: To evaluate periodontal tissue condition on systemic lupus erythematosus (SLE) patients and its characteristics. Material and Methods: This descriptive and cross-sectional study involved 61 SLE patients. Clinical examination of the oral cavity was performed using periodontal index (PI), gingival index (GI), clinical attachment loss (CAL) and number of loose teeth. Also, we evaluated SLE duration, treatment duration, ethnics, marital status, educational background, family income, and occupation. Results: In the evaluation of periodontal tissue, 93.4% had bleeding on probing, 80.3% clinical attachment loss, and 16.3% loose teeth. A total of 54 patients (88.5%) with SLE had periodontitis. Seven subjects had no periodontitis, 11 mild periodontitis, 29 moderate periodontitis and 14 severe periodontitis. Mean Periodontal Index score, Gingival Index, Clinical Attachment Loss (mm), and the number of mobility teeth, Plaque Index and Calculus Index respectively were 2.66 ± 1.20, 1.95 ± 1.02, 0.75 ± 0.59 mm, 1,49 ± 1.77. There was a significant difference in periodontal index score, shown periodontitis between employment and unemployment subjects (p=0.004) and a moderate correlation between periodontitis and occupation. Conclusion: Periodontitis found as manifestations SLE patients, followed by bleeding on probing and loose teeth. Its characteristics is playing a role in periodontitis in SLE patients.

Association of HLA-DRB1*15 and HLA-DQB1* 06 with SLE in Saudis

BACKGROUND AND OBJECTIVESSystemic lupus erythematosus (SLE) is a chronic autoimmune disease characterized by humoral autoimmunity. The etiology of SLE is thought to be multifactorial including environmental, hormonal, and genetic factors. The human leukocyte antigen (HLA) has extensively been associated with the susceptibility to SLE; however, the association is heterogeneous among different ethnic groups. The aim of this study was to determine the association of HLA-A, HLA-B, HLA-DRB1, and HLA-DQB1 with SLE susceptibility in the Saudi population.DESIGN AND SETTINGSA total of 86 consecutive SLE patients attending the rheumatology clinic at King Abdulaziz Medical City, Riyadh, were recruited for this study.METHODSHLA types were determined by the polymerase chain reaction sequence-specific oligonucleotide (PCR-SSP) method in 86 patients and 356 control subjects.RESULTSThe following HLA alleles were found to be positively associated with SLE: HLA-A*29 (OR=2.70; 95% CI=1.03–7.08; P=.0035), HLA-B*51 (OR=1.81; 95% CI=1.17–2.79; P=.0066), HLA-DRB1*15 (OR=1.45; 95% CI=0.98–2.29; P=.063), and HLA-DQB1*06 (OR=1.67; 95% CI=1.19–2.36; P=.0032), whereas HLA-DRB1*16 was negatively associated with the disease (OR=0.18; 95% CI=0.02–1.3; P=.055). HLA-DRB1*15 haplotypes were significantly associated with SLE (OR=2.01, 95% CI=1.20–3.68, P=.008); this was mainly due to the HLA-DRB1* 15-DQB1*06 association.CONCLUSIONSOur data suggest an association between MHC class I and class II (HLA-A*29, HLA-B*51, HLA-DRB1*15, and HLA-DQB1*06) and susceptibility to SLE in the Saudi population. HLA-DRB1*15-DQB1*06 haplotype showed the highest risk factor for the disease that is similar to what was seen in the African American patients, suggesting shared susceptibility genetic factors among these ethnic groups.

Familial Aggregation of High Tumor Necrosis Factor Alpha Levels in Systemic Lupus Erythematosus

Systemic lupus erythematosus (SLE) patients frequently have high circulating tumor necrosis factor alpha (TNF-α) levels. We explored circulating TNF-α levels in SLE families to determine whether high levels of TNF-α were clustered in a heritable pattern. We measured TNF-α in 242 SLE patients, 361 unaffected family members, 23 unaffected spouses of SLE patients, and 62 unrelated healthy controls. Familial correlations and relative recurrence risk rates for the high TNF-α trait were assessed. SLE-affected individuals had the highest TNF-α levels, and TNF-α was significantly higher in unaffected first degree relatives than healthy unrelated subjects (P = 0.0025). No Mendelian patterns were observed, but 28.4% of unaffected first degree relatives of SLE patients had high TNF-α levels, resulting in a first degree relative recurrence risk of 4.48 (P = 2.9 × 10−5). Interestingly, the median TNF-α value in spouses was similar to that of the first degree relatives. Concordance of the TNF-α trait (high versus low) in SLE patients and their spouses was strikingly high at 78.2%. These data support a role for TNF-α in SLE pathogenesis, and TNF-α levels may relate with heritable factors. The high degree of concordance in SLE patients and their spouses suggests that environmental factors may also play a role in the observed familial aggregation.

A young woman with systemic lupus erythematosus and extensive mesenteric vasculitis involving small and medium vessels

History of the present illness The patient had 2 recent hospital admissions. Two months prior to her current presentation, she presented to the emergency department with a tooth abscess for which she underwent incision and drainage, and received a 1-week course of penicillin. One week later, she was admitted with a fever of 40.8°C and was noted to have tooth decay on panoramic radiographs without evidence of an abscess. She was treated with intravenous vancomycin and piperacillin tazobactam for 48 hours and then switched to oral clindamycin. Because of her elevated international normalized ratio (INR), she was unable to undergo tooth extraction prior to discharge. Two weeks later, she was readmitted with 4 days of recurrent fevers, malaise, diffuse arthralgias, and increased dyspnea with minimal exertion. Previous lupus exacerbations were characterized by arthralgias, rash, and hemolytic anemia. On this admission, laboratory evaluation revealed leukocytosis, worsening anemia and thrombocytopenia, creatinine of 0.7 mg/dl, alkaline phosphatase of 127 units/liter (normal value 111), spot urine proteinto-creatinine ratio of 1.47 (prior 1.1), low C3 and C4, and an increase in her double-stranded DNA by enzyme immunoassay from 120 to 768 IU/ml (normal value 30). She was empirically treated with vancomycin and piperacillin tazobactam given her recent tooth infection. The elevated alkaline phosphatase level prompted an abdominal ultrasound that showed multiple small hypoechoic areas in the spleen. An extensive infectious evaluation, including blood cultures, fungal serologies, knee arthrocentesis, magnetic resonance imaging of the lumbar spine, transthoracic and transesophageal echocardiograms, and computed tomography of the chest, abdomen, and pelvis, was negative. Her viral serologies were also unremarkable, other than evidence of IgG seropositivity for cytomegalovirus (CMV) with a negative viral load, consistent with prior exposure. Despite broad-spectrum antibiotics, she remained febrile. Her baseline prednisone dose of 12.5 mg was increased to 60 mg daily for possible lupus flare, after which she defervesced within 48 hours. Her thrombocytopenia was thought to be secondary to SLE-related idiopathic thrombocytopenic purpura because it resolved with high-dose steroids and intravenous immunoglobulin. She was discharged home 11 days after admission. The patient remained afebrile for 1 week at home. During this period she developed new-onset progressive upper abdominal pain with meals lasting 20–30 minutes. She denied associated constitutional symptoms, diarrhea, hematochezia, or melena.

Interferon alpha as a primary pathogenic factor in human lupus

Interferon alpha (IFN-α) is a critical mediator of human systemic lupus erythematosus (SLE). This review will summarize evidence supporting the role for IFN-α in the initiation of human SLE. IFN-α functions in viral immunity at the interface of innate and adaptive immunity, a position well suited to setting thresholds for autoimmunity. Some individuals treated with IFN-α for chronic viral infections develop de novo SLE, which frequently resolves when IFN-α is withdrawn, supporting the idea that IFN-α was causal. Abnormally high IFN-α levels are clustered within SLE families, suggesting that high serum IFN-α is a heritable risk factor for SLE. Additionally, SLE-risk genetic variants in the IFN-α pathway are gain of function in nature, resulting in either higher circulating IFN-α levels or greater sensitivity to IFN-α signaling in SLE patients. A recent genome-wide association study has identified additional novel genetic loci associated with high serum IFN-α in SLE patients. These data support the idea that genetically determined endogenous elevations in IFN-α predispose to human SLE. It is possible that some of these gain-of-function polymorphisms in the IFN-α pathway are useful in viral defense, and that risk of SLE is a burden we have taken on in the fight to defend ourselves against viral infection.

Interferon Alpha as a Primary Pathogenic Factor in Human Lupus

Interferon alpha (IFN-α) is a critical mediator of human systemic lupus erythematosus (SLE). This review will summarize evidence supporting the role for IFN-α in the initiation of human SLE. IFN-α functions in viral immunity at the interface of innate and adaptive immunity, a position well suited to setting thresholds for autoimmunity. Some individuals treated with IFN-α for chronic viral infections develop de novo SLE, which frequently resolves when IFN-α is withdrawn, supporting the idea that IFN-α was causal. Abnormally high IFN-α levels are clustered within SLE families, suggesting that high serum IFN-α is a heritable risk factor for SLE. Additionally, SLE-risk genetic variants in the IFN-α pathway are gain of function in nature, resulting in either higher circulating IFN-α levels or greater sensitivity to IFN-α signaling in SLE patients. A recent genome-wide association study has identified additional novel genetic loci associated with high serum IFN-α in SLE patients. These data support the idea that genetically determined endogenous elevations in IFN-α predispose to human SLE. It is possible that some of these gain-of-function polymorphisms in the IFN-α pathway are useful in viral defense, and that risk of SLE is a burden we have taken on in the fight to defend ourselves against viral infection.

Investigation of the HIN200 Locus in UK SLE Families Identifies Novel Copy Number Variants

We undertook a candidate locus study of the HIN200 gene cluster on 1q21-23 in UK systemic lupus erythematosus (SLE) families. To date, despite mounting evidence demonstrating the importance of these proteins in autoimmune disease, cancer, apoptosis, inflammation, and cell cycle arrest, there has been a dearth of data with respect to the genetic characterisation of the HIN200 locus in SLE or any other disease. We typed 83 single nucleotide polymorphisms (SNPs) across 317 kb of the HIN200 cluster in 428 UK SLE families and sought replication from a European-American lupus cohort. We do not find strong evidence of SNP association in either cohort. Interestingly, we do observe a trend for association with certain HIN200 SNPs and serologic subphenotypes in UK SLE that parallels the association of lupus antibodies with the orthologous murine locus. Furthermore, we find the HIN200 locus to be unexpectedly complex in terms of genetic structural organisation. We have identified a number of copy number variants (CNVs) in this region in healthy French males, HapMap samples, and UK SLE families. In summary, candidate interferon signalling genes show evidence of common CNV in human SLE and healthy subjects. The impact of these CNVs in health and disease remains to be determined.

Analysis of maternal–offspring HLA compatibility, parent‐of‐origin effects, and noninherited maternal antigen effects for HLA–DRB1 in systemic lupus erythematosus

Genetic susceptibility to systemic lupus erythematosus (SLE) is well established, with the HLA class II DRB1 and DQB1 loci demonstrating the strongest association. However, HLA may also influence SLE through novel biologic mechanisms in addition to genetic transmission of risk alleles. Evidence for increased maternal-offspring HLA class II compatibility in SLE and differences in maternal versus paternal transmission rates (parent-of-origin effects) and nontransmission rates (noninherited maternal antigen [NIMA] effects) in other autoimmune diseases have been reported. Thus, we investigated maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 in SLE. The cohort comprised 707 SLE families and 188 independent healthy maternal-offspring pairs (total of 2,497 individuals). Family-based association tests were conducted to compare transmitted versus nontransmitted alleles (transmission disequilibrium test) and both maternally versus paternally transmitted (parent-of-origin) and nontransmitted alleles (using the chi-square test of heterogeneity). Analyses were stratified according to the sex of the offspring. Maternally affected offspring DRB1 compatibility in SLE families was compared with paternally affected offspring compatibility and with independent control maternal-offspring pairs (using Fisher's test) and was restricted to male and nulligravid female offspring with SLE. As expected, DRB1 was associated with SLE (P < 1 x 10(-4)). However, mothers of children with SLE had similar transmission and nontransmission frequencies for DRB1 alleles when compared with fathers, including those for the known SLE risk alleles HLA-DRB1*0301, *1501, and *0801. No association between maternal-offspring compatibility and SLE was observed. Maternal-offspring HLA compatibility, parent-of-origin effects, and NIMA effects at DRB1 are unlikely to play a role in SLE.

Identification of MAMDC1 as a Candidate Susceptibility Gene for Systemic Lupus Erythematosus (SLE)

BackgroundSystemic lupus erythematosus (SLE) is a complex autoimmune disorder with multiple susceptibility genes. We have previously reported suggestive linkage to the chromosomal region 14q21-q23 in Finnish SLE families.Principal FindingsGenetic fine mapping of this region in the same family material, together with a large collection of parent affected trios from UK and two independent case-control cohorts from Finland and Sweden, indicated that a novel uncharacterized gene, MAMDC1 (MAM domain containing glycosylphosphatidylinositol anchor 2, also known as MDGA2, MIM 611128), represents a putative susceptibility gene for SLE. In a combined analysis of the whole dataset, significant evidence of association was detected for the MAMDC1 intronic single nucleotide polymorphisms (SNP) rs961616 (P –value = 0.001, Odds Ratio (OR) = 1.292, 95% CI 1.103–1.513) and rs2297926 (P –value = 0.003, OR = 1.349, 95% CI 1.109–1.640). By Northern blot, real-time PCR (qRT-PCR) and immunohistochemical (IHC) analyses, we show that MAMDC1 is expressed in several tissues and cell types, and that the corresponding mRNA is up-regulated by the pro-inflammatory cytokines tumour necrosis factor alpha (TNF-α) and interferon gamma (IFN-γ) in THP-1 monocytes. Based on its homology to known proteins with similar structure, MAMDC1 appears to be a novel member of the adhesion molecules of the immunoglobulin superfamily (IgCAM), which is involved in cell adhesion, migration, and recruitment to inflammatory sites. Remarkably, some IgCAMs have been shown to interact with ITGAM, the product of another SLE susceptibility gene recently discovered in two independent genome wide association (GWA) scans.SignificanceFurther studies focused on MAMDC1 and other molecules involved in these pathways might thus provide new insight into the pathogenesis of SLE.

Complete complement deficiency in a large cohort of familial systemic lupus erythematosus

Genetic complete deficiency of the early complement components such as C1, C2 and C4 commonly results in a monogenetic form of systemic lupus erythematosus (SLE). However, previous studies have examined groups of complete complement deficient subjects for SLE, while a familial SLE cohort has not been studied for deficiencies of complement. Thus, we undertook the present study to determine the frequency of hereditary complete complement deficiencies among families with two or more SLE patients. All SLE patients from 544 such families had CH50 determined. Medical records were examined for past CH50 values. There were 66 individuals in whom all available CH50 values were zero. All but four of these had a SLE-affected relative with a non-zero CH50; thus, these families did not have monogenetic complement deficient related SLE. The four remaining SLE-affected subjects were in fact two sets of siblings in which three of the four SLE patients had onset of disease at <18 years of age. Both patients in one of these families had been determined to have C4 deficiency, while the other family had no clinical diagnosis of complement deficiency. In this second family, one of the SLE patients had had normal C4 and C3 values, indicating that either C1q or C2 deficiency was possible. Thus, only 2 of 544 SLE families had definite or possible complement deficiency; however, 1 of 7 families in which all SLE patients had pediatric onset and 2 of 85 families with at least 1 pediatric-onset SLE patent had complete complement deficiency. SLE is found commonly among families with hereditary complement deficiency but the reverse is not true. Complete complement deficiency is rare among families with two or more SLE patients, but is concentrated among families with onset of SLE prior to age 18.

Variation in STAT4 is associated with systemic lupus erythematosus in a Finnish family cohort

ObjectivesTo investigate whether 10 single nucleotide polymorphisms (SNPs) and haplotypes in the STAT4 gene, previously associated with systemic lupus erythematosus (SLE) in a Swedish case–control cohort, are also associated with...

Systemic Lupus Erythematosus (SLE) Risk Factors: Novel Proteins Detected From Familial SLE Using Proteomics

Objective In order to investigate the pathogenesis role of proteins in systemic lupus erythematosus (SLE). Methods Protein profiles of 153 serum samples from an SLE family with 7 members, 63 individual SLE patients, and 83 healthy controls were analyzed using MALDI-TOF-MS. Results The protein level at m/z of 9342.23 was significantly higher in the SLE family compared with individual SLE patients and healthy controls, and the protein in individual SLE was significantly higher than healthy controls. The extra proteins are possibly novel peptides instead of autoantibodies or other proteins detected before. Proteins at m/z of 4094.03, 5905.35, and 7973.53 in the SLE family were significantly lower than individual SLE patients and healthy controls, and those in individual SLE were significantly lower than healthy controls. Conclusion The 4 discriminative proteins may play an important role in the pathogenesis of SLE and predict the risk of suffering SLE. Individuals with more protein at an m/z of 9342.23 and less proteins of 4094.03, 5905.35, and 7973.53 may have a higher risk of suffering SLE.

Variation in the upstream region of P-Selectin (SELP) is a risk factor for SLE

Systemic lupus erythematosus (SLE) is a complex autoimmune disease. Genome-wide linkage studies implicated a region containing the adhesion molecule P-Selectin. This family-based study revealed two regions of association within P-Selectin. The strongest signal, from a 21.4-kb risk haplotype, stretched from the promoter into the first two consensus repeat (CR) regions (P=8 × 10−4), with a second association from a 14.6-kb protective haplotype covering CR 2–9 (P=0.0198). The risk haplotype is tagged by the rare C allele of rs3753306, which disrupts the binding site of the trans-activating transcription factor HNF-1. One other variant (rs3917687) on the risk haplotype was significant after permutation (P10000<1 × 10−5), replicated in independent pseudo case-control analysis and was significant by meta-analysis (P=4.37 × 10−6). A third associated variant on the risk haplotype (rs3917657) replicated in 306 US SLE families and was significant in a joint UK-SLE data set after permutation. The protective haplotype is tagged by rs6133 (a non-synonymous variant in CR8 (P=9.00 × 10−4), which also shows association in the pseudo case-control analysis (P=1.09 × 10−3) and may contribute to another signal in P-Selectin. We propose that polymorphism in the upstream region may reduce expression of P-Selectin, the mechanism by which this promotes autoimmunity is unknown, although it may reduce the production of regulatory T cells.

The heritability and genetics of complement C3 expression in UK SLE families

As the central component of the complement system, C3 has sensory and effector functions bridging innate and adaptive immunity. It is plausible that common genetic variation at C3 determines either serum C3 level or susceptibility to systemic lupus erythematosus (SLE), but only a single, Japanese, study has currently showed genetic association. In a cohort of 1371 individuals from 393 UK white European SLE families, we quantified serum C3 and genotyped C3 tagSNPs. Using a Bayesian variance components model, we estimated 39.6% serum C3 heritability. Genotype/serum C3 association was determined by mixed linear models. Single nucleotide polymorphism (SNP) rs344555, located in a haplotype block incorporating the 3' end of C3, was associated with serum C3 (P=0.007), with weaker associations observed for other SNPs in this block. In an extended cohort of 585 SLE families the association between C3 variants and SLE was assessed by transmission disequilibrium test. SNP rs3745568 was associated with SLE (P=0.0046), but not with serum C3. Our disease associated SNP differs from that highlighted in the Japanese study; however, we replicate their finding that genetic variants at the 3' end of C3 are associated with serum C3. Larger studies and further fine mapping will be required to definitively identify functional variants.

Low frequency of CD4+CD25+ Treg in SLE patients: a heritable trait associated with CTLA4 and TGFβ gene variants

BackgroundCD4+CD25+ regulatory T cells play an essential role in maintaining immune homeostasis and preventing autoimmunity. Therefore, defects in Treg development, maintenance or function have been associated with several human autoimmune diseases including Systemic Lupus Erythematosus (SLE), a systemic autoimmune disease characterized by loss of tolerance to nuclear components and significantly more frequent in females.ResultsTo investigate the involvement of Treg in SLE pathogenesis, we determined the frequency of CD4+CD25+CD45RO+ T cells, which encompass the majority of Treg activity, in the PBMC of 148 SLE patients (76 patients were part of 54 families), 166 relatives and 117 controls. SLE patients and their relatives were recruited in several Portuguese hospitals and through the Portuguese Lupus Association. Control individuals were blood donors recruited from several regional blood donor centers. Treg frequency was significantly lower in SLE patients than healthy controls (z = -6.161, P < 0.00001) and intermediate in the relatives' group. Remarkably, this T cell subset was also lower in females, most strikingly in the control population (z = 4.121, P < 0.001). We further ascertained that the decreased frequency of Treg in SLE patients resulted from the specific reduction of bona fide FOXP3+CD4+CD25+ Treg. Treg frequency was negatively correlated with SLE activity index (SLEDAI) and titers of serum anti-dsDNA antibodies. Both Treg frequency and disease activity were modulated by IVIg treatment in a documented SLE case. The segregation of Treg frequency within the SLE families was indicative of a genetic trait. Candidate gene analysis revealed that specific variants of CTLA4 and TGFβ were associated with the decreased frequency of Treg in PBMC, while FOXP3 gene variants were associated with affection status, but not with Treg frequency.ConclusionSLE patients have impaired Treg production or maintenance, a trait strongly associated with SLE disease activity and autoantibody titers, and possibly resulting from the inability to convert FOXP3+CD25- into FOXP3+CD25+ T cells. Treg frequency is highly heritable within SLE families, with specific variants of the CTLA4 and TGFβ genes contributing to this trait, while FOXP3 contributes to SLE through mechanisms not involving a modulation of Treg frequency. These findings establish that the genetic components in SLE pathogenesis include genes related to Treg generation or maintenance.