Biological treatment in ankylosing spondylitis in the Nordic countries during 2010-2016: a collaboration between five biological registries.

OBJECTIVES: Large-scale observational cohorts may be used to study the effectiveness and rare side effects of biological disease-modifying anti-rheumatic drugs (bDMARDs) in ankylosing spondylitis (AS), but may be hampered by differences in baseline characteristics and disease activity across countries. We aimed to explore the research infrastructure in the five Nordic countries regarding bDMARD treatment in AS. METHOD: This observational cohort study was based on data from biological registries in Denmark (DANBIO), Sweden (SRQ/ARTIS), Finland (ROB-FIN), Norway (NOR-DMARD), and Iceland (ICEBIO). Data were collected for the years 2010-2016. Registry coverage, registry inventory (patient characteristics, disease activity measures), and national guidelines for bDMARD prescription in AS were described per country. Incident (first line) and prevalent bDMARD use per capita, country, and year were calculated. In AS patients who started first line bDMARDs during 2010-2016 (n = 4392), baseline characteristics and disease activity measures were retrieved. RESULTS: Registry coverage of bDMARD-treated patients ranged from 60% to 95%. All registries included extensive prospectively collected data at patient level. Guidelines regarding choice of first line drug and prescription patterns varied across countries. During the period 2010-2016 prevalent bDMARD use increased (p < 0.001), whereas incident use tended to decrease (p for trend < 0.004), with large national variations (e.g. 2016 incidence: Iceland 10.7/100 000, Finland 1.7/100 000). Baseline characteristics were similar regarding C-reactive protein, but differed for other variables, including the Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) (range 3.5-6.3) and Ankylosing Spondylitis Disease Activity Score (ASDAS) (2.7-3.8) (both p < 0.0001). CONCLUSION: Collaboration across the five Nordic biological registries regarding bDMARD use in AS is feasible but national differences in coverage, prescription patterns, and patient characteristics must be taken into account depending on the scientific question.

Doubling the single-dose infusion rate of tocilizumab in rheumatoid arthritis is safe and efficacious.

OBJECTIVES: To investigate the impact of enhanced infusion rate of tocilizumab on the occurrence of infusion reactions, overall safety, and efficacy in rheumatoid arthritis (RA). METHOD: We conducted a 24-week multicentre, open-label, randomized parallel group study comparing adverse event (AE) and effect profiles following tocilizumab IV 8 mg/kg every 4 weeks over 31 min vs. standard 60-min infusions in patients with RA and an inadequate clinical response to disease-modifying anti-rheumatic drugs (DMARDs) and/or tumour necrosis factor (TNF)-α inhibitors. RESULTS: A total of 47 patients were enrolled in the study and randomized to fast infusions (n = 25) and controls (n = 22). Incidences of infusion reactions were similar between the two groups, neither of them leading to withdrawal. Likewise, the incidence of additional AEs did not differ between the treatment arms. Two serious adverse events (SAEs) were reported, in the control group. Four patients withdrew due to AEs, two from each arm. Efficacy at week 24 was comparable between groups. CONCLUSIONS: In RA, monthly tocilizumab infusions of 8 mg/kg provided over 31 or 60 min during 24 weeks did not differ concerning safety or efficacy.

Smoking as a risk factor for the radiological severity of rheumatoid arthritis: a study on six cohorts.

BACKGROUND: Smoking is a risk factor for the development of anti -citrullinated protein antibodies (ACPA) positive rheumatoid arthritis (RA). Whether smoking predisposes to severe joint damage progression is not known, since deleterious, protective and neutral observations have been made. OBJECTIVE: To determine the effect of smoking on joint damage progression. METHODS: Smoking status was assessed in 3158 RA patients included in six cohorts (Leiden Early Arthritis Clinic (Leiden-EAC), BARFOT, Lund, Iceland, NDB and Wichita). In total 9412 radiographs were assessed. Multivariate normal regression and linear regression analyses were performed. Data were summarised in a random effects inverse variance meta-analysis. RESULTS: When comparing radiological progression for RA patients that were never, past and current smokers, smoking was significantly associated with more severe joint damage in Leiden-EAC (p=0.042) and BARFOT (p=0.015) RA patients. No significant associations were found in the other cohorts, though a meta-analysis on the six cohorts showed significantly more severe joint damage progression in smokers (p=0.01). Since smoking predisposes to ACPA, analyses were repeated with ACPA as additional adjustment factor. Then the association was lost (meta-analysis p=0.29). CONCLUSIONS: This multi-cohort study indicated that the effect of smoking on joint damage is mediated via ACPA and that smoking is not an independent risk factor for radiological progression in RA.

Association of variants in IL2RA with progression of joint destruction in rheumatoid arthritis.

OBJECTIVE: Heritability studies have suggested an important role of genetic predisposition in the progression of joint destruction in rheumatoid arthritis (RA); the heritability is estimated at 45-58%. Several single-nucleotide polymorphisms (SNPs) have been identified as being associated with RA susceptibility. Our objective was to study the association of several of these loci with progression of joint destruction. METHODS: We studied 1,750 RA patients in 4 independent data sets with 4,732 radiographs scored using the modified Sharp/van der Heijde method. Thirteen susceptibility SNPs that were not previously associated with joint destruction were tested in 596 Dutch RA patients. Subsequently, significant SNPs were studied in data sets of RA patients from North America and Iceland. Data were summarized in inverse-weighted variance meta-analyses. Further, the association with circulating protein levels was studied and the associated region was fine-mapped. RESULTS: In stage 1, 3 loci (AFF3, IL2RA, and BLK) were significantly associated with the rate of joint destruction and were further analyzed in the additional data sets. In the combined meta-analyses, the minor (C) allele of IL2RA (rs2104286) was associated with less progression of joint destruction (P = 7.2 × 10(-4) ). Furthermore, the IL2RA (rs2104286) protective genotype was associated with lower (0.85-fold [95% confidence interval 0.77-0.93], P = 1.4 × 10(-3) ) circulating levels of soluble interleukin-2 receptor α (sIL-2Rα). Additionally, lower sIL-2Rα levels were associated with a lower rate of joint destruction (P = 3.4 × 10(-3) ). The association of IL2RA with the rate of joint destruction was further localized to a 40-kb region encompassing the IL2RA intron 1 and the 5' region of IL2RA and RBM17. CONCLUSION: The present genetic and serologic data suggest that inherited altered genetic constitution at the IL2RA locus may predispose to a less destructive course of RA.

Mannan-binding lectin may facilitate the clearance of circulating immune complexes--implications from a study on C2-deficient individuals.

Deficiency of both mannan-binding lectin (MBL) and complement components C4 and C2 has been associated with increased risk of systemic lupus erythematosus (SLE). MBL can activate the complement system either through C4 and C2 or directly through C3. Circulating immune complexes (CICs) are believed to play a pathogenic role in SLE and MBL has been shown to bind certain forms of immunoglobulins, including IgM, IgG and IgA. Thus, MBL might promote CIC clearance. In order to evaluate this, six individuals with non-functional classical pathway due to the rare homozygous C2 deficiency were chosen, as the classical pathway is known to have a fundamental role in CIC clearance. Four of the six C2-deficient individuals had SLE, two of whom also had MBL deficiency. MBL serum levels and genotypes were compared with the serum levels of CICs, as measured by their content of kappa, lambda, IgM, IgA, IgG and C3 opsonization. The C2-deficient individuals had higher serum levels of CICs than 16 healthy controls (P < 0.0001). Furthermore, an inverse association was observed between MBL and CIC levels in the C2-deficient individuals, which was strongest for IgM-CICs (r = - 0.84, P = 0.037). Moreover, C3 opsonization of the CICs correlated positively with MBL levels in the C2-deficient individuals (r = 0.89, P = 0.017). In conclusion, individuals with C2 deficiency have increased levels of CICs and MBL may facilitate their clearance. Defective CIC clearance might partly explain the increased risk of SLE associated with low MBL.

Characterization of a susceptibility locus for SLE, SLEB5, on chromosome 4p14-13.

Systemic lupus erythematosus is a systemic autoimmune disorder of unknown aetiology but is most likely caused by an interaction between several genetic factors and the environment. In a previously published genome scan we presented linkage to a marker on chromosome 4p13 in Icelandic families. Fine mapping of the region has been performed using 10 multicase families from Iceland and the maximum two-point LOD score was given by marker D4S2974 (Z = 3.57, alpha = 1). Multipoint analyses of the markers in the region suggest a putative disease gene to be located between markers D4S405 and D4S2381. The maximum multipoint LOD score (Z = 3.76) was given for marker D4S2974 in combination with the novel repeat GT4C2. A family-specific haplotype was segregating with the disease in each of eight families although a founder haplotype could not be identified. Analysis of recombination events in the patients delimited the susceptibility locus to approximately 3 cM. The susceptibility locus identified probably contains a mutation that has been enriched in the Icelandic population but is less common in other populations. We also show that this region is not identical to a susceptibility locus for SLE located on 4p16 where we detect no linkage.

Mannan-binding lectin and complement C4A in Icelandic multicase families with systemic lupus erythematosus.

OBJECTIVE: To determine whether low mannan-binding lectin (MBL) and C4A null alleles (C4AQ0) are associated with systemic lupus erythematosus (SLE) in multicase families with SLE. METHODS: Low MBL level was determined by measuring serum levels and by genotyping for mutant structural (B/C/D, designated as 0) and promoter (LX) alleles (by real-time polymerase chain reaction). C4AQ0 was detected by protein electrophoresis and corroborated with haplotype and genotype analysis. In nine Icelandic families, 24 patients with SLE were compared with 83 first-degree and 23 second-degree relatives without SLE. Twenty four unrelated family members and a population group of 330 Icelanders served as controls. RESULTS: Overall, the frequency of low MBL genotypes (0/0, LX/0 and wild-type/0) tended to be higher in patients with SLE than in their first-degree and second-degree relatives (p = 0.06), but the frequency was similar in the families and in the controls (p = 0.6). The frequency of C4AQ0 was, however, increased in patients and their relatives compared with that in the controls (p = 0.04). The combination of low MBL genotypes and C4AQ0 was found more often in the patients than in their relatives (p = 0.03) and controls (p = 0.02). However, low MBL level was observed only in patients and first-degree relatives in five of the nine multicase families. In these five families, patients with SLE had low MBL genotypes more often (64%) than their first-degree (38%) and second-degree (0%) relatives (p = 0.001), and the patients with SLE also had, accordingly, lower MBL levels than their relatives (p = 0.001). CONCLUSIONS: These findings indicate that low MBL levels can predispose people to SLE and highlight the genetic heterogeneity of this disease.

Risk of malignancy in an unselected cohort of Icelandic patients with systemic lupus erythematosus.

In the present literature there is still controversy as to whether patients with systemic lupus erythematosus (SLE) are at increased risk of developing malignant diseases. In recent years a number of epidemiological studies have been conducted and some have suggested an association between SLE and malignant diseases while other studies have not. The objective of this study was to investigate this relationship in an unselected cohort of Icelandic patients with SLE. All patients diagnosed with SLE registered in the Icelandic SLE database were compared to the Icelandic cancer registry. For completeness, hospital charts and outpatient notes were also reviewed. The study period was from 1957 to the end of 2001. The O/E (observed/expected ratio), CI and P-value were calculated for total number of malignancies as well as individual malignancy types. Of 238 patients diagnosed with SLE (213 women and 25 men) 39 malignancies were diagnosed in 36 patients; 32 women and four men. Of the 36 patients, 27 were diagnosed subsequently with SLE and malignant disease. The mean age at diagnosis of SLE was 43.2 years (range 10-81) and at time of diagnosis of malignancy 62.7 years (range 43-86). The O/R for the whole study population was 1.38 (CI 0.89-1.87, P = 0.063), 1.45 for the women (CI 0.91-1.99, P = 0.051) and 1.03 for the men (CI 0.22-2.66, P = 0.560). The O/R for the most frequent malignancies diagnosed subsequently to SLE was 6.43 for squamous cell skin cancer (CI 1.31-18.5, P = 0.012), 5.48 for lymphoma (CI 0.64-19.6, P = 0.052), 2.46 for uterine cancer (CI 0.29-8.78, P = 0.196), 2.0 for ovarian cancer (CI 0.23-7.14, P = 0.264), 1.72 for lung cancer (CI 0.36-4.95, P = 0.254) and 1.6 for breast cancer (CI 0.65-3.23, P = 0.154). The total number of patient-years at risk was 2774 years. The results from this study on an unselected cohort of Icelandic SLE patients do not suggest an overall association between SLE and malignancy. Squamous cell skin cancer was the only individual cancer type that was statistically increased in the population and the numbers for lymphoma were borderline statistically significant.

Increased T-lymphocyte apoptosis/necrosis and IL-10 producing cells in patients and their spouses in Icelandic systemic lupus erythematosus multicase families.

The objective of this study was to evaluate apoptosis and production of IL-10 in SLE patients, their spouses and first-degree relatives in Icelandic SLE multicase families. Previously, increased IL-10 production has been found in all three groups. As IL-10 has been found to induce apoptosis in SLE, the percentage of lymphocytes undergoing apoptosis was evaluated, as well as the possible correlation between apoptosis and IL-10 production. Apoptosis and IL-10 production were studied in SLE patients (n = 12) from SLE multicase families and their spouses (n = 12) and a matched control group of healthy individuals (n = 10). The proportion of T and B lymphocytes undergoing apoptosis at 0, 24, 48 and 72 h was detected by flow cytometry using Annexin V and PI staining and the rate of apoptosis was calculated. IL-10 production was studied simultaneously by ELISpot analysis of freshly isolated peripheral blood mononuclear cells. In addition, T lymphocyte apoptosis at t = 0 was investigated in a group of non-household first-degree relatives (n = 10) and controls (n = 10). Antinuclear and antilymphocyte antibodies were analysed in all the groups. The SLE patients as a group had a significantly increased percentage of T lymphocytes in apoptosis at 0 and 48 h and a significantly higher number of IL-10 producing cells as compared with the healthy controls (P = 0.03, 0.02 and 0.03, respectively). The spouses also had significantly increased percentage of T lymphocytes in apoptosis (t = 0) and a significantly higher number of IL-10-producing cells when compared with healthy controls (P = 0.01 and 0.02, respectively). There were no significant differences between the patients and their spouses. For apoptosis of B lymphocytes no difference was found between the groups. The SLE patients as a group had the highest rate of apoptosis. No correlation between the degree and rate of apoptosis and the number of IL-10-producing cells was detected. The first-degree relatives did not have increased percentage of T lymphocytes undergoing apoptosis at t = 0 compared with healthy controls. The SLE patients had higher titres of ANA compared with the other groups. No correlation was detected between the ANA titre and the percentage of lymphocytes undergoing apoptosis. There was no correlation between disease activity as measured by SLEDAI and apoptosis. In conclusion, our results suggest that environmental factors common to both SLE patients and their spouses are associated both with the increased apoptosis and increased spontaneous production of IL-10, thus providing support for the notion that both environmental and genetic factors influencing apoptosis are of importance for the development of SLE.

Autoantibody profiles in the sera of European patients with myositis.

OBJECTIVE: To determine the prevalence of myositis specific autoantibodies (MSAs) and several myositis associated autoantibodies (MAAs) in a large group of patients with myositis. METHODS: A total of 417 patients with myositis from 11 European countries (198 patients with polymyositis (PM), 181 with dermatomyositis (DM), and 38 with inclusion body myositis (IBM)) were serologically analysed by immunoblot, enzyme linked immunosorbent assay (ELISA) and/or immunoprecipitation. RESULTS: Autoantibodies were found in 232 sera (56%), including 157 samples (38%) which contained MSAs. The most commonly detected MSA was anti-Jo-1 (18%). Other anti-synthetase, anti-Mi-2, and anti-SRP autoantibodies were found in 3%, 14%, and 5% of the sera, respectively. A relatively high number of anti-Mi-2 positive PM sera were found (9% of PM sera). The most commonly detected MAA was anti-Ro52 (25%). Anti-PM/Scl-100, anti-PM/Scl-75, anti-Mas, anti-Ro60, anti-La, and anti-U1 snRNP autoantibodies were present in 6%, 3%, 2%, 4%, 5%, and 6% of the sera, respectively. Remarkable associations were noticed between anti-Ro52 and anti-Jo-1 autoantibodies and, in a few sera, also between anti-Jo-1 and anti-SRP or anti-Mi-2 autoantibodies. CONCLUSIONS: The incidence of most of the tested autoantibody activities in this large group of European patients is in agreement with similar studies of Japanese and American patients. The relatively high number of PM sera with anti-Mi-2 reactivity may be explained by the use of multiple recombinant fragments spanning the complete antigen. Furthermore, our data show that some sera may contain more than one type of MSA and confirm the strong association of anti-Ro52 with anti-Jo-1 reactivity.

Cytokine production, serum levels and disease activity in systemic lupus erythematosus.

OBJECTIVE: T cell abnormalities, B cell hyperactivity and abnormal cytokine production have been implicated to be of pathogenic importance in systemic lupus erythematosus (SLE). The aim of this study was to investigate if ongoing production and serum levels of type 1 and 2 cytokines reflect disease activity and the presence of organ manifestations. METHODS: Fifty-two SLE patients and 29 healthy individuals were investigated. Blood samples were collected for assessment of anti-ds DNA antibodies, cytokine production and serum cytokine levels. Disease activity was simultaneously assessed using the Systemic Lupus Activity Measure (SLAM) index and SLE Disease Activity Index (SLEDAI). ELISPOT analysis of freshly isolated peripheral blood mononuclear cells (PBMC) was used to estimate the production of cytokines (gamma-interferon (IFN-gamma), interleukin-4 (IL-4), IL-6 and IL-10) using both unstimulated cells and cells stimulated with the T cell mitogen phytohaemagglutinin (PHA). Serum levels of IL-10 were determined using an ELISA method, serum levels of IL-6 were determined using a bioassay and anti-ds DNA antibodies were analysed by immunofluorescence. RESULTS: The SLE patient group had significantly increased numbers of cells spontaneously producing IL-10 and IL-6 as compared to healthy controls (P = 0.01 and 0.03, respectively). The number of cells producing IL-10 and IL-6 after PHA-stimulation was also increased in SLE patients (P = 0.01 and < 0.0004, respectively). Serum IL-10 and IL-6 levels were also significantly increased in SLE patients (P < 0.0004 and 0.0005, respectively). Serum IL-10 levels correlated with the titre of anti-ds DNA antibodies in the patients. No correlation was found between disease activity or clinical profiles and the production or serum levels of cytokines except for a weak correlation (not statistically significant) between levels of IL-10 in the sera and disease activity as measured by the SLEDAI but not by the SLAM index. CONCLUSION: Our results confirm earlier reports that SLE patients have an increased production as well as increased serum levels of the type 2 cytokines IL-10 and IL-6. We found no significant correlation between IL-6 and IL-10 and disease activity or clinical profiles. Serum IL-10 levels correlated with the titre of anti-ds DNA antibodies in the SLE patients. In summary, our result indicate that the increased IL-10 production in SLE could be constitutive.

A study of C4AQ0 and MHC haplotypes in Icelandic multicase families with systemic lupus erythematosus.

OBJECTIVE: To study MHC haplotypes and C4AQ0 in Caucasian multicase systemic lupus erythematosus (SLE) families from Iceland. METHODS: Eight families with 26 SLE patients, 98 non-SLE first-degree relatives, and a control group were studied. For statistical analysis one SLE patient and one first-degree relative were randomly chosen from each family. C4 allotyping was performed by protein electrophoresis, HLA typing of class I by the lymphocytotoxicity test, and typing of class II alleles with polymerase chain reaction with sequence specific primers. RESULTS: Six of the 8 families showed a high background of C4A protein deficiency (C4AQ0) and a significant increase was seen in C4AQ0 in the randomly chosen group of patients. A similar tendency that was statistically nonsignificant was seen in first-degree relatives. In the SLE patients C4AQ0 was found on several MHC haplotypes. Half the patients with C4A protein deficiency carry C4AQ0 on the classical C4A deletion haplotype B8-C4AQ0-C4B1-DR3 or variants of it, and the remaining C4A deficient patients on other non-DR3 carrying haplotypes. The transmission of C4AQ0 from parents to patients was in most cases through the family line, although in some instances it originates from outside the multicase SLE family through spouses married into the family. CONCLUSION: In these Caucasian multicase SLE families from Iceland, C4AQ0 shows weaker linkage disequilibrium with DR3 than reported in studies on other white populations, emphasizing the role of ethnicity. The common factor in the MHC haplotypes studied is C4AQ0, supporting a hypothesis that C4AQ0 may be an independent risk factor for SLE.

Development of lupus-related side-effects in patients with early RA during sulphasalazine treatment-the role of IL-10 and HLA.

OBJECTIVE: The development of systemic lupus erythematosus (SLE)-related syndromes during treatment with sulphasalazine has been described and demonstrated to be influenced by genetic factors. The prevalence of this drug-induced condition and the immunological mechanisms involved are less known. The aim of this study was to determine the prevalence of sulphasalazine-induced lupus-like reactions in a well-defined early rheumatoid arthritis (RA) cohort and to analyse the roles of HLA haplotypes, autoantibodies and the B-cell stimulating cytokine interleukin-10 (IL-10) as possible underlying risk factors. Patients and methods. Forty-one consecutive patients with early RA, in whom sulphasalazine was used as the first disease-modifying anti-rheumatic drug in single therapy and was maintained for at least 6 months, were investigated for the occurrence of lupus-related events. Longitudinal analyses of rheumatoid factor (RF), antinuclear antibodies (ANA), anti-double-stranded DNA antibodies and serum IL-10 (ELISA) and the typing of HLA DR and DQ alleles were performed. RESULTS: Four of the 41 patients developed lupus-like disease. Three of four patients who had lupus-related events vs four of 37 patients without side-effects had an HLA DR 0301 haplotype. The patients developing lupus-related side-effects had increased levels of serum IL-10 and a high frequency of ANA in speckled patterns before the onset of therapy. CONCLUSION: The development of SLE-like symptoms and SLE-related autoantibody production was observed more commonly than expected, with an increased risk in patients with SLE-related HLA haplotypes, increased serum IL-10 levels and ANA in speckled patterns. The data suggest that immunomodulation associated with sulphasalazine treatment may contribute to the development of lupus-related reactions in genetically predisposed individuals.

A susceptibility locus for human systemic lupus erythematosus (hSLE1) on chromosome 2q.

To identify chromosomal regions containing susceptibility loci for systemic lupus erythematosus (SLE), we performed genome scans in families with multiple SLE patients from Iceland, a geographical and genetic isolate, and from Sweden. A number of chromosomal regions showed maximum lod scores (Z) indicating possible linkage to SLE in both the Icelandic and Swedish families. In the Icelandic families, five regions showed lod scores greater than 2.0, three of which (4p15-13, Z=3.20; 9p22, Z=2.27; 19q13, Z=2.06) are homologous to the murine regions containing the lmb2, sle2 and sle3 loci, respectively. The fourth region is located on 19p13 (D19S247, Z=2.58) and the fifth on 2q37 (D2S125, Z=2.06). Only two regions showed lod scores above 2.0 in the Swedish families: on chromosome 2q11 (D2S436, Z=2. 13) and 2q37 (D2S125, Z=2.18). The combination of both family sets gave a highly significant lod score at D2S125 of Z=4.24 in favor of linkage for 2q37. This region represents a new locus for SLE. Our results underscore the importance of studying well-defined populations for genetic analysis of complex diseases such as SLE.

Fine mapping of the SLEB2 locus involved in susceptibility to systemic lupus erythematosus.

We have previously reported linkage of systemic lupus erythematosus to chromosome 2q37 in multicase families from Iceland and Sweden. This locus (SLEB2) was identified by linkage to the markers D2S125 and D2S140. In the present study we have analyzed additional microsatellite markers and SNPs covering a region of 30 cM around D2S125 in an extended set of Nordic families (Icelandic, Swedish, and Norwegian). Two-point linkage analysis in these families gave a maximum lod score at the position of markers D2S2585 and D2S2985 (Z = 4.51, PIC = 0.65), by applying a "model-free" pseudo-marker linkage analysis. Based on multipoint linkage analysis in the Nordic families, the most likely location of the SLEB2 locus is estimated to be in the interval between D2S125 and the position of markers D2S2585 and D2S2985, with a peak multipoint lod score of Z = 6.03, assuming a dominant pseudo-marker model. Linkage disequilibrium (LD) analysis was performed using the data from the multicase families and 89 single-case families of Swedish origin, using the same set of markers. The LD analysis showed evidence for association in the single-case and multicase families with locus GAAT3C11 (P < 0.0003), and weak evidence for association was obtained for several markers located telomeric to D2S125 in the multicase families. Thirteen Mexican families were analyzed separately and found not to have linkage to this region. Our results support the presence of the SLEB2 locus at 2q37.

Genetic analysis of the contribution of IL10 to systemic lupus erythematosus.

OBJECTIVE: To study the contribution of the IL10 gene to the susceptibility to systemic lupus erythematosus (SLE). METHODS: Analysis by fluorescent-semiautomated genotyping of a dinucleotide repeat located in the promoter region of the IL10 locus (microsatellite G). RESULTS: No significant difference was found in the frequencies of the microsatellite alleles of 330 Mexican patients with SLE compared to 368 controls from the same population. Two-point linkage analyses were carried out using 13 Mexican, 13 Swedish, and 8 Icelandic families with 2 or more cases with SLE. No linkage was revealed between IL10 and SLE, using a variety of parameter settings. CONCLUSION: Our results do not support that the IL10 gene contributes to the susceptibility to SLE in the populations we studied.

A comparison of genome-scans performed in multicase families with systemic lupus erythematosus from different population groups.

Systemic lupus erythematosus is a disease of unknown etiology. Multiple genetic factors are believed to be involved in its pathogenesis. In addition, and due to genetic heterogeneity, these factors and/or their combinations may be different in different ethnic groups, while some might be shared between populations. We have performed genome scans in multicase families from three different population groups, two from Northern Europe, with a high degree of homogeneity, and the third from a recently admixed population of Mexican Mestizos. Although our family material is relatively small, the results presented here show that using family sets from well defined populations are sufficient to detect susceptibility loci for SLE. Our results also reveal the chromosomal regions most likely to contain susceptibility genes for SLE.

Increased number of interleukin-10-producing cells in systemic lupus erythematosus patients and their first-degree relatives and spouses in Icelandic multicase families.

OBJECTIVE: To evaluate the production of interleukin-10 (IL-10) as well as levels of IgG and antinuclear antibodies (ANA) in systemic lupus erythematosus (SLE) patients and their first-degree relatives and spouses in Icelandic SLE multicase families. METHODS: IL-10 production was studied by enzyme-linked immunospot assay of freshly isolated peripheral blood mononuclear cells. Total IgG and ANA were also investigated. Subjects consisted of 23 SLE patients and 47 of their first-degree relatives in 9 Icelandic multicase families. Subjects were ethnically matched by a group of healthy controls. A separate study investigated 12 SLE patients (also from SLE multicase families) and their spouses and a matched group of healthy controls. A predefined protocol was used to obtain both clinical and laboratory data, including information about SLE and other autoimmune disorders. RESULTS: The SLE patients had a significantly higher number of IL-10-producing cells compared with both first-degree relatives and healthy controls (P = 0.0005 and P < 0.0001, respectively). First-degree relatives also had a significantly higher number of IL-10-producing cells compared with healthy controls (P = 0.01). This was also true for the spouses of SLE patients, who had a higher number of IL-10-producing cells compared with matched healthy controls (P = 0.02). CONCLUSION: SLE patients and their first-degree relatives, as well as a limited number of healthy spouses of SLE patients, had increased numbers of spontaneous IL-10-producing cells. These data support the hypothesis that IL-10 production may be genetically determined, and may predispose one toward development of SLE. This has previously been suggested by studies of SLE patients and their relatives in another ethnic population, using another method for measuring IL-10 production. Although these data are based on a small number of observations, they suggest that not only genetic but also environmental factors may be of importance in determining IL-10 production, since the spouses of SLE patients also had an increased number of IL-10-producing cells.