Interferon gamma gene polymorphism and susceptibility to, and severity of, rheumatoid arthritis

Geospatial analysis of the hospitalisation rate of patients with rheumatoid arthritis in Hunan: a cross-sectional Chinese study

OBJECTIVE

Little is known about spatial variability of hospitalisation rate (HR) of patients with rheumatoid arthritis (RA) worldwide, especially in China.

METHODS

A cross-sectional study was conducted among patients with RA admitted to hospitals in Hunan Province. Global Moran's I and local indicators of spatial association were used to explore the geospatial pattern of the HR of patients with RA. Generalised estimating equation analysis and geographically weighted regression were used to identify the potential influencing factors of the HR of patients with RA.

RESULTS

There were a total of 11 599 admissions, and the average HR was 1.57 per 10 000 population in Hunan. We detected different cluster patterns of the HR among patients with RA by local indicators of spatial association. Age, ethnicity, average temperature, average temperature range, average rainfall, regions, gross domestic product per capita, and doctors and hospitals per 10 000 people were risk factors for the HR. However, only average temperature, gross domestic product per capita and hospitals per 10 000 people showed different regression coefficients on the HR in different counties. The increase in hospitals increased the probability of HR from east to west in Hunan with a positive coefficient, while temperature decreases increased the risk of HR from south to north negatively. Similarly, the growth of gross domestic product per capita decreased the probability of HR from southwest to northeast.

CONCLUSION

A non-random spatial distribution of the HR of patients with RA was demonstrated in Hunan, and average temperature, gross domestic product per capita and hospitals per 10 000 people showed different regression coefficients on the HR in different counties. Our study indicated that spatial and geostatistics may be useful approaches for further study among patients with RA.

Temperature might increase the hospital admission risk for rheumatoid arthritis patients in Anqing, China: a time-series study

Temperature has been studied in relation to many health outcomes. However, few studies have explored its effect on the risk of hospital admission for rheumatoid arthritis (RA). A distributed lag non-linear model (DLNM) was used to analyze associations between mean temperature, diurnal temperature range (DTR), temperature change between neighboring days (TCN), and daily admissions for RA from 2015 to 2019 in Anqing, China. Subgroup analyses based on age, gender, rheumatoid factors, and admission route were performed. In total, 1456 patients with RA were hospitalized. Regarding the cumulative-lag effects of extreme cold temperature (5th percentile = 3℃), the risks of admissions for RA were increased and highest at lag 0-11 (RR = 2.68, 95% CI: 1.23-5.86). Exposing to low (5th percentile = 1.9℃) and high (95th percentile = 14.2℃) DTRs both had increased risks of RA admission, with highest RRs of 1.40 (95% CI: 1.03-1.91) and 1.24 (95% CI: 1.0-1.53) at lag 0 day, respectively. As for TCN, the marginal risk of admission in RA patients was found when exposed to high TCN (95th percentile = 2.9℃) with the largest single-day effect at lag 10 (RR = 1.11, 95% CI: 1.01-1.23). In subgroup analyses, females were more susceptible to extreme cold temperature, low and high DTRs, and high TCN. In regard to extreme cold temperature, significant risk of hospital admission in females only appeared at lag 2 (RR = 1.48, 95% CI: 1.02-2.15) and lag 0-2 (RR = 2.35, 95% CI: 1.11-4.95). It is clear that RA patients exposed to changing temperature may increase risks of admission.

Usefulness of Cytokine Gene Polymorphisms for the Therapeutic Choice in Japanese Patients with Rheumatoid Arthritis

Background

Rheumatoid arthritis (RA) is characterized by systemic synovitis with bone erosion and joint cartilage degradation. Although the analysis of polymorphisms in cytokine-encoding genes is important or understanding the pathophysiology of RA and selecting appropriate treatment for it, few studies have examined such single-nucleotide polymorphisms (SNPs) specifically in Japanese patients. This study was established to investigate the associations between polymorphisms in cytokine-encoding genes, autoantibodies and therapeutic responses in Japanese RA patients.

Methods

The subjects in this study consisted of 100 RA patients and 50 healthy controls. We extracted data on sex, age, disease duration, rheumatoid factor (RF), anti-cyclic citrullinated peptide (anti-CCP) antibody, and therapeutic responses, including to methotrexate (MTX) and biological disease-modifying antirheumatic drugs (DMARDs). Genomic DNA was isolated from peripheral blood, which was genotyped for IL-10, TNF-α, TGF-β₁, and IFN-γ polymorphisms.

Results

Regarding IL-10 (−592 C/A and −819 C/T), significant decreases in the frequencies of the IL-10 (−592) CC genotype and (−819) CC genotype were found in RA patients compared with the levels in controls. For IFN-γ (+874 T/A), a significant decrease in the frequency of the TT genotype was found in RA patients compared with that in controls. Regarding TGF-β₁ (+869 T/C), patients with positivity for anti-CCP antibody had a significantly lower frequency of the CC genotype than those with negativity for it. Furthermore, the IL-10 (−592) CC genotype and (−819) CC genotype might be related to the biological DMARD-response.

Conclusion

Our results suggest that the analysis of polymorphisms in cytokine-encoding genes may be useful when selecting treatment for Japanese RA patients.

Are There Any Common Genetic Risk Markers for Rheumatoid Arthritis and Periodontal Diseases? A Case-Control Study

Background

Several studies suggest that there is a biologically plausible connection between rheumatoid arthritis (RA) and periodontal diseases (PD). Both disorders are characterized as multifactorial diseases potentially sharing common risk factors. Based on the inflammatory nature of RA and PD, the impact of genetic variations of genes of the immune system on both diseases was studied in this study.

Materials and Methods

We conducted a case-control study (n = 201) comparing 101 RA patients suffering from periodontal disease of different severities (no/mild PD vs. severe PD) with 100 systemically healthy controls without RA and severe PD. The genotype, allele, and haplotype distributions of 22 SNPs of 13 pro- and anti-inflammatory cytokines were assessed applying sequence-specific PCR.

Results

Evaluating the impact of cytokine SNPs in RA, we identified the G allele of rs1801275 in IL4Rα (p = 0.043) and the G allele of rs361525 in TNFα (p = 0.005) as disease-associated risk factors in bivariate analyses. In multivariate analyses, these significant associations could not be proven. The A allele of rs2430561 in IFNγ was indicative for severe periodontitis among the patients with rheumatoid arthritis (p = 0.039). Investigating the impact of rs2430561 in IFNγ on comorbidity using binary logistic regression analyses, the A allele was confirmed as an independent risk factor for severe periodontal disease and RA (p = 0.024).

Conclusions

These results emphasize the association of genetic variations in proinflammatory cytokines (TNFα and IFNγ) and cytokine receptor (IL4Rα) and RA and periodontal diseases. In multivariate analyses, the A allele of IFNγ was proven to be a significant marker of RA and PD comorbidities. The study broadens the knowledge about disease-specific differences in genetic composition and provides an improved understanding of a possible association of both diseases.

Analysis of the interferon gamma (rs2430561, +874T/A) functional gene variant in relation to the presence of cardiovascular events in rheumatoid arthritis

OBJECTIVE

Rheumatoid arthritis (RA) is a chronic inflammatory disease associated with increased cardiovascular (CV) morbidity and mortality. Since interferon-gamma (IFN-γ) has a direct effect on inflammation, in this study we assessed the potential association of the IFNG functional gene variant rs2430561 with CV disease in patients with RA.

METHODS

One thousand six hundred and thirty-five patients fulfilling the 1987 American College of Rheumatology classification criteria for RA were genotyped for the IFNG (rs2430561, +874T/A) gene polymorphism using TaqMan genotyping assay. Patients were stratified according to the presence of CV events or not. Logistic regression models to explain the presence of CV disease according to the IFNG rs2430561 allele distribution were performed. The potential influence of this variant in the development of subclinical atherosclerosis was also analyzed in a subgroup of patients with no history of CV events to determine carotid artery intima-media thickness (IMT) (n = 286) and presence of carotid plaques. Levels of the cytokine were determined in a subgroup of patients by ELISA.

RESULTS

Adjusted logistic regression model disclosed that presence of the minor allele A was not associated with increased risk of suffering CV events in RA patients. Besides, differences did not achieve statistical significance regarding carotid IMT and presence of carotid plaques in RA patients carrying IFNG rs2430561 variant allele. Levels of IFN-γ were higher in patients who had suffered CV events compared to patients who did not.

CONCLUSION

Our results do not support a role of IFNG rs2430561 (+874T/A) functional gene variant in the development of CV disease in RA patients.

Analysis of genetic variants of class II cytokine and their receptor genes in psoriasis patients of two ethnic groups from the Volga-Ural region of Russia

BACKGROUND

The molecular basis of pathogenesis of psoriasis remains unclear, but one unifying hypothesis of disease aetiology is the cytokine network model. The class II cytokines (CF2) and their receptors (CRF2) are all involved in the inflammatory processes and single nucleotide polymorphisms (SNPs) in respective genes have been associated with psoriasis in a previous study of the Estonian population.

OBJECTIVE

We performed a replication study of 47 SNPs in CF2 and CRF2 genes in independent cohorts of psoriasis patients of two ethnic groups (Russians and Bashkirs) from the Volga-Ural region of Russia.

METHODS

DNA was obtained from 395 psoriasis patients of two ethnic groups from the Volga-Ural region of Russia and 476 ethnically matched controls. 47 SNPs in the loci of the genes encoding Class II cytokines and their receptors were selected by SNPbrowser version 3.5. Genotyping was performed using the SNPlex™ (Applied Biosystems) platform.

RESULTS

The genetic variant rs30461 previously associated in original case-control study in Estonians, was also associated in Russians (corrected P-value (Pc=0.008, OR=0.44), but did not reach statistical significance in the Bashkir population. Additionally, the haplotype analysis provided that CC haplotype formed by the SNPs rs30461 and rs955155 had a protective effect in Russians (Pc=0.0024, OR=0.44), supporting the involvement of this locus in the protection against psoriasis. Combined meta-analysis of three populations, including 943 psoriasis patients and 812 healthy controls, showed that the IL29 rs30461 C-allele was not associated with decreased risk of psoriasis (P=0.165, OR=0.68). Moreover, stratification of studies by ethnicity revealed a significant association in the European cohort (P=9.506E-006, OR=0.53).

CONCLUSION

Therefore, there is no overall evidence of association between psoriasis and SNP rs30461 of the IL29 gene, but there is some evidence to suggest that an association exists in Europeans. However, this current concept should be considered as preliminary and the results need to be confirmed in future independent studies.

Collagen-induced arthritis as an animal model for rheumatoid arthritis: focus on interferon-γ

Rheumatoid arthritis (RA), an autoimmune disease causing inflammation, destruction, and deformity of the joints, affects around 1% of the world population. It is a systemic disease as patients exhibit extra-articular manifestations as well. Collagen-induced arthritis (CIA) in DBA/1 mice is one of the many animal models used to study possible pathogenic mechanisms of RA. It involves immunizing mice with collagen type II in complete Freund's adjuvant. Here we briefly review the general characteristics of RA and CIA and present an overview of data obtained by studying CIA in several gene knockout mice. In particular, detailed analysis of CIA in interferon-gamma (IFN-γ) receptor-deficient mice has pin-pointed IFN-γ as an important cytokine in the pathogenesis and has exposed new functions of IFN-γ in immunological processes. Pilot trials with exogenous IFN-γ in RA have been indicative of a beneficial effect. That improvement of the disease symptoms by IFN-γ treatment was not spectacular may be explained by the fact that RA is a heterogeneous disease in which the severity of the autoimmune disease is strongly determined by environmental factors.

Interleukin-18 promoter polymorphisms in Japanese patients with rheumatoid arthritis: protective effect of the T allele and T/T genotype at rs360722

Rheumatoid arthritis (RA) is a chronic inflammatory disease with a strong genetic contribution to its pathogenesis. Among numerous candidate genes, cytokine gene polymorphisms have been implicated. Interleukin-18 (IL-18) induces production of tumor necrosis factor-α and promotes T helper (Th)1-type immune responses. This study investigates the association between IL-18 promoter polymorphisms and RA susceptibility. A total of 2471 Japanese case-control samples (1493 RA patients and 978 healthy controls) were examined. Three haplotype tag single-nucleotide polymorphisms, rs1946518A/C, rs360718T/G, and rs360722T/C, spanning from the 5'UTR to intron 1 were genotyped using allelic discrimination with the use of specific TaqMan probes, and three haplotypes (A-T-T, C-T-C, and A-G-C) were determined. Among these polymorphisms, the frequency of the T allele at rs360722, which tags the A-T-T haplotype, was significantly lower in the RA patient group compared with the normal subjects [0.46 versus 0.49, P = 0.0061, Fisher's exact probability test, odds ratio (OR) = 0.85, 95% confidence interval (CI) = 0.75-0.95]. Having the T/T genotype further increased the significance (0.20 versus 0.27, P = 0.0006, OR = 0.72, 95% CI = 0.58-0.86). Therefore, presence of the T allele and T/T genotype at rs360722 reduces the susceptibility of Japanese people to RA.

Correlation of a multi-cytokine panel with clinical disease activity in patients with rheumatoid arthritis

OBJECTIVE

Explore the potential use of a cytokine panel as biochemical markers of disease activity in rheumatoid arthritis (RA) patients.

DESIGN AND METHODS

57 adult RA patients were assessed using five validated clinical disease activity tools: Health Assessment Questionnaire (HAQ), standard 28-joint Disease Activity Score (DAS28), DAS28 using C-reactive protein (DAS28-CRP), Clinical Disease Activity Index (CDAI), and Simple Disease Activity Index (SDAI). Plasma cytokine levels (IL-2, IL-4, IL-6, IL-8, IL-10, VEGF, IFN-γ, TNF-α, IL1α, IL1β, MCP1, and EGF) were measured in 47 of the 57 patients and correlated with clinical indicators.

RESULTS

We found significant correlations between plasma levels of IL-6 and all clinical measures of disease activity; Spearman coefficients (p values) were: HAQ: 0.347(0.017); DAS28: 0.409(0.005); DAS-CRP: 0.378(0.011); CDAI: 0.312(0.033); SDAI: 0.310(0.039); ESR: 0.448(0.002); and CRP: 0.513(0.001). IFN-γ also correlated with DAS-CRP: 0.309(0.039) and SDAI: 0.301(0.044). Furthermore, the levels of IL-6 and IFN-γ increased significantly with worsening disease, as defined by the European League Against Rheumatism (EULAR) classification of disease activity.

CONCLUSION

A significant correlation between plasma levels of IL-6 and clinical disease activity in patients with RA suggests a future role of IL6 as a disease activity marker.

Relationships between specific serum IgE, IgG, IFN-gamma level and IFN-gamma, IFNR1 polymorphisms in patients with penicillin allergy

OBJECTIVE

The findings of numerous studies have suggested that both genetic and environmental influences are involved in the pathogenesis of allergic disease and atopy. We studied the polymorphisms in the interferon (IFN)-gamma (gamma) and IFN-gamma receptor 1 (IFNR1) gene with the aim of clarifying the relationships among these polymorphisms, penicillin allergy and anti-penicillin antibodies.

METHODS

A restriction endonuclease fragment length polymorphism (RFLP)-PCR analysis and sequencing were used to study the IFNR1 and IFN-gamma polymorphisms. The presence and level of eight specific immunoglobulin (Ig)E and IgG antibodies were determined by the radioallergosorbent test (RAST) and enzyme-linked immunosorbent assay (ELISA), respectively.

RESULTS

The positive rates of specific IgE and IgG were 61.11 and 53.92%, respectively. There was no significant difference in the whole-allele of IFN-gamma distribution between patients with a penicillin allergy and control subjects. Allele 7 (18CA repeat) was significantly less frequent in the urticaria group (3.19 vs. 11.93%) than in the controls. There was no difference in IFN-gamma production among different alleles in IFN-gamma. The frequency of G/A (Val/Met) in the IFNR1 gene in allergic patients was significantly less than that in the controls (P < 0.05). There were no significant differences in the positive rate of IgE among different alleles of IFN-gamma. The same was true for the positive rate of IgG.

CONCLUSIONS

The Met/Val allele in IFNR1 gene may have a protective role in the non-penicillin allergic population. The allele 18CA repeat in IFN-gamma gene may be associated with urticaria.

Disease association of two distinct interleukin-18 promoter polymorphisms in Caucasian rheumatoid arthritis patients

Interleukin (IL)-18 is an important mediator of innate and adaptive immunity. We searched for an association of IL-18 promoter single-nucleotide polymorphisms (SNP) with rheumatoid arthritis (RA) in Caucasians. The entire study population was composed of two independent cohorts from Germany (n=200) and Scotland (n=410). Presence of IL-18 SNP at positions -607 and -137 was determined by allele-specific PCR in 327 RA patients and 283 healthy donors (HD). Diplotype distributions of both loci were in Hardy-Weinberg equilibrium (HWE) in the German and Scottish HD cohorts. In contrast, locus -607 was in HW disequilibrium in German, and locus -137 in Scottish RA patients. Diplotypic exact chi(2) tests suggested that -607CC was overrepresented in German, and -137CC in Scottish RA patients, but conservative chi(2) trend analyses could not prove any significant disease association of these single loci. SNP -607 and -137 were in strong linkage disequilibrium. The -607C(*)-137C haplotype was more prevalent in German RA (3.2 vs 1.2%) and in Scottish RA patients (4.1 vs 0.9%) than in the respective HD cohorts. These observations suggest that SNP of both positions contribute to the genetic background of RA pathogenesis.

Genetic variations in IL6 associate with intervertebral disc disease characterized by sciatica

Intervertebral disc disease (IDD) characterized by sciatica is a common disorder affecting about 5% of individuals. Environmental factors can predispose to this disease, but IDD has a strong genetic background. Recent evidence suggests that inflammation is one of the key factors in the etiology of IDD. Here, a possible role of the inflammatory mediator genes was studied in 155 patients with IDD-related sciatica and 179 controls. Forty-eight patients were analyzed for mutations in the IL1A, IL1B, IL6 and TNFA genes, and 16 polymorphisms in 10 candidate cytokine genes (IL1A, IL1B, IL1RN, TNFA, IL2, IL4, IL4R, IL6, IL10, IFNG) were genotyped from all subjects. No disease-causing mutations were identified in IL1A, IL1B, IL6 or TNFA. Allele frequencies were, however, significantly different between the two groups for IL6 SNP, T15A in exon 5 (P=0.007). Furthermore, the genotypes AA and AT of the exon 5 SNP were more common in the patients (P=0.011; OR=4.4, 95% CI=1.2-15.7; AR=7.5%, 1.6-13.1%). Haplotypes were then generated for four IL6 SNPs, G-597A, G-572C, G-174C, and T15A in exon 5. Haplotype GGGA was more common in the patients (P=0.011; OR=4.8, 95% CI=1.6-14.5). To evaluate attributable risk, haplotype pairs were assigned for the individuals. The presence of GGGA/GGGA or GGGA/other genotypes had an OR of 5.4 (95% CI=1.5-19.2). Association of GGGA with disease was highly significant (P=0.0033), and the associated AR was 6.8% (1.9-11.5%). These findings support the role of IL-6 genetic variations in discogenic pain.

Polymorphisms in the genes encoding interferon-gamma and interferon-gamma receptors in multiple sclerosis

Genome screens suggest that several genes, each contributing to a small extent, are involved in multiple sclerosis (MS) susceptibility. Simultaneous analysis of related genes may improve the power to detect such small effects. Interferon-gamma (IFN-gamma), mediating its effects through the IFN-gamma receptor, is a pleiotropic, pro-inflammatory cytokine for which a detrimental effect on the course of MS has been reported. The role of IFN-gamma receptor 1 (IFNGR1) and IFN-gamma receptor 2 (IFNGR2) gene polymorphisms has not been studied in MS, and, for the IFNG gene polymorphism there is only one previous study, which incorporates clinical, but not imaging, data. The aim of this study was to investigate whether polymorphisms in the IFNG and IFNGR1 and IFNGR2 genes are associated with susceptibility to MS, or disease characteristics, as defined by clinical and imaging criteria. Genotypes for IFNG, IFNGR1 and IFNGR2 were determined in 509 patients with MS and in 193 healthy controls. Patient files were reviewed for disease course, age at onset of disease, and rate of progression. Serial magnetic resonance imaging (MRI) data were available for 107 patients. No significant differences in the distribution of IFNG, IFNGR1 and IFNGR2 genotype and allele frequencies were found between patients and controls. A progressive, as opposed to a relapsing, onset was significantly more frequent in carriers of the IFNGR2 allele Arg64 (P = 0.028). Moreover, IFNGR2 allele Arg64 carriers had a lower black hole ratio than non-carriers (P = 0.016). No other associations with clinical parameters, such as age at onset or rate of progression, or with imaging parameters, were observed. The IFNG intron 1 gene polymorphism studied is unlikely to play a major role in MS susceptibility or disease course. The IFNGR1 and IFNGR2 gene polymorphisms studied do not exert an important influence on MS susceptibility, but allele IFNGR2*Arg64 may be associated with a progressive disease onset.

Approaches to identifying genetic predictors of clinical outcome in rheumatoid arthritis

Predicting which patients with rheumatoid arthritis (RA), at presentation, are likely to suffer a severe disease course based on genotype data would be a major clinical advance. It would ensure that patients at highest risk of a severe outcome could be targeted with early aggressive therapies. With a better understanding of interactions between genotype and drug response it would be possible to prescribe treatments most likely to be efficacious and safe for specific patient subgroups. While a clear genetic component has been demonstrated in RA severity, the identification of genetic factors poses a challenge to researchers in the field. Initiatives such as the SNP Consortium and advances in genotyping technology have facilitated the investigation of genetic factors in both disease susceptibility and severity. However, several other factors, such as the availability of suitable longitudinal cohorts, definition of outcome measures, study design, selection of genetic markers, and statistical power, will all contribute to the likely success of genetic studies. Several strategies that have been applied in the pursuit of genetic predictors of clinical outcome in RA. While some encouraging results have been generated, it has so far been difficult to quantify the predictive value of genetic markers and extrapolate the results from genetic studies to clinic patients. Establishing high quality prospective inception cohorts, a more systemic approach to defining suitable outcome measures, and understanding the effects of treatment, will be critical to the eventual identification of good predictive genetic markers.

IFN-gamma polymorphisms (IFN-gamma +2109 and IFN-gamma +3810) are associated with severe hepatic fibrosis in human hepatic schistosomiasis (Schistosoma mansoni)

Schistosome infection is a major public health concern affecting millions of people living in tropical regions of Africa, Asia, and South America. Schistosomes cause mild clinical symptoms in most subjects, whereas a small proportion of individuals presents severe clinical disease (as periportal fibrosis (PPF)) that may lead to death. Severe PPF results from an abnormal deposition of extracellular matrix proteins in the periportal spaces due to a chronic inflammation triggered by eggs and schistosome Ags. Extracellular matrix protein production is regulated by a number of cytokines, including IFN-gamma. We have now screened putative polymorphic sites within this gene in a population living in an endemic area for Schistosoma mansoni. Two polymorphisms located in the third intron of the IFN-gamma gene are associated with PPF. The IFN-gamma +2109 A/G polymorphism is associated with a higher risk for developing PPF, whereas the IFN-gamma +3810 G/A polymorphism is associated with less PPF. The polymorphisms result in changes in nuclear protein interactions with the intronic regions of the gene, suggesting that they may modify IFN-gamma mRNA expression. These results are consistent with the results of previous studies. Indeed, PPF is controlled by a major locus located on chromosome 6q22-q23, closely linked to the gene encoding the alpha-chain of the IFN-gamma receptor, and low IFN-gamma producers have been shown to have an increased risk of severe PPF. Together, these observations support the view that IFN-gamma expression and subsequent signal transduction play a critical role in the control of PPF in human hepatic schistosome infection (S. mansoni).

Complex genetic predisposition in adult and juvenile rheumatoid arthritis

Background

Rheumatoid arthritis (RA) and juvenile rheumatoid arthritis (JRA) are complex multifactorial diseases caused by environmental influences and an unknown number of predisposing genes. The present study was undertaken in order to investigate association of polymorphisms in candidate genes with RA and JRA in German subjects.

Results

Up to 200 unrelated German RA and JRA patients each and 300–400 healthy controls have been genotyped for HLA-DRB1, TNFa, TNFA -238a/g, TNFA -308a/g, TNFA -857c/t, TNFR1 -609g/t, TNFR1 P12P, TNFR2 del 15bp, IKBL -332a/g, IKBL -132t/a, IKBL C224R, CTLA4 -318c/t, CTLA4 T17A, PTPRC P57P, MIF -173g/c, the MIF and IFNG microsatellites as well as for D17S795, D17S807, D17S1821 by polyacrylamide gel electrophoresis, single-strand conformation polymorphism analysis, restriction fragment length polymorphism analysis or allele specific hybridization. None of the investigated genetic markers is associated with both, RA and JRA, but there are some statistically significant differences between patients and controls that have to be discussed sensibly.

Conclusions

The difficulty in investigating the genetics of complex disorders like RA and JRA may arise from genetic heterogeneity in the clinically defined disease cohorts (and generally limited power of such studies). In addition, several to many genes appear to be involved in the genetic predisposition, each of which exerting only small effects. The number of investigated patients has to be increased to establish the possibility of subdivison of the patients according their clinical symptoms, severity of disease, HLA status and other genetic characteristics.

Polymorphisms in the interferon-γ/interleukin-26 gene region contribute to sex bias in susceptibility to rheumatoid arthritis

OBJECTIVE

To determine whether polymorphisms in the interferon-gamma (IFNgamma)/interleukin-26 (IL-26; formerly, AK155) gene cluster contribute to sex-based differential susceptibility to rheumatoid arthritis (RA).

METHODS

Four microsatellite markers, located in a 118-kb interval that contains both the IFNgamma and IL-26 genes on chromosome 12q15, were typed in 251 patients with RA and 198 unrelated healthy controls (all of whom lived in Northern Ireland) by means of polymerase chain reaction-based fragment analysis.

RESULTS

Marker D12S2510, which is located 3 kb 3' from the IL-26 gene, was significantly associated with RA in women (corrected P [P(corr)] = 0.008, 2 degrees of freedom [2 df]) but not in men (P = 0.99, 2 df). A 3-marker haplotype, IFNGCA*13;D12S2510*8;D12S2511*9, was inferred that showed significant underrepresentation in women with RA (odds ratio 0.50, 95% confidence interval 0.32-0.78; P = 0.002, P(corr) = 0.03) but not in men with RA.

CONCLUSION

Our results demonstrate that common polymorphisms in the IFNgamma/IL-26 gene region may contribute to sex bias in susceptibility to RA, by distorting the propensity of female carriers versus male carriers to contract this disease. These results conform to our recent observations of a role for this gene cluster in sex-based differential susceptibility to another Th1-type inflammatory disease, multiple sclerosis.

Genomic analysis of Th1-Th2 cytokine genes in an AIDS cohort: identification of IL4 and IL10 haplotypes associated with the disease progression

Polymorphisms of Th1-Th2 cytokine genes have previously been implicated in the rate of progression to AIDS in seropositive patients. To evaluate further the impact of these genes in the development of AIDS, we have performed an extensive genetic analysis of IL2, IL4, IL6, IL10, IL12p35 and p40, IL13 and IFNgamma. The coding regions and promoters of these genes were sequenced in a Caucasian cohort of 337 HIV-1 seropositive extreme patients (the GRIV cohort) consisting of patients with slow progression and rapid progression, and up to 470 healthy controls. In all, 64 single nucleotide polymorphisms (SNPs) and four deleterious polymorphisms with frequency >1% were identified and evaluated for their association with disease. Statistically significant associations were observed with haplotypes of the IL4 and IL10 genes, but no relation was found with variants of other genes. The catalogue of SNP and haplotypes presented here will facilitate further genetic investigations of Th1-Th2 cytokines in AIDS and other immune-related disorders.

Genetic epidemiology of rheumatoid arthritis

Building on the spectacular success of molecular genetics in defining the biological basis of many rare single gene disorders over the past decade, epidemiologists have turned their attention to unravelling the complex genetic mysteries of common disorders, such as rheumatoid arthritis (RA). As a prelude to any such endeavour it is obviously important to establish that there is a significant genetic component to the disease. The classical approaches of twin and other family recurrence risk studies, coupled with prevalence studies in different ethnic and migrant populations, have been used to estimate the environmental and genetic contributions to RA. However, developing a consensus on these estimates has proved difficult, thereby providing an early warning to the unwary investigator that the road to gene discovery in RA is likely to be a rough ride.