Polymorphism within the tumor necrosis factor alpha (TNF) promoter region in patients with ankylosing spondylitis

Lack of association between TNF polymorphism and ankylosing spondylitis susceptibility in HLA-B27-positive population: a meta-analysis

OBJECTIVE

Human leukocyte antigen (HLA)-B27 plays a crucial role in the pathogenesis of AS. TNF polymorphisms have been reported to be associated with AS susceptibility, but the results of these previous studies have been inconsistent. The aim of this study was to explore whether TNF polymorphism is associated with AS susceptibility in HLA-27-positive population.

METHODS

Our search was done in the Pubmed, Embase, and Cochrane databases (up to March 2020). The pooled and individual odds ratios (ORs) with 95% confidence intervals (CIs) of the minor allele of each locus were presented to assess the associations between TNF polymorphisms and AS in HLA-B27-positive population.

RESULTS

Ten studies from 8 articles were included in this meta-analysis. In the population of HLA-B27-positive patients and random healthy controls, there were statistical significance in the evaluation of association between the minor allele of TNF-238, -308, -857, -1031 and -863 and AS susceptibility, respectively. In the population of HLA-B27-positive patients and HLA-B27-positive healthy controls, there were no statistical differences in the comparison of minor allele of with their respective major allele in the fixed model.

CONCLUSIONS

There was no association of the TNF polymorphisms with AS in the HLA-B27-positive AS group and HLA-B27-positive control group. Polymorphisms of TNF-238, -308, -857, -1031, -863 were associated with AS susceptibility in the HLA-B27-positive AS patients and random control population. Other gene SNPs except TNF may play an important role in AS susceptibility in HLA-B27-positive population.

The association of polymorphisms in TNF and ankylosing spondylitis in common population: a meta-analysis

BACKGROUND

Studies investigating the association between the polymorphisms in TNF and ankylosing spondylitis have been reported the conflicting results. Here we performed a meta-analysis based on the evidence available from the literature up-to-date to further clarify this relationship.

METHODS

Our systematic search was done in the PubMed, Embase and Cochrane databases (up to March 2020). The pooled and individual odds ratios (ORs) with 95% confidence intervals (CIs) of the minor allele of each locus were presented to assess the associations between TNF polymorphisms and AS in different ethnicities in common population.

RESULTS

Seventeen studies, consisting of seven European studies, eight East Asian studies and two Latin-American studies, were included in this meta-analysis. In the total population, the A allele in TNF-238 (OR = 0.702, 95%CI = 0.506-0.973, p = 0.034) and TNF-308 (OR = 0.638, 95%CI = 0.507-0.804, p = 0.000), the C allele in TNF-1031 (OR = 0.594, 95%CI = 0.446-0.791, p = 0.000), the T allele in TNF-850 (OR = 3.462, 95%CI = 1.764-6.798, p = 0.000) and rs769178 (OR = 2.593, 95%CI = 2.175-3.091, p = 0.000) were significantly associated with AS susceptibility. There were no significant association between the minor alleles of TNF-376, TNF-857, TNF-863 and AS susceptibility. There are inconsistent results in the Latin-American population and East Asian population with those in the total population.

CONCLUSIONS

Our meta-analysis suggests that TNF-α polymorphisms at positions - 238, - 308, - 850, - 1031 and rs769178 could have an influence on ankylosing spondylitis susceptibility in the total population. But there is no association of the TNF-376, TNF-857, TNF-863 polymorphisms with ankylosing spondylitis. Some results in the subgroups are not consistent with those in the total population.

Tumor necrosis factor-α promoter -308/238 polymorphism association with less severe disease in ankylosing spondylitis is unrelated to serum TNF-α and does not predict TNF inhibitor response

OBJECTIVE

Despite the clinical efficacy of tumor necrosis factor inhibitors (TNFi), the manner in which TNF-α contributes to disease in patients with ankylosing spondylitis (AS) remains unresolved. We investigated the relationship between TNF-α gene promoter region polymorphism, serum TNF-α levels, and clinical phenotype.

METHODS

We did a cross-sectional and longitudinal cohort study in TNFi-naive patients with AS (n = 335). Clinical data and biological samples were collected during a research visit with genotyping for TNF-α -238 A/G and -308 A/G performed by Taqman RT-PCR and TNF levels determined by sandwich ELISA. Longitudinal TNF levels were monitored in unselected patients (n = 61).

RESULTS

TNF-α -308 GA/AA genotype was present in 14% and TNF-α -238 GA/AA genotype in 1% of patients. TNF-α -308 GA/AA genotype was associated with a reduced risk of uveitis and better spinal function, while TNF-α -238 GA/AA genotype was associated with later age of onset and lower erythrocyte sedimentation rate (ESR). Serum TNF-α level was lower in patients with AS (151 pg/ml) than in controls (263 pg/ml), because more patients with AS had undetectable serum TNF-α (66 vs 25%, p < 0.001). TNFi treatment did not influence serum TNF-α. There was no effect of TNF-α -308/-238 or HLA-B27 genotype on serum TNF-α or subsequent initiation of TNFi.

CONCLUSION

TNF-α -238 or -308 GA/AA genotypes in patients with AS are associated with signs of less severe disease. Serum TNF-α is, however, undetectable in two-thirds of patients with AS and is not influenced by TNF-α promoter genotype or TNFi therapy. These data suggest a more significant role for TNF-α at local sites of inflammation in AS than through systemic effects.

The association between tumor necrosis factor alpha promoter polymorphisms and ankylosing spondylitis: a meta-analysis

BACKGROUND

Studies investigating the association between tumor necrosis factor (TNF)-alpha promoter polymorphisms and ankylosing spondylitis have reported conflicting results. We here performed a meta-analysis based on the evidence currently available from the literature to make a more precise estimation of this relationship.

METHODS

We performed a systematic search of the National Library of Medline and Embase databases before January 2013. This meta-analysis included 14 case-control studies, which included 1607 ankylosing spondylitis cases and 1910 controls.

RESULTS

The combined results based on all studies showed that ankylosing spondylitis cases had a significantly lower frequency of -308GA [OR (codominant model)=0.81, 95% CI=0.66, 0.99, P=0.04], -857CT [OR (codominant model)=0.55, 95% CI=0.32, 0.94, P=0.03], -863AA [OR (codominant model)=0.11, 95% CI=0.01, 0.94, P=0.04], -863CA [OR (codominant model)=0.32, 95% CI=0.18, 0.58, P<0.001], and -1031TC [OR (codominant model)=0.44, 95% CI=0.25, 0.77, P=0.004] genotype. However, ankylosing spondylitis cases had a significantly higher frequency of -238AA [OR (recessive model)=7.43, 95% CI=3.66, 15.05, P<0.001] and -850TT [OR (recessive model)=2.49, 95% CI=1.16, 5.34, P=0.02; OR (codominant model)=2.83, 95% CI=1.28, 6.25, P=0.01] genotype. In the subgroup analysis by race, we found that ankylosing spondylitis cases had a significantly higher frequency of -238AA [OR (recessive model)=7.43, 95% CI=3.66, 15.05, P<0.001] genotype in Caucasians and lower frequency of -857CT [OR (codominant model)=0.53, 95% CI=0.30, 0.94, P=0.03] in Asians.

CONCLUSIONS

Our meta-analysis suggests that TNF-alpha promoter polymorphisms at positions -238, -308, -850, -857, -863 and -1031 could have a small influence on ankylosing spondylitis susceptibility. But there is a lack of association of the TNF-alpha-376G/A and -646G/A polymorphisms with ankylosing spondylitis.

Association between transforming growth factor-α polymorphism and ankylosing spondylitis: a meta-analysis update

OBJECTIVES

The reported results of the relationship between genetic polymorphisms of tumor necrosis factor (TNF)-α -238, -308 locus and ankylosing spondylitis (AS) susceptibility are not always consistent. This article aims to perform a meta-analysis to collect all the relevant studies to date to further clarify the relationship between those genetic polymorphisms and AS.

METHODS

A computer search was carried out up to September 2011 for literature pertaining to AS and TNF-α polymorphisms.

RESULTS

Twenty-two articles were included, with 2,506 cases of AS and 3,023 normal controls. We searched for genotypes A allele vs. G allele, AA vs. GG + GA, and GA + AA vs. GG in a fixed/random-effects model. The effect summary odds ratios (ORs) and 95 % confidence intervals (CIs) were obtained, which shows there was no association between genetic polymorphisms and AS. As the heterogeneity was observed, in a subgroup analysis by ethnicity, the degree of risk of two genes with AS susceptibility was similar in populations of European and Asian origin. For the human leukocyte antigen (HLA)-B27+ population, results were not statistically significant.

CONCLUSION

ORs of various comparisons indicate that there is no association between TNF-α -238, -308 polymorphisms and AS susceptibility in the overall population and in the subgroup of Asian and non-Asian descent.

Relation of HLA-B27, Tumor Necrosis Factor-α Promoter Gene Polymorphisms, and T Cell Cytokine Production in Ankylosing Spondylitis — A Comprehensive Genotype-Phenotype Analysis from an Observational Cohort

Objective.

In a pilot study, a distinct T cell cytokine pattern associated with HLA-B27 status and a tumor necrosis factor-α (TNF-α) promoter gene polymorphism was found at –308 (TNF–308). The objective of our study was to assess these associations in a different cohort of patients with ankylosing spondylitis (AS) and to evaluate any effect on clinical measurements.

Methods.

Peripheral T cell cytokine production of patients with AS (n = 121) from the German Spondyloarthritis Inception Cohort was assessed by flow cytometry and correlated with HLA-B27, TNF–238, and TNF–308, and with clinical measurements.

Results.

In HLA-B27-positive, anti-TNF-naive patients with AS, the percentages of TNF-α-producing (5.02%) and interleukin 10-producing (0.31%) CD8+ cells were significantly lower in comparison to HLA-B27-negative patients (9.52%, p = 0.048, and 0.46%, p = 0.037, respectively). A nonsignificant trend was found for a lower production of TNF-α by CD4+ and interferon-γ by both CD4+ and CD8+ T cells, as compared to HLA-B27-negative patients with AS (p > 0.05 for all comparisons). The A allele at TNF–308 was associated with a lower percentage of TNF-α-producing CD4+ T cells. No significant correlations were found between clinical or radiological measurements and cytokine production or with TNF-α promoter gene polymorphisms.

Conclusion.

Modulation of T cell cytokines by HLA-B27 might play a role in AS pathogenesis in B27-positive individuals. No conclusive data were obtained for the TNF–308 polymorphism on cytokine production, and no effect of cytokines or genetic polymorphisms on clinical manifestations was observed.

Polymorphisms of tumor necrosis factor-α promoter region for susceptibility to HLA-B27-positive ankylosing spondylitis in Korean population

This study designed to assess the relationship between tumor necrosis factor (TNF)-α promoter polymorphisms and disease susceptibility to human leukocyte antigen (HLA)-B27-positive ankylosing spondylitis (AS). One hundred and nineteen HLA-B27(+) AS patients, 95 HLA-B27(+) healthy controls, and 135 random healthy controls were enrolled in this study. Six single nucleotide polymorphisms (SNPs) of the TNF-α promoter at positions -1031T/C, -863C/A, -857C/T, -646G/A, -308G/A, and -238G/A were analyzed. Differences between groups were evaluated using the chi-square test or Fisher's exact test. Haplotypes from each SNP were constructed, and differences in haplotypic frequencies between groups were evaluated. There were significant differences in the allelic and genotypic frequencies of 1031T/C, -863C/A, and -857C/T TNF-α promoters polymorphisms between HLA-B27(+) AS patients and random controls, but not between patients with AS and HLA-B27(+) healthy individuals. TNF-α polymorphisms did not influence the extra-spinal clinical features in patients with AS. The haplotypic sequence -1031T/-863C/-857C/-308G increased the risk of susceptibility to AS compared to random controls (P (corr) < 0.001, OR = 2.756, 95% CI = 1.894-4.010), whereas the sequence -1031C/-863A/-857C/-308G appeared to be associated with decreased susceptibility to AS compared to random controls (P (corr) = 0.006, OR = 0.396, 95% CI = 0.231-0.679). This study indicates that TNF-α promoter polymorphism between controls and AS patients with HLA-B27(+) genetic background is not associated with susceptibility to AS. However, TNF-α polymorphism, irrespective of HLA-B27, increases risk of susceptibility to AS in general population.

Association of CTLA4 gene polymorphism in Iranian patients with ankylosing spondylitis

INTRODUCTION

Cytotoxic T-lymphocyte antigen 4 (CTLA-4) is a costimulatory molecule expressed by activated T cells. This study was performed to investigate the allele and genotype frequencies of CTLA4 gene polymorphisms in Iranian patients with ankylosing spondylitis (AS).

METHODS

One hundred and fifty-seven patients with AS and 103 controls were included in this study. Polymorphisms of CTLA4 gene at positions +49 (in exon 1), -318, and -1,147 (in the promoter region) were studied on the genomic DNA using PCR restriction fragment-length polymorphism method.

RESULTS

The frequencies of the T allele at position -1147 in the patients with AS was significantly increased in comparison with the control group (11% vs. 5%, P = 0.004); whereas the frequencies of C allele at the same position were significantly decreased in the patient group (89% vs. 95%, P = 0.004). Comparison of genotype frequencies at this position showed that the frequency of CT genotype in comparison with other genotypes was overrepresented in the patient group (20% vs. 8%, P = 0.012), while the CC genotype in comparison with other genotypes was decreased (79% vs. 91%, P = 0.012). There was no significant difference on frequencies of genotypes at the positions -318 and +49.

CONCLUSION

This study could suggest an association between specific allele in the promoter region of CTLA4 gene and AS disease.

Tumor necrosis factor alpha -308 gene locus promoter polymorphism: an analysis of association with health and disease

Tumor necrosis factor-alpha (TNF-alpha) is a potent immunomediator and proinflammatory cytokine that has been implicated in the pathogenesis of a large number of human diseases. The location of its gene within major histocompatibility complex and biological activities has raised the possibility that polymorphisms within this locus may contribute to the pathogenesis of wide range of autoimmune and infectious diseases. For example, a bi-allelic single nucleotide substitution of G (TNFA1 allele) with A (TNFA2 allele) polymorphism at -308 nucleotides upstream from the transcription initiation site in the TNF-alpha promoter is associated with elevated TNF-alpha levels and disease susceptibilities. However, it is still unclear whether TNF-alpha -308 polymorphism plays a part in the disease process, in particular whether it could affect transcription factor binding and in turn influence TNF-alpha transcription and synthesis. Several studies have suggested that TNFA2 allele is significantly linked with the high TNF-alpha-producing autoimmune MHC haplotype HLA-A1, B8, DR3, with elevated serum TNF-alpha levels and a more severe outcome in diseases. This review discusses the genetics of the TNF-alpha -308 polymorphism in selected major diseases and evaluates its common role in health and disease.

Lack of association of TNF-alpha promoter polymorphisms with ankylosing spondylitis: a meta-analysis

OBJECTIVES

Genetic factors, in addition to the HLA-B27, could play a role in the pathogenesis of AS. TNF-alpha promoter polymorphisms have been reported to be associated with AS susceptibility, but the results of these previous studies have been inconsistent. The aim of this study was to explore whether TNF-alpha promoter polymorphisms confer susceptibility to AS.

METHODS

We conducted a random effect meta-analysis on the association of the A/A genotype (the recessive effect), the A/A + A/G genotype (the dominant effect) and the A allele of the TNF-alpha -308 and -238 polymorphisms with AS.

RESULTS

Eight studies, consisting of seven European studies and one Latin American study, were included in this meta-analysis. Any association between AS and the TNF-alpha -308 A allele was not found [odds ratio (OR) = 0.911; 95% CI 0.512, 1.286; P = 0.636; I(2) = 73.8]. There was also no association of the TNF-alpha -308 AA and AA+AG genotypes with AS. Meta-analysis of the TNF-alpha -238 polymorphisms showed no association with AS (OR for A allele = 0.930; 95% CI 0.498, 1.737; P = 0.821; I(2) = 71.6). Subgroup analysis by ethnicity and HLA-B27 positivity did not change the results for the association of the TNF-alpha -308 and -238 polymorphisms with AS.

CONCLUSIONS

This meta-analysis including 2247 subjects has shown that there is a lack of association of the TNF-alpha -308 A/G and -238 A/G polymorphisms with AS.

Cytokine production from peripheral blood mononuclear cells in patients with ankylosing spondylitis and their first-degree relatives

BACKGROUND

To understand the cytokine levels in different disease activities of patients with ankylosing spondylitis (AS), we measured proinflammatory and antiinflammatory cytokine production from peripheral blood mononuclear cells (PBMC) in patients with AS and their first-degree relatives (FDR).

METHODS

PBMC were obtained from 26 patients with AS and 24 FDR and then stimulated with PHA for 72 h. In the supernatants, the following three cytokines, tumor necrosis factor-alpha (TNF-alpha), interleukin 1beta (IL-1beta), and IL-10, were measured by ELISA. Disease activity in AS patients was divided into high disease activity (Group 1) and low disease activity (Group 2), based on the Bath AS Disease Activity Index (BASDAI > or =4 or <4). Healthy FDR of AS patients (Group 3) and healthy subjects (Group 4) were used as a control group.

RESULTS

TNF-alpha production from PBMC was significantly increased in Group 1 patients compared to Group 2 patients (1371 +/- 1008 pg/mL vs. 355 +/- 89 pg/mL, p <0.05) or FDR (1371 +/- 1008 pg/mL vs. 552 +/- 89 pg/mL, p <0.05) or healthy subjects (1371 +/- 1008 pg/mL vs. 436 +/- 114 pg/mL, p <0.01). IL-1beta also showed a similarly significant difference between the two groups (Group 1 vs. Group 2, Group 1 vs. Group 4) (p <0.05). In contrast, IL-10 was significantly decreased in Group 1 when compared to Group 2 (126 +/- 64 pg/mL vs. 272 +/- 150 pg/mL, p <0.05).

CONCLUSIONS

Patients with high BASDAI had increased production of TNF-alpha and IL-1beta compared to those with low BASDAI or healthy FDR, suggesting that proinflammatory cytokines may play an important role during active inflammation.

Pharmacogenetic of antirheumatic treatments: clinical implications

Preliminary pharmacogenetic data suggest that germline genetic informations might be of value in individualizing disease-modifying antirheumatic drugs (DMARDs) therapy in various autoimmune chronic inflammatory diseases. Either DMARDs small molecules (DMARDs-SM) or DMARDs biological therapies (DMARDs-BT) might be selected for their lower toxicity or better efficacy based on single-nucleotide polymorphisms (SNPs) of genes governing the metabolism of drugs, or the response of immune cells to proinflammatory molecules, or the proinflammatory molecular activity of immune cells. Data available for one DMARDs-SM, methotrexate, suggest that a careful assessment of the SNPs of four enzymes involved in the folate metabolism allow one to construct a genetic index of toxicity (toxicogenetic index) that might be employed in daily practice to find the patient's most at risk. Only the full knowledge of the various gene polymorphisms controlling the phenotypic manifestations of the inflammatory-immunological milieu of each rheumatic disease will allow one to obtain the clear definition of a personalized medicine. Few different cytokine gene SNPs seem to be of importance in determining the susceptibility to diseases, or the aggressiveness of diseases. The role of genetics in affecting a possible clinical response to DMARDs-BT targeting specific inflammatory molecules or their receptors still has to be defined. However, the available data suggest that cytokine (and/or receptors) gene SNPs might indeed play a role in determining the biological effects, hence the clinical effectiveness of DMARDs-BT. Crucial to this aim will be the prospective analysis of clinical benefits and safety on the basis of the at baseline stratification of gene SNPs in each chronic inflammatory rheumatic disease before starting any new DMARDs-SM or DMARDs-BT.

Polymorphisms within the tumor necrosis factor-alpha promoter region in patients with HLA-B27-associated uveitis: association with susceptibility and clinical manifestations

PURPOSE

The existence of genetic variations in a number of cytokines has been considered to influence susceptibility or relate to disease severity in various autoimmune diseases. Among these, single-nucleotide polymorphisms (SNPs) of the tumor necrosis factor alpha (TNF-alpha) promoter at nucleotides -308 and -238 are considered to be protective against inflammation in HLA-B27-positive individuals, whereas the SNP at position -857 has been associated with disease development in anterior uveitis. We investigate a hypothesized association between the TNF-alpha -857 C-to-T, -308 G-to-A, and the TNF-alpha -238 G-to-A SNPs and the presence of HLA-B27-associated uveitis.

DESIGN

Retrospective case-control study.

PARTICIPANTS

One hundred fourteen Caucasian patients with HLA-B27-associated uveitis were studied. Mean age of patients was 44.9+/-14 years (range, 16-81), and mean duration of HLA-B27-associated uveitis was 115.6+/-104 months (range, 6 months-51 years). Eighty-six patients (75.4%) suffered from an additional systemic manifestation of the disease. Sixty-three unrelated healthy HLA-B27-positive blood donors and 88 unrelated healthy HLA-B27-negative individuals served as controls.

METHODS

Genotypes were determined by polymerase chain reaction.

MAIN OUTCOME PARAMETERS

Association of genotypes at positions -857, -308, and -238 of the TNF-alpha gene with disease development.

RESULTS

Frequencies of the TNF-alpha -308GA and TNF-alpha -238GA genotypes were significantly lower in patients with HLA-B27-associated uveitis (6.1% and 0%, respectively) when compared with the HLA-B27-negative control group, 23% at -308 (P = 0.003), and 7.9% at -238 (P = 0.0003). When compared with healthy HLA-B27-positive controls, a significantly lower frequency of the TNF-alpha -238GA genotype was found among patients (6.3%, P = 0.015). The frequency of the TNF-alpha -308GA genotype was also found to be lower in patients than among HLA-B27-positive control subjects, without, however, reaching statistical significance (6.1%, P = 0.07). No difference in frequencies was seen among the different groups for the SNPs at position -857.

CONCLUSION

Our data suggest that HLA-B27-positive individuals show a higher susceptibility towards development of an intraocular inflammation in the presence of an A allele at nucleotide -238 and, to a lesser degree, at nucleotide -308 of the TNF-alpha gene promoter.

Acute anterior uveitis and HLA-B27

Acute anterior uveitis is the most common form of uveitis. HLA-B27-associated acute anterior uveitis is a distinct clinical entity that has wide-ranging medical significance due to its ocular, systemic, immunologic, and genetic features. The association between HLA-B27 and the spectrum of HLA-B27-associated inflammatory diseases remains one of the strongest HLA-disease associations known to date. This review examines acute anterior uveitis with particular focus on HLA-B27-associated acute anterior uveitis, including the epidemiology, immunopathology, association with HLA-B27 and its subtypes, clinical features, complications, prognosis, and potential new therapies such as anti-TNFalpha therapy and oral HLA-B27-peptide tolerance. There have been substantial recent advances in both clinical and basic scientific research in this field, including studies of the various animal models of acute anterior uveitis and the HLA-B27 transgenic animals, and these are summarized in this review. To the ophthalmologist, HLA-B27-associated acute anterior uveitis is an important clinical entity that is common, afflicts relatively young patients in their most productive years, and is associated with significant ocular morbidity due to its typically recurrent attacks of inflammation and its potentially vision-threatening ocular complications. Furthermore, to the ophthalmologist and the internist, HLA-B27-associated acute anterior uveitis is also of systemic importance due to its significant association with extraocular inflammatory diseases.

Inter-individual and intra-individual variability in TNF-alpha production by human peripheral blood cells in vitro

BACKGROUND

Two assays--isolated peripheral blood mononuclear cells (PBMC) and a whole blood assay (WBA)--are commonly used to study TNF-alpha production by an individual in order to distinguish between high and low cytokine producers. We assessed the reliability and reproducibility of these assays.

METHODS

The PBMC assays (n=5) were performed weekly over a period of 6 weeks and the WBAs (n=4) weekly over a 4-week period. Polymethylmethacrylate particles (approx. 6 x 10(2) particles/cell) and optimal concentrations of endotoxin (6.25 and 12.5 ng/ml) were used as the stimulatory agents in PBMC and WBAs, respectively. TNF-alpha production was measured by ELISA.

RESULTS

There was a high degree of both intra- and inter-individual variability of TNF-alpha secretion, with unpredictable changes in the amount of the cytokine produced by cells from the same donor. This variability could not be eliminated by correcting for cell numbers.

CONCLUSION

The PBMC and WBA models of TNF-alpha production by human peripheral blood cells cannot be used for the evaluation of inter-individual variability in cytokine secretion due to the high intra-individual variability observed. In the case of PBMC this is partly due to differences in the confluency of the cells between individuals.

Is there a future for TNF promoter polymorphisms?

The in vitro study of TNF promoter polymorphism (SNP) function was stimulated by the numerous case-control (association) studies of the polymorphisms in relation to human disease and the appearance of several studies claiming to show a functional role for these SNPs provided a further impetus to researchers interested in the role of TNF in their disease of interest. In this review we consider case-control studies, concentrating on the autoimmune and inflammatory diseases rheumatoid arthritis, multiple sclerosis, ankylosing spondylitis, and asthma, and on infectious diseases including malaria, hepatitis B and C infection, leprosy and sepsis/septic shock. We also review the available evidence on the functional role of the various TNF promoter polymorphisms. In general, case-control studies have produced mixed results, with little consensus in most cases on whether any TNF polymorphisms are actually associated with disease, although results have been more consistent in the case of infectious diseases, particularly malaria. Functional studies have also produced mixed results but recent work suggests that the much studied -308G/A polymorphism is not functional, while the function of other TNF polymorphisms remains controversial. Studies of the TNF region are increasingly using extended haplotypes that can better capture the variation of the MHC region.

The role of tumour necrosis factor (TNF-alpha) in experimental autoimmune uveoretinitis (EAU)

The pleiotropic cytokine tumour necrosis factor-alpha (TNF-alpha) is released from cells that include macrophages and T-cells during inflammatory responses, orchestrating the initiation of further leucocytic infiltration via adhesion molecule upregulation, dendritic cell maturation and survival, macrophage activation and driving Th1 T-cells responses within tissues. Exposure to TNF also plays a role in maintaining tissue homeostasis, particularly relating to resident cell responses of both microglia and retinal pigment epithelium. Depending on the balance between duration and dose of TNF exposure, an environment where full expression of inflammatory and autoimmune responses within tissues may occur. In experimental autoimmune uveoretinitis (EAU), increased tissue concentrations of TNF facilitate the on-going T-cell effector responses and macrophage activation. These are responsible for targeted and bystander tissue damage and can be suppressed by anti-TNF therapies, in particular, those directed at the p55 TNF receptor. The ability to suppress disease experimentally has led to the successful translation of anti-TNF therapy for treatment of uveitis in cohort studies and phase I/II trials where, additionally, altered peripheral blood CD4(+) T-cell profiles can be demonstrated following each treatment.

Predisposing factors in the spondyloarthropathies: new insights into the role of HLA-B27

Spondyloarthropathies represent complex genetic diseases whose development is influenced by environmental factors. Estimates suggest that three to nine loci may be responsible for the majority of the genetic susceptibility to ankylosing spondylitis. The only susceptibility locus identified to date in multiple populations is HLA-B, where several HLA-B27 alleles (subtypes) are strongly associated with disease. Recent evidence implicates cytochrome P450 2D6 as a second locus, although its influence on overall risk appears small. Despite considerable efforts to define how HLA-B27 contributes to disease, its role remains enigmatic. Increasing evidence suggests it has effects that are unrelated to its physiologic function. The basis for this is unknown but may be a consequence of the unusual tendency of this allele to misfold.

Cytokine gene polymorphisms relevant for the spondyloarthropathies

Results of sibling and twin studies suggest that a substantial proportion of susceptibility to spondyloarthropathies arises from genes outside the human leukocyte antigen (HLA) region. There is increasing evidence that the pattern of cytokine secretion influences the course of spondyloarthropathies. A Th2 cytokine pattern (low tumor necrosis factor [TNF]-TNF-alpha low interferon [IFN]-gamma, and high interleukin [IL]-10) dominates in the joints of reactive arthritis patients. For IL-10 and TNF-alpha a substantial proportion of cytokine production is under genetic control and influenced by genetic polymorphisms. Here we review the evidences for association of TNF-alpha and IL-10 polymorphisms with spondyloarthropathies and their functional implications.

Allele typing of human TNFA 5'-flanking region using polymerase chain reaction-preferential homoduplex formation assay (PCR-PHFA): linkage disequilibrium with HLA class I and class II genes in Japanese

Tumor necrosis factor alpha plays a substantial role in a number of conditions such as inflammation, autoimmunity, insulin resistance and sleep. Three new single nucleotide polymorphisms, -1,031 T/C, -863 C/A and -857 T/C, were recently identified in the upstream 5'-flanking region of TNFA in the Japanese population. In the present study, we developed polymerase chain reaction (PCR)-preferential homoduplex formation assay for the single-step allele typing of TNFA, and determined the genotypes of 271 healthy unrelated Japanese individuals. Four haplotypes, -1,031/-863/-857 TCC, TCT, CAC and CCC, were found to constitute the majority, if not all, of the TNFA alleles of healthy Japanese population. These alleles were designated as TNFA-U01, -U02 -U03 and -U04, respectively, in the order of frequency. Based on HLA-A, -B and -DRB1 genotypes together with TNFA genotypes, multi-locus haplotypes were analyzed. Significant positive associations were observed between TNFA-U01 and A*3303, B*5201, B*4403, B*4601, B*0702, DRB1*1502, DRB1*0101, DRB1*1302, between TNFA-U02 and B*5401, B*3501, DRB1*0405, DRB1*0407, between TNFA-U03 and B*4006, B*4002, DRB1*0803, DRB1*0802, DRB1*0403, DRB1*0901, and between TNFA-U04 and B*4801. Four-locus haplotype estimation revealed that A*3303-B*4403-TNFA-U01-DRB1*1302, A*2402-B*5201-TNFA-U01-DRB1*1502 and A*2402-B*5401-TNFA-U02-DRB1*0405 constitute major extended haplotypes in Japanese. Interestingly, TNFA alleles previously shown to have a higher promoter activity (U02, U03) were found to form haplotypes with certain DRB1 alleles associated with T helper 1 (Th1)-dominant diseases such as rheumatoid arthritis, insulin dependent diabetes mellitus and Crohn's disease in Japanese. In contrast, TNFA allele with a low promoter activity (U01) is in linkage disequilibrium with the DRB1 alleles associated with T helper 2 (Th2)-dominant diseases such as atopic dermatitis and ulcerative colitis. These observations raise the possibility that TNFA upstream promoter region polymorphisms contribute to some of the HLA-disease associations.

Cytokines and the immunopathology of the spondyloarthropathies

In contrast to rheumatoid arthritis (RA), the triggering antigens are known in reactive arthritis (ReA) and Lyme arthritis. Thus, in these arthritides the antigen-specific T-cell response can be investigated in much detail and lessons possibly learned for other spondyloarthropathies (SpA) such as ankylosing spondylitis (AS) where T cells may well also play an important role in the pathogenesis. This article focusses on the immunopathology of the SpA, ReA, and AS with special reference to T cells and cytokines.