POLYMORPHISM OF THE TUMOR NECROSIS FACTOR REGION IN RELATION TO DISEASE: AN OVERVIEW

Polymorphisms of Promoter Region of TNF-α Gene in Iranian Azeri Turkish Patients with Behçet's Disease

Behçet's disease (BD) is a complex chronic relapsing inflammatory disorder of unknown etiology. Alterations of the tumor necrosis factor (TNF) expression related to the polymorphic alleles of TNF gene may implicate a pathogenetic role in increased activity of this cytokine in BD. A current study aimed at investigating the possible association between BD and its clinical features in Iranian Azeri Turks with two functional TNF-α gene polymorphisms (at the positions of -238 and -857). A total number of 166 Iranian subjects were enrolled into two different groups; patients with BD (n = 64), and ethnically matched healthy controls (n = 101). The genotype distributions of BD patients and healthy controls were determined. The frequency of TNF-α -857C allele was significantly higher in Behçet's patients than that of healthy controls (P = 0.001; odds ratio [OR] = 2.616; 95% confidence interval [CI] = 1.129-6.160), whereas the frequency of TNF-α -238A allele was similar in both groups. The sole TNF-α haplotype-857C-1031C, was associated with an increase in the risk of developing BD. The TNF-α -857C allele was considerably associated with BD in this cohort. The findings of this study, collectively, indicate that TNF-α -857C-1031C haplotype located in the promoter region of the gene could exert major influence on the susceptibility to BD.

Pro- and anti-inflammatory cytokine gene polymorphism profiles in Bulgarian multiple sclerosis patients

Dysregulation in the expression of pro- and anti-inflammatory cytokines is one of the milestones in multiple sclerosis (MS) development and progression. The aim of this study was to investigate the possible influence of TNF-alpha (-308), TGF-beta (codons 10 and 25), IL-10 (-1082, -819, -592), IL-6 (-174) and IFN-gamma (+874) polymorphisms on susceptibility to multiple sclerosis (MS). Genotyping was performed by PCR-SSP method in 55 MS patients with relapsing-remitting form of the disease and 86 healthy subjects from Bulgarian population. We observed a statistically significant increase in the CC genotype of IL-10 -819 and -592 SNPs coupled with a decreased frequency of the TGF-beta +915 CG genotype in our MS patients (Pc<0.05). No significant differences were observed between MS patients and controls with respect to the distribution of the other cytokine gene polymorphisms investigated. Although the size of the study group is small, these results indicate that polymorphic variations of two of the major anti-inflammatory cytokines, IL-10 and TGF-beta, may play a role in MS susceptibility.

Lack of association of tumor necrosis factor-alpha gene polymorphisms with disease susceptibility and severity in Behçet’s disease

Although it has been reported that the MHC class I molecule, HLA-B51, is a risk factor for Behçet's disease (BD), contribution of the tumor necrosis factor (TNF) genes, which are located in the vicinity of the HLA-B locus, to the genetic susceptibility for BD has yet to be elucidated. The purpose of this study was to analyze the effect of TNF-alpha promoter polymorphisms at positions -308, -238 and -376 on the susceptibility, severity and clinical features of BD. The TNF-alpha gene sequences from 107 patients with BD and 102 healthy subjects were amplified by the polymerase chain reaction. Sequence analysis of the TNF-alpha gene locus, which contains promoter polymorphisms at positions -376, -308, and -238, was performed with a DNA sequencing kit on automated sequencer. The patients were classified according to disease severity and clinical features. Serum TNF-alpha level in the study groups was measured by sandwich enzyme immunoassay. In patients with BD the frequencies of TNF-alpha -308 (19.4% vs 18.4%), -238 (3.7% vs 5.9%), and -376 (0.9% vs 2.9%) gene polymorphisms were not found to be significantly different from those in healthy subjects. The TNF-alpha gene polymorphisms did not show any association with disease severity or clinical features. Serum TNF-alpha level was significantly higher in patients with BD than in healthy controls (3.10 +/- 1.45 pg/ml vs 2.43 +/- 1.94 pg/ml, P < 0.01). Serum TNF-alpha level was not found to be significantly associated with disease severity, activity, clinical findings and TNF-alpha genotypes. The results of this study suggest that the TNF-alpha gene polymorphisms are unlikely to play an important role in the pathogenesis and severity of BD.

The genetic basis for the association of the 8.1 ancestral haplotype (A1, B8, DR3) with multiple immunopathological diseases

An individual's major histocompatibility complex (MHC) ancestral haplotype (AH) is the clearest single determinant of susceptibility to MHC associated immunopathological disease, as it defines the alleles carried at all loci in the MHC. However, the direct effects of any of the 150-200 genes that constitute the MHC are difficult to determine since recombination only occurs at defined hotspots. This review concerns the 8.1 AH (HLA-A1, C7, B8, C4AQ0, C4B1, DR3, DQ2), which is carried by most Caucasians with HLA-B8. It is associated with accelerated human immunodeficiency virus (HIV) disease, and susceptibility to insulin-dependent diabetes mellitus (IDDM), systemic lupus erythematosus, dermatitis herpetiformis, common variable immunodeficiency and IgA deficiency, myasthenia gravis and several other conditions. We have mapped susceptibility genes for HIV, IDDM and myasthenia gravis to the central MHC between HLA-B and the tumour necrosis factor or complement genes. Here we consider which of the remaining 8.1-associated diseases are more closely associated with HLA-DR3 and/or DQ2. Several candidate genes in the central MHC have the potential to modulate immune or inflammatory responses in an antigen-independent manner, as is seen in studies of cultured cells from healthy carriers of the 8.1 AH. Hence these genes may act as a common co-factor in the diverse immunopathological conditions associated with the 8.1 AH.

A promoter polymorphism of tumor necrosis factor alpha associated with systemic lupus erythematosus in African-Americans

OBJECTIVE

The polymorphic tumor necrosis factor alpha (TNFalpha) gene encodes a cytokine involved in inflammation, angiogenesis, and apoptosis. One polymorphic variant is associated with increased production of TNFalpha. This study examined the frequency of this polymorphic variant in African-American patients with systemic lupus erythematosus (SLE) compared with controls.

METHODS

We determined the gene frequency of the polymorphic variant of TNFalpha in an African-American SLE patient population and in a geographically matched African-American control population.

RESULTS

The gene frequency of the TNFalpha -308A polymorphism was higher in the African-American SLE population than in the control population. This relationship was independent of major histocompatibility complex DR alleles.

CONCLUSION

The TNFalpha -308A polymorphism is associated with an increased risk of SLE in African-Americans.

Factors involved in the pathogenesis of HLA-B27 associated arthritis

The role of HLA-B27 in the pathogenesis of ankylosing spondylitis (AS), reactive arthritides (ReA) like Reiter's syndrome (RS) and acute anterior uveitis in unknown. The prevalence of these diseases in B27 positive individuals is five times greater than in the general population. In B27 positive relatives of such patients the prevalence is another ten times greater. In those being HLA-B27/HLA-B60 the prevalence increases again three times. Outside B27 and B60 no other responsible genetic markers have been found, although other factors must play a role to explain the familial preponderance. Since there are no indications that familial exogenous factors are of importance, these are probably genetic. None of the seven subtypes of B27 seems to show a prevalence for these diseases although more studies are urgently needed. This means that probably the so called B pocket in the groove of HLA-B27 molecules, fixing the arginine at position 2 of the peptides which are presented to the receptors of cytotoxic T cells is of pathogenic importance. It is possible that such peptides are derived from or induced by intracellularly proliferating Gram negative bacteria. Indicating these peptides already as arthritogenic and/or uveitogenic is probably too simple. It seems probable that the pathogenetic role of HLA-B27 is that of a common pathway bridging various exogenous factors with several clinical pictures (Figure 1). AAU is mostly unilateral and not always attacking the same eye. Also in B27 associated joint diseases some joints are affected and others not.(ABSTRACT TRUNCATED AT 250 WORDS)

Polymorphism of tumour necrosis factor-alpha (TNF-alpha) at position -308 in relation to ankylosing spondylitis

In addition to HLA-B27, other genetic factors are thought to be involved in the pathogenesis of ankylosing spondylitis (AS). Because of the localization, in the proximity of the HLA-B locus, and the biological activities of TNF-alpha, we investigated the association between AS and a single base polymorphism located at position -308 of the TNF-alpha gene. An allele-specific polymerase chain reaction was developed to monitor this polymorphism. The frequency of the TNF-alpha alleles was determined in 66 AS patients and 37 healthy controls. The TNF-alpha allele frequency was not significantly different between AS patients and controls.