The −308 polymorphism in the tumour necrosis factor (TNF) gene promoter region and ex vivo lipopolysaccharide‐induced TNF expression and cytotoxic activity in Chilean patients with rheumatoid arthritis

Objective. To investigate the association of the 2308 polymorphism in the promoter region of the tumour necrosis factor (TNF) gene with susceptibility to the development of RA. We also explored the expression and cytotoxicity of TNF in relation to the 2308 polymorphism. Methods. We recruited 92 RA patients and 42 healthy control subjects. Genotyping for the TNF promoter was performed by polymerase chain reaction– restriction fragment length polymorphism analysis. To study the overexpression of TNF we used a whole-blood culture system. TNF cytotoxicity was assessed in the L929 cell line. Results. The TNF2 allele was found in 23% of RA patients and 10% of controls. Although both groups showed high variability in serum TNF concentration, in the lipopolysaccharide-induced TNF level and in the cytotoxicity of the cytokine in the L929 cell line, these differences were not associated with the 2308 TNF polymorphism. Conclusion. No associations were found between the 2308 TNF promoter polymorphism, serum and ex vivo TNF levels and the cytotoxic activity of TNF in RA patients. Rheumatoid arthritis (RA) is a systemic autoimmune disease characterized by chronic inflammation of the synovial joints, hyperplasia and overgrowth of synoviocytes, with ensuing destruction of articular cartilage w1x. Cumulative studies suggest that RA occurs in patients whose genetic background includes multiple common genetic risk factors that have been inherited. The association with the major histocompatibility complex (MHC) DRb1 alleles that share the amino acid sequence at position 70‐74 in the binding groove of the MHC has been well recognized in Caucasian patients with RA. Approximately 30% of the genetic susceptibility to RA has been attributed to these alleles w2x. The importance of the unbalanced production of cytokines such as tumour necrosis factor (TNF), interleukin (IL)-1 and IL-6 in affected tissues and the successful introduction of an anti-TNF monoclonal antibody into therapeutic use have suggested that TNF is involved in the pathogenesis of the disease w3, 4x. It has been suggested that variability in the promoter and coding regions wsingle-nucleotide polymorphisms (SNPs)x of the TNF gene may modulate the magnitude of the secretory response of this cytokine w5‐7x. Numerous studies on the possible functional relevance of these polymorphisms as part of transcriptionally functional motifs have been carried out using transient