Increased frequency of the uncommon tumor necrosis factor -857T allele in British and Dutch patients with sarcoidosis

Abstract

Interindividual variation in the expression of tumor necrosis factor (TNF)-alpha suggests the existence of functionally distinct TNF alleles, which might play a role in sarcoidosis. We investigated five potentially functional biallelic TNF promoter polymorphisms at nucleotide positions -1,031(T/C), -863(C/A), -857(C/T), -307(G/A), and -237(G/A) in two clinically well-defined groups of white patients (British [UK] and Dutch [NL]) with sarcoidosis, each with their own control subjects. Polymorphisms were determined using SSP-PCR. A total of 772 individuals were studied (96 UK patients, 354 UK control subjects, 100 NL patients, 222 NL controls). A significant increase in the rarer TNF -857T allele was found in both sarcoidosis populations. In total 25.5% of the sarcoid patients carried the TNF -857T allele versus 14.1% of the control subjects (p = 0.003, p(c) = 0.02). In the sarcoidosis group the allele frequency of this polymorphism was 13.5% versus 7.3% in the control subjects (p = 0.0003, p(c) = 0.002). Subgroup analysis showed a significant increase in the rarer TNF -307A (TNF-2) allele in patients with Löfgren's syndrome (p = 0.006, p(c) = 0.03). Our finding does not necessarily imply that the two polymorphisms relate to different functions; it may be that one or both are in linkage disequilibrium with the causal site. This requires further studies of functionality and linkage disequilibrium.