Promoter region polymorphism in the human TNF-alpha gene is not associated with lichen sclerosus.

The pathogenesis of lichen sclerosus remains unknown. However, it has been frequently associated clinically with autoimmunity. The MHC haplotype A1, B8, DR3 is associated with many autoimmune conditions and has also been associated with the uncommon allele of the tumour necrosis factor (TNF-alpha) promoter polymorphism. This allele is also associated with higher production of TNF in vivo and in vitro, and thus it has been speculated that it is the TNF-alpha gene which underlies the genetic association of many diseases with the autoimmune haplotype. There have been many reports of HLA associations with lichen scleroses, but these have not been concordant. We therefore decided to analyse the TNF-alpha polymorphism in patients with lichen scleroses to determine if TNF-alpha was likely to play a role in susceptibility or severity of lichen scleroses. No association between alleles of the TNF-alpha polymorphism and lichen scleroses was found.

Novel interleukin-1 receptor antagonist exon polymorphisms and their use in allele-specific mRNA assessment.

A variable number of tandem repeats (VNTR) polymorphism has been described in intron 2 of the interleukin-1 receptor antagonist gene. Allele 2 of this polymorphism is associated with many chronic inflammatory diseases. Using direct sequencing of polymerase chain reaction products from individuals of known genotype for the VNTR, we have identified four single base change polymorphisms in exons 1ic and 2 and one upstream of exon 1ic, all of which are probably in linkage disequilibrium with the intron 2 VNTR. The exonic polymorphisms do not alter the encoded amino acid sequence. Using the exon 2 polymorphism as a marker for the intron 2 disease-associated allele, we have been able to analyse allele-specific mRNA in heterozygotic keratinocyte cell lines. The disease-associated allele shows no difference from other alleles in this cell type with respect to mRNA accumulation.

Comparative genetic association of human leukocyte antigen class II and tumor necrosis factor-alpha with dermatitis herpetiformis.

Dermatitis herpetiformis is a chronic subepidermal vesicular autoimmune skin disease characterized by a strong association with the human leukocyte antigen A1-B8-DR3-DQ2 haplotype. Although the strongest major histocompatibility complex association has been shown to be with the DQw2 (DQB1*0201/DQA1*0501) heterodimer, recent evidence has suggested that there may be up to three susceptibility loci within the major histocompatibility complex. Tumor necrosis factor-alpha (TNF-alpha) is a cytokine with a broad range of proinflammatory, immunomodulating, and catabolic activities. We have recently described the first known polymorphism in the human TNF-alpha gene, which is biallelic and lies in the promoter region. The rare allele, TNF2, is in strong linkage disequilibrium with the human leukocyte antigen A1-B8-DR3-DQ2 haplotype. We therefore examined TNF-alpha genotypes in patients with dermatitis herpetiformis and controls and compared the association with that of the class II alleles. Although TNF2 is strongly associated with dermatitis herpetiformis, this was weaker than the association with the class II loci, with DQw2 (DQB1*0201/DQA1*0501) showing the strongest disease association. Of the four patients negative for this marker, only one carried the TNF2 allele. These results indicate that TNF2 is not a major disease susceptibility marker, although our results do not exclude a minor role.

Interleukin 1 receptor antagonist gene polymorphism association with lichen sclerosus.

Cytokines play key roles in immune responses, inflammation and fibrosis. The balance between levels of cytokines, their receptors and specific inhibitors controls inflammatory reactions in tissues. The pathogenesis of lichen sclerosus is unknown but probably involves cytokine mediators such as interleukin 1 (IL-1) and interleukin 1 receptor antagonist (IL-1ra). The IL-1ra is a competitive inhibitor of IL-1 alpha and IL-1 beta, and therefore is a powerful endogenous anti-inflammatory molecule. The gene encoding IL-1ra (designated IL-1RN) has a variable number tandem repeat polymorphism in intron 2. There are five alleles of the gene corresponding to 2, 3, 4, 5 and 6 repeats of an 86-bp sequence. We have determined allele frequencies in a control population and a group of 78 patients with lichen sclerosus. The frequency of one of the alleles is related to increasing disease severity. Thus, IL-1RN may be a candidate gene or severity factor for lichen sclerosus or may possibly be a linked marker to another, as yet undefined, gene.

Severity of alopecia areata is associated with a polymorphism in the interleukin-1 receptor antagonist gene.

One of the most potent pro-inflammatory mediators is the early-acting cytokine interleukin-1. Its actions are regulated by a structurally related anti-inflammatory cytokine known as the interleukin-1 receptor antagonist. We have previously characterized a DNA polymorphism in this gene (IL-1rn) and have found associations between allele 2 and several chronic inflammatory diseases. In the present study, we tested the frequency of allele 2 of the IL-1rn gene in 90 patients with alopecia areata compared with 261 healthy controls. There was a significant association between allele 2 of the polymorphism and the severity of alopecia areata. The frequency of allele 2 increased from 24.1% in the control population to 25.9% in patchy alopecia areata, 36.1% in alopecia totalis, and 47.2% in alopecia universalis (p = 0.005). This severity association is similar to that found in other epithelial-related diseases, including inflammatory bowel disease, lichen sclerosus, and systemic lupus erythematosus.