CTLA4 +49 A/G and CT60 polymorphisms in Dutch coeliac disease patients

Coeliac disease is an autoimmune disorder, characterised by villous atrophy of the small intestine, which results from a T-cell-mediated response to gluten-derived peptides. The cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) is involved in the regulation of T-cell activation and the CTLA4 +49 A/G polymorphism in exon 1 has been implicated in several autoimmune disorders, including coeliac disease. However, this polymorphism was recently excluded as being the causal variant in Graves' disease, autoimmune hypothyroidism and type I diabetes mellitus. This causal variant was mapped to the 3' region of CTLA4, with the CT60 polymorphism showing the strongest association. The aim of this study was to determine the role of the CTLA4 gene in coeliac disease in the Dutch population. The +49 A/G and CT60 polymorphisms were genotyped in a case-control cohort of 215 patients and controls. The frequency of the +49 G-allele was increased in cases, although not significantly. However, the frequency of the CT60 G-allele was increased with borderline significance in coeliac disease patients (P = 0.048), although the genotype distributions did not show a significant difference between cases and controls. These results indicate the involvement of the CTLA4 gene in coeliac disease development. The haplotype carrying the CT60 G-allele was shown to be associated with lower mRNA levels of the soluble CTLA-4 isoform, providing a possible mechanism for the T-cell-mediated destruction of the small intestine.