Evidence for CTLA4 as a susceptibility gene for systemic lupus erythematosus

Several lines of evidence implicate the Cytotoxic T Lymphocyte Antigen 4 (CTLA4) gene in susceptibility to autoimmune disease. We have examined the association of systemic lupus erythematosus (SLE) with polymorhisms within the CTLA4 gene that were previously proposed to regulate CTLA-4 function: a single nucleotide polymorphism (SNP) in position +49 of exon 1 and a dinucleotide repeat in the 3' untranslated region (3'UTR). The 3'UTR repeat showed a significant association with SLE, with one allele conferring susceptibility and another conferring protection to the disease. The associated alleles do not support previous suggestions of an allele size-dependent effect of the 3' UTR polymorphism in autoimmunity development and instead suggest that it is in linkage disequilibrium with a true causative locus. No association of the exon 1 SNP with SLE was found in our population. Given the conflicting results obtained in different studies on the association of SLE with this polymorphism, we performed a meta-analysis including seven previously published studies and the present one. Significantly increased and decreased risks for SLE were found for carriers of the G allele and the A allele, respectively. The functional characterization of disease-associated CTLA4 gene variants is now required to elucidate their role in the pathogenesis of SLE and other autoimmune diseases.