Single nucleotide polymorphisms in the gene encoding the major histocompatibility complex class II transactivator (CIITA) in systemic lupus erythematosus

Background: The major histocompatibility complex (MHC) class II transactivator ( CIITA) is a master switch of antigen presentation and activates expression of the MHC II gene. Insufficient up regulation of MHC class II molecules is reported to be one of the major immunological mechanisms in systemic lupus erythematosus (SLE). Objective: To examine the association between single nucleotide polymorphisms ( SNPs) in the human CIITA gene (MHC2TA) and SLE. Methods: Promoters and coding regions of MHC2TA were evaluated for polymorphisms in 100 patients with SLE and 100 healthy donors. Eight oligonucleotide primer sets that covered the coding region and each promoter region were used for genomic analysis of SNPs. Results: Allele frequencies of previously reported SNPs did not differ between healthy donors and patients with SLE. Additionally, a new polymorphism in an intronic region at nt 485 (ARA/G) was identified, which is close to the polymorphism at nt 474 that has been associated with one of the disease causing CIITA cDNA mutations in bare lymphocyte syndrome. This SNP was found in 11% of patients with SLE and in 3% of healthy donors, suggesting it may have a role in the pathogenesis of SLE. Conclusions: A newly identified polymorphism in an intronic region at nt 485 (A-->A/G) may have an important role in the pathogenesis of SLE.