HLA-G genotype and HLA-G expression in systemic lupus erythematosus: HLA-G as a putative susceptibility gene in systemic lupus erythematosus

Genetic variants in the HLA-G region are associated with Kawasaki disease

Kawasaki disease is an acute, self-limited vasculitis of infants and children, manifest as fever and signs of mucocutaneous inflammation. Treatment with high-dose immunoglobulin reduces systemic inflammation and prevents coronary artery lesions in Kawasaki disease. In this study, we investigated the possible association of the major histocompatibililty complex (MHC) region for the susceptibility to Kawasaki disease using an MHC panel of 2360 single nucleotide polymorphism (SNP) markers. Analysis of data obtained from screening MHC-specific SNP chips with 48 case and 90 control subjects revealed five candidate loci with significance levels of uncorrected p < 0.01. However, only one candidate locus (HLA-G) was confirmed to have a significant association with Kawasaki disease (rs2523790, odds ratio [OR] = 3.00, 95% confidence interval [95% CI] = 1.14-7.91, uncorrected p = 0.0263) in the replication study using 44 new case subjects and the previous 90 controls. In the fine mapping of the HLA-G locus, in particular, a nonsynonymous SNP (C/A) of the HLA-G gene (rs12722477, Leu134Ile) was significantly associated with Kawasaki disease (OR = 3.23, 95% CI = 1.12-9.32). A subgroup analysis showed that this association was more apparent in patients with coronary artery aneurysms (OR = 4.02, 95% CI = 1.23-13.19). Therefore, our results indicate that HLA-G may play a crucial role for the susceptibility to Kawasaki disease.

The 14 bp deletion polymorphisms in HLA-G gene play an important role in the expression of soluble HLA-G in plasma

Soluble human leukocyte antigen-G (sHLA-G) functions as a multiple immunoregulator. A 14 bp insertion (+14 bp)/deletion (-14 bp) polymorphism in exon 8 of the HLA-G gene has been proposed to be associated with HLA-G mRNA stability and the expression of HLA-G. In the current study, a total of 150 normal Chinese Han population had been genotyped for the +14 bp/-14 bp polymorphism, and the expression of plasma sHLA-G was determined with enzyme-linked immunosorbent assay in these case-matched plasma. Data showed that genotype of 14 bp polymorphism was significantly associated with sHLA-G expression. Plasma sHLA-G level with the +14 bp/+14 bp genotype was dramatically lower than that with +14 bp/-14 bp (P = 0.004) and -14 bp/-14 bp genotypes (P = 0.003), while no dramatic difference was observed between the +14 bp/-14 bp and -14 bp/-14 bp genotypes (P > 0.05). In both males and females, plasma sHLA-G with the +14 bp/+14 bp genotype was also significantly lower when compared with other two respective 14 bp genotypes. Data also showed that sHLA-G expression was unrelated to gender. This study suggests that the 14 bp deletion polymorphism in the HLA-G gene plays an important role in sHLA-G expression and that interpretation of the potential biological functions of sHLA-G should be made with caution, taking the polymorphism into consideration.