Abstract: Wen Sijian*, Wu Feiyun, Lin Youkun, Fang Ling. *Department of Dermatology and Venereology, First Affiliated Hospital of Guangxi Medical University, Nanning 530021, China Corresponding author: Lin Youkun, Email: linyoukun7@aliyun.com 【Abstract】 Objective To assess the association between Toll-like receptor 9 （TLR9） gene single nucleotide polymorphisms （SNPs） and systemic lupus erythematosus （SLE） development in Guangxi Zhuang and Han populations, as well as the difference in TLR9 SNPs between the two populations. Methods Totally, 41 SLE patients of Zhuang nationality and 56 of Han nationality, as well as 82 healthy checkup examinees of Zhuang nationality and 120 of Han nationality were enrolled in this study. Venous blood samples were obtained from all of these subjects and subjected to DNA extraction. The single nucleotide polymorphisms in TLR9 gene were detected by PCR-restriction fragment length polymorphism（PCR-RFLP） analysis followed by direct sequencing. Chi-square test and adjusted Chi-square test were conducted to assess the relationship between the genotype and allele frequencies of TLR9 SNPs and some clinical and laboratory parameters of patients with SLE, as well as the differences in genotype and allele frequencies of TLR9 SNPs between the two populations. Results The frequencies of CC, CT and TT genotypes of TLR9 SNP rs352140 were 42.9%, 41.1% and 16.1% respectively in the patients of Han nationality, compared to 38.3%, 55.8% and 5.8% in the healthy controls of Han nationality （all P < 0.05）, but no significant difference was observed in the frequency of C or T allele of the SNP rs352140 between the patients and controls of Han nationality （both P > 0.05）. There was no significant difference in the genotype or allele frequency of TLR9 SNP rs352140 between the patients and healthy controls of Zhuang nationality, or between the patients of Han nationality and Zhuang nationality （all P > 0.05）. The patients with anti-dsDNA antibodies showed a significantly higher frequency of TT genotype （P < 0.05）, but similar T allele frequency at TLR9 SNP rs352140 （P > 0.05） compared with those without. The frequencies of both TT genotype and T allele of TLR9 SNP rs352140 were significantly increased in the patients with a SLE disease activity index （SLEDAI） ≥ 9 compared with those with a SLEDAI < 9 （both P < 0.05）. There was no statistical difference in either the TT genotype or the T allele frequency at TLR9 SNP rs352140 between antinuclear antibody-positive and -negative patients with SLE（both P > 0.05）. Conclusions The TLR9 SNP rs352140 is correlated with several clinical and laboratory parameters of SLE, and might contribute to the susceptibility to SLE in Guangxi Han population.

Key words: Lupus erythematosus, systemic, Toll-like receptor 9, Polymorphism, single nucleotide, Zhuang nationality, Han nationality