ORIGINAL ARTICLE Association of toll-like receptor 9 gene polymorphism in Chinese patients with systemic lupus erythematosus in Taiwan Chung-Ming Huang • Po-Hao Huang • Chi-Lan Chen • Ying-Ju Lin • Chang-Hai Tsai • Wen-Liang Huang • Fuu-Jen Tsai Received: 1 August 2010 / Accepted: 27 March 2011 / Published online: 17 April 2011 Ó Springer-Verlag 2011 Abstract The purpose of this study was to determine whether toll-like receptor 9 (TLR9) gene polymorphisms were markers of susceptibility to or severity of systemic lupus erythematosus (SLE) in Taiwanese patients. The study included 211 healthy individuals and 167 Chinese patients with SLE. Polymorphisms of TLR9 [rs2066807 and rs187084 (-1486 T/C)] were typed from genomic DNA. The genotypes, allelic frequencies, and carriage rates were compared between patients with SLE and control subjects. The relationship between allelic frequencies and clinical manifestations of 167 patients with SLE was evaluated. There was no statistically significant difference in TLR9 (rs2066807) gene polymorphism, allelic fre- quency, and carriage rate between the SLE and control groups. However, for the genotype of TLR9 -1486 T/C (rs187084) polymorphism, there was a statistically signif- icant difference between the SLE and the control groups (P \ 0.001, v 2 = 15.9). Moreover, there was a significant association between the two groups in allelic frequency and carriage rate of the T allele (P \ 0.001, v 2 = 18.5 and P \ 0.01, v 2 = 8.06, respectively). We did not detect any association between the TLR9 genotype and the clinical or laboratory profiles in patients with SLE. The results sug- gest that the TLR9 -1486 T/C (rs187084), but not TLR9 (rs2066807), polymorphism is related to SLE in Taiwanese patients. Keywords TLR-9  SLE  Gene polymorphism Introduction Systemic lupus erythematosus (SLE) is a prototypic immune complex–mediated disease with a broad spectrum of auto- immune phenomena and clinical symptoms. Many immu- nologic abnormalities have been found in patients with SLE, including impaired T-cell responses and dysregulation of B-cell activation, leading to B-cell hyperactivity and over- production of auto-antibodies [1, 2]. Auto-antibodies pro- duced by differentiated B cells play an important role in the pathogenesis of SLE. Toll-like receptor-9 (TLR-9) recognizes CpG motifs in microbial DNA [3]. TLR-9 signalling stimulates innate antimicrobial immunity and modulates adaptive immune responses including autoimmunity against chromatin, such as in SLE [4, 5]. TLR-9 has recently been implicated in the activation of auto-reactive B cells in murine models of SLE C.-M. Huang  P.-H. Huang Division of Immunology and Rheumatology, China Medical University Hospital, Taichung, Taiwan W.-L. Huang Department of Internal Medicine, China Medical University Hospital, Taichung, Taiwan Y.-J. Lin  F.-J. Tsai (&) Department of Medicine Genetics, China Medical University Hospital, No 2 Yuh Der Road, Taichung, Taiwan e-mail: d0704@mail.cmuh.org.tw C.-M. Huang Graduate Institute of Integrated Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan F.-J. Tsai College of Chinese Medicine, China Medical University, Taichung, Taiwan C.-H. Tsai Taichung Asia University, Taichung, Taiwan C.-L. Chen Foo Yin Institute of Technology, Kaohsiung, Taiwan 123 Rheumatol Int (2012) 32:2105–2109 DOI 10.1007/s00296-011-1925-8