Background. Systemic lupus erythematosus (SLE) is a complex immune disease. The genetic variation in the IL-12b gene was found to associate with SLE in Caucasian population. In this study, we examined this association in Chinese Han population by a recently developed method, unlabeled probe-based high resolution melting analysis. Methods. A total of 297 SLE patients and 351 controls were recruited. Unlabeled probe-based high resolution melting analysis (HRMA) was used in genotyping. Results. Statistically significant differences were observed in both genotype and allele frequencies for rs6887695 in the SLE patients as compared with the controls. Minor allele (C) of rs6887695 ( , OR 0.78, [95% CI 0.63-0.98]) was found to be protective against SLE. The association of SNP rs6887695 with the diagnostic criteria of SLE was also examined. Minor allele (C) exerts protective effect on the incidence of arthritis ( , OR = 0.65, 95% CI = 0.47-0.92) and abnormalities of antinuclear antibody ( , OR = 0.68, 95% CI = 0.49–0.95). IL-12b SNPs were irrelevant to other diagnostic criteria of SLE. Summary. Polymorphisms of rs6887695 in IL-12b gene were associated with disease risk, as well as arthritis and antinuclear antibody synthesis, of systemic lupus erythematosus in Chinese population. 1. Introduction Interleukin-12 (IL-12) is a heterodimeric cytokine that is produced during innate immune response by monocytes, macrophages, dendritic cells (DCs), neutrophils, and B cells [1, 2]. The general function of IL-12 is thought to be as an important immunomodulator linking innate recognition of pathogens to development of adaptive immune response [1, 3]. Interleukin (IL-12b), also known as p40, is one of the components of IL-12 which covalently combine with p35 (IL-12a) to form mature IL-12 protein. Otherwise, IL-12b could also interact with p19 (IL-23a) to form the other IL-12 family member, IL-23. IL-23 has strong capacity of induction of a novel subset of T cells, the T-helper-17 (Th17) cells. These novel T-helper cells are characterized by production of IL-17 cytokine which is strongly implicated in the pathophysiology of various autoimmune diseases [4]. Owing to the important role of IL-12 and IL-23 during the immune response, IL-12b, the common component of IL-12 and IL-23, might be a candidate gene of autoimmune disease. Indeed, IL-12b has been found to associate with several autoimmune diseases including psoriasis, rheumatoid arthritis, and type 1 diabetes [5–9]. Systemic lupus erythematosus (SLE) is a complex autoimmune disease with multiple organs affected.
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