Association Study Of SLE And Polymorphisms In TIM-3 Gene In Chinese Han Population

[Background]T-cell immunoglobulin domain and mucin domain (TIM) family consists of three genes on syntenic human chromosome 5q33.2 with no other intervening genes. The human TIM family members are TIM -1, TIM -3 and TIM -4. TIM family members are type I membrane glycoproteins expressed on T cells and containing common structural motifs, namely Ig V domain, highly glycosylated mucin domain and cytoplasmic domain. TIM family members characterized thus far appear to have a role in the regulation of Th1 and Th2 differentiation and T cell mediated immune responses. TIM-3 is specifically expressed on Thl cells. It has been reported that the expression of TIM -3 in some autoimmune disease patients is different from that of controls and some SNPs of TIM -3 have relationship with autoimune diseases, both of which indicates that they are related to autoimmune diseases.Systemic lupus erythematosus (SLE) is characterized by B -cell hyperactivity, autoantibody production, and immune complex deposition in vital organs. SLE has been extensively studied and a large number of abnormalities in both cellular and humoral immunity have been described. Nevertheless, our understanding of the initiating and perpetuating mechanisms in SLE is still incomplete. The imbalance of Th1/Th2 cytokines plays an important role in the onset and development of SLE. Our preliminary studies showed the upregulation of galactin-9, ligand of TIM -3 in peripheral blood monocytes from SLE patients which suggests the involvement of TIM-3 pathway in SLE. However, it needs more studies to uncover the detail role of TIM -3 in SLE.[Objective]Using case-control study to determine the association between SLE and three polymorphisms in TIM-3 gene in Chinese Han population, including two SNPs T-882C and T-574G in TIM-3 promoter region, one SNP A+2398G in TIM-3 coding region. The objective is to study whether the T-882C,T-574G and A+2398G sites have reach genetic equilibrium and discover the difference of the SNPs between the normal control and SLE cases. Furthermore, we expect to screen out the relational SNPs with genetic susceptibly to SLE based this study.[Methods]1. Collect blood samples from SLE patients and healthy controls in the Chinese Han population in North and then extract DNA from the white blood cells in peripheral blood.2. Genotyping: Two SNPs T-882C and T-574G in TIM-3 promoter region and one SNP A+2398G in TIM-3 coding region were genotyped using polymerase chain reaction and restriction fragment length polymorphism(PCR-RFLP) method in 209 SLE patients and 245 healthy controls.3. Evaluate each polymorphism for Hard-Weinberg equilibrium (HWE) using chi-square test and make sure all the polymorphisms were at Hard-Weinberg equilibrium in both SLE patients and healthy controls used in the study.4. Compare the distribution of different genotypes and alleles of every polymorphism in the two groups using chi-square test to determine whether the polymorphism was associated with SLE.5. The ds-DNA, AunA , AHA , rRNP and ACL- IgA ,IgG ,IgM antibodies were analyszed with ELISA. Compare the different genotypes and levels of the five antibodies to discover whether the polymorphism was associated with these antibodies. [Results]1. The alleles of both healthy controls and SLE cases have achieved genetic equilibrium in the three SNP sits (T-882C Healthy: x~2=0 P=1; SLE patients: x~2=0 P=1;T-574G Healthy: x~2=0 P=1; SLE patients: x~2=0 P=1; A+2398G Healthy: x~2=0 P=1; SLE patients: x~2=0 P=1) .2. SNPs T-882C,T-574G and A+2398G were at Hard-Weinberg equilibrium in both SLE patients and healthy controls. Frequencies of TT, TC,CC genotypes at T-882C site was 0, 0.0096, 0.9904 in the SLE patients and 0, 0.0245, 0.9755 in the healthy controls .Frequencies of TT, TG,GG genotypes at T-574G site was 0, 0.0096, 0.9904 in the SLE patients and 0, 0. 0163, 0. 9837 in the healthy controls. Frequencies of AA, AG, GG genotypes at +2398A>G site was 0, 0, 1 in the SLE patients and 0, 0, lin the healthy controls .The genotype and allele frequencies of the three SNPs in SLE patients were not different from those in the healthy controls.3. The carrier of T-882C CT genotype has an decreased risk of SLE ( OR:0.385; 95%CI: 0.077-1.927). The carrier of T-574G GT genotype has an decreased risk of SLE (OR: 0.582;95%CI: 0.106-3.211).4. No significant difference in levels of ds-DNA, AunA , AHA , rRNP and ACLIgA,IgG ,IgM antibdy respectively in different genetype of SLE patients (P >0.05).[Conclusions]SNPs T-882C,T-574G and A+2398G were at Hard-Weinberg equilibrium in both SLE patients and healthy controls. SNPs T-882C,T-574G and A+2398G in TIM-3 gene might not be associated with SLE susceptibility in a Chinese Han population in North. Otherwise, we also found several potential dangerous factors of SLE, The carriers of T-882C CT and T-574G GT genotypes have an decreased risk of SLE. These polymorphisms do not influence the level of ds-DNA, AunA, AHA , rRNP and ACL-IgA,IgG,IgM.