TNFB Gene Polymorphism in Patients with Systemic Lupus Erythematosus in Korean

OBJECTIVES To elucidate the gene frequency of TNFB Ncol polymorphism and its association with HLA class II antigen in patients with systemic lupus erythematosus(SLE) in Korea. METHODS We investigated the gene frequency of the TNFB alleles using DNA obtained from peripheral mononuclar cells in 141 healthy controls and in 58 patients with SLE. The polymorphisms of TNFB gene (735 bp) were studied by Ncol PCR-RELP. A portion of TNFB gene(735 bp) was amplified by PCR and its products were digested with Ncol restriction enzyme. The digested samples of amplified DNA were analyzed by agarose gel electrophoresis. TNFB*1 and TNFB*2 alleles were identified according to polymorphic fragments on Ncol restriction site in the first intron of the TNFB gene. The generic types of HLA-DRBI were also determined by PCR with sequence specific primers(SSP) using genomic DNA from the same subjects. RESULTS The genotypic frequency of TNFB*2 homozygote was significantly increased in patients with SLE compared with controls(RR = 2.36, P = 0.011). The frequency of HLA-DRBI*15 was also significantly increased in patients (RR = 2.27, P = 0.029). However, the increased frequency of TNFB*2 homozygote was apparently increased in nephritis group (RR = 2.79, P = 0.035), whereas the significance of TNFB*2 homozygote was weakend in non-nephritis group. CONCLUSIONS Our results suggest that genetic predisposition of TNFB*2 homozygote is another risk factor in Korean SLE, especially in DR2 negative patients. In addition, TNFB*2 homozygote could have a tendency for the development of nephritis in patients with SLE.