Objective: To examine whether polymorphism within the tumor necrosis factor alpha (TNFalpha) gene is associated with the susceptibility and clinic manifestations to systemic lupus erythematosus (SLE) in the patients of Han ethnic group collected from the Northern China.
Methods: TNF(1) and TNF(2) subtypes of TNFalpha gene were defined by polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis in 89 Chinese patients with SLE and 70 ethnically matched controls from Peking Union Medical College Hospital. All SLE patients were diagnosed by the American Rheumatological Association SLE diagnostic criteria setup in 1982. Human leukocyte antigen (HLA)-DR(2) gene frequency was assigned by PCR with sequence-specific primers (SSP-PCR).
Results: The frequencies of TNF(2) and HLA-DR(2) were significantly increased in SLE patients respectively compared to that of the controls (0.23 vs 0.14, RR = 1.85, P < 0.05; 0.36 vs 0.22, RR = 2.02, P < 0.01). Both TNF(2) and HLA-DR(2) were associated with SLE independently (RR = 3.96, P < 0.05; RR = 3.07, P < 0.05), but there was no association between the two genes. In TNF(2) positive patients, the positive rate of anti-SSA antibody was apparently higher and the incidence of lupus nephritis was significantly increased.
Conclusion: Both TNF(2) and HLA-DR(2) gene may play a role in SLE susceptibility. Anti-SSA antibody and lupus nephritis were strongly associated with TNF(2) gene.