Interleukin-1β (IL-1β) & IL-4 gene polymorphisms in patients with systemic lupus erythematosus (SLE) & their association with susceptibility to SLE

BACKGROUND & OBJECTIVES: Interleukin-1 (IL-1) is one of the pro-inflammatory cytokines that plays a main role in the regulation of immune and inflammatory responses. Interleukin 4 (IL-4) as an anti-inflammatory cytokine regulates balance between Th1 and Th2 immune responses. This study was undertaken to investigate the IL-1β and IL-4 genes polymorphisms in patients with systemic lupus erythematosus (SLE) and also association between the polymorphisms and susceptibility to SLE. METHODS: One hundred and sixty three SLE patients and 180 healthy controls were genotyped for the IL-4 VNTR (variable number tandem repeat), IL-1β C-511T and IL-1β T-31C polymorphisms by polymerase chain reaction (PCR) or PCR-RFLP (restriction fragment length polymorphism) method. RESULTS: The frequencies of CC genotype and C allele of the IL-1β T-31C polymorphism were significantly (P<0.01) lower in SLE patients than controls. Moreover, the frequencies of RP1/RP2 genotype and RP2 allele of IL-4 VNTR polymorphism were significantly (P<0.05) higher in the SLE patients. No association was observed between IL-1β C-511T polymorphism and increased risk of SLE. We observed increased frequency of CT and TT genotypes of IL-1β C-511T polymorphism in SLE patients with malar rash compared to SLE patients without this manifestation. INTERPRETATION & CONCLUSIONS: The present findings suggest that IL-1β T-31C and IL-4 VNTR polymorphisms but not IL-1β C-511T polymorphism may contribute in SLE pathogenesis. In addition, CT and TT genotypes of IL-1β C-511T polymorphism were associated with SLE.