Polymorphisms of IL-1β Gene in Japanese Patients with Sjögren's Syndrome and Systemic Lupus Erythematosus

Objective. Interleukin (IL)-1β is a proinflammatory cytokine involved in various immune responses. Five polymorphisms in the IL-1β gene have been described, and relationships between these polymorphisms and some autoimmune diseases have been reported. Evidence suggests that IL-1β may be involved in the destruction of salivary and lacrimal glands in Sjögren's syndrome (SS). We evaluated the significance of IL-1β gene polymorphisms in SS. Methods. Blood samples were taken from 101 patients with SS, 103 patients with systemic lupus erythematosus (SLE, excluding those with secondary SS), and 106 healthy volunteers. Each polymorphism of the IL-1β gene was analyzed by polymerase chain reaction (PCR) amplification of the polymorphic site, followed by site-specific restriction digestion. Genotype frequencies of each polymorphism in SS patients were compared with those of the controls and SLE patients, and differences between primary and secondary SS patients were also compared. Results. Genotypes CC, TT, and AA in positions -511, -31, and 3877, respectively, were significantly less frequent in SS patients than controls or patients with SLE. No significant differences were found in genotype frequencies of any of the polymorphisms between patients with primary SS and secondary SS. Conclusion. IL-1β gene polymorphisms may affect susceptibility to SS, but not SLE.