Interleukin-1β and interleukin-1 receptor antagonist gene polymorphisms in ankylosing spondylitis

Objective. Since ulcerative colitis and Crohn's disease, which are associated with ankylosing spondylitis (AS), have been found to be variably associated with the IL-1B and the IL-1RN genes encoding interleukin-1beta (IL-1beta) and the interleukin-1 receptor antagonist (IL-1ra), we have investigated whether these polymorphisms in IL-1B and IL-1RN are also involved in AS. Methods. DNA was isolated from peripheral blood of 106 patients with AS and 104 healthy controls. All patients and controls were Dutch Caucasians. Bi-allelic polymorphisms at positions +3953 and -511 in the IL-1B gene, and a penta-allelic polymorphism in intron 2 of the IL-1RN gene were studied by polymerase chain reaction-based methods. Results. Allele IL-1RN*2 was significantly increased in AS (odds ratio=1.60; 95% confidence interval=1.20-2.80; P=0.031) compared with healthy controls, and independent from the polymorphism in loci IL-1B-511 and IL-1B+3953. No significant associations were found between AS and the IL-1B-511 or IL-1B+3953 polymorphisms. Conclusion. Similar to other chronic inflammatory diseases, AS is associated with the IL-1RN*2 allele. Further studies are necessary to determine the biological significance of these findings in relation to susceptibility or severity of the disease.