Background:Behçet’s disease (BD) is a chronic inflammatory disease that may involve many systems including mucocutaneous, vascular, articular, gastrointestinal, neurological and cardiopulmonary systems. Although the pathogenic mechanisms of BD remain unclear, increased release of proinflammatory cytokines and chemokines may play a role in inflammatory stages of the disease.Objectives:IL-1 theta is a member of IL-1 family. A variety of tissue cells, such as endothelial cells, keratinocytes, dendritic cells macrophages, B cells can produce IL-1 theta under the stimulation of pro-inflammatory factors. Several studies have shown that IL-1 theta can promote the production of proinflammatory cytokines. In this study, we investigated the relationship between serum IL- 1 theta levels and disease activity and clinical findings of BD.Methods:59 patients with BD (48 female, 11 male) and 20 healthy controls (17 female, 3 male; mean age 41.0 ± 9.3 years) were enrolled in this study. Thirty five patients were in active stage (mean age; 40.3 ± 11.0 years, median disease duration 7 years) and 24 patients were in inactive stage (mean age; 42.9 ± 13.2 years, median disease duration; 8 years). Serum IL-1 theta levels were evaluated by ELISA.Results:The mean serum IL-1 theta levels were 8.65 ± 4.41 pg/ml in patients with BD and 3.9 ± 2.54 pg/ml in healthy controls. The mean serum IL-1 theta levels were 10.34 ± 5.52 pg/ml in active patients with BD and 6.92 ± 2.43 pg/ml in inactive patients with BD. Serum IL-1 theta levels were significantly high in active Behçet’s patients compared with in inactive Behçet’s patients (p<0.01) and the controls (P<0.001).Serum IL-1 theta levels were significantly higher in the presence of neurological, vascular and mucocutaneous involvement in subgroup analysis according to the clinical findings of Behçet’s patients. IL-1 theta levels were negatively correlation with Platelet count and ESR (r=0.332 p=0.050, r=0.382 p=0.024 respectively). There was no statistically significant difference between IL-1 theta levels disease duration, and CRP.Conclusion:In this study, we demonstrated that serum IL-1 theta levels were significantly elevated in patients with BD. The high levels of serum IL-1 theta, in active and inactive patients with BD suggest that IL-1 theta may play a significant role of in the pathogenesis of BD.References:[1]Salmaninejad, A., et al. Genetics and immunodysfunction underlying Behçet’s disease and immunomodulant treatment approaches. Journal of immunotoxicology, 2017.14(1): 137-151.[2]Nara, K., et al. Involvement of innate immunity in the pathogenesis of intestinal Behcet’s disease. Clin Exp Immunol, 2008.152(2): 245-51.[3]Dalghous, A.M., et al. Expression of cytokines, chemokines, and chemokine receptors in oral ulcers of patients with Behcet’s disease (BD) and recurrent aphthous stomatitis is Th1-associated, although Th2-association is also observed in patients with BD. Scand J Rheumatol, 2006.35(6):472-5.[4]Uzkeser, H., et al. Is mean platelet volume a new activity criteria in Behçet’s disease? Blood Coagulation & Fibrinolysis, 2015.26(7): 836-839.Disclosure of Interests:None declared