Girard Charlotte, Rech Jürgen, Brown Michael, Allali Danièle, Roux-Lombard Pascale, Spertini François, Schiffrin Eduardo J, Schett Georg, Manger Bernhard, Bas Sylvette, Del Val Greg, Gabay Cem
Division of Rheumatology, Department of Internal Medicine Specialties, University Hospitals of Geneva, Geneva, Switzerland.
Department of Internal Medicine 3, University Erlangen-Nuremberg, Erlangen, Germany.
Rheumatology (Oxford). 2016 Dec;55(12):2237-2247. doi: 10.1093/rheumatology/kew300. Epub 2016 Sep 10.
IL-18 is a pro-inflammatory cytokine of the IL-1 family that is naturally inhibited by IL-18 binding protein (IL-18BP). High levels of IL-18 have been described in the serum of adult-onset Still's disease (AOSD) patients, but only total IL-18 levels (including inactive IL-18 bound to IL-18BP) have been measured. With a specific immunoassay, we aimed to measure free IL-18 serum levels in AOSD patients and other rheumatic diseases.
An ELISA was developed to measure free IL-18. Its sensitivity and specificity were tested by spiking recombinant IL-18 or IL-18BP in serum and PBS supplemented with 5% BSA. The binding affinity of IL-18 to IL-18BP was calculated by titration experiments using the ELISA and by Biacore analysis. Sera of 37 AOSD patients and 138 controls (40 healthy controls, 30 RA, 29 SLE, 21 AS and 18 PsA) were assayed for free IL-18, IL-18BP, total IL-18 and other cytokines. Correlations were performed between free IL-18 and markers of disease activity in AOSD patients.
Free IL-18 serum levels were significantly higher in AOSD patients (median 8.89 pg/ml) than in healthy and disease controls (1.37 pg/ml; P < 0.01). Free IL-18 serum levels correlated with AOSD activity. The affinity of IL-18 to IL-18BP was found to be much higher than previously described, with a dissociation constant ranging from 30 to 50 pM.
Free IL-18 levels are specifically elevated in AOSD compared with other inflammatory diseases, suggesting that IL-18 represents a potential target for the treatment of AOSD.
白细胞介素18（IL-18）是IL-1家族的一种促炎细胞因子，天然受到IL-18结合蛋白（IL-18BP）的抑制。成人斯蒂尔病（AOSD）患者血清中IL-18水平较高，但此前仅检测了总IL-18水平（包括与IL-18BP结合的无活性IL-18）。我们旨在通过一种特异性免疫测定法检测AOSD患者及其他风湿性疾病患者血清中游离IL-18的水平。
开发了一种酶联免疫吸附测定（ELISA）法来检测游离IL-18。通过在血清以及添加5%牛血清白蛋白（BSA）的磷酸盐缓冲液（PBS）中加入重组IL-18或IL-18BP来测试其灵敏度和特异性。利用ELISA滴定实验和生物传感器分析（Biacore分析）计算IL-18与IL-18BP的结合亲和力。检测了37例AOSD患者和138例对照者（40例健康对照、30例类风湿关节炎患者、29例系统性红斑狼疮患者、21例强直性脊柱炎患者和18例银屑病关节炎患者）血清中的游离IL-18、IL-18BP、总IL-18及其他细胞因子。对AOSD患者游离IL-18水平与疾病活动标志物进行相关性分析。
AOSD患者血清中游离IL-18水平（中位数8.89 pg/ml）显著高于健康对照和疾病对照（1.37 pg/ml；P < 0.01）。游离IL-18血清水平与AOSD疾病活动相关。发现IL-18与IL-18BP的亲和力远高于此前报道，解离常数范围为30至50 pM。
与其他炎症性疾病相比，AOSD患者游离IL-18水平特异性升高，提示IL-18可能是AOSD治疗的潜在靶点。
