Objectives: Coeliac disease is a multifactorial disorder influenced by environmental, genetic and immunological factors. Interleukin (IL)-21 has been linked to an increase disease risk and the serum level of IL-21 seems to be increased in CD compared to a healthy control population.

Methods: Sera were collected from 160 CD patients, 120 untreated and 40 following a gluten-free diet, and form 45 healthy subjects. Serum IL-21 was evaluated by specific ELISA tests.

Results: Our data show that patients with untreated CD display IL-21 concentrations significantly higher than both treated-CD patients (following a gluten-free diet) and controls. In addition, serum IL-21 correlates with serum titres of anti-tTG IgA autoantibodies. Finally, our results show a correlation of this cytokine with duodenal mucosal damage.

Conclusions: A role of gluten, as antigen with stimulatory function on IL-21 production, seems to be confirmed by the longitudinal analyses showing that the gluten-free diet decreases to a nearly undetectable amount this cytokine. In addition, the finding of a positive correlation between the serum amount of IL-21 and the grade of duodenal mucosa damage suggests a strong immunomodulatory effect of this cytokine on cytotoxic T lymphocyte functions. This study provides an extra evidence to emerging data on the potential role IL-21 in CD pathogenesis, suggesting its involvement in the development and progression of CD.

Significance statement: In untreated CD, serum IL-21 shows higher levels compared with treated CD and healthy subjects. Serum amounts of IL-21 correlate with anti-tTG IgA autoantibodies and with duodenal mucosa damage.

目的：腹腔疾病是一种受环境，遗传和免疫因素影响的多因素疾病。与健康对照组相比，白介素（IL）-21与疾病风险增加相关，并且CD中IL-21的血清水平似乎升高。

方法：从160名CD患者，120名未接受治疗的患者和40名接受无麸质饮食的患者中收集血清，形成45名健康受试者。通过特异性ELISA测试评估血清IL-21。

结果：我们的数据显示，未经CD治疗的患者显示IL-21浓度显着高于经CD治疗的患者（遵循无麸质饮食）和对照。另外，血清IL-21与抗tTG IgA自身抗体的血清滴度相关。最后，我们的结果显示了该细胞因子与十二指肠粘膜损伤的相关性。

结论：面筋作为一种对IL-21产生具有刺激功能的抗原的作用似乎已通过纵向分析得到了证实，该分析表明，不含面筋的饮食减少了几乎无法检测到的这种细胞因子。另外，在IL-21的血清量和十二指肠粘膜损伤程度之间存在正相关的发现表明该细胞因子对细胞毒性T淋巴细胞功能具有强的免疫调节作用。这项研究为有关IL-21在CD发病机理中潜在作用的新兴数据提供了额外的证据，表明它参与了CD的发展和进程。

重要性声明：与未经治疗的CD和健康受试者相比，未治疗的CD中的血清IL-21含量更高。血清中IL-21的含量与抗tTG IgA自身抗体以及十二指肠粘膜损伤有关。