Clinical Relevance of IL-17 during SLIT on AR to HDM

Objective To investigate the clinical relevance of serum IL‐17 levels in AR patients treated with sublingual immunotherapy (SLIT) to identify the function of TH17 cells and IL‐17 in AR. Method The patients with AR to HDM starting to receive SLIT in Seoul National University Hospital between June 2008 and August 2010 were enrolled. We detected serum IL‐17 levels via ELISA before and 1 and 2 years after starting SLIT. Symptom diaries, rescue medication use, and other immunological parameters were analyzed. Results Longer onset of symptoms and moderate to severe symptoms were significantly related to higher serum IL‐17 levels before starting SLIT. HDM‐specific IgE significantly increased between the baseline and the first year of SLIT, while HDM‐specific IgG4 had no significant change. There was a significant positive correlation between serum ECP and IL‐17 levels during SLIT. The changes of serum IL‐17 and total IgE levels for 1 year had an inverse relationship with the effectiveness of SLIT. Changed serum IL‐17 levels at the first year was the most significant factor in relation to the effectiveness of SLIT by multivariate analysis. Conclusion Serum IL‐17 levels in AR correlated with duration from symptom onset, symptom severity, and serum ECP levels. Changes of serum IL‐17 levels during SLIT are expected to be a prognostic factor to predict the effectiveness of SLIT. Thus, IL‐17 and TH17 cells might have an important role in AR pathogenesis.