Background and aims: The effects of maintenance infliximab for Crohn's disease vary widely among patients. The aim of this study was to examine the cytokine profiles and to identify possible markers predictive of therapeutic effect of maintenance infliximab. Methods: Cytokine profiles of 35 Crohn's disease patients under maintenance infliximab therapy were analyzed prospectively. Blood samples were obtained prior to, and 2 and 6. weeks after infliximab infusion. Circulating cytokine values of interleukin (IL)-23, IL-17A, IL-12, IL-6, interferon gamma (IFN-γ), and tumor necrosis factor alpha (TNF-α) were compared according to the disease activity and therapeutic efficacy. Patients were classified into either the active or quiescent phase according to their disease activity at baseline. Patients were also divided into a sustained response group and non-sustained response group according to therapeutic efficacy of infliximab determined 2 and 6. weeks after infliximab infusion. Results: At baseline, serum levels of IL-23 (p < 0.05), IL-17A (p < 0.01), IFN-γ (p < 0.05), and IL-6 (p < 0.01) were significantly higher in active Crohn's disease than in quiescent disease. These cytokine levels remained unchanged during the follow-up period. When serum cytokine levels were compared between groups classified by therapeutic efficacy of infliximab, patients in the non-sustained response group had a significantly higher level of serum IL-17A than those in the sustained response group (p < 0.05). There were also trends toward higher serum IL-23 and IL-12 in the former than in the latter. Conclusion: Higher levels of IL-17A, IL-23, and IL-12 at baseline may be predictive markers for poor therapeutic response to maintenance infliximab therapy.
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