Background Inflammatory bowel disease (IBD) is a group of recurrent gastrointestinal disorders, involving Crohn disease (CD) and ulcerative colitis (UC), that is characterized by chronic mucosal inflammation and extraintestinal symptoms. Rheumatic abnormalities of a broad spectrum of symptoms, from arthralgia to spondyloarthritis (SpA), are the most common extraintestinal manifestations of IBD. The pathogenesis of IBD-related arthritis is unclear.
Objectives In this study, we analyzed the serum cytokine concentrations (interleukins: IL-10, IL-18, IL-21, IL-23, interferon γ) in patients with IBD-associated spondyloarthritis and patients with IBD not complicated with SpA symptoms.
Methods The study group consisted of 75 patients (44 female/29 male, age 43,7±12,3 year) suffering from IBD alone (n=35) or with IBD accompanied by arthritis (n=39), i.e. spondyloarthritis (IBD-SpA, n=16) or ankylosing spondylitis (IBD-AS, n=23). The control group included age and sex matched healthy volunteers (n=42). Serum cytokine concentrations were measured using commercially available kits from eBioscience, San Diego, CA, USA (Platinum ELISA for IL-18, ReadySetGo ELISAs for IL-10, IL-21, IL-23, interferon γ).
Results The concentrations of IL-23 (the mean ± SEM =156 ±14 vs 115±49 pg/ml) and IL-21 (232±79 vs 20.6 ±8 pg/ml) were significantly higher (p<0.0001) in the total group of patients than control sera. Similar significant elevation of IL-21 and IL-23 was found in IBD (146±35 and 133±40 pg/ml, respectively), IBD-SpA (124±48 and 151±37 pg/ml, respectively) and IBD-AS (194±62 and 417±228 pg/ml, respectively) groups comparing with control sera (p≤0.001). There was no significant difference between control and patients groups in the serum concentrations of other tested cytokines, except IL-18. The levels of IL-18 were significantly lower in the sera of IBD-AS group than in healthy volunteers (59±19 vs 180±36 pg/ml, p=0.02). Although we failed to show significant difference in serum cytokine concentrations between IBD and IBD-SpA or IBD-AS patients, in the IBD-AS group there was again tendency to downregulation of serum IL-18 in comparison with patients suffering from IBD alone (59±19 vs 121 ±27 pg/ml, p=0.08).
Conclusions Significant elevation of serum IL-21 and IL-23 found in IBD patients irrespectively of complication with SpA suggests implication of these cytokines in the underlying disease pathology. On the other hand, diminution of serum IL-18 in IBD-AS may point to protective action of this cytokine in AS development.
Supported by grant 2012/05/N/NZ5/02839 from the National Science Centre of Poland.
Disclosure of Interest None declared