Mo1739 LPS Stimulated Whole Blood Cytokine Production and the Association With Disease Characteristics in Patients With Quiescent Crohn's Disease

Abstract

Introduction: Individual cytokine production is for 60-70% under genetic control, but levels of secreted cytokines after stimulation with lipopolysaccharide (LPS) vary widely between individuals. In various fields of inflammatory diseases the variation in LPS stimulated cytokine production has been linked with disease behavior. So far, studies in patients with Crohn's disease (CD) used single nucleotide polymorphisms (SNPs) as surrogate marker to identify patients with a high innate cytokine production, but it may be more accurate to measure cytokine production itself for this purpose. Our aim was to measure levels of tumor necrosis factor alpha (TNF-α), interleukin (IL)-1β, IL-6 and IL-10 after whole blood stimulation with LPS and correlate this with historical disease characteristics of patients with CD who are currently in remission. Methods: Only CD patients in remission and not on immunosuppressants or biologicals, were eligible for participation as drugs or disease activity can modulate cytokine production. Remission was defined as Harvey-Bradshaw Index <5, with normal C-reactive protein (<10 mg/L) and leukocyte levels. Whole blood samples were incubated with E.coli O55:B5 LPS (1 ng/ml) for 4 hours (TNF-α) or 24 hours (IL-1β, IL6 and IL-10). Cytokine levels were determined in supernatants with specific enzyme-linked immunosorbent assays (ELISAs). Non-parametric statistics were used to test correlations between cytokine levels and historical disease characteristics. Results: Sixty-nine patients (50 female / 19 male) were included. Mean disease duration at inclusion was 24.1 (SD= 11.5) years and the average age was 51.2 (SD=12.3) years. No relation was found between disease localization (ileal vs. colon vs. ileocolonic) or disease behavior (presence of fistulas or strictures) and levels of TNF-α, IL-1β, IL-6 and IL-10. Additional analyses were performed to compare mild and severe disease based on phenotype (ileal disease without fistulas versus ileocolonic disease with fistulas), number of bowel resections and percentage of years in which the patient received immunosuppressants or biologicals. A significant difference (p= 0.04) for IL-6 was found between patients with a single (median 2258 pg/ml, interquartile range [1630-2726]) and those with multiple resections (2816 pg/ml [1851-3531]) (see Table). Conclusion: In conclusion, our results show a relation between IL-6 levels and the number of bowel resections. Altogether, the use of LPS stimulated cytokine production as a biomarker to predict disease behavior in CD seems limited. Relation between cytokine production and disease severity.