Complement activation in plasma before and after Infliximab treatment in Crohn disease

Abstract

Background: Crohn disease is characterized by up‐regulated intestinal inflammation mainly caused by increased tumour necrosis factor alpha (TNF‐α) levels. However, the complement system (C) may also have a role in maintaining inflammation. Methods: Plasma from 26 patients with Crohn disease complicated by fistulizing ano‐rectal disease was collected before and after three Infliximab infusions (5 mg kg ⁻¹ ). Results: Before treatment, the C3‐activation capacities (C3‐AC) in plasma from patients with Crohn disease were comparable with values obtained from healthy controls. The classical C pathway‐mediated C3‐AC, mannan‐binding lectin C4‐AC, leucocyte count, C‐reactive protein concentration and Crohn Disease Activity Index decreased significantly 8 weeks after the first infusion of Infliximab (P < 0.04, Wilcoxon test). Conclusions: Before treatment, all three C pathways were within the normal range in plasma from patients with Crohn disease; the decrease observed in the classical pathway‐mediated C3‐AC after treatment with Infliximab reflects a general down‐regulation in immune activation.

• Complement
• Crohn disease
• TNF‐α