Neutrophil extracellular traps in pediatric inflammatory bowel disease.

Neutrophil extracellular traps (NETs) are fibers composed of chromatin and neutrophil proteins released by activated neutrophils. NETs trap and kill microbes, activate dendritic and T cells, and are implicated in autoimmune and vascular diseases. The pathogenesis of inflammatory bowel disease (IBD) is multifactorial and characterized by chronic active mucosal inflammation with controversial contribution of neutrophils. Our aim is to describe the involvement of NETs in pediatric IBD. We retrospectively examined biopsies from the small bowel and colon of children at diagnosis of Crohn's disease (CD) or ulcerative colitis (UC). The biopsies were labeled for neutrophil elastase, myeloperoxidase, DNA, chromatin and histones in order to identify NETs. Samples of two children with normal colonoscopy served as controls. Twelve patients (5 boys) were included, 6 with CD and 6 with UC. Their average age was 12.2 years (range 5-16). NETs were found in all samples from patients and not in the samples from the two controls. This is the first demonstration of the presence of NETs in biopsies taken from the small bowel and colon of pediatric patients with IBD. More studies are needed in order to identify the role of NETs in CD/UC pathogenesis.