Posted 02/22/2005 on Medscape.

David E. Elliott; Robert W. Summers; Joel V. Weinstock

Abstract and Introduction

Abstract

Purpose of Review: Inflammatory bowel disease is an emerging illness associated with socioeconomic development. The current epidemic of immune-mediated diseases may result from our loss of exposure to parasitic worms (helminths). This review summarizes some of the recent findings showing that helminths induce regulatory circuits that could prevent and treat inflammatory bowel disease.
Recent Findings: Inflammatory bowel disease appears to result from a dysregulated immune response. Although genes influence the risk of inflammatory bowel disease, it seems that critical changes in our environment have permitted its expression. One such change is the eradication of helminths. Helminths can impede interleukin-12, interferon gamma, and tumor necrosis factor α release and promote interleukin-10, transforming growth factor β, and regulatory T-cell production. Helminths can prevent and reverse intestinal inflammation in animal models of inflammatory bowel disease. In clinical studies of patients with inflammatory bowel disease, exposure to the helminth Trichuris suis reduces disease activity.
Summary: If harboring helminths protects against immune-mediated disease, then these animals must be viewed in a new light. Are there "good" helminths in addition to bad? Instead of being detestable objects marked for eradication, helminths should be viewed as useful animals that may produce important compounds helpful for therapy of human disease.

Introduction

This article summarizes some of the evidence that inflammatory bowel disease (IBD) results from an excessive immune response, reviews regulatory factors that control intestinal inflammation, shows that an environmental change permits development of IBD, and explains why the loss of exposure to helminths may be important for the emergence of IBD. The article also reviews some of our recent studies showing that helminths can inhibit or reverse colitis in animal models of IBD and that patients with IBD improve when exposed to Trichuris suis.