Discovering the cause of inflammatory bowel disease: lessons from animal models.

The precise cause of inflammatory bowel disease remains unclear. Relevant animal models are important tools for studying the underlying mechanisms of inflammation and disease pathogenesis. The purpose of this review is to summarize the various types of animal models available for use in inflammatory bowel disease research and to illustrate how these models have contributed to a better understanding of the etiopathogenesis of inflammatory bowel disease, particularly focusing on papers published during calendar year 1999. Studies using appropriate animal models have provided important discoveries in this field of investigation. These include determination of the key role that pathogenic and regulatory T cells, proinflammatory and immunoregulatory cytokines, indigenous bacterial flora, and putative predisposing genes play in the disease process. The availability of new animal models that closely resemble the human disease is expected to allow further characterization of the initiating event(s) in inflammatory bowel disease and lead to a possible cure for this devastating disease.