The gut flora as a forgotten organ

Ann M O'Hara, Fergus Shanahan

Author Affiliations

  1. Ann M O'Hara1 and
  2. Fergus Shanahan*,1,2
  1. 1 Alimentary Pharmabiotic Centre, University College Cork, National University of Ireland, Cork, Ireland
  2. 2 Department of Medicine, University College Cork, National University of Ireland, Cork, Ireland
  1. *Corresponding author. Tel: + 353 21 4901226; Fax: + 353 21 4345300 E‐mail: f.shanahan{at}
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The intestinal microflora is a positive health asset that crucially influences the normal structural and functional development of the mucosal immune system. Mucosal immune responses to resident intestinal microflora require precise control and an immunosensory capacity for distinguishing commensal from pathogenic bacteria. In genetically susceptible individuals, some components of the flora can become a liability and contribute to the pathogenesis of various intestinal disorders, including inflammatory bowel diseases. It follows that manipulation of the flora to enhance the beneficial components represents a promising therapeutic strategy. The flora has a collective metabolic activity equal to a virtual organ within an organ, and the mechanisms underlying the conditioning influence of the bacteria on mucosal homeostasis and immune responses are beginning to be unravelled. An improved understanding of this hidden organ will reveal secrets that are relevant to human health and to several infectious, inflammatory and neoplastic disease processes.

  • Received February 23, 2006.
  • Accepted April 24, 2006.
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