Small intestine: Edited by William F. Stenson and David H. AlpersMicrobial influences on the small intestinal response to radiation injuryPackey, Christopher Da; Ciorba, Matthew AbAuthor Information aDivision of Gastroenterology, Department of Microbiology and Immunology, University of North Carolina, Chapel Hill, North Carolina, USA bDivision of Gastroenterology, Washington University School of Medicine, Saint Louis, Missouri, USA Correspondence to Matthew A. Ciorba, MD, Division of Gastroenterology, Washington University School of Medicine, 660 South Euclid Avenue, Box #8124, Saint Louis, MO 63110, USA Tel: +1 314 362 9054; e-mail: [email protected] Current Opinion in Gastroenterology: March 2010 - Volume 26 - Issue 2 - p 88-94 doi: 10.1097/MOG.0b013e3283361927 Buy Metrics Abstract Purpose of review Injury to the small bowel from ionizing radiation occurs commonly in patients undergoing cancer therapy and less commonly in instances of accidental radiation overexposure. Several lines of evidence now suggest that dynamic interactions between the host's enteric microbiota and innate immune system are important in modulating the intestinal response to radiation. Here, we will review recent developments in the area of acute radiation enteropathy and examine the current state of knowledge regarding the impact of host–microbial interactions in the process. Recent findings There is promise in the development and testing of new clinical biomarkers including serum citrulline. Toll-like receptor agonists and innate immune system signaling pathways including nuclear factor-kappa B profoundly alter intestinal epithelial cell apoptosis and crypt survival after radiation exposure. Germ-free conditions, probiotics and antibiotics are each identified as modifiers of disease development and course. A human study suggested that luminal microbiota composition may influence the host's intestinal response to radiation and may change in those developing postradiation diarrhea. Summary New knowledge implies that investigations aimed at deciphering the microbiome–host interactions before and after small bowl radiation injury may eventually allow prediction of disease course and offer opportunities for the development of novel therapeutic or prophylactic strategies. © 2010 Lippincott Williams & Wilkins, Inc.