Deficiency Of Immune System Peacekeeper Pinpointed In Mice As Cause Of Ulcerative Colitis
In a series of mouse experiments, researchers at the Harvard School of Public Health (HSPH) have pinpointed a specific immune deficiency as the likely fundamental cause of ulcerative colitis, a chronic, sometimes severe inflammatory disease of the colon or large intestine that afflicts half a million Americans. Remarkably, the researchers also found that once the disease was established in mice, it could be passed from mother to offspring and even between adult animals, with potential implications for public health and prevention.
The researchers have linked ulcerative colitis in mice to a deficiency of a molecular "peacekeeper" in the immune system, allowing harmful bacteria in the large intestine to breach the bowel's protective lining and trigger damaging inflammation.
In a paper being posted online on Thursday, October 4, 2007, by the journal Cell, a team led by Laurie Glimcher, Irene Heinz Given Professor of Immunology at HSPH (pictured), details a series of immunological events by which a shortage of a regulatory protein called T-bet opens the way to a bacterial attack on the intestinal wall. The resulting inflammation, in turn, causes the characteristic colitis marked by open sores, or ulcerations, throughout the colon. The first co-authors of the paper are Wendy Garrett, a research fellow in the laboratory of Glimcher and a clinical fellow at Dana-Farber Cancer Institute, and Graham Lord, formerly at HSPH and now a Professor of Medicine at King's College, London.
To listen to a podcast of the lead HSPH researchers and to view a brief slide demonstration of the inflammation process, visit here.
The key abnormality is a deficiency of the T-bet protein in "dendritic" cells - white blood cells that capture identifying antigens of foreign microbes and activate the immune defenses. T-bet, discovered in 2000 in Glimcher's laboratory, is a "master regulator gene," a transcription factor that orchestrates a pro-inflammatory response of the immune system. T-bet had been found to play a role in the body's handling of infectious microbes and cancer cells and has been implicated in rheumatoid arthritis and asthma, but the discovery of its pivotal part in the innate immune system in inflammatory bowel disease came as a total surprise.
"We have identified a new molecular player, T-bet, and when it's missing, there is spontaneous onset of the disease in the mice," said Glimcher.