Crohn's due to weakened immune system

The BBC reports on a Lancet study that indicates that Crohn's may be due to a "weakened immune system failing to destroy bacteria".

The UCL team compared the immune system response of Crohn's patients and healthy individuals to minor injuries, such as skin abrasions.

They found the Crohn's patients produced much lower numbers of infection-fighting white blood cells called neutrophils, and lower quantities of chemicals involved in the inflammatory process.

...

The researchers believe that, because Crohn's patients have weakened immune systems, they are unable to destroy bacteria that penetrate the intestinal wall.

Thus the bacteria are left to build up in the tissue, stimulating the secretion of inflammatory chemicals that trigger the symptoms of Crohn's.

Forbes has further specific information:

Segal and his colleagues measured the number of neutrophils (white blood cells) produced by Crohn's patients in response to trauma in the bowel and on the surface of the skin.

Surprisingly, these patients produced 79 percent fewer neutrophils and inflammatory mediators compared with healthy individuals subjected to the same trauma.

When a harmless form of bacteria was injected under the skin, blood flow in healthy volunteers increased tenfold over 24 hours. But in people with Crohn's disease, blood flow increased only fourfold.

...

But others feel that the work does not really break new ground. "There have been other studies in the last year or two that Crohn's disease is really a problem dealing with bacteria in the colon and the inflammation is set up because there's more of a defective immune response to the bacteria in the gut," said Dr. John Thompson, director of the division of pediatric gastroenterology and nutrition at the University of Miami's Miller School of Medicine.