When the Nod2 gene is damaged, researchers said, the immune system probably overreacts and mistakenly attacks healthy intestinal cells, causing chronic inflammation. He did not participate in the studies. So it's a very ancient part of the immune system. Crohn's Disease causes severe diarrhoea, bleeding, fever and malnutrition. It is closely related to ulcerative colitis, so physicians often group the two disorders as inflammatory bowel disease.
Researchers believe that immune cells in the gut overreact to the presence of bacteria.
The resulting inflammation causes the intestinal lining to ulcerate and break down. The US study tested DNA supplied by 416 families with a history of Crohn's Disease. The French study tested 235 families. Both groups focused on chromosome 16. Previous studies showed it was a promising site for genes involved with recognising invading microbes.