Gastrointestinal infections can cause the immune system to attack some of the billions of microbes that are normally tolerated in the mammalian gut.
Yasmine Belkaid at the National Institute of Allergy and Infectious Diseases in Bethesda, Maryland, and her team demonstrated this immune response when they infected mice with the parasite Toxoplasma gondii. The infection caused the bacteria normally resident in the gut to breach the gut wall (pictured), activating the animals' immune systems. This triggered immune cells called T cells to target the gut bacteria. The T cells then developed into long-lasting memory T cells — providing an immunological record of the response.
As a result, a bout of food poisoning could have enduring consequences for the immune system, and could even contribute to the development of inflammatory bowel disease, the researchers suggest.
Science http://dx.doi.org/10.1126/science.1220961 (2012)