Lymphoid Cells produced in the Gut keep the Commensal Bacteria in Check

gut lymphoid tissue

Although we are familiar with the important role that the thousands of bacteria residing in our gut play, e.g. aiding in digestion and promoting a healthy immune system, what we do not realize is that the location of these commensal bacteria in the gut is a crucial factor. When these bacteria spread beyond the gut and into the blood stream, they may lead chronic inflammation. This condition is commonly seen in diseases like inflammatory bowel disease, obesity, viral hepatitis and infection with HIV. In these conditions, the commensal bacteria are dislocated from their usual place in the gut and then turn into bad bugs. Earlier studies conducted by the researchers from the Perelman School of Medicine at the University of Pennsylvania have revealed that the immune cells present in the mucosa of the gut, as well as those present in the skin and lungs prevent the entry of bacteria, viruses and other pathogens into the blood stream. However, it was not known until know that the immune cells present in the gut also play a role in containing the commensal bacteria to their specific location in the gut.

A new study, published in the recent issue of the journal Science has found that the innate lymphoid cells (ILCs) which produce interleukin-22 are present in the intestinal tissues of healthy mammals. These ILCs play a vital part in containing the commensal bacteria in their location and the depletion of these ILCs can lead to the dissemination of these bacteria and systemic inflammation.

The researchers, led by David Artis and Gregory F. Sonnenberg, have identified that these commensal bacteria belong to a group called Alcaligenes. They found that dissemination of Alcaligenes to tissues outside the gut may lead to Crohn’s disease and progressive hepatitis C. Alcaligenes-specific systemic immune responses were observed in these conditions. The researchers have opined that targeting these specific commensal bacteria or targeting ILC responses may be a way of treating these chronic conditions.


Thursday, June 21, 2012