The intestine is the main site where the body interacts with bugs from the external environment. In health there is a balance between an inflammatory response required to clear nasty infections and a “regulatory” response which prevents inflammation from getting out of control, essentially preventing IBD. It is known that a population of the immune T cells (discussed previously) is particularly important in regulation. These are called regulatory T cells (Tregs). These Tregs are either naturally produced in the thymus (the organ where most T cells are developed – see previous blog ) or “naïve” T cells which may then be “educated” in the intestine to become regulatory; called induced or iTregs.
This paper showed specially manipulated mice that lacked just the induced (i)Tregs unexpectedly did not suffer from severe inflammation, such as seen in Crohn’s disease. Rather, they had a more “allergic” type of inflammation, such as seen in asthma (and in a modified form, in ulcerative colitis). They also had a different composition of bacteria in their intestine. The authors suggest this shows that in mice, it is the “natural” or “thymic” Treg cells that are important for restraining severe auto-immune disease but the induced Tregs may play more of a role in preventing allergy and controlling gut bacteria. This study is important, not just in helping to understanding the role of the gut in the immune system, but also because laboratories are in the process of trying to use Treg cells in treatments of various autoimmune diseases, and it is therefore critical to understand their functions as much as possible.
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