• Does the immune system go to “school” in the gut?

    The body contains 10 times as many bacteria as “human” cells. Our immune system must therefore learn to live in balance with these bacteria. It is not fully understood how this is done, but immune cells called “T cells” (discussed previously) in the gut play a central role. Before birth our T cells are educated in an organ called the thymus. This education is to ensure that our T cells do not attack our own cells. It is not known how our cells learn to tolerate normal bacteria in the gut (“microbiota”), instead of attacking them like a nasty infection, for example Salmonella.

    This research proposes a new method by which our T cells are taught to live with our normal microbiota. The scientists have conducted a complex series of experiments on genetically altered mice, to allow them to learn about T cell-bacteria interactions. In this system, some T cells, rather than being taught in the thymus, are educated directly by the microbiota in the colon, and this teaches them not to attack the bacteria, but to tolerate them. Intriguingly, it was shown that when this education did not occur, the mice developed colitis. While this is a mouse model only, it is a new concept in bacteria-human interactions in the gut, and may have profound implications for IBD research and future therapies.

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