GI response to non-harmful bacteria very primitive
The body does not respond to harmful and non-harmful bacteria in the same way. This researcher suggests that the method the GI tract uses to deal with these bacteria is very primitive; suggesting that this relationship between us and our bacteria has been around for a long, long time.
Science 2000;288:2222-2226 The immunoglobulin IgA produced in gut mucosa to keep intestinal flora in check is produced by a “primitive” T cell-independent mechanism. “The immune system in the intestine sees and responds to the enormous load of nonpathogenic bacteria (greater than 500 thousand billion) in an apparently primitive way,” Dr. Macpherson told Reuters Health. “The bacteria do not seem to penetrate the body much, and the IgA response by the intestine that we have discovered is important in keeping them out.” According to Dr. Macpherson, the findings may have implications for research into disorders like Crohn’s disease and ulcerative colitis, which involve an inflammatory response to commensal intestinal bacteria. “It is pretty reasonable to suppose that failure to dampen down the inflammatory reactions to them is the key, but we don’t know the relative importance of the pathway that we have described in this,” he said.