As some researchers have put it, "A huge proportion of your immune system is actually in your [gastrointestinal] tract." So, how do bacteria and the immune system interact?
New research now illuminates part of the answer to this question. It reveals that the "friendly" bacteria collaborate with both the cells that line the inside of our intestines and with immune cells to regulate the immune system's response to infection.
The researchers found that the friendly bacteria interact with both the epithelial cells that line the inside of our gut and with our immune cells to find the right "dosage" of the immune response.
"We found that when we gave the laboratory animals antibiotics, the antigen-presenting cells did not make IL-10."
"When we put back bacteria in the animals' guts, only bacteria that could attach to the intestinal epithelium triggered IL-10 production by antigen-presenting cells and reduced the inflammatory response," Prof. Diehl explains.
"It's somewhat counterintuitive because microbes that can attach to the intestinal epithelium are thought of as pathogens that can potentially cause disease."
"But, in this case we found that the attachment of bacteria to the epithelium was not causing disease; on the contrary, it was necessary to promote a balanced regulation of the T cell responses and helped protect the gut," she says.