How’s this for a mystery: You have more bacteria living in your small intestine than cells in your body, and your immune system does nothing:
For years, scientists have wondered whether the same mechanism is at work in tissues that come in regular contact with bacteria and other microbial organisms. The small intestine, for example, which absorbs essential nutrients from food and drink and protects the body from invasive microbes, is literally teeming with bacteria, which help break down waste. The presence of so many bacteria is a potential trigger for an immune system response. Why do T cells almost always ignore the small intestine, leaving this vital tissue unharmed?
No, the butler doesn’t do it.
Normally, dendridic cells by displaying antigens teach the immune system what not to attack. But not in the small intestine. Instead, stromal cells in the lymph node do it. Why should you care? Scientist wonder if this method to keep healthy tissue from being attacked by the immune system can’t be used in autoimmune diseases such as Type 1 diabetes and multiple sclerosis.
