Abstract
The intestinal mucosa has a unique immune system composed of a variety of unique immune cell populations which actively react with potentially pathogenic microbes. However, the intestinal immune system need to simultaneously remain tolerant towards the vast majority of non-pathogenic microbiota. Although it still remains unclear how this delicate balance is maintained in the intestine, a combination of gnotobiotic techniques and the latest immunological evidence has contributed to significant advances in our understanding of how host-microbiota interactions modulate mucosal immune systems. In particular, segmented filamentous bacteria and bacterial species falling within clusters VI and XIVa of the class Clostridia have been shown to profoundly affect the generation and function of mucosal immune cells, including Th17 cells and Treg cells.
