IL10 and colitis: For example, Bacteroides fragilis, a member of the normal human microbiome, produces polysaccharide A, which regulates the systemic murine helper T cell (Th)1-Th2 balance [8] and induces the development of interleukin (IL)-10-producing regulatory T cells that protect against murine colitis and experimental autoimmune encephalomyelitis [9], [11].