CSF2 and inflammatory bowel disease: Under pro-inflammatory conditions, Th17 cells can trans-differentiate into anti-inflammatory T regulatory type 1 (Tr1) cells in the intestine (23) whereas in experimental models of inflammatory bowel disease and multiple sclerosis, Th17 cells have been shown to also promote pro-inflammatory pathogenic immune responses by gaining IFN-γ and/or GM-CSF production (20, 24).