CD40 and colitis: By regulating the maintenance and function of ILC3, Ahr is critical for the clearance of Citrobacter rodentium, a murine pathogen that models human enterohemorrhagic Escherichia coli and enteropathogenic E. coli infections in the gut (12, 13, 64), as well as for the pathology of anti-CD40-incuced colitis (64).