P. mirabilis is a pathobiont52,72 that carries virulence factors such as Proteus toxic agglutinin and type III secretion systems.73 In addition, Viladomiu and Metz et al. demonstrate that the large subunit of propanediol dehydratase (PduC) encoded by Adherent-invasive E. coli (AIEC) triggers IL-1β secretion from CX3CR1+ MNPs.56 Similar to P. mirabilis, IL-1β induced by PduC-encoding AIEC also causes severe pathology in DSS-induced colitis in Il10-deficient mice. Here, CX3CR1 is linked to colitis.