In mice colonized with the Gram-negative mucus-associated pathobiont Mucispirillum schaedleri, combined deficiency of IBD-susceptibility gene nucleotide-binding oligomerization domain-containing protein 2 (Nod2) and the cytochrome b-245 beta-chain subunit of phagocyte NADPH oxidase develop spontaneous colitis after weaning as the protection afforded by maternal antibodies begins to wane.103 The disease is characterized by an expansion of M. schaedleri due to impaired recruitment of luminal neutrophils necessary to clear the bacteria. Here, NOD2 is linked to colitis.