Finally, another member of the CARD/NOD family, CARD4/NOD1 that encodes an intracellular receptor with the ability to recognize a unique tripeptide motif (diaminopimelic acid) found in Gram-negative bacterial PGN (47), has been proposed as an IBD susceptibility gene, since three polymorphic variants have been reported to be associated with IBD in two different Caucasian populations (48), adding further interest to the PPR pathways. Here, NOD1 is linked to inflammatory bowel disease.