Nod2, also known as caspase recruitment domain-containing protein 15, CARD15, and inflammatory bowel disease protein 1, is a monocyte-specific cytoplasmic protein containing two N-terminal caspase recruitment domains (CARD domains), and multiple leucine-rich repeats with a predicted molecular weight 115 kD. Alternative initiation produces two isoforms of Nod2. Nod2 is thought to confer responsiveness to intracellular bacterial lipopolysaccharide (LPS), and defects in Nod2 have been linked to several diseases including Blau syndrome, Crohns's disease, and ulcerative colitis. Knock-out animals has been shown to have dramatically altered responses to bacterial pathogens in the gut. Nod2 binds to the receptor interacting kinase 1 protein via CARD-CARD interaction and induces NF-kappaB and IKK-gamma. The NOD-15 monoclonal antibody recognizes the human Nod2 protein and has been shown to be useful for Western blotting. The NOD-15 antibody does not cross-react with human Nod1.