Here we focus on the cytosolic PRR NOD2 (nucleotide oligomerization domain 2)2 (#285), which senses bacterial infection by recognizing the peptidoglycan breakdown product MDP (muramyl di-peptide)3,4, and the adaptor protein RIP2 (receptor-interacting protein 2, also known as RICK5. Here, RIPK2 is linked to bacterial infectious disease.