NOD2 and inflammatory bowel disease: IBD: Inflammatory bowel disease; Th: T helper; IL: Interleukin; TNF: Tumor necrosis factor; TGF: Transforming growth factor; CCR: Chemokine receptor; CD: Cluster of differentiation; T-bet: T-box expressed in T cells; STAT: Signal transducer and activator of transcription; GATA: GATA transcription factor; NF-kB: Nuclear factor kappa-light-chain-enhancer of activated B cells; NOD2: Nucleotide-binding oligomerization domain-containing protein 2.