NOD2 and inflammatory bowel disease: Several candidate genes for IBD susceptibility have been identified, including nucleotide-binding oligomerization domain containing 2 (NOD2) [3-5], tumour necrosis factor (TNF) [6], members of the toll-like receptor (TLR) family [7], IL-4 [8] and IL-18 [9], and a number of genes encoding transporter molecules, such as the ATP-binding cassette, sub-family B (MDR/TAP), member 1 (ABCB1) [10,11] and solute carrier family 22 (organic cation/ergothioneine transporter), member 4 (SLC22A4) genes [12,13].