NOD2 and inflammatory bowel disease: A study including 19,735 cases with IBD (10,856 cases with CD and 8,879 cases with UC) of known smoking status found that 2 variants in HLA and NOD2 gene regions interacted with smoking in influencing CD risk, and smoking modified the disease risk of some variants in opposite directions for CD vs UC (35), which indicated that the effects of smoking on IBD risk depend on genetic variants.