ABCB1 and inflammatory bowel disease: No study has evaluated the putative modulation of ABCB1 in mucosa of IBD patients by anti‐TNF treatment, and a single in vitro study on Caco‐2 cell lines showed that in vitro TNFα treatment induced diminution of MDR1 mRNA levels (Belliard, Lacour, Farinotti, & Leroy, 2004).