Although parenterally administered anti-TNF agents may interact with the intestinal microbiota at the site of mucosal inflammation [i.e., intramucosal bacteria as reported for CD and UC (Moussata et al., 2011)] and can “leak” to the intestinal lumen (Derijks et al., 2018) likely facilitated by a disrupted barrier, it remains to be elucidated to what extent microbiota-driven degradation occurs in IBD patients and how relevant this is regarding treatment response. This evidence concerns the gene TNF and inflammatory bowel disease.