Although the precise mechanisms of this transmigration remain unclear, the upregulation of mucosal addressin cell adhesion molecule 1 (MadCAM‐1), a ligand for α4β7 integrin expressed in vessels in the colonic lamina propria of patients with IBD and experimental animal models including DSS‐induced colitis models,105, 106, 107 suggest that an enhanced interaction between α4β7 integrin and MadCAM‐1 plays a role in accelerating the influx of oral Th17 cells into the inflamed gut (Figure 2). Here, MADCAM1 is linked to colitis.