Thank you for the opportunity to reply to Smids et al regarding our paper in Gastroenterology. Etrolizumab, a humanized monoclonal antibody specific for β7 integrin, blocks both α4β7:MAdCAM-1 as well as αEβ7:E-cadherin interactions. In our phase II study, we observed that patients with higher than median levels of αE at baseline had higher remission rates following etrolizumab treatment.1 Both αE and the cytolytic protein granzyme A were found to be higher in baseline biopsies of etrolizumab-treated patients who achieved remission compared with those who did not achieve remission.