Background: Infiltration of GI by T lymphocytes is a pathogenic mechanism both in ulcerative colitis (UC) and in Crohn's disease (CD). Vedolizumab (VDZ) is a humanized monoclonal antibody binding with high affinity to α4β7 integrin blocking α4β7+-MAdCAM-1 interaction, hence blocking a key step in GI lymphocytes T infiltration. VDZ has demonstrated a therapeutic effect in UC and CD. Investigators still lack of adequate biomarkers to predict clinical response to biological treatments, specially avoiding invasive procedures.