MAdCAM-1 is a 58-66kD type I glycoprotein, also known as Mucosal addressin cell adhesion molecule-1. This mucosal vascular addressin is a member of the Ig superfamily found on fetus and neonatal endothelial cells. In adults, MAdCAM-1 is predominately expressed on high endothelial venule (HEV) of Peyer's patches, mesenteric lymph nodes and gut lamina propria. It is also expressed on vascular endothelium in mammary glands and pancreas. MAdCAM-1, through its interaction with integrin alpha4beta7 or CD62L, is involved in lymphocyte tethering, rolling, and homing. It has been reported that immobilized MAdCAM-1 is able to co-stimulate T cell proliferation. The MECA-367 antibody blocks the interaction of MAdCAM-1 with its counter-receptor both in vitro and in vivo. In vivo administration of the mAb is able to reduce T-cell mediated inflammation in some gastrointestinal diseases.