ITGA4 (Integrin Subunit Alpha 4), also known as CD49d, and ITGB7 (Integrin Subunit Beta 7) form the heterodimeric integrin α4β7. This receptor is primarily expressed on subsets of lymphocytes and mediates the gut-specific homing of T cells by binding to MAdCAM-1 on intestinal endothelium. Aberrant expression of α4β7 is linked to inflammatory bowel disease (IBD), where it drives pathological lymphocyte infiltration into the gut mucosa, and also plays a role in HIV pathogenesis by facilitating viral spread and intestinal homing. Drug development has yielded vedolizumab, an FDA-approved monoclonal antibody that blocks α4β7-MAdCAM-1 interaction for the treatment of ulcerative colitis and Crohn’s disease. Additionally, natalizumab targets the α4 subunit, blocking both α4β1 and α4β7, and is approved for multiple sclerosis and Crohn’s disease.