Integrin alpha 4 beta 1, also called VLA4, is an integrin family adhesion receptor that shares the beta 1 subunit with eleven other family members and the alpha 4 subunit with Integrin alpha 4 beta 7. The integrin alpha 4 beta 1 and its counter receptor vascular cell adhesion molecule-1 (VCAM-1) mediate well-described cell-cell interactions that are critical for immune function.