The CD29 (HI29a) antibody recognizes the 130-kDa transmembrane glycoprotein integrin β1 subunit which is the common β1 chain of the very late antigen (VLA) forming a non-covalent heterodimeric complex with several integrins α subunits that are receptors for extracellular matrix proteins such as collagen, fibronectin and osteopontin. CD29 has a broad tissue distribution including lymphocytes, monocytes, platelets, fibroblasts, and endothelial cells, whereas it is weakly expressed in granulocytes and absent in erythrocytes. CD29 is an important adhesion molecule involved in cell-cell and cell-extracellular matrix interactions. CD29 plays a critical role in the functional activity of lymphocytes by influencing cellular migration patterns as well as by transducing intracellular signals that influence lymphocyte function.