Integrins are transmembrane receptors that mediate the attachment between a cell and its surroundings, such as other cells or the extracellular matrix (ECM). Integrins are obligate heterodimers containing two distinct chains, called the α (alpha) and β (beta) subunits. The molecular mass of the integrin subunits can vary from 90 kDa to 160 kDa. Beta subunits have four cysteine-rich repeated sequences. Both α and β subunits bind several divalent cations. Integrins have two main functions: Attachment of the cell to the ECM and signal transduction from the ECM to the cell. However, they are also involved in a wide range of other biological activities, including immune patrolling, cell migration, and binding to cells by certain viruses, such as adenovirus, echovirus, hantavirus, and foot and mouth disease viruses. Research studies have implicated β1 integrin in various activities including embryonic development, blood vessel, skin, bone, and muscle formation, as well as tumor metastasis and angiogenesis.