CD104 is a 205 kD type I transmembrane glycoprotein, known as integrin beta4 chain or beta4 integrin, that associates with integrin alpha6 (CD49f) forms alpha6/beta4 (CD49f/CD104) heterodimer. CD104 is expressed on epithelial cells (especially on the proliferative basal layer epithelial cells in skin), endothelial cells, Schwann cells, certain tumor cells and a subset of pre-T cells. CD49f/CD104 is an adhesion receptor for laminins (especially laminin 5) and keratin filaments and is involved in the regulation of hemidesmosome formation and of cell proliferation and activation.