CD11a is a member of the integrin family of cell adhesion molecules. It is a glycoprotein expressed in combination with the CD18 beta chain. CD11a is a member of the beta 2 integrin family. These molecules function in cell adhesion and specifically bind to CD54, ICAM2, ICAM3. CD11a is expressed on thymocytes, T and B lymphocytes, granulocytes, monocytes, and macrophages.