Integrins are cell adhesion receptors that are heterodimers composed of non-covalently associated α and β subunits (PMID: 9779984). CD11b, also known as Integrin alpha M or CR3A, belongs to the integrin alpha chain family. CD11b forms an α/β heterodimer with CD18 (integrin β2). CD11b/CD18 is implicated in various adhesive interactions of monocytes, macrophages and granulocytes as well as in mediating the uptake of complement-coated particles and pathogens (PMID: 9558116; 20008295). CD11b/CD18 is a receptor for the complement protein fragment iC3b, and is also a receptor for fibrinogen, factor X and ICAM1 (PMID: 2971974; 15485828).