CD11b is the integrin alpha M chain. Integrins are heterodimeric integral membrane proteins composed of an alpha chain and a beta chain. This I-domain containing alpha integrin combines with the beta 2 chain (ITGB2) to form a leukocyte-specific integrin referred to as macrophage receptor 1 ('Mac-1'), or inactivated-C3b (iC3b) receptor 3 ('CR3'). The alpha M beta 2 integrin is important in the adherence of neutrophils and monocytes to stimulated endothelium, and also in the phagocytosis of complement coated particles.Synonyms: CD11 antigen-like family member B, CR-3 alpha chain, CR3A, Cell surface glycoprotein MAC-1 subunit alpha, ITGAM, Integrin alpha-M, Leukocyte adhesion receptor MO1, MAC1, Neutrophil adherence receptor