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Integrin alpha M (ITGAM) is one protein subunit that forms the heterodimeric integrin alpha-M beta-2 (α_Mβ₂) molecule, also known as macrophage-1 antigen (Mac-1) or complement receptor 3 (CR3).^[1] ITGAM is also known as CR3A, and cluster of differentiation molecule 11B (CD11B). The second chain of α_Mβ₂ is the common integrin β₂ subunit known as CD18, and integrin α_Mβ₂ thus belongs to the β₂ subfamily (or leukocyte) integrins.^[2]

α_Mβ₂ is expressed on the surface of many leukocytes involved in the innate immune system, including monocytes, granulocytes, macrophages, and natural killer cells.^[1] It mediates inflammation by regulating leukocyte adhesion and migration and has been implicated in several immune processes such as phagocytosis, cell-mediated cytotoxicity, chemotaxis and cellular activation.^[1] It is involved in the complement system due to its capacity to bind inactivated complement component 3b (iC3b).^[3] The ITGAM (alpha) subunit of integrin α_Mβ₂ is directly involved in causing the adhesion and spreading of cells but cannot mediate cellular migration without the presence of the β2 (CD18) subunit.^[1]

1. ^ ^{a b c d} Solovjov D, Pluskota E, Plow E (2005). "Distinct roles for the alpha and beta subunits in the functions of integrin alphaMbeta2". J Biol Chem 280 (2): 1336-45. PMID 15485828. 
2. ^ Larson R, Springer T. "Structure and function of leukocyte integrins". Immunol Rev 114: 181-217. PMID 2196220. 
3. ^ Arnaout M, Todd R, Dana N, Melamed J, Schlossman S, Colten H (1983). "Inhibition of phagocytosis of complement C3- or immunoglobulin G-coated particles and of C3bi binding by monoclonal antibodies to a monocyte-granulocyte membrane glycoprotein (Mol)". J Clin Invest 72 (1): 171-9. PMID 6874946. 

• integrin

• MeSH Integrin+alphaM

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