CD11b (integrin alpha-M, ITGAM, integrin alpha-X, ITGAX) is a 165 kDa adhesion molecule that associates non-covalently with integrin beta-2 (CD18). The CD11b/CD18 heterodimeric complex is also known as integrin alpha-M beta-2, Mac-1, and CR3 (complement receptor 3). CD11b is expressed on the surface of monocytes/macrophages, granulocytes, activated lymphocytes, a subset of NK cells, a subset of dendritic cells, and microglia in the brain. CD11b/CD18 functions as the receptor for ICAM-1 (CD54), ICAM-2 (CD102), ICAM-4 (CD242), CD14, CD50, CD23, heparin, iC3b, fibrinogen, and Factor X -these adhesions are critical for cell-cell and cell-matrix interactions. CD11b is expressed on 8% of spleen cells, 44% of bone marrow cells, and less than 1% of thymocytes, and is commonly used as a microglial marker in nervous tissue. The expression of CD11b increases during monocyte maturation and expression levels vary on tissue macrophages. Further, peritoneal macrophages are reported to express higher levels of CD11b than splenic macrophages. Diseases associated with CD11b dysfunction include systemic lupus erythematosus 6 and ITGAM-related susceptibility to systemic lupus erythematosus.
CD11 antigen-like family member B; CD11B (p170); cell surface glycoprotein MAC-1 alpha subunit; cell surface glycoprotein MAC-1 subunit alpha; complement component receptor 3 alpha-a; complement receptor type 3; CR-3 alpha chain; integrin alpha-M; leukocyte adhesion receptor MO1; Mac-1 alpha; Mac-1 alpha (Mac1A); macrophage antigen alpha; MGC117044