CD11c, also known as the Integrin alpha X subunit, is a 150 kDa type I transmembrane protein that noncovalently heterodimerizes with the Integrin beta 2 subunit (CD18). This heterodimeric protein (Integrin alpha X beta 2) is also known as p150/p95 and complement receptor type 4 (CR4). Integrin alpha X beta 2 is expressed on macrophages, dendritic cells, hairy cell leukemias, and some other leukocyte subsets. aXb2 shares some adhesion partners with aMb2 including Complement iC3b, ICAMs, vWF, and Fibrinogen. Other binding partners, such as Osteopontin, Thy-1, Plasminogen, Heparin are unique to aXb2. Integrin alpha X beta 2 adhesion mediates cell proliferation, degranulation, chemotactic migration, and phagocytosis of complement-opsonized particles.