Integrin alpha M

Integrin αM (ITGAM) is a protein subunit that can form heterodimeric integrin α-Mbeta-2 (αMβ2) molecules, also known as macrophage-1 antigen (Mac-1) or complement receptor 3 (CR3). ITGAM, also known as CR3A, is a cluster of differentiation molecules 11B (CD11B). The second chain of αMβ2 is a common integrin β2 subunit called CD18, so integrin αMβ2 belongs to the β2 subfamily (or leukocyte) integrin.

αMβ2 is expressed on the surface of many white blood cells involved in the innate immune system, including monocytes, granulocytes, macrophages and natural killer cells. It mediates inflammation by regulating the adhesion and migration of leukocytes, and is related to various immune processes such as phagocytosis, cell-mediated cytotoxicity, chemotaxis and cell activation. It participates in the complement system because it has the ability to bind the inactivated complement component 3b (iC3b). The ITGAMα subunit of integrin αMβ2 is directly involved in causing cell adhesion and spreading, but if β2 (CD18) subunit is not present, it cannot mediate cell migration.