Complement Receptor 3
The integrin Mac-1, better known as complement receptor 3 (CR3), is a heterodimer of the CD11b (ITGAM) alpha chain and the CD18 (ITGB2) beta chain and belongs to the beta-2 integrins. Abundant on monocytes, macrophages, neutrophils and NK cells, CR3 binds iC3b-opsonized particles to drive complement-mediated phagocytosis, and it also recognizes ICAM-1, fibrinogen and beta-glucans. Signaling through CR3 controls adhesion, spreading, respiratory-burst priming and outside-in activation of myeloid cells during inflammation. Because ITGB2 mutations cause leukocyte adhesion deficiency type 1, CR3 function is central to host defense, and recombinant CD11b/CD18 reagents support adhesion, phagocytosis and ligand-blocking assays.
