Description
Complement receptor type 1 (CR1/CD35) is a type I transmembrane glycoprotein that is expressed on the surface of B cells, neutrophils, monocytes, and renal podocytes. As a component of the host’s innate immune system, CR1/CD35 expressed on neutrophils and monocytes binds to ligands coated with complement opsonins C3b and C4b, thereby promoting phagocytosis and pro-inflammatory cytokine production. CR1/CD35 also participates in negative regulation of the complement cascade through its ability to promote dissociation of C3 and C5 convertases and by serving as one of multiple cofactors for factor-I-mediated cleavage and inactivation of C3b and C4b.