CD35, also known as complement receptor 1 (CR1), is a 220-300 kDa N-glycosylated member of the RCA (regulators of complement activation) family of proteins. CD35 binds and internalizes particles and immune complexes that are opsonized with MBL or complement components C3b, C3i, C4b, or C1q. CD35 additionally protects the cell from complement-mediated lysis by serving as a cofactor for Factor I and inhibiting the C3 and C5 convertases. The extracellular domain (ECD) of human CD35 contains 30 tandem SCR/SUSHI repeats.
