Once cleaved C3b can either generate C3 or C5 convertases, as mentioned above, or else covalently bind to the microbial surface, tagging the cell for phagocytosis in a process known as opsonization. Additionally, C3b molecules can attach to the Fc regions of antigen-bound antibodies leading to phagocytosis or movement to the liver, where the C3b-tagged immune complex is then destroyed.
After cleavage, C3b can generate either C3 or C5 convertases as previously mentioned, or it can covalently bind to the microbial surface for tagging and phagocytosis through opsonization. Additionally, C3b molecules can adhere to the Fc regions of antibodies bound to antigens, leading to phagocytosis or transport to the liver where the tagged immune complex is destroyed.