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Opsonization

Antibodies, when present, neutralize the toxic effects of capsules and greatly promote phagocytosis. This effect is known as opsonization (Gr. opsonin=to prepare food for). Antigens that have bound antibody and CI, C4, C2, and C3 are far more easily phagocytized than the antigen alone. The addition of C5 further enhances phagocytosis of the immune complex. Complement-depen­dent opsonization may be important in -limiting bacterial infections, particularly in capsulated bacteria.