Antibody Activated Endocytosis (Antibody Opsonization)
Antibody opsonization is the process by which the pathogen is marked for ingestion and eliminated by the phagocytes. The major class if immunoglobulin in the blood is IgG, which is produced in large amount during secondary immune responses. Besides activating the complement system, the tail of an IgG molecule binds to specific receptors on macrophages and nutrophils. These phagocytic cells then bind, ingest and destroy infecting microorganisms that have become coated with IgG antibodies. The macrophages recognize bacteria that have been coated with antibody (opsonized). This antibody mediated recognition helps in faster phagocytosis. Opsonin is a substance that coats foreign antigens, making them more susceptible to macrophages and other leukocytes.