Immune Response to Infectious Diseases CHAPTER 17 397 VISUALIZING CONCEPTS ① Toxin neutralization C3b C lysis ④ Anaphylatoxins mediate Chemotaxis C3a, C4a, C5a Mast cell Mediators一 Neutr Macrophage FIGURE 17-8 Antibody-mediated mechanisms for combating increase phagocytosis. (4)C3a, C4a, and C5a, generated by antibody. infection by extracellular bacteria (1)Antibody neutralizes bacterial initiated complement activation, induce local mast cell degranulation, toxins. (2)Complement activation on bacterial surfaces leads to releasing substances that mediate vasodilation and extravasation complement-mediated lysis of bacteria. (3) Antibody and the com- of lymphocytes and neutrophils (5)Other complement split prod plement split product C3b bind to bacteria, serving as opsonins to ucts are chemotactic for neutrophils and macrophagesImmune Response to Infectious Diseases CHAPTER 17 397 VISUALIZING CONCEPTS Mast cell Opsonization and phagocytosis Anaphylatoxins mediate mast cell degranulation Complement–mediated lysis Toxin neutralization C3b C3b C3b C3b C3b C3b Toxin Bacteria Complement activation C3a, C4a, C5a Mediators Extravasation Macrophage Macrophage Neutrophil Lymphocyte 3 5 Chemotaxis 2 4 1 FIGURE 17-8 Antibody-mediated mechanisms for combating infection by extracellular bacteria. (1) Antibody neutralizes bacterial toxins. (2) Complement activation on bacterial surfaces leads to complement-mediated lysis of bacteria. (3) Antibody and the com￾plement split product C3b bind to bacteria, serving as opsonins to increase phagocytosis. (4) C3a, C4a, and C5a, generated by antibody￾initiated complement activation, induce local mast cell degranulation, releasing substances that mediate vasodilation and extravasation of lymphocytes and neutrophils. (5) Other complement split prod￾ucts are chemotactic for neutrophils and macrophages