Activation of the complement system causes which effects?

Activation of the complement system causes which effects?

• A. Platelet aggregation
• B. Activation of the complement system causes increased permeability, phagocytosis, chemotaxis
• C. Lymphocyte apoptosis
• D. Mast cell degranulation

Answer: (B)

Complement activation drives inflammation by generating fragments that coordinate vascular, cellular, and microbe-targeting responses. The anaphylatoxins C3a and C5a promote vasodilation and increase vascular permeability, contributing to swelling and allowing larger numbers of immune cells to reach the site. C3b acts as an opsonin, coating pathogens and making them easier for phagocytes to recognize and engulf, which enhances phagocytosis. C5a is also a potent chemoattractant, drawing neutrophils and macrophages to the area (chemotaxis). Together, increased permeability, enhanced phagocytosis via opsonization, and chemotaxis reflect the principal effects of complement activation. The membrane attack complex (C5b-9) can lyse certain pathogens, but the described effects focus on the inflammatory and phagocytic roles of the system.

Complement activation drives inflammation by generating fragments that coordinate vascular, cellular, and microbe-targeting responses. The anaphylatoxins C3a and C5a promote vasodilation and increase vascular permeability, contributing to swelling and allowing larger numbers of immune cells to reach the site. C3b acts as an opsonin, coating pathogens and making them easier for phagocytes to recognize and engulf, which enhances phagocytosis. C5a is also a potent chemoattractant, drawing neutrophils and macrophages to the area (chemotaxis). Together, increased permeability, enhanced phagocytosis via opsonization, and chemotaxis reflect the principal effects of complement activation. The membrane attack complex (C5b-9) can lyse certain pathogens, but the described effects focus on the inflammatory and phagocytic roles of the system.