What are the three primary outcomes once the complement system has been activated?

• A. Phagocytosis, Growth inhibition, Lysis
• B. Phagocytosis, Inflammation, Lysis
• C. Inflammation, Clotting, Healing
• D. Infection control, Pain management, Healing

Answer: (B)

The activation of the complement system leads to several key outcomes that are crucial to the innate immune response. The three primary outcomes are phagocytosis, inflammation, and lysis.

Phagocytosis occurs when activated complement proteins enhance the ability of phagocytes, such as macrophages and neutrophils, to recognize and engulf pathogens. This is often mediated by opsonization, where complement components coat pathogens, making them more attractive targets for phagocytes.

Inflammation is another critical outcome, as the complement system generates inflammatory mediators that recruit immune cells to the site of infection or injury. This process increases blood vessel permeability and stimulates the release of histamines, leading to the classic signs of inflammation: redness, heat, swelling, and pain. The inflammatory response is vital for containing infections and promoting healing.

Lysis refers to the direct destruction of pathogens through the formation of a membrane attack complex (MAC) on their surfaces, leading to cell lysis and death. This is particularly effective against certain bacteria and contributes to the elimination of infectious agents.

Together, these three outcomes serve to enhance the body’s ability to fight infections and promote a protective response, aligning perfectly with the role of the complement system in immunological defense. This framework is