Questions: Bacteria invading a wound are clumped together by antibodies. The exposed Fc regions are bound by a macrophage and the entire clump of cells is engulfed. Which two effector functions of antibodies does this example describe?

The answer is B: Opsonization and D: Agglutination.

Explanation for each option:

A. Complement activation: This refers to the process by which antibodies trigger the complement system, a series of proteins that assist in destroying pathogens. While complement activation is an important function of antibodies, it is not directly described in the scenario provided.

B. Opsonization: This is the process by which antibodies coat a pathogen, marking it for phagocytosis by immune cells such as macrophages. In the scenario, the antibodies clump the bacteria together and expose their Fc regions, which are recognized and bound by macrophages, leading to phagocytosis. This describes opsonization.

C. Precipitation: This involves the formation of insoluble complexes when antibodies bind to soluble antigens, causing them to precipitate out of solution. This is not relevant to the scenario, as it involves bacteria, not soluble antigens.

D. Agglutination: This is the clumping together of cells or particles, typically by antibodies. In the scenario, the bacteria are clumped together by antibodies, which is a clear example of agglutination.

In summary, the two effector functions of antibodies described in the scenario are opsonization and agglutination.