Which immune process is activated by the formation of an antigen-antibody complex?

The formation of an antigen-antibody complex plays a pivotal role in the immune response, particularly in the process of phagocytosis. When antibodies bind to specific antigens on pathogens—such as bacteria and viruses—this complex enhances the visibility of the pathogen to phagocytes (such as macrophages and neutrophils). These immune cells have receptors that recognize the Fc region of antibodies, enabling them to identify and engulf the antibody-coated pathogens more efficiently.

This binding not only marks the pathogen for destruction but also can trigger various biological responses that culminate in the elimination of the pathogen. Phagocytosis is essential for clearing infections and dead cells, and it is often one of the first lines of defense during an immune response.

While the other processes listed—clonal selection, inflammation, and signal transduction—are also important components of the immune response, they do not primarily stem from the formation of an antigen-antibody complex in the same direct manner as phagocytosis. Clonal selection involves the proliferation of specific lymphocytes in response to an antigen, inflammation is a broader response involving various immune cells and mediators, and signal transduction refers to the intracellular signaling pathways activated upon receptor binding, which can occur in multiple immune processes.