What does it mean for an antibody to activate complement?

• A. It leads to the production of antibodies
• B. It results in antibody neutralization
• C. It causes chemotaxis of phagocytes and inflammation
• D. It enhances the binding of antigens

Answer: (C)

When an antibody activates complement, it leads to a cascade of biochemical events that can significantly enhance the immune response. One of the primary outcomes of complement activation is the recruitment of phagocytes to the site of infection, a process known as chemotaxis. This not only helps to attract immune cells, such as neutrophils and macrophages, to the area but also promotes inflammation, which serves to localize and eliminate pathogens more effectively.

The activation of the complement system can lead to the formation of a membrane attack complex that can directly lyse invading pathogens, thereby directly contributing to the clearance of infection. It also results in the opsonization of pathogens, marking them for destruction by phagocytes, which further amplifies the immune response.

The other choices focus on different aspects of immune function, such as the production of antibodies or the neutralization of pathogens, but they do not encapsulate the broad and critical role of complement activation in enhancing phagocyte attraction and promoting inflammation during an immune response.