Microbiology Practice Exam

What does the Fc region of an antibody primarily interact with?

1. Antigens

2. Complement proteins

3. Pathogen receptors

4. Cytokines

The correct answer is: Complement proteins

The Fc region of an antibody primarily interacts with complement proteins, which plays a crucial role in the immune response. The Fc region, or fragment crystallizable region, is the tail part of the antibody that mediates interactions with other components of the immune system, including complement proteins. When an antibody binds to an antigen via its Fab region, the Fc region can then bind to the complement proteins, leading to a cascade of events that enhance the immune response. This interaction is essential for opsonization, where pathogens coated with antibodies become more recognizable to phagocytes, and for the activation of the complement system, which can lead to lysis of pathogens or recruitment of immune cells. Understanding the role of the Fc region is critical in immunology since it bridges the adaptive immune response (via antibody production) with the innate immune mechanisms.