American Board of Surgery Qualifying Exam (ABS QE) Practice Test

What is the significant role of macrophages in the immune system?

1. Phagocytosis of pathogens

2. Production of antibodies

3. Regulating the allergic response

4. Activation of memory cells

The correct answer is: Phagocytosis of pathogens

Macrophages play a pivotal role in the immune system primarily through their ability to conduct phagocytosis, which involves the engulfing and digestion of pathogens such as bacteria and viruses. These cells are equipped to recognize, ingest, and destroy intruders, making them essential components of the innate immune response. In addition to directly eliminating pathogens, macrophages also contribute to the immune response by acting as antigen-presenting cells. After digesting pathogens, they process and present antigens on their surface to T cells, thereby linking innate and adaptive immunity. This function not only helps to clear infections but also plays a critical role in activating other immune cells, including lymphocytes, to generate a more robust and specific immune response. While the other choices present important functions within the immune system, they are not the primary role of macrophages. Antibody production is chiefly carried out by B cells, regulating allergic responses is mainly the function of mast cells and basophils, and activating memory cells is predominantly a role fulfilled by T cells and B cells. Thus, macrophages are best known for their role in phagocytosis and initiating the immune response, making them crucial to the defense against pathogens.