AEMCA Practice Exam

What role do monocytes play in the immune system?

1. To form antibodies

2. As small phagocytes

3. As large phagocytes

4. To produce red blood cells

The correct answer is: As large phagocytes

Monocytes play a crucial role in the immune system primarily as large phagocytes. They are a type of white blood cell that is part of the innate immune response. Monocytes circulate in the bloodstream and migrate into tissues, where they differentiate into macrophages or dendritic cells. These transformed cells can engulf and digest pathogens, dead cells, and debris through the process of phagocytosis. This is vital for the body's defense against infection and for initiating an adaptive immune response, as they help present antigens to T cells. Other options may address different functions or types of cells in the immune system. For example, the formation of antibodies is primarily the role of B cells, which are another type of lymphocyte. Small phagocytes refer more to neutrophils, which are smaller white blood cells involved in acute inflammation and the first line of defense against infections. Finally, the production of red blood cells is a function of hematopoietic stem cells in the bone marrow, not monocytes. Hence, the role of monocytes as large phagocytes is clearly articulated in their function within the immune response.