Microbiology Practice Exam

Which immune system component is crucial for antigen presentation?

1. B-cells

2. Macrophages

3. Plasma cells

4. Memory cells

The correct answer is: Macrophages

Macrophages play a crucial role in antigen presentation due to their ability to ingest pathogens and process their antigens effectively. After phagocytosing an antigen, macrophages break it down into smaller peptide fragments. These peptides are then displayed on their surface using major histocompatibility complex (MHC) molecules, particularly MHC class II for extracellular antigens. This display is essential as it allows T-helper cells to recognize the antigen, facilitating a subsequent activation of the immune response. By presenting antigens in this way, macrophages not only help in alerting T-cells to the presence of pathogens but also play a vital role in orchestrating the entire immune response. This function is particularly important in adaptive immunity, helping to ensure that the body can create a tailored response to specific pathogens. B-cells, plasma cells, and memory cells each have their distinct functions in the immune system, such as producing antibodies and maintaining long-term immunity, but they are not primarily responsible for the initial presentation of antigens to T-cells.