AEMCA Practice Exam

Which cells are primarily located in the medulla of lymph nodes?

1. B-cells

2. Plasma cells and monocytes

3. T-cells

4. Macrophages

The correct answer is: Plasma cells and monocytes

The medulla of lymph nodes is primarily populated by plasma cells and monocytes. Plasma cells are differentiated B-cells, which are crucial for antibody production. Once B-cells encounter their specific antigen and undergo activation, they migrate to the medulla, where they differentiate into plasma cells, producing large quantities of antibodies that are released into the lymphatic circulation. Monocytes, which can differentiate into macrophages or dendritic cells, also play a critical role within the medullary region by aiding in phagocytosis and presenting antigens to T-cells. This activity is essential for the adaptive immune response and enhances the ability of the lymph node to filter lymph and respond to infections. Other cell types such as T-cells and B-cells are more commonly found in the cortex of the lymph nodes, where they undergo activation and proliferation. While macrophages are present throughout the lymph node, including the medulla, the primary identity of the medullary area is characterized by the presence of plasma cells and monocytes, which play a central role in the immune response at this location.