Which cells predominantly make up the medulla of the thymus?

• A. Immature T cells and plasma cells
• B. Mature T cells, epithelial cells, dendritic cells, macrophages
• C. Only lymphocytes
• D. Macrophages and adipocytes

Answer: (B)

The medulla of the thymus is primarily composed of mature T cells alongside several important supporting cells, which include epithelial cells, dendritic cells, and macrophages. This composition is essential for the proper functioning of the thymus in T cell maturation and selection processes.

Mature T cells in the medulla have already undergone the critical training phase that occurs in the cortex of the thymus. The presence of epithelial cells is crucial as they provide a structured environment and produce thymic hormones that aid in T cell maturation. Dendritic cells play an important role in presenting antigens to the T cells, thus facilitating the selection process that ensures only those T cells which can adequately respond to antigens survive. Macrophages contribute by clearing out apoptotic cells and other debris, maintaining a supportive microenvironment necessary for the maturation process.

This variety of cell types found in the medulla is essential for generating a functional and well-regulated T cell population, which is crucial for the adaptive immune response.