Which statement best describes Hassall's corpuscles?

• A. They are sites of B cell colonization in lymph nodes
• B. They are structures located in the thymus with an uncertain function
• C. They are components of the spleen's white pulp
• D. They are produced by plasma cells in bone marrow

Answer: (B)

Hassall's corpuscles are structures in the thymus, specifically in the medulla, and their function is not clearly defined. They are formed by concentric layers of epithelial reticular cells and often have a keratinized center. This uncertain role is what exam questions emphasize. They are not sites of B cell colonization (that occurs in lymph nodes), not components of the spleen’s white pulp (which contains PALS and lymphoid follicles), and not produced by plasma cells in the bone marrow. In short, their primary note in immunology is that they’re thymic medullary structures with an unclear function.