Multiple myeloma is characterized by proliferation of which type of B cells?

• A. Monoclonal B cells
• B. Polyclonal B cells
• C. Naive B cells
• D. Memory B cells

Answer: (A)

Multiple myeloma is driven by a single malignant B-cell clone that has differentiated into plasma cells. These cancerous plasma cells proliferate in the bone marrow and produce large amounts of one specific immunoglobulin, creating a monoclonal gammopathy. In contrast, a polyclonal B cell response involves many different B cell clones and a mixture of antibodies, which is not seen in myeloma. Naive B cells are immature and not the proliferating malignant population, and memory B cells are a distinct, antigen-experienced subset not characteristically expanding in this disease. Thus, the proliferating cells are monoclonal B cells.