Where do B lymphocytes mature?

• A. Thymus
• B. Bone marrow
• C. Spleen
• D. Lymph node

Answer: (B)

B lymphocytes mature in the bone marrow. Here, hematopoietic stem cells give rise to B-cell precursors that undergo rearrangement of their immunoglobulin genes to form a functional B-cell receptor. Through this maturation process, B cells are tested for functionality and self-reactivity (central tolerance) before they leave the marrow. Once mature, they migrate to peripheral secondary lymphoid organs like the spleen and lymph nodes, where they can encounter antigens, become activated, and differentiate into plasma cells and memory B cells. In contrast, T cells complete maturation in the thymus, and the spleen and lymph nodes mainly serve as sites for antigen exposure and lymphocyte activation rather than maturation.