Where does B-cell maturation primarily occur?

B-cell maturation primarily occurs in the bone marrow. This is the key site where B-cells, a type of lymphocyte responsible for humoral immune responses, develop from hematopoietic stem cells. During their time in the bone marrow, these precursor B-cells undergo several stages of development, including heavy and light chain gene rearrangement, which is essential for the generation of a diverse repertoire of antibodies.

After completing their maturation process, B-cells that successfully express functional B-cell receptors leave the bone marrow and move to peripheral lymphoid organs, including the spleen, where they can encounter antigens and participate in immune responses. The spleen serves as an important site for B-cell activation and proliferation after they leave the bone marrow, but they do not mature there.

The thymus, in contrast, is primarily involved in T-cell maturation, while the liver does not play a direct role in B-cell development. Thus, the bone marrow is the definitive site for B-cell maturation.