Final answer:
During rapid B lymphocyte division, the germinal centers in the lymphoid tissue expand to accommodate the increased activity as part of the immune response.
Step-by-step explanation:
When B lymphocytes are dividing rapidly, the germinal centers of the lymphoid tissue enlarge. Within the lymph nodes, these germinal centers consist of a proliferation of B cells that are surrounded by T cells and other accessory cells. The enlargement of germinal centers indicates a heightened immune response as B cells undergo clonal expansion to produce antibodies to fight infection. These centers are critical to the adaptive immune system's response to encountering antigens.