Final answer:
The areas known as white pulp are where lymphocytes are suspended by reticular fibers in the spleen, and it is where the adaptive immune response is mounted, mainly involving germinal centers of B cells.
Step-by-step explanation:
Areas of lymphocytes suspended by reticular fibers in the spleen are known as white pulp. The spleen is an encapsulated organ that filters blood and traps pathogens and antigens. The white pulp of the spleen is where adaptive immune responses are generated, particularly the responses of T cells and B cells. It consists of germinal centers with rapidly dividing B cells surrounded by T cells and other accessory cells such as macrophages and dendritic cells. These germinal centers are crucial for the activation and differentiation of B lymphocytes as they respond to antigens.