Final answer:
B cells mature in the bone marrow and T cells in the thymus; afterward, they localize to secondary lymphoid tissues like the lymph nodes, spleen, and tonsils.
Step-by-step explanation:
B cells develop in the bone marrow, while T cells develop in the thymus. The mature naive lymphocytes re-localize in the secondary lymphoid tissues: lymph nodes, spleen, and tonsils. Both types of lymphocytes are critical for the adaptive immune response, and after their development, they travel through the circulatory system and enter the lymphatic system, where they search for pathogens. The bone marrow is the site where B cells mature, thus the designation 'B' cell, and similarly, T cells get their name from their maturation site, the thymus.