<P> The lymphatic system consists of lymphatic organs, a conducting network of lymphatic vessels, and the circulating lymph . </P> <P> The primary or central lymphoid organs generate lymphocytes from immature progenitor cells . </P> <P> The thymus and the bone marrow constitute the primary lymphoid organs involved in the production and early clonal selection of lymphocyte tissues . Bone marrow is responsible for both the creation of T cells and the production and maturation of B cells . From the bone marrow, B cells immediately join the circulatory system and travel to secondary lymphoid organs in search of pathogens . T cells, on the other hand, travel from the bone marrow to the thymus, where they develop further . Mature T cells join B cells in search of pathogens . The other 95% of T cells begin a process of apoptosis, a form of programmed cell death . </P> <P> Secondary or peripheral lymphoid organs, which include lymph nodes and the spleen, maintain mature naive lymphocytes and initiate an adaptive immune response . The peripheral lymphoid organs are the sites of lymphocyte activation by antigens . Activation leads to clonal expansion and affinity maturation . Mature lymphocytes recirculate between the blood and the peripheral lymphoid organs until they encounter their specific antigen . </P>

What is the difference between primary and secondary lymphoid organs