Primary organs consist of Bone marrow and thymus. Bone marrow is the site of B-Cells maturation. While thymus receives the immature T-Cells from the Bone Marrow.Secondary ograns consist of Spleen and lymph nodes. Spleen functions as a primary defense against blood pathogens. While lymph nodes play three important roles, they form a zone of contact between antigen presenting cells, B-cells and T-cells, storage and proliferation of lymphocytes, and primary defense against tissue pathogens.