The paracortex contains lymphocytes and accessory cells along with supporting cells and it is the predominant site for T lymphocytes within the lymph node. The various types of T cell enter the node from the blood via the HEVs. When activated they form lymphoblasts which divide to produce a clone of T cells responding to a specific antigen. Activated T cells then pass into the circulation to reach peripheral sites. The medullary cords are rich in plasma cells which produce antibodies that pass out of the node via the efferent lymphatic.
Macrophages are also numerous within the medulla.
Lymph passes into the node through the afferent lymphatic into the marginal sinus, though the cortical sinuses to reach the medullary sinuses before leaving via the efferent lymphatic. Particulate matter in the lymph is removed by macrophages. Antigens are taken up by antigen presenting cells and these facilitate the specific immune response. The spleen is located in the upper left quadrant of the abdomen. It has two main functions acting as part of the immune system and as a filter.