Illustration based on a scanning electron micrograph of a sectioned human lymph node. Lymph nodes are encapsulated, kidney shaped structures; most occur at intervals along lymph vessels. Functions include filtration" of lymph by scavenging macrophages, production & storage of both antibody-secreting B-lymphocytes involved in humoral immunity, and of T-lymphocytes involved in cell-mediated immune response. A labyrinth of cells and cell processes in the inner medullary sinuses serves to slow the flow of fluid through the node & facilitates actions of lymphatic cells involved in the immune response processes. Magnification: x700 at 35mm size (approx.)"