Phagocytes and lymphocytes remove foreign organisms and cell debris. Synthesis of all blood cell types. B cells mature here. Stores both red and white blood cells. Filters and clears out old red or white blood cells.
T cells mature in the thymus.
Red area due to increased blood flow. Hot due to increased metabolism and blood flow. This helps to inhibit bacterial or viral reproduction. Swollen due to fluid leaking from the capillaries which will travel back through the lymph system. A moderate fever helps fight infections in several ways.