Spleen red pulp. Light micrograph of a section through the red pulp of the spleen. This type of spleen tissue is involved in filtering and breaking down old or defective red blood cells (erythrocytes, red). The red pulp consists of connected cords of tissue (termed the cords of Bilroth) which contain large numbers of immune system cells, such as macrophages, as well as erythrocytes. Blood passes through the red pulp through specialised blood vessels called venous sinuses. Magnification unknown.