Neutrophils are the most abundant type of white blood cells produced by the bone marrow and form an essential part of the innate immune system. A large number of neutrophils are held in reserve in the bone marrow to accommodate for their short lifespan. Neutrophils are derived from a Dextran red cell sedimented population of cells. Following red cell sedimentation, granulocytes are separated using a density gradient and red cell lysis. Cells are then purified through the use of indirect selection.