Leukocyte-promoting factor

Leukocyte-promoting factor, also known as leukopoietin, is an obsolete term used to describe substances that are produced by neutrophils when they encounter a foreign antigen. It stimulates the bone marrow to increase the rate of leukopoiesis, in order to replace the neutrophils that will inevitably be lost when they begin to phagocytose the foreign antigens.