The dysgenetic thymus in nu/nu mice is a potent source of colony stimulating factor (CSF).

During in vitro incubation, the pulmonary and thymic tissue of mice released a colony stimulating factor (CSF) supporting the development of colonies of granulocytes and macrophages from bone marrow progenitors. Cardiac, splenic, renal and bone marrow tissues were not active. The dysgenetic thymus of nude mice was a very potent source of CSF during in vitro incubation.