[42] The macrophage colony-stimulating factor, CSF-1

This chapter discusses the macrophage colony-stimulating factor—that is, CSF. The production of granulocytes and macrophages from immature hemopoietic progenitor cells in tissue culture is dependent on the presence of a group of specific growth factors. These factors are termed the CSFs because in semisolid culture media they stimulate individual hemopoietic progenitor cells to form colonies of granulocytes and macrophages. They are believed to regulate granulocyte and macrophage production in intact animals although their in vivo effects have not been elucidated. At least 4 CSF subclasses can be defined by the kind of mature cells they produce in culture. The CSF bioassay is based on the CSF-dependent formation of colonies of granulocytes and/or macrophages by bone marrow cells cultured in semisolid agar or methyl cellulose medium. For large numbers of assays the agar culture method is more rapid and less expensive. However, good cellular morphology of stained colony cells is more easily obtained with colonies from methyl cellulose cultures. Bioassays may be carried out in a number of species including chickens or man. Methods for the bioassay of murine and human CSFs are also described further in the chapter.