In vitro production of colony-stimulating factors by Listeria-immune spleen cells.

The survival of mice during Listeria monocytogenes infection is dependent on the efficiency of the early phases of host defenses. These early host defenses consist primarily of the production of bone marrow-derived monocytes and granulocytes and their accumulation at the site of infection. Two important parameters that are believed to affect the production of leukocytes during early infection are the number of leukocyte progenitors in bone marrow and the secretion of colony-stimulating factors (CSFs). At least four discrete CSFs, as determined by an in vitro colony forming assay, have been described: macrophage CSF (M-CSF), granulocyte CSF (G-CSF), granulocyte-macrophage CSF (GM-CSF), and multi-CSF (IL-3) (1). CSFs not only help to regulate the production of phagocytic cells, but also affect the function of mature phagocytes. For example, macrophages stimulated by CSFs secrete increased levels of oxygen reduction products (2) and have increased anti-tumor activity (3,4).