Nonimmune mice infected with Listeria monocytogenes exhibited elevated expression of
macrophage colony-stimulating factor (
M-CSF)
mRNA and the enhanced migration of
Mac-1 antigen-positive bone marrow-derived mononuclear phagocytes (
BMMP) to their livers. Treatment with monoclonal anti-
M-CSF antibody diminished the traffic of
BMMP and promoted the replication of listeriae. Immune animals infected with listeriae expressed significantly lower levels of
M-CSF mRNA than did nonimmune animals. Moreover, listerial
infections did not elicit the migration of
BMMP to the livers of immune mice, nor did anti-
M-CSF affect the capacity of immune animals to respond to
infection. Adoptive immunization experiments suggest that T lymphocytes can mediate protective immunity to listeriae in the absence of
M-CSF and migrating
BMMP. These findings indicate that
M-CSF and the enhanced migration of
BMMP are critical factors in primary but not secondary host defenses to listerial
infections.