Macrophage colony-stimulating factor in murine candidiasis: Serum and tissue levels during infection and protective effect of exogenous administration

Serum and tissue concentrations of the macrophage-specific colony-stimulating factor (CSF-1) and the number of CSF-1-responsive cells in bone marrow were investigated in mice chronically infected with a low-virulence strain of the opportunistic zoopathogenic yeast Candida albicans. CSF-1 levels in serum, brain, kidney, liver, and lung were significantly increased shortly after infection and remained elevated during the 2 weeks preceding the onset of specific T cell-dependent immunity. The number of monocytic precursor cells was also increased in the bone marrow of infected mice. When macrophages from naive donors were exposed in vitro to purified murine CSF-1, their anticandidal activity in vitro appeared to be enhanced. CSF-1 was also administered in vivo to prospective recipients of a lethal C. albicans challenge. The results showed that the factor could effectively potentiate the animals' resistance to the yeast, as shown by increased survival times and reduced recovery of viable C. albicans from the organs of the CSF-1-treated mice. Therefore, the present data suggest that CSF-1 is likely to contribute to early resistance to fungal infection and could be successfully exploited in experimental models of antifungal immunotherapy.