Granulocyte colony-stimulating factor (G-CSF) stimulates a subset of granulocyte colony forming cells and when administered to neutropenic individuals results in recovery of blood neutrophil numbers to normal levels. Therefore, G-CSF may be a useful therapeutic agent for infections in immunocompromised hosts. However, to date there has been only limited information that G-CSF activates the antimicrobial activity of neutrophils. In the present study, we found that recombinant G-CSF promotes the anti-Candida albicans activity of normal human blood polymorphonuclear (PMN) cells in vitro using both a 3H-glucose uptake procedure and a Candida colony counting assay. As little as 0.1 ng/ml G-CSF induced significant anti-Candida activity in the PMN cultures. G-CSF treatment also enhanced superoxide anion production by the PMNs in response to f-MLP as determined by the superoxide dismutase inhibitable cytochrome C reduction method. Such results show that G-CSF can promote the antimicrobial activity of peripheral blood PMNs against C. albicans.

Legionella pneumophila readily grows in cultures of thioglycollate (TGC)‐induced macrophages (MPs) from A/J mice, but not in MPs from BALB/c mice or other mouse strains. In the present study, the growth of Legionella pneumophila in MPs from A/J and BALB/c mice, as well as hybrids of the two strains and back‐crossed mice, was investigated to determine whether the permissiveness of growth of these bacteria was due to an inherited trait of the MPs. The MPs from all A/J mice supported the growth of Legionella, regardless of whether they were obtained from TGC or casein injected donors, but the cells from the mice given TGC supported growth of L. pneumophila much better than cells from mice injected with casein. Furthermore, MPs obtained from all BALB/c mice treated with either TGC or casein were nonpermissive for the growth of L. pneumophila. MPs from approximately 46% of the back‐crossed ACF1 to A/J mice were permissive for L. pneumophila growth, while MPs from all ACF1 to back‐crossed BALB/c mice were found to be nonpermissive. MPs from approximately 19% of ACF2 mice were permissive for L. pneumophila. Killing activities of MPs using temperature sensitive mutants of Salmonella typhimurium were variable and did not correlate with permissiveness or nonpermissiveness for growth of L. pneumophila. In addition, the number of inflammatory cells in the peritoneal cavity induced in response to TGC did not correlate with the permissiveness or nonpermissiveness of the MPs from various mouse strains to Legionella, indicating the permissive nature of the cells is controlled by genetic mechanisms involving a recessive phenotype but differs from resistance genes such as Ity important for replication of S. typhimurium.

No abstract