Cell growth and antimicrobial activity of mouse peritoneal macrophages in response to glucocorticoids, choleragen and lipopolysaccharide

Innate immune responses of primary murine macrophage-lineage cells and RAW 264.7 cells to ligands of Toll-like receptors 2, 3, and 4

Although studies have been performed to characterize responses of macrophages from individual anatomical sites (e.g., alveolar macrophages) or of murine-derived macrophage cell lines to microbial ligands, few studies compare these cell types in terms of phenotype and function. We directly compared the expression of cell surface markers and functional responses of primary cultures of three commonly used cells of monocyte-macrophage lineage (splenic macrophages, bone marrow-derived macrophages, and bone marrow-derived dendritic cells) with those of the murine-leukemic monocyte-macrophage cell line, RAW 264.7. We hypothesized that RAW 264.7 cells and primary bone marrow-derived macrophages would be similar in phenotype and would respond similarly to microbial ligands that bind to either Toll-like receptors 2, 3, and 4. Results indicate that RAW 264.7 cells most closely mimic bone marrow-derived macrophages in terms of cell surface receptors and response to microbial ligands that initiate cellular activation via Toll-like receptors 3 and 4. However, caution must be applied when extrapolating findings obtained with RAW 264.7 cells to those of other primary macrophage-lineage cells, primarily because phenotype and function of the former cells may change with continuous culture.

A glucocorticoid antagonist, mifepristone affects anti-Candida activity of murine neutrophils in the presence of prednisolone in vitro and experimental candidiasis of prednisolone-treated mice in vivo

The effects of a glucocorticoid-antagonist, mifepristone on the suppressive action of prednisolone for anti-Candida activity of murine neutrophils were examined. Prednisolone suppressed inhibitory activity of neutrophils to mycelial growth of Candida albicans. This suppression was cancelled in the presence of 10(-7)-10(-6) M of mifepristone in vitro. Corresponding to this in vitro action, mifepristone protected prednisolone-treated mice from lethal C. albicans infection in vivo. These results suggest that glucocorticoid-induced vulnerability to Candida infection may be recovered or normalized by application of mifepristone.

Suppression of anti-Candida activity of murine and human neutrophils by glucocorticoids

Effects of glucocorticoid (GC) compounds on inhibitory activity of neutrophils to mycelial growth of Candida albicans were examined by in vitro crystal violet staining method with 14 hr coculture. Both GC hormones (hydrocortisone > or = 6 x 10(-7) M and corticosterone > or = 10(-6)M) and anti-inflammatory GC agents (prednisolone > or = 10(-7) M and dexamethasone > or = 10(-8) M) significantly suppressed anti-Candida activity of murine casein-induced neutrophils. Anti-Candida activity of human neutrophils prepared from peripheral blood was also suppressed by hydrocortisone (> or = 6 x 10(-7) M). These GC compounds did not affect the Candida growth in the absence of neutrophils. Steroidal compounds without anti-inflammatory activity, cholesterol, cholic acid, aldosterone did not suppress neutrophil activity. These results suggest that GCs at their physiological or clinical concentration may suppress anti-Candida activity of neutrophils in vivo.

Lipopolysaccharide significantly enhances erythrophagocytosis but marginally stimulates the phagocytosis of Staphylococcus aureus in mouse peritoneal macrophages

The influence of lipopolysaccharide (LPS) on phagocytic and bactericidal functions of normal mouse peritoneal macrophages was investigated. Preincubation of macrophages with LPS enhanced their capacity for phagocytosis of antibody coated sheep red blood cells 5-fold, but phagocytosis of antibody coated Staphylococcus aureus was enhanced only 1.2-ld. Phagocytosis and intracellular killing of unopsonised or normal rabbit serum opsonised S. aureus was not affected by the LPS treatment of macrophages.

Microbicidal activity of bone marrow cells. Augmentation of Candida killing activity of the cells by culturing with fibroblast conditioned medium

Mouse bone marrow cells were seeded in 96-well trays and infected with twofold serially diluted Candida parapsilosis. Outgrowth of the fungi in each well was determined after a 48-hr incubation period. Freshly collected cells demonstrated a candidacidal activity which increased with increase in the number of cells seeded. When fresh cells were cultivated with conditioned medium of mouse embryo fibroblasts, the candidacidal activity continuously increased for a few days and reached a plateau. The activity was augmented more than 1,000-fold compared with that of fresh marrow cells. It is suggested that augmentation is due not to the increase in number of effector cells but to the maturation of effector cells. Carrageenan, which is specifically cytotoxic to macrophages, inhibited augmentation of the activity. Therefore, it appears that most effector cells that matured by cultivation with the conditioned medium belong to the monocyte-macrophage lineage.