Suppression of splenic macrophage Candida albicans phagocytosis following in vivo depletion of natural killer cells in immunocompetent BALB/c mice and T-cell-deficient nude mice

Abstract

The resistance of mice to systemic infections caused by Candida albicans is associated with activated splenic macrophages. In addition, there is a correlation between natural killer (NK) cell activation and the resistance to systemic candidiasis. The present study was designed to clarify the role of NK cells in the control of splenic macrophage C. albicans phagocytosis by either depleting NK cells (anti‐asialo GM1 treatment) or maintaining them in an activated state (tilorone treatment) in both immunocompetent BALB/c mice and T‐cell‐deficient nude mice. The results of the in vitro phagocytosis assays were analyzed by flow cytometry and demonstrate the pivotal role of NK cells in controlling the capacity of splenic macrophages to phagocytose C. albicans. In summary, these data provide evidence that the NK cells are the main inducers of phagocytic activity of splenic macrophages and that they mediate the protection against C. albicans systemic infection.

NK Cells Mediate Increase of Phagocytic Activity but Not of Proinflammatory Cytokine (Interleukin-6 [IL-6], Tumor Necrosis Factor Alpha, and IL-12) Production Elicited in Splenic Macrophages by Tilorone Treatment of Mice during Acute Systemic Candidiasis

“…In another set of experiments, NK cell-depleted athymic nude mice were treated orally with tilorone on day Ϫ1, and then a flow cytometric phagocytosis assay was performed. The results also showed a decrease in the percentage of phagocytic cells in NK cell-depleted mice from that in control athymic nude mice (2).…”

Evaluation of the E test for the assessment of synergy of antibiotic combinations against multiresistant Pseudomonas aeruginosa isolates from cystic fibrosis patients

“…These The best established formats of in vitro phagocytosis assays are based on the incubation of the phagocytes (neutrophils or macrophages) with a fluorescently labelled foreign material for a defined period of time, ranging from several minutes to several hours. Fluorescein or corresponding dye substitutes are most frequently used as labels, but other dyes are also possible (Algarra et al, 2002), of which pH-sensitive dyes could be of particular interest (Beletskii et al, 2005). Labelling of all kinds of material is achieved by its incubation with an amino-reactive derivative of the dye, such as fluorescein isothiocyanat (FITC) (Liu et al, 2000) or carboxyfluorescein succinimidyl ester (FAM-SE; Busetto et al, 2004).…”

“…As a prerequisite fluorescence from particles, which were only attached or did not interact with the phagocytes at all, had to be eliminated. This distinction was achieved by extensive washing (Algarra et al, 2002;Peiser et al, 2000), treatment with lysozyme (Hrabak et al, 2006), but most frequently by quenching of fluorescence by trypan blue (Wang et al, 2006;Wan et al, 1993;Bjerknes and Bassoe, 1984). Trypan blue absorbs light in the range from 475 -675 nm (Wang et al, 2006), which covers the wavelength of fluorescein fluorescence emission (519 nm) so that fluorescein fluorescence is efficiently quenched by trypan blue.…”

Killed Candida albicans Yeasts and Hyphae Inhibit Gamma Interferon Release by Murine Natural Killer Cells

“…In addition, the interaction of lymphokine-activated killer cells and Candida albicans does not inhibit or kill the fungal pathogen by means of the lymphokine-activated killer cell lytic machinery, but through the secretion of cytokines which have stimulatory effects on phagocytic cells (2). Therefore, antifungal immunity mediated by NK cells appears to occur by the secretion of cytokines that activate phagocytic cells (1,2). However, whether NK cells are stimulated directly by the fungus or in response to signals generated by activated bystander cells remains to be established (26).…”