β-Glucan derived from cell walls of Candida albicans is a potent immune modulator. It has been shown to induce trained immunity in monocytes via epigenetic and metabolic reprogramming and to protect from lethal sepsis if applied prior to infection. Since β-glucan-trained monocytes have not been classified within the system of mononuclear phagocytes we analyzed these cells metabolically, phenotypically and functionally with a focus on monocyte-to-macrophage differentiation and compared them with naïve monocytes and other types of monocyte-derived cells such as classically (M1) or alternatively (M2) activated macrophages and monocyte-derived dendritic cells (moDCs). We show that β-glucan inhibits spontaneous apoptosis of monocytes independent from autocrine or paracrine M-CSF release and stimulates monocyte differentiation into macrophages. β-Glucan-differentiated macrophages exhibit increased cell size and granularity and enhanced metabolic activity when compared to naïve monocytes. Although β-glucan-primed cells expressed markers of alternative activation and secreted higher levels of IL-10 after lipopolysaccharide (LPS), their capability to release pro-inflammatory cytokines and to kill bacteria was unaffected. Our data demonstrate that β-glucan priming induces a population of immune competent long-lived monocyte-derived macrophages that may be involved in immunoregulatory processes.
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Leonhardt, Julia; Große, Silke; Marx, Christian; Siwczak, Fatina; Stengel, Sven; Bruns, Tony; Bauer, Reinhard; Kiehntopf, Michael; Williams, David L.; Wang, Zhao Qi; Mosig, Alexander S.; Weis, Sebastian; Bauer, Michael; and Heller, Regine. 2018. Candida Albicans β-Glucan Differentiates Human Monocytes Into a Specific Subset of Macrophages. Frontiers in Immunology. Vol.9(NOV). https://doi.org/10.3389/fimmu.2018.02818 PMID: 30555483