Flying under the radar: Histoplasma capsulatum avoidance of innate immune recognition. (May 2019)

• Record Type: Journal Article
• Authors: Ray, Stephanie C.; Rappleye, Chad A.
• Is Part Of: Seminars in cell & developmental biology. Volume 89(2019)
• Page Start: 91
• Page End: 98
• Publication Date: 2019-05
• Subjects: Fungal pathogenesis -- Dimorphism -- Cell wall -- β-glucan -- Dectin-1 -- Complement receptor; Cytology -- Periodicals; Developmental biology -- Periodicals; 571.6
• DOI: 10.1016/j.semcdb.2018.03.009
• Languages: English
• ISSNs: 1084-9521

Abstract

Abstract: The dimorphic fungal pathogen Histoplasma capsulatum takes advantage of the innate immune system, utilizing host macrophages as a proliferative niche while largely avoiding stimulation of signaling host receptors. As a result, innate immune cells are unable to control H. capsulatum on their own. Not all host phagocytes respond to H. capsulatum in the same way, with neutrophils and dendritic cells playing important roles in impeding fungal growth and initiating a protective TH 1 response, respectively. Dendritic cells prime T-cell differentiation after internalization of yeasts via VLA-5 receptors and subsequent degradation of the yeasts. Dendritic cell-expressed TLR7 and TLR9 promote a type I interferon response for TH 1 polarization. In contrast to dendritic cells, macrophages provide a hospitable intracellular environment. H. capsulatum yeasts enter macrophages via binding to phagocytic receptors. Simultaneously, α-glucan masks immunostimulatory cell wall β-glucans and a secreted endoglucanase removes exposed β-glucans to minimize recognition of yeasts by Dectin-1. This review highlights how phagocytes interact with H. capsulatum yeasts and the mechanisms H. capsulatum uses to limit the innate immune response.