Fig. 7

Mucor circinelloides can be activated out of innate granulomas by immunosuppression in vivo. (A) To investigate the potential of disease activation out of innate granulomas, we selected innate granuloma-positive larvae and immersed them in dexamethasone-containing culture medium to induce immune suppression. While control larvae showed 15.4% mortality, 92.5% of larvae transferred into dexamethasone-containing medium died over the time course of this experiment. (B) Representative image showing that larvae that had succumbed to infection presented with extensive hyphal growth (scale bar, 100 μm). (C) Further microscopic examination revealed that dexamethasone resulted in reduction in innate granuloma size and onset of hyphal growth. The top panels show a representative innate granuloma in the hindbrain ventricle at 24 hpi (before onset of dexamethasone treatment) (maximum-intensity projection of fluorescence z-stack with 19 sections every 4 μm together with bright-field image and overlay, with spores [S] in cyan and macrophages [M] in red; scale bar, 100 μm). The bottom panels show the same innate granuloma at 48 hpi (24 h post-onset of dexamethasone treatment) showing hyphal formation (arrow), reduction in innate granuloma size, and dissemination of spores (asterisks) (maximum-intensity projection of fluorescence z-stack with 36 sections every 4 μm together with bright-field image and overlay, with spores in cyan and macrophages in red; scale bar, 100 μm).