Grain formation over time.
Grain formation of M. mycetomatis strain mm55 within Galleria mellonella larvae (100 times magnified). At 4h, 24h, 3 days and 7 days post infection grain formation is shown. Histological slides are stained with HE (panels A,B,C,D), Grocott (E,F,G,H) to demonstrate the presence of fungal hyphae and Sirius red to demonstrate the presence of collagen(I, J, K, L). As is seen in panels A, E and I small grains are already visible at 4h after infection. Hardly any immune cells are present (panel A), and no collagen is seen surrounding the grain (panel I). After 24h the grains are larger and cement material starts to form (panel B). At 3 days post infection, the grain has become encapsulated with collagen (panel K). This collagen capsule disappears at day 7 (panel L), a time point at which many immune cells are shown to be present surrounding the grain (panel D).
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