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. 2011 May 26;7(5):e1002047. doi: 10.1371/journal.ppat.1002047

Figure 1. Capsule enlargement can be elicited by mammalian and protozoan cells regardless of viability, but not by mechanical stimulus.

Figure 1

A) The C. neoformans (Cn) cells were incubated alone in PBS, with live and heat-killed A. castellanii (Ac), live and heat-killed J774.14 macrophage-like cells (Mac), and polystyrene beads. Live amoebae and macrophages were more effective than heat-killed cells in triggering capsular enlargement. In contrast, there was no enlargement in the presence of the polystyrene beads, when compared to incubation in PBS alone. Each assay was performed independently on 3 separate days and the numbers shown represent the average of a minimum of 50 C. neoformans cells. B) Capsule enlargement activity of A. castellanii extracts as a function of temperature. Activity assays were done at 4°C, room temperature (RT), 28°C, and 37°C. This experiment was done two times on separate days and each condition represents a minimum of 50 cells. C) Representative C. neoformans cells suspended in India ink showing enlargement of the polysaccharide capsule after incubation with A. castellani (40x). (*) indicates P<0.001 for capsule enlargement for each condition when compared to control incubation alone in PBS.