Fig 2. Plasmatocytes from adult flies phagocytose and control Leishmania parasites.

DsRed-expressing amastigotes were injected alone or with polystyrene beads in Hml(Δ)Gal4-eGFP flies. At indicated times, hemocytes were harvested from the hemolymph and analyzed by confocal microscopy. (A) In eGFP-expressing hemocytes from flies injected with polystyrene beads and amastigotes, the cells contained large amounts of intracellular beads (blue) and just one intracellular parasite (red) confirming the inhibitory effect of beads in phagocytosis. (B) 24 h post-injection, plasmatocytes from flies injected only with parasites contained several amastigote forms, while at 72 h after infection some amastigotes differentiated to the long and flagellated promastigote form and were observed inside plasmatocytes (arrow in (C)). (D) Phagocytosis blockage by injection of polystyrene beads increased the parasite burden of flies over time. The control group, flies not injected with beads, prevented parasite growth without completely clearing infection. Parasite burdens were assayed by limiting dilution of single flies, with a minimum of 12 animals per time point. Whiskers represent 10%-90% limits of the sample. Statistical significance was determined by two-way ANOVA.