Release of Hepatic Plasmodium yoelii Merozoites into the Pulmonary Microvasculature
Figure 8
Merosomes Accumulate in the Lungs and Release Merozoites into the Pulmonary Microcirculation
(A) Ex vivo confocal microscopy of a mouse lung 52 h after infection with PyGFP shows a large merosome located inside an alveolar capillary.
(B) A group of individual merozoites inside pulmonary capillaries.
(C) Small parasite aggregates and individual merozoites (arrowheads) fanning out in one direction from a merosome (arrow). This asymmetric parasite distribution suggests that merosomes release merozoites into the pulmonary microcirculation. (A–C) Bars = 10 μm.
(D–G) Mouse lung fixed 52 h after infection with P. yoelii. The frozen section was immunolabeled with MSP-1 followed by protein A-FITC (D, green) indicating that the merozoites are intact. Labeling with goat-anti-ASGR-1 followed by rabbit anti-goat IgG-TX (E, red) revealed the absence of the receptor on the merosomal membrane. Nuclei were visualized by Hoechst staining (F, blue).
(H) Electron micrograph showing well-preserved merozoites (∗) in the lumen of an alveolar capillary. Only fragments of the merosomal membrane are detectable (arrows). *, merozoite; A, alveolar lumen. Bar = 1 μm.
(I) Free merozoites released into the lumen of a pulmonary capillary. *, merozoite; E, erythrocyte. Bar = 1 μm.
(J) Alveolar capillary showing an erythrocyte (arrow) harboring a recently invaded merozoite in addition to several uninfected erythrocytes. *, merozoite; E, erythrocyte. Bar = 1 μm.