Experimental Cerebral Malaria Pathogenesis—Hemodynamics at the Blood Brain Barrier
Figure 3
Leukocyte recruitment to cortical postcapillary venules during ECM and hyperparasitemia.
A) CBA/CaJ mice were infected with PbA, PyXL, or no parasites, subjected to craniotomy at the time of neurological signs or the parasitemia exceeding 50%, and prepared for intravital microscopy. CD8+ T cells, CD4+ T cells, Gr-1+ neutrophils, CD14+ monocytes, and CD11b+ macrophages were labeled by intravenous inoculation of mAb against CD8+a, CD4+, GR-1, CD14, and CD11b, respectively. Significantly larger numbers of CD8+ T cells, neutrophils and macrophages were found in postcapillary venules from mice with ECM compared to hyperparasitemia (P<0.05). The density of CD4+ T cells and monocytes was not significantly different. Most of the arrested leukocytes are macrophages followed by neutrophils, CD8+ T cells, CD4+ T cells, and monocytes. The data represent the mean cell density/mm2 ± STD. Significance (*, P<0.05; **, P<0.001) was determined with 1-way ANOVA. See Tables S2–S6 for details. B) Compared to mice with ECM (PbA), significantly less CD8+ T cells are recruited to postcapillary venules from mice with hyperparasitemia (PyXL). Treatment with FTY720 reduces the density of CD8+ T cells to levels similar to those found in PyXL infected mice. No arrested CD8+ T cells were found in the cortical microvasculature from uninfected mice. Vascular leakage was observed in mice with ECM (day 6–8; 76 measurements from 5 mice), but not in FTY720-treated PbA-infected mice (day 8; 19 measurements from 4 mice), PyXL infected mice with hyperparasitemia (day 5; 20 measurements from 6 mice), or uninfected control mice (>10 mice). C) Leukocytes were isolated from the brains of PbA-infected (day 6–8), PbA-infected/FTY720-treated (day 9), or PyXL-infected mice (day 5) and analyzed by flow cytometry. Most of the ECM-associated leukocytes are F4/80+ macrophages followed by Ly-6C+ monocytes, Ly-6G+ neutrophils, CD8+ T cells, and CD4+ T cells. Significance (*, P<0.05; **, P<0.01) was determined with 1-way ANOVA followed by Tukey's test for multiple comparisons. See Table S7 for details. D) FTY720 treatment of PbA-infected mice reduces the number of CD45hi ( = blood-derived) macrophages significantly to a level similar to that found in PyXL-infected mice with hyperparasitemia. No significant differences were found for CD45lo ( = parenchymal) macrophages. See Table S7 for details.