Plasmodium falciparum-Derived Uric Acid Precipitates Induce Maturation of Dendritic Cells
Figure 1
Uric acid precipitates accumulate within P. falciparum-infected red blood cells in vitro.
Uric acid immunostaining (red) and DAPI labeling of nuclei (blue) of P. falciparum-infected red blood cells at different stages of development: ring (A), trophozoite (B and C), schizont (D) and merozoite (ruptured schizont with free merozoites) (E). Uninfected control red blood cells (F) are shown. Merged images with phase contrast are shown in the right column. Hemozoin can be observed as intracellular dark areas in B – E (a representative hemozoin crystal is marked by an arrow in panel E). Bar is 5 µm. (G) Quantitation of infected erythrocytes (iRBC) that exhibit uric acid immunostaining at different stages of development (Troph, Trophozoites; Schiz, schizonts, as shown in panels D and E). Data are displayed as mean ± SEM (n = 100 individual iRBC quantified from three independent experiments). (H) P. falciparum-infected schizonts incubated with anti-uric acid antibodies preabsorbed with uric acid crystals (iRBC UA preab) showed low levels of uric acid immunolocalization, compared to iRBC labeled with unprocessed anti-uric acid antibodies (iRBC UA). Staining with secondary antibodies alone (iRBC Cy3 alone) was used as a control. Data are displayed as mean ± SEM (n = 200 individual iRBCs or RBCs quantified from three independent experiments; ***p<0.001 relative to iRBC UA). (I) Quantitation of uric acid levels in supernatant (SN) and pellet fractions from lysates of purified P. falciparum-infected schizonts (iRBC) or uninfected erythrocytes (RBC). A colorimetric absorbance assay was used to determine uric acid levels. Data are displayed as mean ± SEM (n = 3 independent experiments; ***p<0.001 relative to control RBC pellet).