Extramedullary myelopoiesis in malaria is established by mobilizing CCR2⁺ myeloid-restricted BM progenitors.

<p><b>A.</b> Expression of message for <i>Ifng</i> and IFN-γ induced chemokines in organ samples from pre-immune and mice infected with <i>P. chabaudi</i> at day 7. Three to four individual organ samples each were obtained from two independent experiments and analyzed by RT-PCR. <b>B.</b> Phenotype of LIN⁻ cells in the spleen of C57BL/6 and <i>Ccr2</i>-null mice at day 7 after infection with <i>P. chabaudi</i> stained for indicated marker. Results in <b>B.–E.</b> are obtained form three infection experiments with 4–5 mice per group each. <b>C.</b> Absolute numbers of LIN⁻ c-Kit^hi CD27⁺ CD16/32⁻ (CD27⁺ CMPs) and CD16/32⁺ (GMPs) cells in the spleen of C57BL/6 and <i>Ccr2</i>-null animals in steady state or at day 7 after infection with <i>P. chabaudi</i> as quantified by flow cytometry. Results are shown as mean ± SEM from three independent experiments with 4–5 animals per group (**: <i>P</i>≤0.01, Mann-Whitney U-test). <b>D.</b> Changes in the absolute number of clonogenic myeloid progenitors (CFU-GM) in the BM and the spleen in uninfected mice and at day 7 after infection with <i>P. chabaudi</i>. Data for <i>Ccr2</i>-null mice and controls were obtained in three experiments with 4–5 samples per experiment and shown as mean ± SEM of total number of CFU-GM per organ (*: <i>P</i>≤0.05, **: <i>P</i>≤0.01, two-tailed Student's <i>t</i>-test). <b>E.</b> Phenotype of intrasplenic myeloid precursors during acute infection with <i>P. chabaudi</i>. Lineage-negative (Ter-119, CD3, CD11c, CD19, NK1.1) cells were stained for CD11b versus CD115 (M-CSF receptor) allowing the resolution of early myeloid precursors as c-Kit^hi Ly-6C⁻. <b>F.</b> Absolute numbers of early myeloid precursors (LIN⁻ c-Kit^hi CD115⁺ CD11b⁻ Ly-6C⁻) in the spleen of uninfected mice and at day 7 after infection. Representative staining and splenic cellularity were obtained from three independent infection experiments with 3–5 animals per group. Data represent mean ± SEM of cell number per spleen (**: <i>P</i>≤0.01, Mann-Whitney U-test). <b>G.</b> Course of malaria infection in C57BL/6 and <i>Ccr2</i>-null mice inoculated with blood stages of the malaria parasite <i>P. chabaudi</i>. Parasitemia was counted on the indicated days. Results for four infection experiments with 4–5 animals per time point in each experiment are shown as mean ± SEM (*: <i>P</i>≤0.05, **: <i>P</i>≤0.01, Mann-Whitney U-test).