Fig. 2

Emergency granulopoiesis occurs following intravenous E. coli (5–10 × 10³ cfu) infection.

(A), The drastic expansion of SB⁺ neutrophils (red arrows) in the CHT of an infected embryo when compared with that treated with PBS at 2 dpi (4 dpf). (B), Calculation of the data obtained for SB⁺ neutrophils at different time points after infection (15.60 ± 2.80 vs 28.20 ± 5.27; 65.71 ± 10.60 vs 55.20 ± 4.76; 149.50 ± 8.70 vs 77.60 ± 9.45; 207.60 ± 39.15 vs 128.80 ± 15.00; 96.40 ± 23.80 vs 56.40 ± 6.33 in E. coli vs PBS group at each time point. N = 8 in each group). (C,D), Fluorescence images (C) and calculation (D) of lyz-GFP⁺ neutrophils in PBS (25.11 ± 2.58; N = 9) or E. coli (16.50 ± 1.84; N = 10) treated larval CHT at 6 hpi. The red signals indicate the bacteria phagocytosed by lyz-GFP⁺ neutrophils (white arrows). (E), The percentage of lyz-GFP⁺ neutrophils that are co-stained with TUNEL at 6 hpi (9.31 ± 1.87 vs 0.63 ± 0.37 in E. coli vs PBS group. N = 10 in each group). (F), Time-lapse imaging of an infected Tg(lyz:eGFP) CHT from 1 dpi to 1.5 dpi. Obvious generation, expansion and maturation of lyz-GFP⁺ neutrophils are observed. Scale bars, 20 μm. See also Video S4. 4a, 4b and 8a, 8b in (F) showing the dividing lyz-GFP⁺ cells. (G), SB⁺ signals (red arrows) in the runx1 mutant treated by either PBS or E. coli at 2 dpi (4 dpf). (H), WISH of pu.1 (red arrows) in the CHT of an embryo challenged with PBS or E. coli at 2 dpi (4 dpf). (I), The number of the pu.1⁺ myeloid progenitors at different time points after challenge (45.88 ± 5.87 vs 59.63 ± 4.29; 203.38 ± 5.02 vs 79.88 ± 8.70; 214.50 ± 13.98 vs 78.16 ± 6.89 in E. coli vs PBS group at each time point. N = 8 in each group). Scale bars, 20 μm.