Limited contribution of HSCs to emergency myelopoiesis and type I IFN stimulation. (A-D) Fgd5^{ZsGreen:CreERT2}/R26^LSL-tdRFP mice were TAM-induced and injected with LPS (n = 8) or PBS (n = 12). (B) Neutrophil count in the peritoneal cavity 24 hours after LPS/PBS injection. (C) Plasma levels of interleukin 6 (IL-6) 90 minutes after LPS/PBS injection. (D) Fraction of RFP-labeled cells (relative to ES HSCs) between LPS and saline-treated animals. Data from 2 independent experiments. (E) Labeled R26^rtTA/Col1A1^H2B-GFP animals were IP injected with LPS (n = 14) or PBS (n = 13) and the average number of additional divisions in response to LPS was determined. Data from 2 independent experiments. (F-J) Fgd5^{ZsGreen:CreERT2}/R26^LSL-tdRFP (in panels F and I, n = 4-6 per condition) and R26^rtTA/Col1A1^H2B-GFP (in panels G, H, and J, n = 4-7 per condition) mice were subcutaneously injected with G-CSF or PBS for 5 consecutive days. Numbers of LEK HSPCs in spleen (G) or PB (H) of R26^rtTA/Col1A1^H2B-GFP animals on d6. (I) Fraction of RFP-labeled cells (relative to ES HSCs). (J) Average number of additional divisions in response to G-CSF. (K-O) Fgd5^{ZsGreen:CreERT2}/R26^LSL-tdRFP (in panels K-N, n = 4-8 per condition) and R26^rtTA/Col1A1^H2B-GFP (in panel O, n = 4-7 per condition) mice were IP injected with pI:C or PBS following either a single (once) or repetitive (8 times) administration protocol. (L) PB leukocyte and reticulocyte numbers 7 days after 1 time pI:C. (M-N) Fraction of RFP-labeled cells (relative to ES HSCs). (O) Average number of additional divisions in response to pI:C. (P) Net effects of LPS, G-CSF, or pI:C perturbation on RFP label propagation (% label increase relative to ES HSCs; transformation and display of data as in Figure 1P). MFI, mean fluorescence intensity; PL, peritoneal lavage.