Figure 2.

Decreased BM hematopoietic progenitors in Pep^−/− mice are observed after IFN-α induction. (A–D) Pep^+/+ and Pep^−/− mice were infected with Ad5-IFN-α5 (10⁹ PFU/mouse [A and B] or 10⁸ PFU/mouse [C and D]). BM progenitor composition was analyzed 14 d after infection. Lineage⁻ cells were gated on cKit and Sca-1 to analyze early hematopoietic progenitors (HSC, MPP2, and MPP3) in the Lin⁻ Sca-1⁺ cKit⁺ (LSK) population. Megakaryocyte, erythrocyte progenitors (MEP), and myeloid progenitors (CMP/GMP) were analyzed in the Lin⁻ Sca-1⁻ cKit⁺ (LS⁻K) populations. BM progenitors from A and C were enumerated from Pep^+/+ (open bar) and Pep^−/− (grey bar) mice on day 14 after infection with Ad5-IFN-α5 (10⁹ PFU/ml [B]; 10⁸ PFU/ml [D]). (E and F) Mice were injected i.p. with poly(I:C) (200 µg/mouse) and BM progenitor composition analyzed after 24 h as described in A–D. HSC, LSK CD150⁺ CD34⁻CD48⁻; MPP2, LSK CD150⁺CD34⁺CD48^‑; MPP3, LSK CD150⁺CD34⁺CD48⁺; MEP, LS⁻K CD16/19⁻CD34⁻; CMP, LS⁻K CD16/CD19^intCD34⁺; GMP, LS⁻K CD16/19^hiCD34⁺. (G) Sca-1 expression on total cKit⁺ BM cells was quantitated by fluorescence intensity. Pep^+/+ (open circle) and Pep^−/− (grey square) mice were treated with poly(I:C) for 24 h and BM progenitors analyzed by FACS. n = 5 mice/group in the poly(I:C)-treated cohort. n = 5 mice/genotype for all experiments. Data shown are representative of three independent experiments for A and E, and two independent experiments for C. Values in all graphs represent means ± SEM. Statistical analysis was done by two-tailed paired Student’s t test; *, P < 0.05; **, P < 0.01; ***, P < 0.001.