IL27Ra⁺ HSCs serves as a reservoir for myeloid recovery upon inflammation. (A-H) WT and IL27Ra^−/− mice were injected with LPS (1 mg/kg) intraperitoneally, then the mice were analyzed at indicated time points (N = 3-5 mice per group for each time point, mice in day 0 are considered as control; data are shown as mean ± SEM.). (A-C) These histograms showing the percentage of (A) myeloid cell (CD11b⁺), (B) B cell (B220⁺), and (C) T cell (CD3⁺) in peripheral blood of WT and IL27Ra^−/− mice at indicated time points. (D-F) These histograms showing the frequency of (D) CMP, (E) GMP, and (F) HSCs in bone marrow of WT and IL27Ra^−/− mice at indicated time points. (G) This line plots depict the percentage of IL27Ra⁺ HSCs and IL27Ra⁻ HSC in bone marrow of WT mice at indicated time points. (H) Representative western blots showing the expression of p-ERK, ETS1, and IL27Ra in cKit⁺ bone marrow cells of WT mice at indicated time points. (I) This chart illustrates the proposed model of inflammation-induced TNF-α→ERK→ETS1→IL27Ra promotes hematopoietic stem cell aging.