Fig. 2

BM engraftment. Absolute counts of a total BM cells, b LSKs, c LT-HSCs, d ST-HSCs, and e MPPs. Unirradiated mice were used as controls. f Representative flow cytometry analysis of IL-21R expression on the surface of LSKs. Isotype control is shown in black line whereas IL-21R staining is shown in filled gray histogram. g Representative flow cytometry experiment analyzing the frequency of LSKs in response to ascending doses of IL-21 (0–1000 ng/ml). Equivalent volume of PBS or IL-7 at 25 ng/ml was used as controls. h Quantification of LSK frequency derived from the experiment shown in g i Representative intracellular Ki-67 staining in WT versus IL-21R^−/− LSK 48 h post-treatment with 50 ng/ml of IL-21. j Quantification of KI-67⁺ LSKs derived from the experiment shown in i. All experiments were conducted at least three times with *P < 0.05, **P < 0.01, ***P < 0.0001, and ****P < 0.00001