Figure 6. Myeloid-derived Histamine Protects MB-HSCs from Myelosuppressive Injury.

(A) Quantification of Hdc-GFP^hi HSCs in irradiated Hdc-GFP mice (n = 4 - 6 per time point). (B) Number of BM Hdc-GFP⁺ myeloid cells in (A). (C) Competitive reconstitution comparison between 3 Gy-irradiated 1,500 Hdc-GFP^hi and Hdc-GFP^lo HSPCs (n = 5 per group). (D and E) Number of total HSCs (D) or myeloid cells (E) in 5 Gy-irradiated Hdc-GFP (n = 4) and Hdc^−/−; Hdc-GFP mice (n = 6). (F) Blood chimerism of lethally irradiated recipients transplanted with 5 × 10⁵ unfractionated Hdc-GFP⁺ donor BM cells along with Sca-1-depleted CD45.1 BM cells (n = 5 each treatment). (G) Survival of 8Gy- irradiated mice pre-treated with either H₂ agonist or PBS (n = 15 per group). (H) Absolute number of BM Hdc-GFP^hi HSPCs and MPP (MPP3) in LPS or PBS-treated mice at 24 hours (n = 3 - 6 per group). (I) Protective effect of H₂ agonist on LPS-induced sepsis mice (n = 5 per group). Data were analyzed with one-way analysis of variation (ANOVA) with Bonferroni post-hoc test (A, B, and I), two-tailed Student’s t-test (C-E, F, and H), or Logrank test (G). See also Figure S6.

For all panels, ± SEM is shown. *p < 0.05; **p < 0.01; ***p < 0.001. n.s., not significant. n.d., not detectable. n indicates biological replicates. For all experiments greater than or equal to two independent experiments were performed unless otherwise indicated.