ACK2 treatment leads to increased multilineage and KLS chimerism. Peripheral blood was analyzed 4 weeks after transplantation and the lineage composition of donor cells was compared with the lineage composition of host cells. (A) Gating strategy to determine donor granulocyte (Gr-1⁺), B-cell (CD19⁺), and T-cell (CD3⁺) populations. (B) Lineage-specific chimerism for granulocytes, B cells, and T cells. N = 4-9 mice per group. *P < .05 and **P < .01 by ANOVA with Tukey’s multiple comparison test. (C) Total number of donor KLS cells harvested from long bones 1 and 20 weeks after transplantation. Treated mice were previously injected with 5 µg per fetus 7 days before neonatal transplantation (n ≥ 3 from ≥2 independent experiments for each group). Data presented as mean ± SEM. *P < .05 and **P < .01 by Student t test. (D) Peripheral blood CD45 chimerism compared with BM KLS chimerism in mice previously treated with ACK2 (5 µg per fetus) in utero at 1 and 20 weeks. N ≥ 7 per group. **P < .01 by Student t test.