Enhanced human blood cell engraftment in NOD/SCID mice. 100 000 human CB CD34⁺ cells were injected into the tail vein of pre-irradiated NOD/SCID mice with no priming of cells (none, ⋄) or following priming of cells with ARP₂₆ for 2 to 4 hours and injection with human ARP₂₆ (▪) or ASP₄₃ (▴). Bone marrow was harvested 6 weeks after transplantation. (A) CD34⁺, CD45⁺, and CD41⁺ human cells were detected using flow cytometry and monoclonal antibodies, n = 12, 16, and 8 mice, respectively. (B) Quantitative real-time PCR using human TNFα primers to detect human DNA in the mouse bone marrow. Sensitivity limit was 10%. n = 12, 16, and 8 mice, respectively. Asterisks denote significant differences. Lines represent mean values. (C) Precultured CD34⁺ cells expanded with ARP₂₆ improve platelet counts. 100 000 human CD34⁺ cells were injected into mice (n = 9) together with 100 000 to 200 000 CD34⁺ cells cultured for 10 days with no supplement (control, ctrl), 2 nM ARP₂₆, 2 nM ASP₄₃, or human TPO/SCF (T/S). Human platelets per mL of mouse blood were quantified using anti CD41, specific for human platelets. The mean differences (denoted by lines) between groups were large with statistical differences observed in the experimental group of mice that received CD34⁺ cells stimulated with synthetic peptide ARP in vitro for 10 days together with fresh CB CD34⁺ cells (asterisks).