Overexpression of RGS-regulated effectors or priming with their ligands improve HSPC engraftment. CD34⁺ cells were (A) transduced with C3AR1, C5AR1, or MMP14 lentiviral vectors or (B) stimulated with C3a, C5a, or CCL1 (1 μg/mL; 30 minutes), and intravenously infused into sublethally irradiated NOD/SCID mice. Human CD45⁺ cells were enumerated in the recipient BM and spleens at 8 weeks after transplantation. Shown are representative flow cytometry plots illustrating the detection of engrafted hematopoietic cells. (A) Four mice per group. (B) Two mice per group. Statistics: 2-tailed, paired Student t test. P values are indicated.