Suppression of single-donor predominance by cotransplantation of MSC from third-party bone marrow. (A) Effect of MSC cotransplantation on donor distribution as analyzed by PCR-SSOP. Total MNCs equivalent to 3 × 10⁴ CD34⁺ cells from each UCB unit were infused into NOD/SCID mice in single (CM1-CM4) or mixed (CM1 + 2, CM3 + 4) transplantations, as described, except that 4 × 10⁴ MSCs were coinfused into each recipient. The donor origin of the engrafted cells was identified by PCR on the HLA-DR locus, followed by hybridization to allele-specific probes (R1 for CM1, R5 for CM2, R11 for CM3, and R6 for CM4, respectively). Shown are the results of 2 experiments using pairs of 5 mismatch UCBs. (B) MSC-mediated coengraftment as assessed by RQ-STR. Shown are the profiles for donor distribution analyzed by RQ-PCR on representative STR markers with percentage reconstitution of dominant donor cells artificially named as donor A. (C) Increase in overall engraftment in MSC cotransplanted double cord transplantation over single-unit transplantation. Total engraftment of human cord blood cells was measured by antihuman CD45/71, as described. Shown are the engraftment levels of single or double cord transplantations (each n = 8) in cohorts including one 3-mismatch pair, two 5-mismatch pairs, and one full-mismatch pair.