Effect of pretransplantation conditioning on donor cell engraftment in the cerebral cortex. (A) Percentage of male donor cells identified in cerebral cortex biopsy specimen from patients conditioned with MA-TBI (TBI >1000 cGy), NMA-TBI, nonmyeloablative conditioning, (TBI <300 cGy), MA-Bu-Treo, or 2 separate stem cell transplantations (double Tx). Data are expressed as donor cell percentage relative to total number of microglial cells. Microglia cells represent ∼12% of the cellularity in the cerebral cortex, based on parallel IBA1 IHC studies (supplemental Figure 2). (B) Effect of posttransplantation survival on donor cell engraftment in the cerebral cortex. The data are expressed as the percentage of donor cells relative to the total number of microglial cells. Gray square, myeloablative transplantation; blue inverted triangle, nonmyeloablative transplantation; red circle, double transplantations. DTs, double transplantations; MA-Bu-Treo, busulfan- or treosulfan-based myeloablation; MA-TBI, TBI-based myeloablation; NMA-TBI, TBI-based nonmyeloablation.