LT engraftment patterns and the origins of T cells are different after TLI/ATG vs TBI conditioning. A total of 10 000 KTLS-HSC from B6 (H-2b) donors was infused into B6 (H-2b), BALB.B (H-2b), and BALB/c (H-2d) recipients. (A) Compiled data of percent donor chimerism achieved in the blood for B cells (left) and Mac1⁺ (CD11b⁺) myeloid cells (right) at 3 months post-HCT following TLI/ATG conditioning. There was no engraftment in MHC-mismatched BALB/c recipients. (B) Compiled percent donor chimerism achieved in the blood for B cells (left) and Mac1⁺ (CD11b⁺) myeloid cells (right) at 3 months post-HCT following TBI conditioning (950 cGy for B6; 800 cGy for BALB), showing full donor chimerism in both lineages in all groups. (C) Bar graphs display percent donor chimerism of CD4⁺CD8⁺ immature thymic T cells and peripheral blood TCRβ⁺ T cells with low level of donor chimerism in both populations in B6 and BALB.B, but not BALB/c recipients following TLI/ATG conditioning. (D) Thymic T cells were largely donor derived across all groups, and peripheral blood T cells were mixed chimeric following TBI. N = 4 to 8 animals per experimental group.