TLI/ATG effectively ablates lymphoid organs. Absolute cell counts of lymphoid organs of mice at 24 hours after lethal TBI, and 24 hours after the last TLI dose; FACS plots of tissues from representative animals. (A) Bar graph shows the absolute spleen cell counts revealing no significant difference between TBI and TLI/ATG-conditioned groups. FACS plots show CD4⁺ and CD8⁺ T cells in spleens of TBI vs TLI/ATG-conditioned and unconditioned WT mice. (B) Bar graph shows the absolute cell counts per thymus with lower numbers of thymocytes in TLI-treated vs TBI-treated animals. FACS plots show the shifts of single and positive CD4⁺ and CD8⁺ T-cell populations in conditioned vs unconditioned mice. (C) Bar graphs show the absolute cell numbers of cervLN (top left), mesLN (top, second from left), and axLN (top, second from right) revealing lower cellularity following TLI/ATG as compared with TBI. FACS plots demonstrate CD4⁺ and CD8⁺ depletion in LN in WT mice (top right), after TLI/ATG (bottom 3 left; cervical, mesenteric and axillary LN), and TBI-conditioning (bottom right). (D) Compiled data on the proportion of CD4⁺CD25⁺FoxP3⁺ Treg of all CD4⁺ cells and (E) their absolute numbers in spleen (left), cervLN (second from left), mesLN (second from right), and axLN (right) in untreated (black solid), TBI-conditioned (white solid), and TLI/ATG-treated (striped) mice are shown. N = 3 to 7 animals per experimental group. Only statistically significant P values are displayed.