Tc17 cells develop early post–allo-SCT in both central lymphoid and GVHD target organs. (A-D) CD8⁺YFP⁺ population development in lethally irradiated allogeneic (B6.IL-17^CreRosa26^eYFP→ B6D2F1) or (C) syngeneic (B6.IL-17^CreRosa26^eYFP→B6) mice transplanted with G-CSF–mobilized grafts. (A) Time-course analysis of CD8⁺YFP⁺ frequencies and absolute numbers within the CD8⁺ T-cell compartment 3, 7, 14, and 21 days posttransplant (mean ± SEM, n = 4-15 pooled mice/group from 2-4 independent experiments). pLN, peripheral (axillary and inguinal) lymph node; mLN, mesenteric lymph node. (B) Representative FACS analyses of CD8⁺YFP⁺ T cells 7 days after allo-SCT. (C) Representative FACS analyses (mLN) and CD8⁺YFP⁺ absolute numbers 7 days after syngeneic or allogeneic SCT (mean ± SEM, n = 6-10 pooled mice/group from 2 independent experiments; **P < .01, ****P < .0001). (D) Representative FACS analyses and frequencies of CD8⁺ T cells 7 days after allo-SCT costained with Annexin V and 7-AAD viability dye (mean ± SEM, n = 9-10 mice/group).