Putative T_N-cell origin of posttransplant T_SCM. (A) Representative frequency (out of 12) of CD45RO⁻CCR7⁺ T cells in a patient a day 0 and day 3 post–haplo-HSCT. (B) Representative (out of 12) CD31 and CD95 expression on NL-CD4⁺ T cells from the PB and BM of a donor and from the PB of the related recipient at different times post–haplo-HSCT. A scheme with the nomenclature of subsets according to phenotype is depicted on the left. NL, CD45RO⁻CCR7⁺. Numbers in plots indicate the percentage of cells in the gates. (C) Mean ± SEM CD31 expression on PB CD4⁺CD95⁻ cells and CD4⁺ T_SCM from marrow donors (D) and CD4⁺ T_SCM from the related recipients (R; n = 12) at day 7 post–haplo-HSCT. *P < .05 vs D T_SCM; Wilcoxon test. (D) Fold change in CD95 median fluorescence intensity (MFI) in different T-cell subsets (n = 19) between day 3 and day 7. *P < .05 vs NL; Wilcoxon-paired test. (E) Representative analysis of CD95 expression by T_N cells following incubation with different stimuli. Histograms are referred to the CD25⁻CD69⁻ nonalloreactive population, as specified in the text. (F) Summary of the data obtained in panel E (n = 8; 4 independent experiments; *P < .05 vs allo-APCs, Wilcoxon-paired test). (G) CFSE dilution and CD31 expression by FACS-sorted T-cell subsets following incubation with allo-APCs for 5 days. D, donor; R, recipient.