Despite early recovery of NK cell counts after PT-Cy–based HSCT, NK cell phenotype normalization occurs only several months after transplantation. (A) Absolute counts of NK cells (red circles) and T cells (blue squares) detected in the PB of 10 patients followed long-term after HSCT with PT-Cy (from days 30 to 360). A reference physiological cell count interval (mean ± SD) obtained from 5 healthy controls is shown for NK cells (light red box) and T cells (light blue box). (B) The proportion of NK cells out of total lymphocytes in the infused donor graft (day 0) and longitudinally after HSCT is displayed for 10 OSR patients. (C-F) Flow cytometry histograms depicting the expression of selected markers on CD56⁺CD3⁻ NK cells in the donor graft (day 0) or from patient PB obtained longitudinally after transplant in 10 OSR patients. For all panels, gray boxes show reference values (mean ± SD) obtained analyzing 5 healthy controls. (C) Expression of maturation markers. (D) Expression of KIRs and lectin-type receptors. (E) Expression of markers of exhaustion or activation. (F) Expression of natural cytotoxicity receptors. Unless otherwise specified, data are shown as mean ± SEM.