NK cell recovery after haploidentical HSCT with posttransplant cyclophosphamide: Dynamics and clinical implications

Antonio Russo, Giacomo Oliveira, Sofia Berglund, Raffaella Greco, Valentina Gambacorta, Nicoletta Cieri, Cristina Toffalori, Laura Zito, Francesca Lorentino, Simona Piemontese, Mara Morelli, Fabio Giglio, Andrea Assanelli, Maria Teresa Lupo Stanghellini, Chiara Bonini, Jacopo Peccatori, Fabio Ciceri, Leo Luznik, Luca Vago

Research output: Contribution to journalArticlepeer-review

75 Scopus citations


The use of posttransplant cyclophosphamide (PT-Cy) as graft-versus-host disease (GVHD) prophylaxis has revolutionized haploidentical hematopoietic stem cell transplantation (HSCT), allowing safe infusion of unmanipulated T cell-replete grafts. PT-Cy selectively eliminates proliferating alloreactive T cells, but whether and how it affects natural killer (NK) cells and their alloreactivity is largely unknown. Here we characterized NK cell dynamics in 17 patients who received unmanipulated haploidentical grafts, containing high numbers of mature NK cells, according to PT-Cy-based protocols in 2 independent centers. In both series, we documented robust proliferation of donor-derived NK cells immediately after HSCT. After infusion of Cy, a marked reduction of proliferating NK cells was evident, suggesting selective purging of dividing cells. Supporting this hypothesis, proliferating NK cells did not express aldehyde dehydrogenase and were killed by Cy in vitro. After ablation of mature NK cells, starting from day 15 after HSCT and favored by the high levels of interleukin-15 present in patients' sera, immature NK cells (CD62L+NKG2A+KIR-) became highly prevalent, possibly directly stemming from infused hematopoietic stem cells. Importantly, also putatively alloreactive single KIR1 NK cells were eliminated by PT-Cy and were thus decreased in numbers and antileukemic potential at day 30 after HSCT. As a consequence, in an extended series of 99 haplo-HSCT with PT-Cy, we found no significant difference in progression-free survival between patients with or without predicted NK alloreactivity (42% vs 52% at 1 year, P = NS). Our data suggest that the majority of mature NK cells infused with unmanipulated grafts are lost upon PT-Cy administration, blunting NK cell alloreactivity in this transplantation setting.

Original languageEnglish (US)
Pages (from-to)247-262
Number of pages16
Issue number2
StatePublished - Jan 11 2018

ASJC Scopus subject areas

  • Biochemistry
  • Immunology
  • Hematology
  • Cell Biology


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