Cryopreservation of Hemopoietic Cells for Allotransplant: Altered Immune Cell Subsets and Clinical Implications.

Cryopreservation of allogeneic peripheral blood stem cells was widely adopted during the SARS-CoV-2 pandemic. We evaluated transplant-related complications and graft product composition in a retrospective (n = 62) and prospective (n = 47) series of patients transplanted from an HLA-identical donor comparing cryopreserved (n = 50) versus fresh (n = 59) peripheral blood stem cell grafts. Primary endpoints were hematological reconstitution and cumulative incidence of grade II-IV acute graft versus host disease. Median times to neutrophil and platelet recovery were longer in the cryopreserved group compared with the fresh group: 18 vs. 16 days (p < 0.001) and 20 vs. 14 days (p < 0.001), respectively. The cumulative incidence of grade II-IV acute graft versus host disease at day 100 and of poor graft function at 1 year was significantly higher in the cryopreserved group: 34% vs. 10.1%, (p = 0.0017) and 20% vs. 1.6% (p < 0.001), respectively. To characterize immune cell profiles in fresh and cryopreserved samples, a representative subset was analyzed by mass cytometry, revealing a higher number of T-cell populations known to modulate immune responses and promote graft engraftment in fresh samples. Thus, cryopreservation of allogeneic peripheral blood stem cells is associated with increased incidence of acute graft versus host disease and poor graft function.