Posttransplantation cyclophosphamide prevents graft-versus-host disease by inducing alloreactive T cell dysfunction and suppression
Lucas P. Wachsmuth, … , Ronald E. Gress, Christopher G. Kanakry
Lucas P. Wachsmuth, … , Ronald E. Gress, Christopher G. Kanakry
Published March 26, 2019
Citation Information: J Clin Invest. 2019;129(6):2357-2373. https://doi.org/10.1172/JCI124218.
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Research Article Immunology Transplantation

Posttransplantation cyclophosphamide prevents graft-versus-host disease by inducing alloreactive T cell dysfunction and suppression

Abstract

Posttransplantation cyclophosphamide (PTCy) recently has had a marked impact on human allogeneic hematopoietic cell transplantation (HCT). Yet our understanding of how PTCy prevents graft-versus-host disease (GVHD) largely has been extrapolated from MHC-matched murine skin-allografting models that were highly contextual in their efficacy. Herein, we developed a T cell–replete, MHC-haploidentical, murine HCT model (B6C3F1→B6D2F1) to test the putative underlying mechanisms: alloreactive T cell elimination, alloreactive T cell intrathymic clonal deletion, and suppressor T cell induction. In this model and as confirmed in four others, PTCy did not eliminate alloreactive T cells identified using either specific Vβs or the 2C or 4C T cell receptors. Furthermore, the thymus was not necessary for PTCy’s efficacy. Rather, PTCy induced alloreactive T cell functional impairment, which was supported by highly active suppressive mechanisms established within one day after PTCy that were sufficient to prevent new donor T cells from causing GVHD. These suppressive mechanisms included the rapid, preferential recovery of CD4+CD25+Foxp3+ regulatory T cells, including those that were alloantigen specific, which served an increasingly critical function over time. Our results prompt a paradigm shift in our mechanistic understanding of PTCy. These results have direct clinical implications for understanding tolerance induction and for rationally developing novel strategies to improve patient outcomes.

Authors

Lucas P. Wachsmuth, Michael T. Patterson, Michael A. Eckhaus, David J. Venzon, Ronald E. Gress, Christopher G. Kanakry

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Figure 10

PTCy rapidly induces suppressive mechanisms that prevent new splenocytes not exposed to PTCy from causing GVHD.

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PTCy rapidly induces suppressive mechanisms that prevent new splenocytes...
Recipient B6D2F1 mice were transplanted as in Figure 1 and received vehicle or PTCy on days +3 and +4. On day (A) +126, (B) +28, or (C) +5, all groups were reinfused with vehicle or with 40 × 106 or 120 × 106 splenocytes from new 10- to 12-week-old B6C3F1 donor mice. A shows the original treatments for each group, and all were reinfused with 120 × 106 splenocytes. Survival was compared using the exact log-rank test. Weight and clinical score AUCs were compared using Wilcoxon’s rank sum test. AUC comparisons for B are over days +28 to +130, as the groups were identically treated prior to that time point. All other AUCs are over the entire evaluation period. P values show comparisons between the first and second groups (shown first) and the first and third groups (shown second).