Graft-versus-host disease (GVHD) is a major complication and limitation to the broad application of hematopoietic stem cell transplantation. Cell therapy has emerged as a promising strategy for the treatment of immune-mediated disorders and induction of tolerance. Here we evaluated the role of human CD4⁺CD25^– effector T cells or CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) on induction of xenogeneic GVHD. We first performed a dose-titration of CD4⁺CD25^– T cells to establish a model for acute xenogeneic GVHD. CD4⁺CD25^– T cells (1 x 10⁶; 2 x 10⁶; 3 x 10⁶) sorted from human peripheral blood mononuclear cells (PBMC) were transplanted into NOD/SCID/IL2rg^null (NSG) mouse recipients conditioned with 200 cGy total body irradiation (TBI). All NSG recipients of CD4⁺CD25^– T cells engrafted, with a range of donor CD4⁺ T cell chimerism from 19% to 82%. Eighty-two percent of mice (n = 11) that received 2 – 3 x 10⁶ CD4⁺CD25^– T cells developed clinical GVHD with symptoms including diffuse erythema, alopecia, hunched posture, reduced mobility and weight loss 35 to 83 days after transplantation, indicating that donor CD4⁺CD25^– T cells are critical mediators of GVHD. CD4⁺CD25⁺Foxp3⁺ Treg play an important role in induction and maintenance of immunologic tolerance. It has been shown that donor CD4⁺CD25⁺Foxp3⁺ Treg inhibit lethal GVHD after allogeneic bone marrow transplantation in mice. We first evaluated Foxp3 expression in CD25^dim vs. CD25^bright cells and found that human CD4⁺CD25^bright cells had a significantly higher level of Foxp3 expression compared with the CD4⁺CD25^dim cells (83% vs. 25%). To test whether adoptive transfer of human CD4⁺CD25⁺Foxp3⁺ Treg prevents acute xenogeneic GVHD, CD4⁺CD25^bright cells were sorted from mobilized human PBMC. 2 x 10⁶ CD4⁺CD25^– T cells plus 0.4 – 0.6 x 10⁶ CD4⁺CD25^bright Treg were transplanted into NSG mice conditioned with 200 cGy of TBI (n = 3). All mice were engrafted with 9.7% to 36.3 % donor CD4⁺ T cell chimerism. No GVHD symptoms were observed in mice that received an additional CD4⁺CD25⁺Foxp3⁺ Treg for up to 70 days after transplantation. These data suggest that donor CD4⁺CD25⁺Foxp3⁺ Treg inhibit the proliferation and activation of donor CD4⁺CD25^– T cells in vivo, resulting in GVHD-prevention. Adoptive transfer CD4⁺CD25⁺Foxp3⁺ Treg may offer an opportunity for GVHD prevention in both allogeneic and xenogeneic tolerance induction.

CITATION INFORMATION: Huang Y., Merchak A., Xu H., Chhabra A., Khalil A., Wen Y., Binion M., Badder M., Kahn L., Ildstad S. CD4⁺CD25^bright Regulatory T Cells Prevent Acute Xenogeneic GVHD Am J Transplant. 2017;17 (suppl 3).

« Back to 2018 American Transplant Congress