Allogeneic HSC transplantation is commonly utilized for the treatment of hematologic malignancies and autoimmune diseases. However, allogeneic HSC transplantation is limited by potential for the development of GVHD. These risks can be overcome through less toxic nonmyeloablative conditioning and cell depletion strategies that remove GVHD-causing cells while retaining engraftment-enhancing, tolerogenic cells. Human CD8⁺TCR^– facilitating cells from G-CSF mobilized PBMC enhance engraftment of human HSC in NOD/SCID/IL2rg^null (NSG) recipients. We first performed a dose titration of T cells for the induction of acute xenogeneic GVHD. 50 x 10⁶ T-cell depletion (TCD)-mPBMC plus T cells (from 0.05 x 10⁶ to 5 x 10⁶) were transplanted into conditioned (325 cGy TBI) NSG recipients (n=22). All mice that received T cells developed clinical GVHD with symptoms including hunched posture, reduced mobility and weight loss. All mice expired between 14 days and 24 days after transplantation. To test whether TCD from mPBMC prevents GVHD and retains engraftment-potential in NSG mice, TCD of human mPBMC was performed using AutoMACS. 30 x 10⁶,50 x 10⁶ or 70 x 10⁶ TCD-mPBMC or non-TCD-mPBMC were transplanted into NSG recipients conditioned with 325 cGy. 100% of NSG recipients treated with 30 x 10⁶ (n=3), 50 x 10⁶ (n=3), or 70 x 10⁶ (n=3) TCD-mPBMC engrafted, with an average of 27% ± 19%, 58% ± 28%, or 42% ± 18% donor chimerism, respectively in PB. Mice receiving TCD-mPBMC survived over 30 days. All conditioned NSG mice (n=6) receiving 30 x10⁶ to 50 x10⁶ non-TCD-mPBMC expired before 12 days. Immunohistochemical analysis of the spleen, liver, and lung from recipients of mPBMC using an anti-human CD45 mAb, showed that numbers of human CD45⁺ cells present in spleen, but few human CD45⁺ cells in the liver and lung. Our data suggest that (1) NOD/SCID/IL2rg^null (NSG) mice are a highly sensitive to human T cells which quickly induce acute GVHD, and (2) depletion of T cells from donor mPBMC while maintaining facilitating cells prevents GVHD and established human HSC engraftment in xenogeneic NSG recipients.

CITATION INFORMATION: Huang Y, Xu H, Merchak A, Chhabra A, Wen Y, Kahn L, Ildstad S. Depletion of T-Cells from G-CSF Mobilized Human PBMC Prevents Acute GVHD in NSG Mice. Am J Transplant. 2017;17 (suppl 3).

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