Role of Deletion of Donor-Reactive T Cells in Long-Term Human Allograft Tolerance Achieved Via Combined Kidney and Bone Marrow Transplantation (CKBMT).

Publication Type:

Journal Article

Source:

American Journal of Transplantation, Volume 14, p.221-222 (2014)

Keywords:

2014, August 2014, Human Biology Division, Public Health Sciences Division

Abstract:

BACKGROUND: The need for tolerance protocols in organ transplantation is underscored by the morbidity associated with chronic immunosuppression and the inability to prevent chronic rejection. Induction of donor chimerism is currently the most promising strategy to achieve renal allograft tolerance in humans. In an ITN-sponsored trial, 7 of 10 CKBMT recipients have accepted their graft for several years in the absence of any immunosuppression, with development of donor-specific unresponsiveness in in vitro assays. Donor chimerism was present for less than 3 weeks in these patients and the precise mechanism of tolerance remains unknown. Differentiating between deletional tolerance and anergy has previously been impossible due to the lack of markers to track the thousands of alloreactive T cell clones. METHODS: Amplification of TCRβCDR3 with primers for all 54 Vβ and 13 Jβ regions adapted for solid phase PCR enables sequencing of millions of T cell clones, including rare clones (ImmunoSEQ; AdaptiveTM). High throughput CDR3 sequencing of a transplant recipient’s donor-reactive T cells in a one-way mixed lymphocyte reaction pre-transplant enables identification of the donor-specific TCRs that can be tracked post-transplant in peripheral blood. RESULTS: We have validated and optimized a novel technique for detecting and tracking donor-reactive T cells and studied a cohort of 4 CKBMT and 2 conventional kidney transplant recipients. In all tolerant (3 of 4 CKBMT) patients, a highly statistically significant decrease in circulating donor-reactive CD4 and CD8 clones was seen in the blood by 6 to 24 months post-transplant, with further reductions over time. In contrast, the non-tolerant CKBMT patient and 2 conventional transplant patients showed no reductions in circulating donor-reactive CD4 or CD8 clones and in some cases showed increases in circulating anti-donor CD4 clones. CONCLUSIONS: This is the first study to identify and track the pre-existing repertoire of donor-reactive T cell clones and track their fate following transplantation. The results of this TCR analysis in CKBMT demonstrate that a reduction of donor-reactive T cells may play a significant role in the maintenance of tolerance.

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