Post doctoral Columbia University New York, New York, United States
Introduction/Rationale: Xenotransplantation of pig organs is a promising strategy to address the organ shortage; however, rejection poses a barrier to its widespread adoption. Pig-to-decedent human transplantation provides an opportunity to study immune barriers to xenotransplantation. We followed donor-reactive T cell dynamics in a long-term (61-day) pig-to-decedent human kidney
Methods: We developed a method to identify xeno donor-reactive T cell clones (XDRTCCs) by TCRB CDR3 sequencing and tracked them in the circulation and xenograft. scRNA and TCR sequencing of human leukocytes isolated from the kidney graft were used to investigate the functional phenotypes of XDRTCCs infiltrating the kidney as well as additional immune responses against the xenograft.
Results: We observed an expansion of both CD4 and CD8 XDRTCCs in the circulation. However, CD8 XDRTCCs demonstrated more striking expansions, constituting 10% of the total CD8 repertoire at POD28 and about 30% at POD33 and POD49, both of which were established rejection timepoints. Normalizing the total quantity of circulating XDRTCCs post-transplant to their pre-transplant baseline revealed clear XDRTCC enrichment, with increases up to 11-fold at POD49 for CD8 cells. scRNA sequencing data on graft-infiltrating leukocytes revealed RNA species characteristic of effector T cells and NK cells and APCs only in the POD33 rejecting kidney specimen. Interrogation of scRNA/TCR seq data for XDRTCCs revealed infiltrating XDRTCCs that expressed some effector genes such as GZMA, GZMB and PRF1 as well as the costimulatory molecule ICOS and some coinhibitory molecules, including PDCD1, LAG3, CTLA4, and TIGIT.
Conclusion: The findings provide insight into the clonal dynamics of xenoreactive T cells and their contribution to rejection in xenotransplantation and demonstrates the importance of tracking xenoreactive T cell repertoires to better understand immune responses in xenotransplantation and suggests that specific T cell clones might serve as biomarkers for rejection monitoring.
