Identification of expanded T-cell clones by spectratyping in nonfunctioning kidney transplants

Clinical application of immune repertoire sequencing in solid organ transplant

Background

Measurement of T cell receptor (TCR) or B cell receptor (BCR) gene utilization may be valuable in monitoring the dynamic changes in donor-reactive clonal populations following transplantation and enabling adjustment in therapy to avoid the consequences of excess immune suppression or to prevent rejection with contingent graft damage and to indicate the development of tolerance.

Objective

We performed a review of current literature to examine research in immune repertoire sequencing in organ transplantation and to assess the feasibility of this technology for clinical application in immune monitoring.

Methods

We searched MEDLINE and PubMed Central for English-language studies published between 2010 and 2021 that examined T cell/B cell repertoire dynamics upon immune activation. Manual filtering of the search results was performed based on relevancy and predefined inclusion criteria. Data were extracted based on study and methodology characteristics.

Results

Our initial search yielded 1933 articles of which 37 met the inclusion criteria; 16 of these were kidney transplant studies (43%) and 21 were other or general transplantation studies (57%). The predominant method for repertoire characterization was sequencing the CDR3 region of the TCR β chain. Repertoires of transplant recipients were found to have decreased diversity in both rejectors and non-rejectors when compared to healthy controls. Rejectors and those with opportunistic infections were more likely to have clonal expansion in T or B cell populations. Mixed lymphocyte culture followed by TCR sequencing was used in 6 studies to define an alloreactive repertoire and in specialized transplant settings to track tolerance.

Conclusion

Methodological approaches to immune repertoire sequencing are becoming established and offer considerable potential as a novel clinical tool for pre- and post-transplant immune monitoring.

Porcine-Stimulated Human Tr1 Cells Showed Enhanced Suppression in Xenoantigen Stimulation Response

Type 1 regulatory T (Tr1) cells play a fundamental role in maintaining and inducing immune tolerance. Our preliminary study demonstrated that an interleukin- (IL-) 10-mediated pathway is a possible regulatory mechanism underlying the xenoantigen-specific human Treg enhanced suppressive capacity. Here, we developed a feasible protocol for expanding IL-10-induced xenoantigen-specific human Tr1 cells in vitro which would be more efficient in transplantation immunotherapy efficiency. In this study, xenoantigen-specific Tr1 cells are generated from human naive CD4+ T cells expanded for two subsequent xenoantigen-stimulation cycles with recombinant human IL-10. The phenotype and suppressive capacity of xenoantigen-stimulated Tr1 cells are assessed, and the mechanism of their suppression is studied. Tr1 cells can be induced by porcine xenoantigen stimulation combined with IL-10, IL-2, and IL-15, displaying an increased expression of CD49b, CTLA-4, and LAG-3 without expressing Foxp3 which also showed an effector memory Treg phenotype and expressed high levels of CD39. After xenoantigen stimulation, the IL-10 and IL-5 gene expression in Tr1 cells increased, secreting more IL-10, and xenoantigen-stimulated Tr1 cells changed their T cell receptor (TCR) Vβ repertoire, increasing the expression of TCR Vβ2, TCR Vβ9, and TCR Vβ13. In a pig to human mixed lymphocyte reaction (MLR), xenoantigen-stimulated Tr1 cells displayed enhanced suppressive capacity via CD39 in a dose-dependent manner. Moreover, IL-5 could affect the proliferation of xenoantigen-specific Tr1 cells, but not their phenotypes' expression. This study provides a theory and feasible method for immune tolerance induction in clinical xenotransplantation.