Immunological characteristics of renal transplant tolerance in humans

Immune-Related Genes for Predicting Future Kidney Graft Loss: A Study Based on GEO Database

Objective

We aimed to identify feature immune-related genes that correlated with graft rejection and to develop a prognostic model based on immune-related genes in kidney transplantation.

Methods

Gene expression profiles were obtained from the GEO database. The GSE36059 dataset was used as a discovery cohort. Then, differential expression analysis and a machine learning method were performed to select feature immune-related genes. After that, univariate and multivariate Cox regression analyses were used to identify prognosis-related genes. A novel Riskscore model was built based on the results of multivariate regression. The levels of these feature genes were also confirmed in an independent single-cell dataset and other GEO datasets.

Results

15 immune-related genes were expressed differently between non-rejection and rejection kidney allografts. Those differentially expressed immune-related genes (DE-IRGs) were mainly associated with immune-related biological processes and pathways. Subsequently, a 5-immune-gene signature was constructed and showed favorable predictive results in the GSE21374 dataset. Recipients were divided into the high-risk and low-risk groups according to the median value of RiskScore. The GO and KEGG analysis indicated that the differentially expressed genes (DEGs) between high-risk and low-risk groups were mainly involved in inflammatory pathways, chemokine-related pathways, and rejection-related pathways. Immune infiltration analysis demonstrated that RiskScore was potentially related to immune infiltration. Kaplan-Meier survival analysis suggested that recipients in the high-risk group had poor graft survival. AUC values of 1- and 3-year graft survival were 0.804 and 0.793, respectively.

Conclusion

Our data suggest that this immune-related prognostic model had good sensitivity and specificity in predicting the 1- and 3-year kidney graft survival and might act as a useful tool for predicting kidney graft loss.

Identification of Biomarkers for Predicting Allograft Rejection following Kidney Transplantation Based on the Weighted Gene Coexpression Network Analysis

Kidney transplantation is the promising treatment of choice for chronic kidney disease and end-stage kidney disease and can effectively improve the quality of life and survival rates of patients. However, the allograft rejection following kidney transplantation has a negative impact on transplant success. Therefore, the present study is aimed at screening novel biomarkers for the diagnosis and treatment of allograft rejection following kidney transplantation for improving long-term transplant outcome. In the study, a total of 8 modules and 3065 genes were identified by WGCNA based on the GSE46474 and GSE15296 dataset from the Gene Expression Omnibus (GEO) database. Moreover, the results of Gene Ontology (GO) annotation and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis showed that these genes were mainly involved in the immune-related biological processes and pathways. Thus, 317 immune-related genes were selected for further analysis. Finally, 5 genes (including CD200R1, VAV2, FASLG, SH2D1B, and RAP2B) were identified as the candidate biomarkers based on the ROC and difference analysis. Furthermore, we also found that in the 5 biomarkers an interaction might exist among each other in the protein and transcription level. Taken together, our study identified CD200R1, VAV2, FASLG, SH2D1B, and RAP2B as the candidate diagnostic biomarkers, which might contribute to the prevention and treatment of allograft rejection following kidney transplantation.

Single-Cell Profiling of Kidney Transplant Recipients With Immunosuppressive Treatment Reveals the Dynamic Immune Characteristics

Kidney transplantation is currently the first choice of treatment for various types of end-stage renal failure, but there are major limitations in the application of immunosuppressive protocols after kidney transplantation. When the dose of immunosuppressant is too low, graft rejection occurs easily, while a dose that is too high can lead to graft loss. Therefore, it is very important to explore the immune status of patients receiving immunosuppressive agents after kidney transplantation. To compare the immune status of the recipient’s whole peripheral blood before and after receipt of immunosuppressive agents, we used single-cell cytometry by time-of-flight (CyTOF) to detect the peripheral blood immune cells in five kidney transplant recipients (KTRs) from the Department of Organ Transplantation of Zhujiang Hospital of Southern Medical University before and after receiving immunosuppressive agents. Based on CyTOF analysis, we detected 363,342 live single immune cells. We found that the immune cell types of the KTRs before and after receipt of immunosuppressive agents were mainly divided into CD4+ T cells, CD8+ T cells, B cells, NK cells/γδ T cells, monocytes/macrophages, granulocytes, and dendritic cells (DCs). After further reclustering of the above cell types, it was found that the immune cell subclusters in the peripheral blood of patients underwent major changes after receipt of immunosuppressants. After receiving immunosuppressive therapy, the peripheral blood of KTRs had significantly increased levels of CD57+NK cells and significantly decreased levels of central memory CD4+ T cells, follicular helper CD4+ T cells, effector CD8+ T cells, effector memory CD8+ T cells and naive CD8+ T cells. This study used CyTOF to classify immune cells in the peripheral blood of KTRs before and after immunosuppressive treatment, further compared differences in the proportions of the main immune cell types and immune cell subgroups before and after receipt of immunosuppressants, and provided relatively accurate information for assessment and treatment strategies for KTRs.

Clinical Operational Tolerance and Immunosuppression Minimization in Kidney Transplantation: Where Do We Stand?

BACKGROUND

The 20th century represents a breakthrough in the transplantation era, since the first kidney transplantation between identical twins was performed. This was the first case of tolerance, since the recipient did not need immunosuppression. However, as transplantation became possible, an immunosuppression-free status became the ultimate goal, since the first tolerance case was a clear exception from the hard reality nowadays represented by rejection.

METHODS

A plethora of studies was described over the past decades to understand the molecular mechanisms responsible for rejection. This review focuses on the most relevant studies found in the literature where renal tolerance cases are claimed. Contrasting, and at the same time, encouraging outcomes are herein discussed and a glimpse on the main renal biomarkers analyzed in this field is provided.

RESULTS

The activation of the immune system has been shown to play a central role in organ failure, but also it seems to induce a tolerance status when an allograft is performed, despite tolerance is still rare to register. Although there are still overwhelming challenges to overcome and various immune pathways remain arcane; the immunosuppression minimization might be more attainable than previously believed.

CONCLUSION

. Multiple biomarkers and tolerance mechanisms suspected to be involved in renal transplantation have been investigated to understand their real role, with still no clear answers on the topic. Thus, the actual knowledge provided necessarily leads to more in-depth investigations, although many questions in the past have been answered, there are still many issues on renal tolerance that need to be addressed.

Immunological biomarkers of tolerance in human kidney transplantation: An updated literature review

The half-life of transplanted kidneys is <10 years. Acute or chronic rejections have a negative impact on transplant outcome. Therefore, achieving to allograft tolerance for improving long-term transplant outcome is a desirable goal of transplantation field. In contrast, there are evidence that distinct immunological characteristics lead to tolerance in some transplant recipients. In contrast, the main reason for allograft loss is immunological responses. Various immune cells including T cells, B cells, dendritic cells, macrophages, natural killer, and myeloid-derived suppressor cells damage graft tissue and, thereby, graft loss happens. Therefore, being armed with the comprehensive knowledge about either preimmunological or postimmunological characteristics of renal transplant patients may help us to achieve an operational tolerance. In the present study, we are going to review and discuss immunological characteristics of renal transplant recipients with rejection and compare them with tolerant subjects.

Accumulation of High Levels of Monocytic Myeloid-Derived Suppressor Cells Enhances Graft Survival in Almost-Tolerant Kidney Transplant Recipients

BACKGROUND

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature cells that suppress immune responses during organ transplantation and participate in mediating long-term graft survival and immune tolerance in animal transplant models. However, their role in regulating transplant tolerance in human subjects is not well understood. In the present study, we investigated the role of MDSCs in mediating long-term graft survival in almost-tolerant kidney transplant recipients (ATKTRs) and the mechanism(s) responsible for increasing MDSC numbers in these recipients.

METHODS

Peripheral blood mononuclear cells (PBMCs) from whole blood samples were collected from 30 ATKTRs (graft survival, > 10 years after kidney transplant [KTx]) treated with low doses of immunosuppressive drugs and with stable kidney function, 10 short-term graft survival kidney transplant recipients (STKTRs; graft survival, ∼1-3 years post-KTx) with stable kidney function, and 10 healthy donors (HDs). MDSC and regulatory T cell (Tregs) levels were analyzed using multicolor flow cytometry in PBMCs.

RESULTS

ATKTRs had significantly higher levels of monocytic MDSCs (P < .001) and CD4⁺CD25⁺FoxP3⁺ Tregs than STKTRs and HDs. Furthermore, the M-MDSC levels correlated positively with the survival rates, estimated glomerular filtration rates (eGFRs) of grafts, and the levels of CD4⁺CD25⁺FoxP3⁺ Tregs in ATKTRs.

CONCLUSIONS

Accumulation of high levels of MDSCs was observed in ATKTRs. Changes in MDSC levels may play important roles in mediating transplant tolerance and regulating Tregs. Therefore, we propose that MDSCs may be potentially used for recognizing tolerant transplant recipients and guiding dosage reduction for immunosuppressive drugs for KTx.

Cyclophosphamide-induced tolerance in kidney transplantation avoids long-term immunosuppressive therapy

There has recently been remarkable progress in immunosuppressive agents, such as tacrolimus and cyclosporine. Therefore, the rate of organ establishment has improved in transplantation. However, immunosuppressive agents generally suppress the function of T cells. Thus, opportunistic infections, such as cytomegalovirus infection, are still a major problem in kidney transplantation. Induction of specific tolerance to avoid immunosuppressive drug therapy after kidney transplantation is considered as the ultimate goal of transplantation. Various factors induce tolerance that involves establishment of hematopoietic chimerism and various cell subsets. In particular, we have carried out various studies regarding the cyclophosphamide-induced tolerance system. Tolerance is induced after establishment of hematopoietic chimerism after donor bone marrow transplantation. At the clinical stage, kidney transplantation before administration of cyclophosphamide after transfusion of bone marrow to create hematopoietic chimera is considered to be one of the most successful protocols. Furthermore, recent studies have shown the involvement of multiple populations of immune cells in preserving immunological tolerance and promoting long-term renal grafts. The present review focuses on how cyclophosphamide and other immune factors induce tolerance in kidney transplantation.

CD147 blockade as a potential and novel treatment of graft rejection

Cluster of differentiation (CD)147 is highly involved in the T cell activation process. High CD147 expression is observed on the surfaces of activated T cells, particularly CD4+ T cells. In organ transplantation, it is important to prevent graft rejection resulting from the excessive activation of T cells, particularly CD4+ T cells, which exhibit a key role in amplifying the immune response. The present study aimed to investigate the effects of CD147 blockade in vitro and in vivo and used a transplant rejection system to assess the feasibility of utilizing CD147 antibody-based immunosuppressant drugs for the treatment of graft rejection. The effects of CD147 antibodies were evaluated on lymphocyte proliferation stimulated by phytohemagglutinin or CD3/CD28 magnetic beads and in a one-way mixed lymphocyte reaction (MLR) system in vitro. For the in vivo analysis, an allogeneic skin transplantation mouse model was used. CD147 antibodies were effective against lymphocytes, particularly CD4+T lymphocytes, and were additionally effective in the one-way MLR system. In the allogeneic skin transplantation mouse model, the survival of transplanted skin was extended in the CD147 antibody-treated group. Furthermore, the level of inflammatory cell infiltration in transplanted skin was reduced. CD147 blockade decreased the serum levels of interleukin (IL)-17 and the proportions of peripheral blood CD4+ and CD8+ memory T cells. The data demonstrated that CD147 blockade suppressed skin graft rejection, primarily by suppressing CD4+T and memory T cell proliferation, indicating that CD147 exhibits great potential as a target of immunosuppressant drugs.