Tolerance in Kidney Transplantation: What Is on the B Side?

Continued dysregulation of the B cell lineage promotes multiple sclerosis activity despite disease modifying therapies

A clear understanding of the origin and role of the different subtypes of the B cell lineage involved in the activity or remission of multiple sclerosis (MS) is important for the treatment and follow-up of patients living with this disease. B cells, however, are dynamic and can play an anti-inflammatory or pro-inflammatory role, depending on their milieu. Depletion of B cells has been effective in controlling the progression of MS, but it can have adverse side effects. A better understanding of the role of the B cell subtypes, through the use of surface biomarkers of cellular activity with special attention to the function of memory and other regulatory B cells (Bregs), will be necessary in order to offer specific treatments without inducing undesirable effects.

Increased frequency of CD39+CD73+ regulatory T cells and Deltex-1 gene expression level in kidney transplant recipients with excellent long-term graft function

BACKGROUND

The ability of regulatory T cells (Tregs) to limit inflammatory responses has been demonstrated. However, different subpopulations of this cell have varying abilities to suppress alloreactive immune responses. The primary goal of this study was to assess the frequency of CD4⁺FOXP3⁺CD39⁺CD73⁺ Tregs and Deltex-1 gene expression on long-term renal transplant function.

METHODS

A total of 49 subjects were divided into 3 groups: (i) the excellent long-term graft function (ELTGF) group, (ii) the chronic graft dysfunction (CGD) group, and (iii) the healthy control (HC) group. Following sample collection, peripheral blood mononuclear cells (PBMCs) were isolated, and the Deltex-1 gene expression level and the frequency of CD4⁺FOXP3⁺CD39⁺CD73⁺ Tregs were evaluated.

RESULTS

The ELTGF group had more CD4⁺FOXP3⁺ Tregs than the CGD group, but the difference was not statistically significant (P = 0.07). However, the frequency of CD4⁺FOXP3⁺CD39⁺CD73⁺ Tregs and the ratio of these cells to total CD4⁺ lymphocytes significantly increased in the ELTGF group than in the CGD group (P = 0.04 and P = 0.02 respectively). In addition, the expression level of the Deltex-1 gene was significantly lower in the CGD group than in the other 2 groups (P = 0.01 and P = 0.04 respectively).

CONCLUSIONS

Given the increased frequency of CD4⁺FOXP3⁺CD39⁺CD73⁺ Tregs and the expression level of the Deltex-1 gene in the ELTGF group, it appears that these factors probably improved function and long-term survival of the transplanted organ through the suppression of alloreactive responses and reduction of inflammation. In other words, one of the immunological mechanisms involved in the CGD group may be a deficiency in Tregs.

Bone marrow mesenchymal stem cells repress renal transplant immune rejection by facilitating the APRIL phosphorylation to induce regulation B cell production

Bone marrow mesenchymal stem cells (BMSCs) exert pivotal roles in suppressing immune rejection in organ transplantation. However, the function of BMSCs on immune rejection in renal transplantation remains unclear. This study aimed to evaluate the effect and underlying mechanism of BMSCs on immune rejection in renal transplantation. Following the establishment of the renal allograft mouse model, the isolated primary BMSCs were injected intravenously into the recipient mice. Enzyme-linked immunosorbent assay, flow cytometry, hematoxylin-eosin staining, and Western blot assays were conducted to investigate BMSCs' function in vivo and in vitro. Mechanistically, the underlying mechanism of BMSCs on immune rejection in renal transplantation was investigated in in vivo and in vitro models. Functionally, BMSCs alleviated the immune rejection in renal transplantation mice and facilitated B cell activation and the production of IL-10⁺ regulatory B cells (Bregs). Furthermore, the results of mechanism studies revealed that BMSCs induced the production of IL-10⁺ Bregs by facilitating a proliferation-inducing ligand (APRIL) phosphorylation to enhance immunosuppression and repressed renal transplant rejection by promoting APRIL phosphorylation to induce IL-10⁺ Bregs. BMSCs prevent renal transplant rejection by facilitating APRIL phosphorylation to induce IL-10⁺ Bregs.

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.

Biomarkers and Pharmacogenomics in Kidney Transplantation

This review is focused on present and future biomarkers, along with pharmacogenomics used in clinical practice for kidney transplantation. It aims to highlight biomarkers that could potentially be used to improve kidney transplant early and long-term graft survival, but also potentially patient co-morbidity. Future directions for improving outcomes are discussed, which include immune tolerance and personalising immunosuppression regimens.

Mechanisms and biomarkers of immune quiescence in kidney transplantation

This review discusses the current understanding of biomarkers of immune quiescence based on reviews of published literature in kidney transplant operational tolerance and mechanistic studies based on a better characterization of the stable, well-functioning renal allograft.

Regulatory B cells: the cutting edge of immune tolerance in kidney transplantation

Kidney transplantation is the optimal treatment for end-stage renal diseases. Although great improvement has been achieved, immune tolerance is still the Holy Grail that every organ transplant practitioner pursues. The role of B cells in transplantation has long been considered simply to serve as precursors of plasma cells, which produce alloantibodies and induce antibody-mediated rejection. Recent research indicates that a specialized subset of B cells plays an important role in immune regulation, which has been well demonstrated in autoimmune diseases, infections, and cancers. This category of regulatory B cells (Bregs) differs from conventional B cells, and they may help develop a novel immunomodulatory therapeutic strategy to achieve immune tolerance in transplantation. Here, we review the latest evidence regarding phenotypes, functions, and effectors of Bregs and discuss their diverse effects on kidney transplantation.