B-cell depletion improves islet allograft survival with anti-CD45RB

Renoprotective anti-CD45RB antibody induces B cell production in systemic lupus erythematosus based on single-cell RNA-seq analysis

OBJECTIVE

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease that commonly affects the kidney. Single-cell RNA sequencing (scRNA-seq) technology is a powerful tool for characterizing individual cells and elucidating biological mechanisms at the cellular level. The purpose of this study was to identify the mechanism underlying kidney injury in SLE using scRNA-seq technology.

METHODS

scRNA-seq data of peripheral blood mononuclear cells (PBMCs) in SLE were retrieved from the GEO database, followed by batch effect elimination, dimensionality reduction, cluster analysis, cell annotation and enrichment analysis. A model of SLE was developed in NZB/WF1 mice. Effects of anti-CD45RB antibody on the SLE-induced kidney injury were evaluated, and we measured the distribution of regulatory T cells and B cells in mouse spleen and kidney tissues, levels of kidney function-related indexes, deposition of IgG and C3 in the glomeruli, and the levels of inflammatory cytokines.

RESULTS

CD45RB was a specific marker gene of B cell clusters and had influence on the B cells. anti-CD45RB antibody treatment induced regulatory B cells and consequently arrested the kidney injury caused by SLE. In addition, depletion of regulatory T cells was found to partially undermine the alleviatory effect of anti-CD45RB antibody on SLE-induced kidney injury.

CONCLUSION

Collectively, our data suggest that anti-CD45RB antibody can prevent the SLE-induced kidney injury, pointing to anti-CD45RB antibody as a potential therapeutic strategy in kidney injury-related disease.

Protective Effect of Mesenchymal Stem Cells on Isolated Islets Survival and Against Hypoxia Associated With the HIF-1α/PFKFB3 Pathway

Islets have a high demand for oxygen and most of them will die of hypoxia injury before and after transplantation. Hypoxic damage is one of the key factors associated with islet graft dysfunction. Mesenchymal stem cells (MSCs) have multiple functions and can enhance the therapeutic effect of islet transplantation. In this study, islets were cultured together with or without MSCs derived from umbilical cord (hUC-MSCs) under normal and hypoxic conditions. The effect of hUC-MSCs on the survival and function of isolated islets was detected by immunofluorescence and ELISA. Hypoxia-inducible factor 1 alpha (HIF-1α) and PFKFB3 mRNA and protein expression in different conditions were tested by real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and Western Blot. The islets co-cultured with hUC-MSCs have improved viability and function compared with islets cultured alone. The mRNA transcription of HIF-1α in the co-cultured group increased. The protein expression of PFKFB3 increased with the increase of HIF-1α. This study found that hUC-MSCs could protect islets from dysfunction caused by hypoxia, and HIF-1α/PFKFB3 played an important role in hypoxic resistance, suggesting a potential strategy to improve the outcome of islet transplantation.

Induction of Immune Tolerance in Islet Transplantation Using Apoptotic Donor Leukocytes

Allogeneic islet transplantation has become an effective treatment option for severe Type 1 diabetes with intractable impaired awareness due to hypoglycemic events. Although current immunosuppressive protocols effectively prevent the acute rejection associated with initial T cell activation in recipients, chronic rejection has remained an obstacle for achieving long-term allogeneic islet engraftment. The development of donor-specific immune tolerance to the allograft is the ultimate goal given its potential ability to overcome chronic rejection and disregard the need for maintenance immunosuppression, which may be toxic to islet grafts. Recently, a breakthrough in tolerance induction during allogeneic islet transplantation using apoptotic donor lymphocytes (ADLs) in a non-human primate model had been reported. Several studies have suggested that the clonal depletion, anergy, and expansion of the antigen-specific regulatory immune network are the mechanisms for donor-specific tolerance with ADLs, which act synergistically to induce robust transplant tolerance. This achievement represents a huge step forward toward the clinical application of immune tolerance induction. We herein summarize the reported operational induction therapies in islet transplantation using the ADLs. Moreover, a few obstacles for the engraftment of transplanted islets, such as islet immunogenicity and instant blood-mediated response, which need to be resolved in the future, are also discussed.

Immunosuppressive Mechanisms of Regulatory B Cells

Regulatory B cells (Bregs) is a term that encompasses all B cells that act to suppress immune responses. Bregs contribute to the maintenance of tolerance, limiting ongoing immune responses and reestablishing immune homeostasis. The important role of Bregs in restraining the pathology associated with exacerbated inflammatory responses in autoimmunity and graft rejection has been consistently demonstrated, while more recent studies have suggested a role for this population in other immune-related conditions, such as infections, allergy, cancer, and chronic metabolic diseases. Initial studies identified IL-10 as the hallmark of Breg function; nevertheless, the past decade has seen the discovery of other molecules utilized by human and murine B cells to regulate immune responses. This new arsenal includes other anti-inflammatory cytokines such IL-35 and TGF-β, as well as cell surface proteins like CD1d and PD-L1. In this review, we examine the main suppressive mechanisms employed by these novel Breg populations. We also discuss recent evidence that helps to unravel previously unknown aspects of the phenotype, development, activation, and function of IL-10-producing Bregs, incorporating an overview on those questions that remain obscure.

Transplant Islets Into the Pinna of the Ear: A Mouse Islet Transplant Model

BACKGROUND

Islets transplanted under the ear skin would allow easy observation of the graft response and survival in vivo. This research was designed to establish an efficient mouse islet transplant model to probe the dynamic cellular interplay in vivo.

METHODS

Green fluorescent protein transgenic mice and BALB/c mice were used as donors and recipients. All recipients were divided into 6 groups of 6 mice each. First, we treated the transplant recipients, including diabetes induction, autologous epididymal fat pad, and MATRIGEL transplant to the ears. Then, 1. we transplanted isolated islets to the ear/ear with fat/ear with MATRIGEL; and 2. transplanted islets with collagen + basic fibroblast growth factor or islets with collagen + vascular endothelial growth factor. Mice in the control group received a sham transplantation with phosphate buffer saline. All recipients were then observed for 30 days with blood glucose (BG) monitoring. Finally, ears were removed with graft on day 28 for histologic examination.

RESULTS

It was suggested that transplant of islets alone could not correct hyperglycemia. Fat, MATRIGEL, collagen, and growth factors have the similar function to form a microenvironment conducive to islet survival. The effect of islet transplantation for correcting hyperglycemia of the fat modification group was better than other groups (P < .05). BG could be normalized, and living islets were detected by anti-insulin immunohistochemistry.

CONCLUSIONS

Transplant islets into the ear with transplanted autologous fat is the optimal way which can be used to analyze the allograft response in vivo and track cell population and migration using labels by confocal microscopy.

Phenotypically distinct anti-insulin B cells repopulate pancreatic islets after anti-CD20 treatment in NOD mice

AIMS/HYPOTHESIS

Autoreactive B cells escape immune tolerance and contribute to the pathogenesis of type 1 diabetes. While global B cell depletion is a successful therapy for autoimmune disease, the fate of autoreactive cells during this treatment in autoimmune diabetes is unknown. We aimed to identify and track anti-insulin B cells in pancreatic islets and understand their repopulation after anti-CD20 treatment.

METHODS

We generated a double transgenic system, the VH125.hCD20/NOD mouse. The VH125 transgenic mouse, expressing an increased frequency of anti-insulin B cells, was crossed with a human CD20 (hCD20) transgenic mouse, to facilitate B cell depletion using anti-CD20. B cells were analysed using multiparameter and ImageStream flow cytometry.

RESULTS

We demonstrated that anti-insulin B cells were recruited to the pancreas during disease progression in VH125.hCD20/NOD mice. We identified two distinct populations of anti-insulin B cells in pancreatic islets, based on CD19 expression, with both populations enriched in the CD138^int fraction. Anti-insulin B cells were not identified in the plasma-cell CD138^hi fraction, which also expressed the transcription factor Blimp-1. After anti-CD20 treatment, anti-insulin B cells repopulated the pancreatic islets earlier than non-specific B cells. Importantly, we observed that a CD138^intinsulin⁺CD19^- population was particularly enriched after B cell depletion, possibly contributing to the persistence of disease still observed in some mice after anti-CD20 treatment.

CONCLUSIONS/INTERPRETATION

Our observations may indicate why the loss of C-peptide is only temporarily delayed following anti-CD20 treatment in human type 1 diabetes.

Anti-CD45RB Antibody Therapy Attenuates Renal Ischemia-Reperfusion Injury by Inducing Regulatory B Cells

BACKGROUND

Regulatory B cells are a newly discovered B cell subset that suppresses immune responses. Recent studies found that both anti-CD45RB and anti-Tim-1 treatments regulate immune responses by inducing regulatory B cells; however, the role of these cells in renal ischemia-reperfusion injury (IRI) is unknown.

METHODS

Using mouse models, including T cell-deficient (RAG1 knockout and TCRα knockout) mice and B cell-deficient (μMT) mice, we investigated the effects of regulatory B cells and anti-CD45RB on IRI and the mechanisms underlying these effects.

RESULTS

Adoptive transfer of regulatory B cells before or after IRI attenuated renal IRI. Anti-CD45RB treatment with or without anti-Tim-1 before IRI increased renal infiltration of CD19⁺Tim-1⁺ regulatory B and regulatory T cells. Anti-CD45RB decreased serum creatinine levels, pathologic injury score, tubular apoptosis, and proinflammatory cytokines levels, whereas IL-10 levels increased. Following IRI, anti-CD45RB with or without anti-Tim-1 also induced regulatory B cells, improving renal function and tubular regeneration. In RAG1 knockout mice with B cell transfer, TCRα knockout mice, and wild-type mice with T cell depletion, anti-CD45RB increased regulatory B cells and attenuated IRI. However, anti-CD45RB did not attenuate IRI in RAG1 knockout mice with T cell transfer or μMT mice and induced only mild improvement in wild-type mice with B cell depletion. Furthermore, B cell-deficient mice receiving B cells from IL-10 knockout mice (but not from wild-type mice) did not show renal protection against IRI when treated with anti-CD45RB.

CONCLUSIONS

Anti-CD45RB treatment attenuated acute renal injury and facilitated renal recovery after IRI through induction of IL-10⁺ regulatory B cells, pointing to anti-CD45RB as a potential therapeutic strategy in renal IRI.

Differential Impact of Chronic Hyperglycemia on Humoral Versus Cellular Primary Alloimmunity

Diabetes is prevalent among solid organ transplant recipients and is universal among islet transplant recipients. Whereas diabetes is often considered to result in an immune-compromised state, the impact of chronic hyperglycemia on host alloimmunity is not clear. Potential immune-modifying effects of obesity, autoimmunity, or diabetogenic agents like streptozotocin may confound understanding alloimmunity in experimental models of diabetes. Therefore, we sought to determine the role of chronic hyperglycemia due to insulinopenia on alloimmunity using the nonautoimmune, spontaneously diabetic H-2^b-expressing C57BL/6 Ins2^Akita mice (Akita). Akita mice harbor a mutated Ins2 allele that dominantly suppresses insulin secretion, resulting in lifelong diabetes. We used BALB/c donors (H-2^d) to assess alloimmunization and islet transplantation outcomes in Akita recipients. Surprisingly, chronic hyperglycemia had little effect on primary T-cell reactivity after alloimmunization. Moreover, Akita mice readily rejected islet allografts, and chronic hyperglycemia had no impact on the magnitude or quality of intragraft T-cell responses. In contrast, allospecific IgM and IgG were significantly decreased in Akita mice after alloimmunization. Thus, whereas diabetes influences host immune defense, hyperglycemia itself does not cause generalized alloimmune impairment. Our data suggest that immune compromise in diabetes due to hyperglycemia may not apply to cellular rejection of transplants.

The roles of IL-2 and IL-10 enhance anti-CD45RBmAb immune inhibition in allograft skin

As a new type of immune tolerance inducer, anti-CD45RB monoclonal antibodies (anti-CD45RBmAb) can prolong the graft survival time of animal organs or cell transplantation as well as induce stable immune tolerance. Both interleukin (IL)-2 and IL-10 have important roles in the induction and maintenance of immunological tolerance. However, whether these cytokines combined with anti-CD45RBmAb can promote immune tolerance is poorly understood. Therefore, we investigated the effect of IL-2 and IL-10 in vitro and in vivo on the tolerance induction by anti-CD45RBmAb. The changes of Treg and Th17 cells and Th1/Th2 cytokines in anti-CD45RBmAb induced prolongation of skin allograft survival in mice. The finding of a role for IL-2 is novel, of interest, IL-2 promoted anti-CD45RBmAb-induced CD4(+) T cell differentiation into Treg and Th2 cells and suppressed Th17 and Th1 cells. IL-2 enhanced the induction of immune tolerance by anti-CD45RBmAb and significantly prolonged skin graft survival time in vivo. In contrast, this effect should be demonstrated experimentally by neutralizing IL-2 and inhibition of the effect of anti-CD45RBmAb, and neutralizing IL-10 showed no effect for anti-CD45RBmAb-induced tolerance. These data reveal that IL-2 significantly enhances anti-CD45RBmAb-induced immune tolerance via up-regulated T regulatory (Treg) cells and the balance of Th1/Th2 shifts. Conversely, IL-10 showed no effect on anti-CD45RBmAb-induced tolerance.

Involvement of suppressive B-lymphocytes in the mechanism of tolerogenic dendritic cell reversal of type 1 diabetes in NOD mice

The objective of the study was to identify immune cell populations, in addition to Foxp3+ T-regulatory cells, that participate in the mechanisms of action of tolerogenic dendritic cells shown to prevent and reverse type 1 diabetes in the Non-Obese Diabetic (NOD) mouse strain. Co-culture experiments using tolerogenic dendritic cells and B-cells from NOD as well as transgenic interleukin-10 promoter-reporter mice along with transfer of tolerogenic dendritic cells and CD19+ B-cells into NOD and transgenic mice, showed that these dendritic cells increased the frequency and numbers of interleukin-10-expressing B-cells in vitro and in vivo. The expansion of these cells was a consequence of both the proliferation of pre-existing interleukin-10-expressing B-lymphocytes and the conversion of CD19+ B-lymphcytes into interleukin-10-expressing cells. The tolerogenic dendritic cells did not affect the suppressive activity of these B-cells. Furthermore, we discovered that the suppressive murine B-lymphocytes expressed receptors for retinoic acid which is produced by the tolerogenic dendritic cells. These data assist in identifying the nature of the B-cell population increased in response to the tolerogenic dendritic cells in a clinical trial and also validate very recent findings demonstrating a mechanistic link between human tolerogenic dendritic cells and immunosuppressive regulatory B-cells.