Targeting of IL-6 pathway with pharmaceutic antibodies is an applicable approach to allogeneic desensitization in transplantation. To achieve a safe and effective antibody suppression, we are obligated further investigation to determine the root cause of IL-6 accumulation in the blood and the mechanism(s) by which anti-IL6 antibodies induce disturbance in homeostasis of IL6 and soluble IL6R.

Interleukin-6 (IL-6) is a cytokine with critical innate and adaptive immunity functions. Its diverse immunological and physiological actions include direction of immune cell differentiation, initial response to invading pathogens and ischemic injury, sustained plasma cell growth, and immunoglobulin production. IL-6 transcriptional dysregulation is commonly seen in patients with autoimmune or inflammatory disorders. Emerging information suggests that IL-6 transcription is upregulated in patients with kidney and heart transplant rejection and may account for perpetuation of inflammatory responses in the allograft, leading to allograft rejection and vasculopathy. IL-6-directed therapeutics include monoclonal antibodies directed at IL-6, the IL-6 receptor (IL-6R), and Janus kinase inhibitors. IL-6-mediated signaling to cell targets is unique, involving classic signaling (IL-6->IL-6R) cell membrane receptors, transsignaling (IL-6->soluble IL-6R->gp130) which activates any cell, and the recently discovered IL-6/IL-6R transpresentation in which antigen-presenting cells synthesize and express IL-6/IL-6R complexes, which are transported through the cell membrane subsequently interacting with gp130 to costimulate T cells. Currently, there are new trials in autoimmunity and heart and kidney transplantation to determine effectiveness of inhibiting IL-6/IL-6R to ameliorate chronic allograft rejection and coronary allograft vasculopathy. Therapeutic trials aimed at prevention of ischemia/reperfusion injury to allografts based on animal data should be considered.

Our data demonstrate that a maximal suppression can be achieved by combined therapies targeting multiple pathways critical of CD4 T-cell activation, B/plasma cell activation and antibody production.

Purpose BCMA, a member of the tumor necrosis factor receptor superfamily (TNFRSF17), is selectively expressed during plasma cell differentiation while being nearly absent on naive and memory B cells. Therefore, BCMA appears as a highly selective antigen for mature B-cell targeting. The current study investigated BCMA expression by peripheral B cells and plasma cells during the development of de novo alloantibody responses. Methods A mouse model of allo-sensitization induced by skin allograft was used to study BCMA expression by B cell subsets and plasma cells. Blood samples were collected weekly for measurement of anti-HLA.A2 IgM and IgG titers. PBMCs and splenic lymphocytes were analyzed in FACS for identification of B cell subsets expressing surface BCMA. Splenic B-cells were isolated using EasySep B-cell isolation kit. mRNA expression of TNFRSF17 was studied in quantitative PCR. Results qPCR demonstrated a significant increase in TNFRSF17 mRNA expression by splenic B-cells isolated from HLA.A2 sensitized mice (p=0.004 vs. naïve control). Multi-perimeter FACS analysis of splenic lymphocytic cells showed that cell surface BCMA (CD269) was expressed by the majority of CD38+CD138+ plasma cells (60-80%), and by members of CD19+CD23+sIgD+ mature B-cells. CD269 was scarcely expression by early transitional B-cells (CD93+/CD19+/CD23-). Following skin grafting BCMA was increasingly expressed on mature B cells and plasma cells at Days 14 (p=0.03 vs. naïve control mice), 21(p=0.004) and 28(p=0.0001) PTx. Increase in BCMA expression by B cells was associated with high DSA IgG titers in the blood, indicating plasmablast differentiation. Conclusion Our data demonstrate that BCMA are increasingly expressed by B/plasma cells during the development of de novo alloantibody responses. Thus, targeting BCMA may serve as a new treatment strategy for desensitization in HLA highly sensitized transplant patients. BCMA, a member of the tumor necrosis factor receptor superfamily (TNFRSF17), is selectively expressed during plasma cell differentiation while being nearly absent on naive and memory B cells. Therefore, BCMA appears as a highly selective antigen for mature B-cell targeting. The current study investigated BCMA expression by peripheral B cells and plasma cells during the development of de novo alloantibody responses. A mouse model of allo-sensitization induced by skin allograft was used to study BCMA expression by B cell subsets and plasma cells. Blood samples were collected weekly for measurement of anti-HLA.A2 IgM and IgG titers. PBMCs and splenic lymphocytes were analyzed in FACS for identification of B cell subsets expressing surface BCMA. Splenic B-cells were isolated using EasySep B-cell isolation kit. mRNA expression of TNFRSF17 was studied in quantitative PCR. qPCR demonstrated a significant increase in TNFRSF17 mRNA expression by splenic B-cells isolated from HLA.A2 sensitized mice (p=0.004 vs. naïve control). Multi-perimeter FACS analysis of splenic lymphocytic cells showed that cell surface BCMA (CD269) was expressed by the majority of CD38+CD138+ plasma cells (60-80%), and by members of CD19+CD23+sIgD+ mature B-cells. CD269 was scarcely expression by early transitional B-cells (CD93+/CD19+/CD23-). Following skin grafting BCMA was increasingly expressed on mature B cells and plasma cells at Days 14 (p=0.03 vs. naïve control mice), 21(p=0.004) and 28(p=0.0001) PTx. Increase in BCMA expression by B cells was associated with high DSA IgG titers in the blood, indicating plasmablast differentiation. Our data demonstrate that BCMA are increasingly expressed by B/plasma cells during the development of de novo alloantibody responses. Thus, targeting BCMA may serve as a new treatment strategy for desensitization in HLA highly sensitized transplant patients.

Arising of donor specific antibodies (DSA) pre-disposes transplanted organ to antibody-mediated rejection. Development of therapies to effectively suppress DSA has become strategically important. We recently demonstrated in a proof of concept study that a strong suppression of DSA in recall responses is achievable by using a multi-targeting desensitization therapy. Here, we extend our investigation to examine the impact of the therapy on peripheral B-cell subsets.

Abstract Interleukin 6 (IL‐6) is a cytokine critical to the function of innate and adaptive immunity. IL‐6 has a diverse acumen of immunologic and physiologic activities including direction of immune cell differentiation and initial responses to invading pathogens and ischemic injury. Dysregulation of IL‐6 transcription is often seen in patients with autoimmune and inflammatory disorders. Emerging information also suggests IL‐6 transcription dysregulation is present in patients with kidney and heart transplant rejection and may account for perpetuation of inflammatory responses in the allograft. IL‐6 directed therapeutics include monoclonal antibodies aimed at IL‐6 and the IL‐6 receptor (IL‐6R) as well as Janus kinase (JAK) inhibitors. IL‐6‐mediated signalling to cell targets is unique and involves classic signalling (IL‐6‐>IL‐6R) cell membrane receptors, trans‐signalling (IL‐6‐>soluble IL‐6R‐>gp130), which can activate any cell and the newly described IL‐6/IL‐6R trans‐presentation where antigen‐presenting cells (APC) express IL‐6/IL‐6R complexes and co‐stimulate T‐cells. Currently, there are new trials in autoimmunity and specifically heart and kidney transplantation to determine efficacy in blocking IL‐6/IL‐6R for amelioration of chronic allograft rejection. Key Concepts IL‐6 is a multifunctional cytokine, produced by almost every stromal cell and immune cell in the human body. IL‐6 plays an important role in the induction of T fh cells that are critical for initiation of GC formation and progression of naïve B‐cells to plasma cells and production of high‐affinity antibodies. IL‐6 signalling inhibition is emerging as a therapeutic approach to a number of conditions varying from autoimmune diseases, cancer and organ transplantation. IL‐6 mediates injury to allografts in humans. IL‐6 directed therapeutics may be a consideration for long‐term maintenance therapy to reduce chronic injury to the allografts.

Control of donor specific antibodies (DSA) is critical for ABMR-free graft survival. Highly effective therapies for DSA suppression, however, have not been achieved. Here, we report a proof of concept study to use combined therapies to suppress DSA by targeting multiple pathways in B/plasma cell responses in allo-sensitization.

Emerging of donor specific antibodies (DSA) following transplantation is an indicator of allogenic sensitization and a predisposing factor for antibody mediated rejection. Though various methods of alloantibody detection exist, a timely and accurate test to identify allo-sensitization has not been clinically available. We report here, a study of blood CD38+/CD138+ plasma cells during the development of DSA responses in an attempt to develop a new tool for early diagnosis of allo-sensitization.

Attaining consistent robust engraftment in the structurally normal liver is an obstacle for cellular transplantation. Most experimental approaches to increase transplanted cells' engraftment involve recipient-centered deleterious methods such as partial hepatectomy or irradiation which may be unsuitable in the clinic. Here, we present a cell-based strategy that increases engraftment into the structurally normal liver using a combination of magnetic targeting and proliferative endoderm progenitor (EPs) cells. Magnetic labeling has little effect on cell viability and differentiation, but in the presence of magnetic targeting, it increases the initial dwell time of transplanted EPs into the undamaged liver parenchyma. Consequently, greater cell retention in the liver is observed concomitantly with fewer transplanted cells in the lungs. These highly proliferative cells then significantly increase their biomass over time in the liver parenchyma, approaching nearly 4% of total liver cells 30 d after transplant. Therefore, the cell-based mechanisms of increased initial dwell time through magnetic targeting combined with high rate of proliferation in situ yield significant engraftment in the undamaged liver.

Tofacitinib is a Janus Kinase Inhibitor currently approved by FDA for treatment of rheumatoid arthritis. In considering its effect in reducing B cell proliferation and autoimmune antibodies, we recently carried out a study to evaluate whether tofacitinib has suppressive effect on alloantibody responses in a skin graft model of HLA-A2 sensitization.

Recent data indicate that exosome, a nanosized membrane particle secreted by cells has immune regulatory properties, including anti-inflammation functions. Donor specific antibodies (DSA) are major hurdle in organ transplantation. A highly effective antibody suppression strategy, however, remains elusive. This study was designed to test if exosomes can suppress alloantibody production.

The success of kidney transplants is limited by the lack of robust improvements in long-term survival. It is now recognized that alloimmune responses are responsible for the majority of allograft failures. Development of novel therapies to decrease allosensitization is critical. The lack of new drug development in kidney transplantation necessitated repurposing drugs initially developed in oncology and autoimmunity. Among these is tocilizumab (anti-IL-6 receptor [IL-6R]) which holds promise for modulating multiple immune pathways responsible for allograft injury and loss. Interleukin-6 is a cytokine critical to proinflammatory and immune regulatory cascades. Emerging data have identified important roles for IL-6 in innate immune responses and adaptive immunity. Excessive IL-6 production is associated with activation of T-helper 17 cell and inhibition of regulatory T cell with attendant inflammation. Plasmablast production of IL-6 is critical for initiation of T follicular helper cells and production of high-affinity IgG. Tocilizumab is the first-in-class drug developed to treat diseases mediated by IL-6. Data are emerging from animal and human studies indicating a critical role for IL-6 in mediation of cell-mediated rejection, antibody-mediated rejection, and chronic allograft vasculopathy. This suggests that anti-IL-6/IL-6R blockade could be effective in modifying T- and B-cell responses to allografts. Initial data from our group suggest anti-IL-6R therapy is of value in desensitization and prevention and treatment of antibody-mediated rejection. In addition, human trials have shown benefits in treatment of graft versus host disease in matched or mismatched stem cell transplants. Here, we explore the biology of IL-6/IL-6R interactions and the evidence for an important role of IL-6 in mediating allograft rejection.