Importance of IL-6 inhibition in prevention and treatment of antibody-mediated rejection in kidney allografts

Inhibition of inflammation by IL-6 blockade in xenotransplantation

The inflammatory cytokine interleukin 6 (IL-6) plays a role in both acute and chronic organ allotransplant rejection. Data suggest that IL-6 inhibition may help prevent or reverse rejection, with large multi-center trials now underway. However, the evidence for the benefit of IL-6 inhibitors in xenotransplantation is limited. IL-6 inhibition has been explored in nonhuman-primate models of xenotransplantation, but no clear consensus exists on its efficacy or the best mode of IL-6 inhibition (anti-IL-6 antibodies, or through IL-6 receptor [IL-6R] blockade). Extra considerations for IL-6 blockade exist in xenotransplantation, as both recipient (human) and xenograft-derived (porcine) IL-6 may play roles. The systemic inflammation seen in xenograft recipients (SIXR) contributes to significant morbidity and mortality for the recipient through coagulation dysfunction and augmentation of the immune response. Anti-IL-6 antibodies (e.g., siltuximab) bind to human IL-6 and prevent IL-6R activation, but do not bind to porcine IL-6, and so have no effect in preventing graft-driven inflammatory processes. In contrast, IL-6R inhibitors (e.g., tocilizumab) inhibit IL-6 activity by blocking binding of human and porcine IL-6 to human IL-6R. Although IL-6R blockade cannot prevent the effect of IL-6 on porcine cells, it probably prevents graft-derived IL-6 from contributing to an inflammatory response in the host. This review outlines the role of IL-6 in xenotransplantation and discusses mechanisms for inhibiting IL-6 to improve recipient survival.

Management of concurrent severe COVID-19 pneumonia and antibody-mediated rejection following kidney transplantation: a case report

Background

Due to its high mutation rate, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has recurrently emerged worldwide in recent years, leading to an increased incidence of rejection following kidney transplantation and a worsened prognosis for recipients. The management of the concomitant occurrence of SARS-CoV-2 infection and rejection in kidney transplant recipients poses significant challenges, with limited available experience on this topic. This study presents a case report highlighting the simultaneous manifestation of severe corona virus disease 2019 (COVID-19) pneumonia and acute antibody-mediated rejection (ABMR) during the early post-transplantation period.

Methods

The recipient underwent the renal transplantation from a deceased donor after brain death and received comprehensive management including antiviral therapy, adjustment of immunosuppressive medications, and relevant supportive care during the course of SARS-CoV-2 infection. In the overlapping period of severe COVID-19 pneumonia and ABMR, we implemented plasma exchange (PE) combined with intravenous immunoglobulin (IVIG) and rituximab treatment, while closely monitoring infection-related indicators and elucidate the impact of PE on SARS-CoV-2 antibodies.

Results

The administration of PE did not significantly impact the level of SARS-CoV-2 IgG antibody. Meanwhile, the combination of PE, IVIG, and rituximab treatment effectively reversed ABMR without exacerbating SARS-CoV-2 infection.

Conclusion

The timely administration of antiviral and anti-rejection therapies in the early stage of renal transplant recipient can lead to favorable outcome in case of SARS-CoV-2 infection and concurrent ABMR.

Daratumumab followed by tocilizumab for treatment of late antibody-mediated rejection in renal transplant recipients with high or moderate levels of de novo donor-specific antibodies: a pilot study

BACKGROUND

Effective treatment of late antibody-mediated rejection (late AMR) is still an unmet medical need. Clearing donor-specific antibody (DSA) and preventing its rebound is the ideal goal of treatment.

METHODS

We have summarized the clinical data from seven patients with late or chronic active AMR after renal transplantation who received daratumumab (Dara)-based treatment first (Phase 1) and then tocilizumab (TCZ) therapy (Phase 2). Phase 1 consisted of an intensive treatment period (Dara plus PP/IVIG) and a maintenance treatment period (Dara alone). The main clinical indicators were DSA, Banff scores and renal function.

RESULTS

After 4 to 17 weeks of intensive treatment, the MFI values of DSA in five of the seven patients fell below 5,000. During Dara maintenance treatment, only one patient's DSA became negative, and the remaining six patients' DSAs remained relatively stable or showed rebound. However, after TCZ treatment was begun, the DSA eventually became negative in three patients and decreased to low levels (< 3,500) in the other three patients. Also, our treatment stabilized renal function in all patients. At 24-28 months after treatment, renal biopsy showed partial remission of microvascular inflammation in four of six patients. In addition, capillary C4d deposition became negative in all patients (P = 0.001), and the mean score of i-IFTA was significantly reduced (P = 0.012). Other chronic injury scores did not change significantly.

CONCLUSIONS

This new therapy combining Dara and TCZ achieved a good desensitization effect, providing an important reference point for designing better-optimized treatment of late or chronic active AMR in the future.

TRIAL REGISTRATION

This retrospectively study was approved by the Ethics Committee of Tongji Hospital, Wuhan, China (TJ-IRB20230729).

The Promising Effect of Tocilizumab on Chronic Antibody-Mediated Rejection (cAMR) of Kidney Transplant

Background: Chronic antibody-mediated rejection (cAMR) constitutes a serious challenge in the long-term success of organ transplantation. It is associated with donor-specific antibodies (DSAs) which activate a complement pathway in response to the presence of human leukocyte antigens (HLAs) on the graft, which results in chronic inflammation and leads to graft dysfunction. One of the recent promising methods of cAMR treatment is a recombinant humanized anti-interleukin-6 receptor (IL-6R) monoclonal antibody referred to as Tocilizumab (TCZ). The aim of the presented systematic review is to explore the existing knowledge regarding the effect of tocilizumab treatment on cAMR and to perform a meta-analysis of the available data. Methods: A systematic review was performed using the PRISMA 2020 Checklist and Flow diagram. A systematic review protocol was registered in PROSPERO: CRD42024510996. The bias assessment was obtained with Methodical Index for Non-Randomized Studies (MINORS), whereas meta-analysis was performed using MedCalc. Results: Five clinical trials with a total number of 105 patients were included in our review. The mean loss of eGFR in time was -0.141 mL/min/1.73 m2 (95% CI: -0.409 to 0.126; p = 0.298) and was found to be statistically insignificant. The heterogeneity was low and was equal to I2 = 0.00%. The authors demonstrated a reduction in DSA titer by TCZ (-0.266 MFI (95% CI: -0.861 to 0.329; p = 0.377)). In the majority of studies, eGFR stabilization was associated with a reduction in DSAs. Conclusions: TCZ pharmacotherapy insignificantly reduced DSA titer and eGFR. Despite promising outcomes of potential eGFR stabilization, there is a need for large randomized controlled trials comparing standard management of cAMR and tocilizumab treatment.

Translation Research in Therapeutic Approaches from Conventional to Novel Nano-therapeutics for Rheumatoid Arthritis Treatment

Rheumatoid arthritis is a systemic autoimmune disorder related to joint inflammation, bone erosion, and deformity. Numerous studies indicate that the causes and consequences of RA are still being debated, and therapeutic strategies are in the translation stage. Non-steroidal anti-inflammatory drugs continue to be often used to relieve pain. Still, due to their poor efficacy, failure to halt the spread of the disease, and undesirable adverse effects, they are no longer regarded as first-line treatments. The development of biologic DMRDs designed to reduce the inflammatory response led to substantial changes to the strategy for managing this disease. Although biologic DMRDs have made significant strides in the management of Rheumatoid arthritis, certain patients' lack of response to biological approaches and therapy cessation due to systemic toxicity are unresolved problems. Therefore, to improve the in vivo effect and reduce systemic adverse effects, new approaches are needed to proactively target and transport therapeutic molecules to target sites. The intriguing method of nanotechnology enables the encapsulation of drugs to prevent their deterioration and systemic adverse effects. The next generation of Rheumatoid arthritis therapies might be based on advances in nanomaterial-based drug delivery, Trojan horse, and antibody targeting approaches. This article presents an overview of the advancements in Rheumatoid arthritis therapy, ranging from traditional methods to recent cutting-edge, ongoing pre-clinical and clinical approaches.

Network meta-analysis of pharmacological treatment for antibody-mediated rejection after organ transplantation

Objective

This study aims to assess the efficacy of pharmacological interventions in mitigating graft injury in transplant patients with antibody-mediated rejection (AMR) through a network meta-analysis (NMA).

Methods

A search was conducted on databases such as Cochrane Library, PubMed, EmBase, and Web of Science for randomized controlled trials (RCTs) on pharmacological interventions for alleviating graft injury following AMR. The search was performed for publications up to April 12, 2024. Two reviewers conducted independent reviews of the literature, extracted data, and assessed the risk of bias (ROB) in the included studies using the ROB assessment tool recommended by the Cochrane Handbook for Systematic Reviews of Interventions 5.1.0. A Bayesian NMA was conducted using R 4.4.0, RStudio software, and the GeMTC package to assess the outcomes in estimated glomerular filtration rate (eGFR), mean fluorescence intensity (MFI), g-score, and infection under pharmacological treatments.

Results

A total of 8 RCTs involving 215 patients and 6 different pharmacological treatments were included in this NMA. The results indicated that the increase in eGFR by eculizumab (SUCRA score: 81) appeared to be more promising. The decrease in MFI by bortezomib (SUCRA score: 72.3), rituximab (SUCRA score: 68.2), and clazakizumab (SUCRA score: 67.1) demonstrated better efficacy. The decrease in g-score by eculizumab (SUCRA score: 74.3), clazakizumab (SUCRA score: 72.2), and C1INH (SUCRA score: 63.6) appeared to have more likelihood. For infection reduction, clazakizumab (SUCRA score: 83.5) and bortezomib (SUCRA score: 66.8) might be better choices.

Conclusion

The results of this study indicate that eculizumab has the potential to enhance eGFR and reduce g-score. Bortezomib demonstrates superior efficacy in reducing MFI. Clazakizumab appears to be more effective in reducing infections.

Systematic review registration

https://www.crd.york.ac.uk/prospero/, identifier CRD42024546483.

Clinical Implications of Skin Cancer in Kidney Transplant Recipients in the Era of Immune Checkpoint Inhibitors

Long-term survival has improved in kidney transplant recipients (KTRs) due to effective surgical techniques and anti-rejection therapies. Chronic immunosuppression associated with it has led to several types of skin cancers leading to substantial morbidity and mortality. Structured patient education including sun protective behaviors, regular dermatological surveillance, nicotinamide, long-chain omega-3 polyunsaturated fatty acids (PUFAs), early switch to mammalian target of rapamycin inhibitors (mTORis), combining them with low-dose calcineurin inhibitors (CNIs), can decrease the cancer risk. Checkpoint inhibitors (CPIs) are the major backbone of the treatment of advanced skin cancers. Unfortunately, these agents can increase the risk of graft rejection. Prospective studies done so far looking at combining steroids with CPI in treatment of skin cancer in KTRs have shown mixed results. Adoption of the weight-based approach of CPI has shown to decrease the amount of drug exposure with acceptable outcomes in the general population, which is something that can be studied in KTRs with skin cancer. Also, it is reasonable to consider surveillance allograft biopsies in KTRs receiving CPIs to detect early subclinical rejection. More studies are needed to develop guidelines to safely treat this population with minimal graft rejection. We conducted a comprehensive literature review from PubMed on skin cancer in kidney transplant patients, focusing on incidence, risk factors, protective behaviors, financial and treatment implications, especially with regards to CPIs therapy. We also discussed potential newer treatment options that will decrease skin cancer risk, as well as graft rejection.

Systematic review of microRNAs in human acute kidney injury

INTRODUCTION

Early diagnosis of acute kidney injury (AKI) is limited with current tools. MicroRNAs (miRNAs) are implicated in AKI pathogenesis in preclinical models, but less is known about their role in humans. We conducted a systematic review to identify dysregulated miRNAs in humans with AKI.

METHODS

We searched Ovid MEDLINE, Embase, Web of Science, and CENTRAL (August 21, 2023) for studies of human subjects with AKI. We excluded reviews and pre-clinical studies without human data. The primary outcome was dysregulated miRNAs in AKI. Two reviewers screened abstracts, reviewed full texts, performed data extraction and quality assessment (Newcastle Ottawa Scale).

RESULTS

We screened 2,456 reports and included 92 for synthesis without meta-analysis. All studies except one were observational. Studies were grouped by etiology of AKI: cardiac surgery-associated (CS-AKI, n = 13 studies), sepsis (n = 25), nephrotoxic (n = 9), kidney transplant (n = 26), and other causes (n = 19). In total, 128 miRNAs were identified to be dysregulated across AKI studies (45 miRNAs upregulated, 55 downregulated, 28 both). miR-21 was the most frequently reported (n = 17 studies) and it was increased in all etiologies except CS-AKI where it was decreased (n = 3 studies). Study limitations included bias due to targeted approaches, absence of clinical data/controls, and miRNA normalization methods. Overall study quality was fair (median 5/9, range 2-8 points).

CONCLUSION

Dysregulated miRNAs, particularly miR-21, have potential as AKI biomarkers. These results should be interpreted cautiously due to methodological limitations. Standardized methods and unbiased approaches are needed to validate candidate miRNA biomarkers.Registration: International Prospective Register of Systematic Reviews (PROSPERO CRD42020201253).

A systematic review and meta-analysis of factors contributing to post-kidney transplant anemia and the effect of erythropoietin-stimulating agents

BACKGROUND

The effects of various risk and associated factors on post-kidney transplant anemia (PTA) have not been fully compared and estimated. This meta-analysis aims to elucidate factors contributing to PTA and determine the influence of erythropoietin-stimulating agents (ESAs) on renal outcomes, thus offering potential pathways for enhanced management strategies post-transplant.

METHODS

A systematic review was conducted in electronical database. Studies reporting on risk factors (with cause-effect relationships) and associated factors (without definite cause-effect relationships) of PTA, and the effects of ESAs on post-kidney transplant outcomes, were included. Pooled odds ratios (ORs) and weighted mean differences (WMDs) were analyzed using random-effects models.

RESULTS

This systematic review encompassed 38,233 patients from 85 studies. Factors increased PTA risk included African American, older donor age, human antigen leukocyte mismatches, and low pre-transplant hemoglobin levels. Poor allograft function, high interleukine-6, Cytomegalovirus, delayed graft function, allograft rejections, immunosuppressive medications, and renin-angiotensin system blockades were associated with PTA. Native autosomal dominant polycystic kidney disease was a protective factor against PTA. Administration of ESAs with the aim of normalizing hemoglobin levels in patients with chronic allograft dysfunction slowed the decline in eGFR and reduce the risk of death, with a pooled OR of 0.36 (95% CI: 0.14 to 0.89; p = 0.040).

CONCLUSIONS

The risks and associated factors for PTA have been elucidated, underscoring the need for individualized treatment approaches. Late ESA therapy, aimed at hemoglobin normalization, suggests a renal-protective effect and reduced mortality, which should be considered in the management of PTA.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42024545330.

Characterization of Tissue Immunity Defense Factors of the Lip in Primary Dentition Children with Bilateral Cleft Lip Palate

BACKGROUND

Bilateral cleft lip palate is a severe congenital birth defect of the mouth and face. Immunity factors modulate immune response, inflammation, and healing; therefore, they are vital in the assessment of the immunological status of the patient. The aim of this study is to assess the distribution of Gal-10, CD-163, IL-4, IL-6, IL-10, HBD-2, HBD-3, and HBD-4 in tissue of the bilateral cleft lip palate in primary dentition children.

METHODS

Five patients underwent cheiloplasty surgery, where five tissue samples of lip were obtained. Immunohistochemical staining, semi-quantitative evaluation, and non-parametric statistical analysis were used.

RESULTS

A statistically significant increase in HBD-2, HBD-3, and HBD-4 was found in skin and mucosal epithelium, hair follicles, and blood vessels. A notable increase was also noted in IL-4, IL-6, and IL-10 in the mucosal epithelium and CD163 in blood vessels. The connective tissue of patients presented with a statistically significant decrease in Gal-10, IL-10, and HBD-3. Spearman's rank correlation revealed multiple significant positive and negative correlations between the factors.

CONCLUSIONS

Upregulation of CD163 points to increased angiogenesis but the increase in IL-4 and IL-10 as well as the decrease in Gal-10 points to suppression of excessive inflammatory damage. Decreased connective tissue healing and excessive scarring are suggested by the decrease in HBD-3 and IL-10 and the increase in IL-6.

New Therapies for Highly Sensitized Patients on the Waiting List

Exposure to HLA alloantigens through pregnancy, blood products, and previous transplantations induce powerful immunologic responses that create an immunologic barrier to successful transplantation. This is commonly detected through screening for HLA antibodies using Luminex beads coated with HLA antigens at transplant evaluation. Currently accepted approaches to desensitization include plasmapheresis/low-dose or high-dose intravenous Ig plus anti-CD20. However, these approaches are often unsuccessful because of the inability to remove high titer circulating HLA antibodies and limit rebound responses by long-lived anti-HLA antibody secreting plasma cells (PCs) and memory B cells (B MEM ). This is especially significant for patients with a calculated panel reactive antibody of 99%-100%. Newer desensitization approaches, such as imlifidase (IgG endopeptidase), rapidly inactivate IgG molecules and create an antibody-free zone by cleaving IgG into F(ab'2) and Fc fragments, thus eliminating complement and cell-mediated injury to the graft. This represents an important advancement in desensitization. However, the efficacy of imlifidase is limited by pathogenic antibody rebound, increasing the potential for antibody-mediated rejection. Controlling antibody rebound requires new strategies that address the issues of antibody depletion and inhibition of B MEM and PC responses. This will likely require a combination of agents that effectively and rapidly deplete pathogenic antibodies and prevent immune cell activation pathways responsible for antibody rebound. Here, using anti-IL-6 receptor (tocilizumab) or anti-IL-6 (clazakizumab) could offer long-term control of B MEM and PC donor-specific HLA antibody responses. Agents aimed at eliminating long-lived PCs (anti-CD38 and anti-B-cell maturation antigen×CD3) are likely to benefit highly HLA sensitized patients. Complement inhibitors and novel agents aimed at inhibiting Fc neonatal receptor IgG recycling will be important in desensitization. Administering these agents alone or in combination will advance our ability to effectively desensitize patients and maintain durable suppression post-transplant. After many years of limited options, advanced therapeutics will likely improve efficacy of desensitization and improve access to kidney transplantation for highly HLA sensitized patients.

Chronic Active Antibody-mediated Rejection: Opportunity to Determine the Role of Interleukin-6 Blockade

Chronic active antibody-mediated rejection (caAMR) is arguably the most important cause of late kidney allograft failure. However, there are no US Food and Drug Administration (FDA)-approved treatments for acute or chronic AMR and there is no consensus on effective treatment. Many trials in transplantation have failed because of slow and/or inadequate enrollment, and no new agent has been approved by the FDA for transplantation in over a decade. Several lines of evidence suggest that interleukin-6 is an important driver of AMR, and clazakizumab, a humanized monoclonal antibody that neutralizes interleukin-6, has shown promising results in phase 2 studies. The IMAGINE trial (Interleukin-6 Blockade Modifying Antibody-mediated Graft Injury and Estimated Glomerular Filtration Rate Decline) (NCT03744910) is the first to be considered by the FDA using a reasonably likely surrogate endpoint (slope of estimated glomerular filtration rate decline >1 y) for accelerated approval and is the only ongoing clinical trial for the treatment of chronic rejection. This trial offers us the opportunity to advance the care for our patients in need, and this article is a call to action for all transplant providers caring for patients with caAMR.

Translating B cell immunology to the treatment of antibody-mediated allograft rejection

Antibody-mediated rejection (AMR), including chronic AMR (cAMR), causes ~50% of kidney allograft losses each year. Despite attempts to develop well-tolerated and effective therapeutics for the management of AMR, to date, none has obtained FDA approval, thereby highlighting an urgent unmet medical need. Discoveries over the past decade from basic, translational and clinical studies of transplant recipients have provided a foundation for developing novel therapeutic approaches to preventing and treating AMR and cAMR. These interventions are aimed at reducing donor-specific antibody levels, decreasing graft injury and fibrosis, and preserving kidney function. Innovative approaches emerging from basic science findings include targeting interactions between alloreactive T cells and B cells, and depleting alloreactive memory B cells, as well as donor-specific antibody-producing plasmablasts and plasma cells. Therapies aimed at reducing the cytotoxic antibody effector functions mediated by natural killer cells and the complement system, and their associated pro-inflammatory cytokines, are also undergoing evaluation. The complexity of the pathogenesis of AMR and cAMR suggest that multiple approaches will probably be required to treat these disease processes effectively. Definitive answers await results from large, double-blind, multicentre, randomized controlled clinical trials.

Advances in desensitization for human leukocyte antigen incompatible kidney transplantation

PURPOSE OF REVIEW

Human leukocyte antigen (HLA) sensitization is a major barrier to kidney transplantation induced by exposure to alloantigens through pregnancy, blood product exposure and previous transplantations. Desensitization strategies are undertaken to improve the chances of finding compatible organ offers. Standard approaches to desensitization include the use of plasmapheresis/low dose intravenous immunoglobulin (IVIG) or high dose IVIG plus anti-CD20. However, current methods to reduce HLA antibodies are not always successful, especially in those with calculated panel reactive antibody 99-100%.

RECENT FINDINGS

Newer desensitization strategies such as imlifidase [immunoglobulin G (IgG) endopeptidase] rapidly inactivates IgG molecules and creates an "antibody-free zone", representing an important advancement in desensitization. However, pathogenic antibodies rebound, increasing allograft injury that is not addressed by imlifidase. Here, use of anti-IL-6R (tocilizumab) or anti-interleukin-6 (clazakizumab) could offer long-term control of B-memory and plasma cell DSA responses to limit graft injury. Agents aimed at long-lived plasma cells (anti-CD38 and anti-BCMAxCD3) could reduce or eliminate HLA-producing plasma cells from marrow niches. Other agents such as complement inhibitors and novel agents inhibiting the Fc neonatal receptor (FcRn) mediated IgG recycling will likely find important roles in desensitization.

SUMMARY

Use of these agents alone or in combination will likely improve the efficacy and durability of desensitization therapies, improving access to kidney transplantation for immunologically disadvantaged patients.

Fine-tuning tumor- and allo-immunity: advances in the use of immune checkpoint inhibitors in kidney transplant recipients

Cancer is a common complication after kidney transplantation. Kidney transplant recipients (KTR) have a 2- to 4-fold higher risk of developing cancer compared to the general population and post-transplant malignancy is the third most common cause of death in KTR. Moreover, it is well known that certain cancer types are overrepresented after transplantation, especially non-melanoma skin cancer. Immune checkpoint inhibitors (ICI) have revolutionized the treatment of cancer, with remarkable survival benefit in a subgroup of patients. ICI are monoclonal antibodies that block the binding of specific co-inhibitory signaling molecules. Cytotoxic T lymphocyte-associated antigen-4 (CTLA-4), programmed cell death protein 1 (PD-1), and its ligand programmed cell death ligand 1 (PD-L1) are the main targets of ICI. Solid organ transplant recipients (SOTR) have been excluded from clinical trials owing to concerns about tumor response, allo-immunity, and risk of transplant rejection. Indeed, graft rejection has been estimated as high as 48% and represents an emerging problem. The underlying mechanisms of organ rejection in the context of treatment with ICI are poorly understood. The search for restricted antitumoral responses without graft rejection is of paramount importance. This review summarizes the current knowledge of the use of ICI in KTR, the potential mechanisms involved in kidney graft rejection during ICI treatment, potential biomarkers of rejection, and how to deal with rejection in clinical practice.

New treatment for antibody-mediated rejection: interleukin-6 inhibitors

Following kidney transplantation, antibody-mediated rejection (AMR) occurs when the antibodies of the immune system attack the transplanted organ, leading to damage of the kidney tissue. De novo human leukocyte antigen donor-specific antibodies (HLA-DSAs) play a key role in AMR. Current therapeutic approaches include intravenous immunoglobulin, anti-CD20 antibodies, and plasmapheresis. In cases resistant to treatment, proteasome inhibitors and C5 inhibitors may be employed. Nevertheless, a pressing need exists for new medications to improve transplant survival and reduce complications. In the context of AMR, interleukin (IL)-6 is instrumental in the development and maturation of B cells into plasma cells, which then produce HLA-DSAs targeting the allograft. IL-6 inhibitors are currently under investigation and show promise due to the essential role of IL-6 in the immune response; however, additional research is necessary.

Combined Use of Tocilizumab and Mesenchymal Stem Cells Attenuate the Development of an Anti-HLA-A2.1 Antibody in a Highly Sensitized Mouse Model

Sensitization to HLA can result in allograft loss for kidney transplantation (KT) patients. Therefore, it is required to develop an appropriate desensitization (DSZ) technique to remove HLA-donor-specific anti-HLA antibody (DSA) before KT. The aim of this research was to investigate whether combined use of the IL-6 receptor-blocking antibody, tocilizumab (TCZ), and bone-marrow-derived mesenchymal stem cells (BM-MSCs) could attenuate humoral immune responses in an allo-sensitized mouse model developed using HLA.A2 transgenic mice. Wild-type C57BL/6 mice were sensitized with skin allografts from C57BL/6-Tg (HLA-A2.1)1Enge/J mice and treated with TCZ, BM-MSC, or both TCZ and BM-MSC. We compared HLA.A2-specific IgG levels and subsets of T cells and B cells using flow cytometry among groups. HLA.A2-specific IgG level was decreased in all treated groups in comparison with that in the allo-sensitized control (Allo-CONT) group. Its decrease was the most significant in the TCZ + BM-MSC group. Regarding the B cell subset, combined use of TCZ and BM-MSC increased proportions of pre-pro B cells but decreased proportions of mature B cells in BM (p < 0.05 vs. control). In the spleen, an increase in transitional memory was observed with a significant decrease in marginal, follicular, and long-lived plasma B cells (p < 0.05 vs. control) in the TCZ + BM-MSC group. In T cell subsets, Th2 and Th17 cells were significantly decreased, but Treg cells were significantly increased in the TCZ+BM-MSC group compared to those in the Allo-CONT group in the spleen. Regarding RNA levels, IL-10 and Foxp3 showed increased expression, whereas IL-23 and IFN-γ showed decreased expression in the TCZ + BM-MSC group. In conclusion, combined use of TCZ and BM-MSC can inhibit B cell maturation and up-regulate Treg cells, finally resulting in the reduction of HLA.A2-specific IgG in a highly sensitized mouse model. This study suggests that the combined use of TCZ and BM-MSC can be proposed as a novel strategy in a desensitization protocol for highly sensitized patients.