Role of T cells in graft rejection and transplantation tolerance

Innate and Adaptive Immune Responses in Intestinal Transplant Rejection: Through the Lens of Inflammatory Bowel and Intestinal Graft-Versus-Host Diseases

Intestinal transplantation is a life-saving procedure utilized for patients failing total parenteral nutrition. However, intestinal transplantattion remains plagued with low survival rates and high risk of allograft rejection. The authors explore roles of innate (macrophages, natural killer cells, innate lymphoid cells) and adaptive immune cells (Th1, Th2, Th17, Tregs) in inflammatory responses, particularly inflammatory bowel disease and graft versus host disease, and correlate these findings to intestinal allograft rejection, highlighting which effectors exacerbate or suppress intestinal rejection. Better understanding of this immunology can open further investigation into potential biomolecular targets to develop improved therapeutic treatment options and immunomonitoring techniques to combat allograft rejection and enhance patient lives.

Protein Phosphatase 2A Activation Promotes Heart Transplant Acceptance in Mice

BACKGROUND

Although heart transplantation is the definitive treatment for heart failure in eligible patients, both acute and chronic transplant rejection frequently occur. Protein phosphatase 2A (PP2A) activity is critical in maintaining tissue and organ homeostasis. In this study, we evaluated the effect of a novel class of small molecule activators of PP2A (SMAPs) on allograft rejection in a mouse heterotopic heart transplantation model.

METHODS

Recipient mice were administered with DT-061 (a pharmaceutically optimized SMAP) or vehicle by oral gavage beginning 1 d after transplantation. Histological and immunofluorescence analyses were performed to examine allograft rejection. Regulatory T cells (Treg) from recipient spleens were subjected to flow cytometry and RNA sequencing analysis. Finally, the effect of DT-061 on smooth muscle cells (SMCs) migration and proliferation was assessed.

RESULTS

DT-061 treatment prolonged cardiac allograft survival. SMAPs effectively suppressed the inflammatory immune response while increasing Treg population in the allografts, findings corroborated by functional analysis of RNA sequencing data derived from Treg of treated splenic tissues. Importantly, SMAPs extended immunosuppressive agent cytotoxic T lymphocyte-associated antigen-4-Ig-induced cardiac transplantation tolerance and allograft survival. SMAPs also strongly mitigated cardiac allograft vasculopathy as evidenced by a marked reduction of neointimal hyperplasia and SMC proliferation. Finally, our in vitro studies implicate suppression of MEK/ERK pathways as a unifying mechanism for the effect of PP2A modulation in Treg and SMCs.

CONCLUSIONS

PP2A activation prevents cardiac rejection and prolongs allograft survival in a murine model. Our findings highlight the potential of PP2A activation in improving alloengraftment in heart transplantation.

Solid organ transplantation and gut microbiota: a review of the potential immunomodulatory properties of short-chain fatty acids in graft maintenance

Transplantation is the treatment of choice for several end-stage organ defects: it considerably improves patient survival and quality of life. However, post-transplant recipients may experience episodes of rejection that can favor or ultimately lead to graft loss. Graft maintenance requires a complex and life-long immunosuppressive treatment. Different immunosuppressive drugs (i.e., calcineurin inhibitors, glucocorticoids, biological immunosuppressive agents, mammalian target of rapamycin inhibitors, and antiproliferative or antimetabolic agents) are used in combination to mitigate the immune response against the allograft. Unfortunately, the use of these antirejection agents may lead to opportunistic infections, metabolic (e.g., post-transplant diabetes mellitus) or cardiovascular (e.g., arterial hypertension) disorders, cancer (e.g., non-Hodgkin lymphoma) and other adverse effects. Lately, immunosuppressive drugs have also been associated with gut microbiome alterations, known as dysbiosis, and were shown to affect gut microbiota-derived short-chain fatty acids (SCFA) production. SCFA play a key immunomodulatory role in physiological conditions, and their impairment in transplant patients could partly counterbalance the effect of immunosuppressive drugs leading to the activation of deleterious pathways and graft rejection. In this review, we will first present an overview of the mechanisms of graft rejection that are prevented by the immunosuppressive protocol. Next, we will explain the dynamic changes of the gut microbiota during transplantation, focusing on SCFA. Finally, we will describe the known functions of SCFA in regulating immune-inflammatory reactions and discuss the impact of SCFA impairment in immunosuppressive drug treated patients.

Beyond FOXP3: a 20-year journey unravelling human regulatory T-cell heterogeneity

The initial idea of a distinct group of T-cells responsible for suppressing immune responses was first postulated half a century ago. However, it is only in the last three decades that we have identified what we now term regulatory T-cells (Tregs), and subsequently elucidated and crystallized our understanding of them. Human Tregs have emerged as essential to immune tolerance and the prevention of autoimmune diseases and are typically contemporaneously characterized by their CD3+CD4+CD25high CD127lowFOXP3+ phenotype. It is important to note that FOXP3+ Tregs exhibit substantial diversity in their origin, phenotypic characteristics, and function. Identifying reliable markers is crucial to the accurate identification, quantification, and assessment of Tregs in health and disease, as well as the enrichment and expansion of viable cells for adoptive cell therapy. In our comprehensive review, we address the contributions of various markers identified in the last two decades since the master transcriptional factor FOXP3 was identified in establishing and enriching purity, lineage stability, tissue homing and suppressive proficiency in CD4+ Tregs. Additionally, our review delves into recent breakthroughs in innovative Treg-based therapies, underscoring the significance of distinct markers in their therapeutic utilization. Understanding Treg subsets holds the key to effectively harnessing human Tregs for immunotherapeutic approaches.

Cyclosporine A-resistant CAR-T cells mediate antitumour immunity in the presence of allogeneic cells

Chimeric antigen receptor (CAR)-T therapy requires autologous T lymphocytes from cancer patients, a process that is both costly and complex. Universal CAR-T cell treatment from allogeneic sources can overcome this limitation but is impeded by graft-versus-host disease (GvHD) and host versus-graft rejection (HvGR). Here, we introduce a mutated calcineurin subunit A (CNA) and a CD19-specific CAR into the T cell receptor α constant (TRAC) locus to generate cells that are resistant to the widely used immunosuppressant, cyclosporine A (CsA). These immunosuppressant-resistant universal (IRU) CAR-T cells display improved effector function in vitro and anti-tumour efficacy in a leukemia xenograft mouse model in the presence of CsA, compared with CAR-T cells carrying wild-type CNA. Moreover, IRU CAR-T cells retain effector function in vitro and in vivo in the presence of both allogeneic T cells and CsA. Lastly, CsA withdrawal restores HvGR, acting as a safety switch that can eliminate IRU CAR-T cells. These findings demonstrate the efficacy of CsA-resistant CAR-T cells as a universal, 'off-the-shelf' treatment option.

Inhibition of Prostaglandin-Degrading Enzyme 15-PGDH Mitigates Acute Murine Lung Allograft Rejection

PURPOSE

Acute rejection is a frequent complication among lung transplant recipients and poses substantial therapeutic challenges. 15-hydroxyprostaglandin dehydrogenase (15-PGDH), an enzyme responsible for the inactivation of prostaglandin E2 (PGE2), has recently been implicated in inflammatory lung diseases. However, the role of 15-PGDH in lung transplantation rejection remains elusive. The present study was undertaken to examine the expression of 15-PGDH in rejected lung allografts and whether inhibition of 15-PGDH ameliorates acute lung allograft rejection.

METHODS

Orthotopic mouse lung transplantations were performed between donor and recipient mice of the same strain or allogeneic mismatched pairs. The expression of 15-PGDH in mouse lung grafts was measured. The efficacy of a selective 15-PGDH inhibitor (SW033291) in ameliorating acute rejection was assessed through histopathological examination, micro-CT imaging, and pulmonary function tests. Additionally, the mechanism underlying the effects of SW033291 treatment was explored using CD8+ T cells isolated from mouse lung allografts.

RESULTS

Increased 15-PGDH expression was observed in rejected allografts and allogeneic CD8+ T cells. Treatment with SW033291 led to an accumulation of PGE2, modulation of CD8+ T-cell responses and mitochondrial activity, and improved allograft function and survival.

CONCLUSION

Our study provides new insights into the role of 15-PGDH in acute lung rejection and highlights the therapeutic potential of inhibiting 15-PGDH for enhancing graft survival. The accumulation of PGE2 and modulation of CD8+ T-cell responses represent potential mechanisms underlying the benefits of 15-PGDH inhibition in this model. Our findings provide impetus for further exploring 15-PGDH as a target for improving lung transplantation outcomes.

The fate of adipose tissue and adipose-derived stem cells in allograft

Utilizing adipose tissue and adipose-derived stem cells (ADSCs) turned into a promising field of allograft in recent years. The therapeutic potential of adipose tissue and ADSCs is governed by their molecular secretions, ability to sustain multi-differentiation and self-renewal which are pivotal in reconstructive, genetic diseases, and cosmetic goals. However, revisiting the existing functional capacity of adipose tissue and ADSCs and their intricate relationship with allograft is crucial to figure out the remarkable question of safety to use in allograft due to the growing evidence of interactions between tumor microenvironment and ADSCs. For instance, the molecular secretions of adipose tissue and ADSCs induce angiogenesis, create growth factors, and control the inflammatory response; it has now been well determined. Though the existing preclinical allograft studies gave positive feedback, ADSCs and adipose tissue are attracted by some factors of tumor stroma. Moreover, allorecognition is pivotal to allograft rejection which is carried out by costimulation in a complement-dependent way and leads to the destruction of the donor cells. However, extensive preclinical trials of adipose tissue and ADSCs in allograft at molecular level are still limited. Hence, comprehensive immunomodulatory analysis could ensure the successful allograft of adipose tissue and ADSCs avoiding the oncological risk.

Immune Responses to Sequential Binocular Transplantation of Allogeneic Retinal Progenitor Cells to the Vitreous Cavity in Mice

Intravitreal transplantation of allogeneic human retinal progenitor cells (hRPCs) holds promise as a treatment for blinding retinal degenerations. Prior work has shown that neural progenitors are well-tolerated as allografts following single injections; however, sequential delivery of allogeneic cells raises the potential risk of host sensitization with subsequent immune rejection of grafts. The current study was designed to assess whether an immune response would be induced by repeated intravitreal transplants of allogeneic RPCs utilizing the mouse animal model. We injected murine retinal progenitor cells (gmRPCs), originally derived from donors with a C57BL/6 genetic background, into BALB/c recipient mice in order to provide safety data as to what might be expected following repeated treatment of patients with allogeneic human cell product. Immune responses to gmRPCs were mild, consisting of T cells, B cells, neutrophils, and natural killer cells, with macrophages clearly the predominating. Animals treated with repeat doses of gmRPCs did not show evidence of sensitization, nor was there immune-mediated destruction of the grafts. Despite the absence of immunosuppressive treatments, allogeneic gmRPC grafts survived following repeat dosing, thus providing support for the preliminary observation that repeated injection of allogeneic RPCs to the vitreous cavity is tolerated in patients with retinitis pigmentosa.

IL-10 modified mRNA monotherapy prolongs survival after composite facial allografting through the induction of mixed chimerism

Vascularized composite allotransplantation has great potential in face transplantation by supporting functional restoration following tissue grafting. However, the need for lifelong administration of immunosuppressive drugs still limits its wide use. Modified mRNA (modRNA) technology provides an efficient and safe method to directly produce protein in vivo. Nevertheless, the use of IL-10 modRNA-based protein replacement, which exhibits anti-inflammatory properties, has not been shown to prolong composite facial allograft survival. In this study, IL-10 modRNA was demonstrated to produce functional IL-10 protein in vitro, which inhibited pro-inflammatory cytokines and in vivo formation of an anti-inflammatory environments. We found that without any immunosuppression, C57BL/6J mice with fully major histocompatibility complex (MHC)-mismatched facial allografts and local injection of IL-10 modRNA had a significantly prolonged survival rate. Decreased lymphocyte infiltration and pro-inflammatory T helper 1 subsets and increased anti-inflammatory regulatory T cells (Tregs) were seen in IL-10 modRNA-treated mice. Moreover, IL-10 modRNA induced multilineage chimerism, especially the development of donor Treg chimerism, which protected allografts from destruction because of recipient alloimmunity. These results support the use of monotherapy based on immunomodulatory IL-10 cytokines encoded by modRNA, which inhibit acute rejection and prolong allograft survival through the induction of donor Treg chimerism.

P-glycoprotein, FK-binding Protein-12, and the Intracellular Tacrolimus Concentration in T-lymphocytes and Monocytes of Kidney Transplant Recipients

BACKGROUND

. Transplant recipients may develop rejection despite having adequate tacrolimus whole blood predose concentrations (C 0 ). The intra-immune cellular concentration is potentially a better target than C 0 . However, little is known regarding intracellular tacrolimus concentration in T-lymphocytes and monocytes. We investigated the tacrolimus concentrations in both cell types and their relation with the expression and activity of FK-binding protein (FKBP)-12 and P-glycoprotein (P-gp).

METHODS

. T-lymphocytes and monocytes were isolated from kidney transplant recipients followed by intracellular tacrolimus concentration measurement. FKBP-12 and P-gp were quantified with Western blot, flow cytometry, and the Rhodamine-123 assay. Interleukin-2 and interferon-γ in T-lymphocytes were measured to quantify the effect of tacrolimus.

RESULTS

. Tacrolimus concentration in T-lymphocytes was lower than in monocytes (15.3 [8.5-33.4] versus 131.0 [73.5-225.1] pg/million cells; P < 0.001). The activity of P-gp (measured by Rhodamine-123 assay) was higher in T-lymphocytes than in monocytes. Flow cytometry demonstrated a higher expression of P-gp (normalized mean fluorescence intensity 1.5 [1.2-1.7] versus 1.2 [1.1-1.4]; P = 0.012) and a lower expression of FKBP-12 (normalized mean fluorescence intensity 1.3 [1.2-1.7] versus 1.5 [1.4-2.0]; P = 0.011) in T-lymphocytes than monocytes. Western blot confirmed these observations. The addition of verapamil, a P-gp inhibitor, resulted in a 2-fold higher intra-T-cell tacrolimus concentration. This was accompanied by a significantly fewer cytokine-producing cells.

CONCLUSIONS

. T-lymphocytes have a higher activity of P-gp and lower concentration of the FKBP-12 compared with monocytes. This explains the relatively lower tacrolimus concentration in T-lymphocytes. The addition of verapamil prevents loss of intracellular tacrolimus during the cell isolation process and is required to ensure adequate intracellular concentration measurement.

The Value of Single-cell Technologies in Solid Organ Transplantation Studies

Single-cell technologies open up new opportunities to explore the behavior of cells at the individual level. For solid organ transplantation, single-cell technologies can provide in-depth insights into the underlying mechanisms of the immunological processes involved in alloimmune responses after transplantation by investigating the role of individual cells in tolerance and rejection. Here, we review the value of single-cell technologies, including cytometry by time-of-flight and single-cell RNA sequencing, in the context of solid organ transplantation research. Various applications of single-cell technologies are addressed, such as the characterization and identification of immune cell subsets involved in rejection or tolerance. In addition, we explore the opportunities for analyzing specific alloreactive T- or B-cell clones by linking phenotype data to T- or B-cell receptor data, and for distinguishing donor- from recipient-derived immune cells. Moreover, we discuss the use of single-cell technologies in biomarker identification and risk stratification, as well as the remaining challenges. Together, this review highlights that single-cell approaches contribute to a better understanding of underlying immunological mechanisms of rejection and tolerance, thereby potentially accelerating the development of new or improved therapies to avoid allograft rejection.

Preservation of antigen-specific responses in cryopreserved CD4+ and CD8+ T cells expanded with IL-2 and IL-7

Objectives

We sought to develop medium throughput standard operating procedures for screening cryopreserved human peripheral blood mononuclear cells (PBMCs) for CD4⁺ and CD8⁺ T cell responses to potential autoantigens.

Methods

Dendritic cells were loaded with a peptide cocktail from ubiquitous viruses or full-length viral protein antigens and cocultured with autologous T cells. We measured expression of surface activation markers on T cells by flow cytometry and cytometry by time of flight 24-72 h later. We tested responses among T cells freshly isolated from healthy control PBMCs, cryopreserved T cells, and T cells derived from a variety of T cell expansion protocols. We also compared the transcriptional profile of CD8⁺ T cells rested with interleukin (IL)7 for 48 h after 1) initial thawing, 2) expansion, and 3) secondary cryopreservation/thawing of expanded cells. To generate competent antigen presenting cells from PBMCs, we promoted differentiation of PBMCs into dendritic cells with granulocyte macrophage colony stimulating factor and IL-4.

Results

We observed robust dendritic cell differentiation from human PBMCs treated with 50 ng/mL GM-CSF and 20 ng/mL IL-4 in as little as 3 days. Dendritic cell purity was substantially increased by magnetically enriching for CD14⁺ monocytes prior to differentiation. We also measured antigen-dependent T cell activation in DC-T cell cocultures. However, polyclonal expansion of T cells with anti-CD3/antiCD28 abolished antigen-dependent upregulation of CD69 in our assay despite minimal transcriptional differences between rested CD8⁺ T cells before and after expansion. Furthermore, resting these expanded T cells in IL-2, IL-7 or IL-15 did not restore the antigen dependent responses. In contrast, T cells that were initially expanded with IL-2 + IL-7 rather than plate bound anti-CD3 + anti-CD28 retained responsiveness to antigen stimulation and these responses strongly correlated with responses measured at initial thawing.

Significance

While screening techniques for potential pathological autoantibodies have come a long way, comparable full-length protein target assays for screening patient T cells at medium throughput are noticeably lacking due to technical hurdles. Here we advance techniques that should have broad applicability to translational studies investigating cell mediated immunity in infectious or autoimmune diseases. Future studies are aimed at investigating possible CD8⁺ T cell autoantigens in MS and other CNS autoimmune diseases.

Intracellular monitoring by dendritic cells – a new way to stay informed – from a simple scavenger to an active gatherer

Dendritic cells (DCs) are required for the initiation of the adaptive immune response. Their ability to acquire antigens in the periphery is a critical step in this process. DCs express a wide variety of adhesion molecules and possess an extremely fluid plasma membrane that facilitates scavenging the extracellular environment and capturing material like exosomes, apoptotic bodies, and pathogens. Besides these standard routes, the acquisition of antigens by DCs can be further facilitated by tunneling nanotubes, trogocytosis, and gap junctions. However, in this article, we will argue that this is an incomplete picture, as certain observations in the literature cannot be explained if we assume DCs acquire antigens only through these means. Instead, it is more likely that DCs preferentially use adhesion molecules to form long-lasting cell-cell interactions to actively siphon material from cells they are in direct contact with. It is highly likely that DCs use this mechanism to continually capture membrane and cytosolic material directly from surrounding cells, which they scan to assess the health of the donor cell. Doing so would provide an array of advantages for the host immune system, as it would not be reliant on compromised cells to release antigens into the extracellular milieu. Therefore, we propose updating our view of DC antigen acquisition to include a process of active, contact-dependent capture of material directly from neighboring cell cytosol (cytocytosis), which we would term intracellular monitoring.

Association Between the Intracellular Tacrolimus Concentration in CD3 + T Lymphocytes and CD14 + Monocytes and Acute Kidney Transplant Rejection

BACKGROUND

Intracellular tacrolimus concentration in peripheral blood mononuclear cells (PBMCs) (TAC [PBMC] ) has been proposed to better represent its active concentration than its whole blood concentration. As tacrolimus acts on T lymphocytes and other white blood cells, including monocytes, we investigated the association of tacrolimus concentration in CD3 + T lymphocytes (TAC [CD3] ) and CD14 + monocytes (TAC [CD14] ) with acute rejection after kidney transplantation.

METHODS

From a total of 61 samples in this case-control study, 28 samples were obtained during biopsy-proven acute rejection (rejection group), and 33 samples were obtained in the absence of rejection (control group). PBMCs were collected from both cryopreserved (retrospectively) and freshly obtained (prospectively) samples. CD3 + T lymphocytes and CD14 + monocytes were isolated from PBMCs, and their intracellular tacrolimus concentrations were measured.

RESULTS

The correlation between tacrolimus whole-blood and intracellular concentrations was poor. TAC [CD3] was significantly lower than TAC [CD14] (median 12.8 versus 81.6 pg/million cells; P < 0.001). No difference in TAC [PBMC] (48.5 versus 44.4 pg/million cells; P = 0.82), TAC [CD3] (13.4 versus 12.5 pg/million cells; P = 0.28), and TAC [CD14] (90.0 versus 72.8 pg/million cells; P = 0.27) was found between the rejection and control groups. However, freshly isolated PBMCs showed significantly higher TAC [PBMC] than PBMCs from cryopreserved samples. Subgroup analysis of intracellular tacrolimus concentrations from freshly isolated cells did not show a difference between rejectors and nonrejectors.

CONCLUSIONS

Differences in TAC [CD3] and TAC [CD14] between patients with and without rejection could not be demonstrated. However, further optimization of the cell isolation process is required because a difference in TAC [PBMC] between fresh and cryopreserved cells was observed. These results need to be confirmed in a study with a larger number of patients.

METTL3 inhibition reduces N6 -methyladenosine levels and prevents allogeneic CD4+ T-cell responses

Alloreactive CD4+ T cells play a central role in allograft rejection. However, the post-transcriptional regulation of the effector program in alloreactive CD4+ T cells remains unclear. N6 -methyladenosine (m6 A) RNA modification is involved in various physiological and pathological processes. Herein, we investigated whether m6 A methylation plays a role in the allogeneic T-cell effector program. m6 A levels of CD4+ T cells from spleens, draining lymph nodes and skin allografts were determined in a skin transplantation model. The effects of a METTL3 inhibitor (STM2457) on CD4+ T-cell characteristics including proliferation, cell cycle, cell apoptosis and effector differentiation were determined after stimulation of polyclonal and alloantigen-specific (TEa; CD4+ T cells specific for I-Eα52-68 ) CD4+ T cells with α-CD3/α-CD28 monoclonal antibodies and cognate CB6F1 alloantigen, respectively. We found that graft-infiltrating CD4+ T cells expressed high m6 A levels. Administration of STM2457 reduced m6 A levels, inhibited T-cell proliferation and suppressed effector differentiation of polyclonal CD4+ T cells. Alloreactive TEa cells challenged with 40 μm STM2457 exhibited deficits in T-cell proliferation and T helper type 1 cell differentiation, a cell cycle arrest in the G0 phase and elevated cell apoptosis. Moreover, these impaired T-cell responses were associated with the diminished expression levels of transcription factors Ki-67, c-Myc and T-bet. Therefore, METTL3 inhibition reduces the expression of several key transcriptional factors for the T-cell effector program and suppresses alloreactive CD4+ T-cell effector function and differentiation. Targeting m6 A-related enzymes and molecular machinery in CD4+ T cells represents an attractive therapeutic approach to prevent allograft rejection.

Genome-wide association study biomarkers in T-cell mediated rejection: selective effect according to the Banff classification

BACKGROUND

A genome-wide association study (GWAS) in kidney transplant recipients reported the association of two polymorphisms located in the PTPRO gene and upstream of the CCDC67 (DEUP1) gene with increased risk of acute T cell-mediated rejection (TCMR). We aimed at replicating the assessment of mentioned associations and additionally ascertaining the influence of treatment and clinical features of the patients.

METHODS

The polymorphisms, PTPRO-rs7976329 and CCDC67-rs10765602 were genotyped by TaqMan chemistry in 641 consecutive kidney transplant recipients. The diagnosis of rejection was confirmed by biopsy and categorized according to the Banff classification. Associations were evaluated by Chi-square test or Fisher's exact test when necessary and multivariate logistic regression.

RESULTS

Considering the GWAS study we only replicated the association of the PTPRO-rs7976329*C allele in the Banff grade < II subjects. However, the homozygous mutant genotypes of both polymorphism seemed to increase the risk of TCMR Banff grade < II in the overall cohort and after stratification by Thymoglobulin induction therapy. In the multivariate analysis, we confirmed the association of PTPRO-rs7976329 with TCMR Banff grade < II, independently of the Thymoglobulin induction therapy and of CCDC67-rs10765602 only in the group of patients not receiving Thymoglobulin induction therapy. No association of these polymorphisms with TCMR Banff grade ≥ II was observed in either the overall cohort or in the subgroups stratified by Thymoglobulin therapy.

CONCLUSIONS

Our study shows that the increased risk of TCMR related to polymorphisms PTPRO-rs7976329 and CCDC67-rs10765602 previously reported in a GWAS was replicated only in homozygous patients who presented TCMR Banff grade < II and for the minor allele of either polymorphism.

T Cells With Activated STAT4 Drive the High-Risk Rejection State to Renal Allograft Failure After Kidney Transplantation

In kidney transplantation, deteriorated progression of rejection is considered to be a leading course of postoperative mortality. However, the conventional histologic diagnosis is limited in reading the rejection status at the molecular level, thereby triggering mismatched pathogenesis with clinical phenotypes. Here, by applying uniform manifold approximation and projection and Leiden algorithms to 2,611 publicly available microarray datasets of renal transplantation, we uncovered six rejection states with corresponding signature genes and revealed a high-risk (HR) state that was essential in promoting allograft loss. By identifying cell populations from single-cell RNA sequencing data that were associated with the six rejection states, we identified a T-cell population to be the pathogenesis-triggering cells associated with the HR rejection state. Additionally, by constructing gene regulatory networks, we identified that activated STAT4, as a core transcription factor that was regulated by PTPN6 in T cells, was closely linked to poor allograft function and prognosis. Taken together, our study provides a novel strategy to help with the precise diagnosis of kidney allograft rejection progression, which is powerful in investigating the underlying molecular pathogenesis, and therefore, for further clinical intervention.

Tacrolimus CYP3A Single-Nucleotide Polymorphisms and Preformed T- and B-Cell Alloimmune Memory Improve Current Pretransplant Rejection-Risk Stratification in Kidney Transplantation

Achieving fast immunosuppression blood exposure after kidney transplantation is key to abrogating both preformed and de novo anti-donor humoral and cellular alloresponses. However, while tacrolimus (TAC) is the cornerstone immunosuppressant inhibiting adaptive alloimmunity, its blood exposure is directly impacted by different single-nucleotide polymorphisms (SNPs) in CYP3A TAC-metabolizing enzymes. Here, we investigated how functional TAC-CYP3A genetic variants (CYP3A4*22/CYP3A5*3) influence the main baseline clinical and immunological risk factors of biopsy-proven acute rejection (BPAR) by means of preformed donor-specific antibodies (DSAs) and donor-specific alloreactive T cells (DSTs) in a large European cohort of 447 kidney transplants receiving TAC-based immunosuppression. A total of 70 (15.7%) patients developed BPAR. Preformed DSAs and DSTs were observed in 12 (2.7%) and 227 (50.8%) patients, respectively. According to the different CYP3A4*22 and CYP3A5*3 functional allele variants, we found 4 differential new clusters impacting fasting TAC exposure after transplantation; 7 (1.6%) were classified as high metabolizers 1 (HM1), 71 (15.9%) as HM2, 324 (72.5%) as intermediate (IM), and 45 (10.1%) as poor metabolizers (PM1). HM1/2 showed significantly lower TAC trough levels and higher dose requirements than IM and PM (p < 0.001) and more frequently showed TAC underexposure (<5 ng/ml). Multivariate Cox regression analyses revealed that CYP3A HM1 and IM pharmacogenetic phenotypes (hazard ratio (HR) 12.566, 95% CI 1.99–79.36, p = 0.007, and HR 4.532, 95% CI 1.10–18.60, p = 0.036, respectively), preformed DSTs (HR 3.482, 95% CI 1.99–6.08, p < 0.001), DSAs (HR 4.421, 95% CI 1.63–11.98, p = 0.003), and delayed graft function (DGF) (HR 2.023, 95% CI 1.22–3.36, p = 0.006) independently predicted BPAR. Notably, a significant interaction between T-cell depletion and TAC underexposure was observed, showing a reduction of the BPAR risk (HR 0.264, 95% CI 0.08–0.92, p = 0.037). Such variables except for DSAs displayed a higher predictive risk for the development of T cell-mediated rejection (TCMR). Refinement of pretransplant monitoring by incorporating TAC CYP3A SNPs with preformed DSAs as well as DSTs may improve current rejection-risk stratification and help induction treatment decision-making.

Typical and atypical properties of peripheral nerve allografts enable novel strategies to repair segmental-loss injuries

We review data showing that peripheral nerve injuries (PNIs) that involve the loss of a nerve segment are the most common type of traumatic injury to nervous systems. Segmental-loss PNIs have a poor prognosis compared to other injuries, especially when one or more mixed motor/sensory nerves are involved and are typically the major source of disability associated with extremities that have sustained other injuries. Relatively little progress has been made, since the treatment of segmental loss PNIs with cable autografts that are currently the gold standard for repair has slow and incomplete (often non-existent) functional recovery. Viable peripheral nerve allografts (PNAs) to repair segmental-loss PNIs have not been experimentally or clinically useful due to their immunological rejection, Wallerian degeneration (WD) of anucleate donor graft and distal host axons, and slow regeneration of host axons, leading to delayed re-innervation and producing atrophy or degeneration of distal target tissues. However, two significant advances have recently been made using viable PNAs to repair segmental-loss PNIs: (1) hydrogel release of Treg cells that reduce the immunological response and (2) PEG-fusion of donor PNAs that reduce the immune response, reduce and/or suppress much WD, immediately restore axonal conduction across the donor graft and re-innervate many target tissues, and restore much voluntary behavioral functions within weeks, sometimes to levels approaching that of uninjured nerves. We review the rather sparse cellular/biochemical data for rejection of conventional PNAs and their acceptance following Treg hydrogel and PEG-fusion of PNAs, as well as cellular and systemic data for their acceptance and remarkable behavioral recovery in the absence of tissue matching or immune suppression. We also review typical and atypical characteristics of PNAs compared with other types of tissue or organ allografts, problems and potential solutions for PNA use and storage, clinical implications and commercial availability of PNAs, and future possibilities for PNAs to repair segmental-loss PNIs.

Histocompatibility and Reproduction: Lessons from the Anglerfish

Reproduction in certain deep-sea anglerfishes involves the permanent attachment of dwarf males to much larger females and fusion of their tissues leading to the establishment of a shared circulatory system. This unusual phenomenon of sexual parasitism enables anglerfishes to maximize reproductive success in the vast and deep oceans, where females and males otherwise rarely meet. An even more surprising phenomenon relates to the observation that joining of genetically disparate male and female anglerfishes does not evoke a strong anti-graft immune rejection response, which occurs in vertebrates following allogeneic parabiosis. Recent studies demonstrated that the evolutionary processes that led to the unique mating strategy of anglerfishes coevolved with genetic changes that resulted in loss of functional genes encoding critical components of the adaptive immune system. These genetic alterations enabled anglerfishes to tolerate the histoincompatible tissue antigens of their mate and prevent the occurrence of reciprocal graft rejection responses. While the exact mechanisms by which anglerfishes defend themselves against pathogens have not yet been deciphered, it is speculated that during evolution, anglerfishes adopted new immune strategies that compensate for the loss of B and T lymphocyte functions and enable them to resist infection by pathogens.

EYE DISEASE IN KIDNEY TRANSPLANTATION: CLINICAL CHALLENGES IN A UNIQUE PATIENT POPULATION

Eye disease is common among kidney transplant recipients and their management is challenging. Chronic kidney disease is associated with ocular complications, both independently and in the context of various systemic disorders. In addition, chronic immunosuppression predisposes kidney transplant recipients to an array of long-term ocular issues. This may be broadly categorized into infections, malignancies, and other immunosuppression-specific side effects. The interdependence of kidney disease, transplant pharmacotherapy and ocular health therefore requires a multispecialty approach. Although the kidney transplant population has grown along with the burden of associated oculopathies, systematic guidelines targeting this patient group are lacking. This evidenced-based narrative review summarizes the pertinent issues that may present in the ophthalmic and optometric clinical settings, with emphasis on collaborative management and directions for future research.

Bioactive compounds in green tea may improve transplant tolerance: A computational systems biology analysis

BACKGROUND

Green tea (Camellia sinensis) has bioactive compounds that have been shown to possess nutritive effects on various biomolecular processes such as immunomodulation. This research explores the immunomodulatory effects of green tea in reducing transplant rejection.

METHOD

The study employs computational systems biology: 1) to identify biomolecular mechanisms of immunomodulation in transplant rejection; 2) to identify the bioactive compounds of green tea and their specific effects on mechanisms of immunomodulation in transplant rejection; and, 3) to predict the quantitative effects of those bioactive compounds on immunomodulation in transplant rejection.

RESULTS

Three bioactive compounds of green tea - epicatechin (EC), gallic acid (GA), and epigallocatechin gallate (EGCG), were identified for their potential effects on immunomodulation of transplant rejection. Of the three, EGCG was the only one determined to enhance anti-inflammatory activity by: 1) upregulating synthesis of HO-1 that is known to promote Treg and Th2 phenotypes associated with enabling transplant tolerance; and, 2) downregulating pro-inflammatory cytokines IL-2, IL-17, IFN-γ, TNF-α, NO, IL-6, and IL-1β that are known to promote Th1 and Th17 phenotypes associated with transplant rejection.

CONCLUSIONS

To the best of our knowledge, this study provides the first molecular mechanistic understanding the clinical nutritive value of green tea, specifically the bioactive compound EGCG, in enabling transplant tolerance.

The potential of ex vivo lung perfusion on improving organ quality and ameliorating ischemia reperfusion injury

Allogeneic lung transplantation (LuTx) is considered the treatment of choice for a broad range of advanced, progressive lung diseases resistant to conventional treatment regimens. Ischemia reperfusion injury (IRI) occurring upon reperfusion of the explanted, ischemic lung during implantation remains a crucial mediator of primary graft dysfunction (PGD) and early allo-immune responses. Ex vivo lung perfusion (EVLP) displays an advanced technique aiming at improving lung procurement and preservation. Indeed, previous clinical trials have demonstrated a reduced incidence of PGD following LuTx utilizing EVLP, while long-term outcomes are yet to be evaluated. Mechanistically, EVLP may alleviate donor lung inflammation through reconditioning the injured lung and diminishing IRI through storing the explanted lung in a non-ischemic, perfused, and ventilated status. In this work, we review potential mechanisms of EVLP that may attenuate IRI and improve organ quality. Moreover, we dissect experimental treatment approaches during EVLP that may further attenuate inflammatory events deriving from tissue ischemia, shear forces or allograft rejection associated with LuTx.

High-Throughput immunogenetics for precision medicine in cancer

Cancer is characterized by an extremely complex biological background, which hinders personalized therapeutic interventions. Precision medicine promises to overcome this obstacle through integrating information from different 'subsystems', including the host, the external environment, the tumor itself and the tumor micro-environment. Immunogenetics is an essential tool that allows dissecting both lymphoid cancer ontogeny at both a cell-intrinsic and a cell-extrinsic level, i.e. through characterizing micro-environmental interactions, with a view to precision medicine. This is particularly thanks to the introduction of powerful, high-throughput approaches i.e. next generation sequencing, which allow the comprehensive characterization of immune repertoires. Indeed, NGS immunogenetic analysis (Immune-seq) has emerged as key to both understanding cancer pathogenesis and improving the accuracy of clinical decision making in oncology. Immune-seq has applications in lymphoid malignancies, assisting in the diagnosis e.g. through differentiating from reactive conditions, as well as in disease monitoring through accurate assessment of minimal residual disease. Moreover, Immune-seq facilitates the study of T cell receptor clonal dynamics in critical clinical contexts, including transplantation as well as innovative immunotherapy for solid cancers. The clinical utility of Immune-seq represents the focus of the present contribution, where we highlight what can be achieved but also what must be addressed in order to maximally realize the promise of Immune-seq in precision medicine in cancer.

DNA-PKcs kinase activity stabilizes the transcription factor Egr1 in activated immune cells

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is known primarily for its function in DNA double-stranded break repair and nonhomologous end joining (NHEJ). However, DNA-PKcs also has a critical yet undefined role in immunity impacting both myeloid and lymphoid cell lineages spurring interest in targeting DNA-PKcs for therapeutic strategies in immune-related diseases. To gain insight into the function of DNA-PKcs within immune cells, we performed a quantitative phosphoproteomic screen in T cells to identify phosphorylation targets of DNA-PKcs. Our results indicate that DNA-PKcs phosphorylates the transcription factor Egr1 (early growth response protein 1) at serine 301. Expression of Egr1 is induced early upon T cell activation and dictates T cell response by modulating expression of cytokines and key costimulatory molecules such as IL (interleukin) 2, IL6, IFNγ, and NFκB. Inhibition of DNA-PKcs by treatment with a DNA-PKcs specific inhibitor NU7441 or shRNA knockdown increased proteasomal degradation of Egr1. Mutation of serine 301 to alanine via CRISPR-Cas9 reduced EGR1 protein expression and decreased Egr1-dependent transcription of IL2 in activated T cells. Our findings identify DNA-PKcs as a critical intermediary link between T cell activation and T cell fate and a novel phosphosite involved in regulating Egr1 activity.

Cytotoxic T Lymphocytes (CTLs) and Kidney Transplantation: An Overview

Involvement of T lymphocytes in kidney transplantation is a well-developed topic; however, most of the scientific interest focused on the different type of CD4+ lymphocyte subpopulations. Few authors, instead, investigated the role of CD8+ T cells in renal transplantation and how deleterious they can be to long-term allograft survival. Recently, there has been a renewed interest in the CD8+ T cells involvement in the transplantation field with the aim to investigate the immunological mechanisms underlying the infiltration of CD8+ T cells and their biological functions in human kidney allografts. The purpose of the present review is to highlight the role of allo-reactive cytotoxic T lymphocytes (CTLs) CD8⁺ subset in allograft kidney recipients and their related clinical complications.

Preformed T cell alloimmunity and HLA eplet mismatch to guide immunosuppression minimization with tacrolimus monotherapy in kidney transplantation: Results of the CELLIMIN trial

Personalizing immunosuppression is a major objective in transplantation. Transplant recipients are heterogeneous regarding their immunological memory and primary alloimmune susceptibility. This biomarker-guided trial investigated whether in low immunological-risk kidney transplants without pretransplant DSA and donor-specific T cells assessed by a standardized IFN-γ ELISPOT, low immunosuppression (LI) with tacrolimus monotherapy would be non-inferior regarding 6-month BPAR than tacrolimus-based standard of care (SOC). Due to low recruitment rates, the trial was terminated when 167 patients were enrolled. ELISPOT negatives (E-) were randomized to LI (n = 48) or SOC (n = 53), E+ received the same SOC. Six- and 12-month BPAR rates were higher among LI than SOC/E- (4/35 [13%] vs. 1/43 [2%], p = .15 and 12/48 [25%] vs. 6/53 [11.3%], p = .073, respectively). E+ patients showed similarly high BPAR rates than LI at 6 and 12 months (12/55 [22%] and 13/66 [20%], respectively). These differences were stronger in per-protocol analyses. Post-hoc analysis revealed that poor class-II eplet matching, especially DQ, discriminated E- patients, notably E-/LI, developing BPAR (4/28 [14%] low risk vs. 8/20 [40%] high risk, p = .043). Eplet mismatch also predicted anti-class-I (p = .05) and anti-DQ (p < .001) de novo DSA. Adverse events were similar, but E-/LI developed fewer viral infections, particularly polyoma-virus-associated nephropathy (p = .021). Preformed T cell alloreactivity and HLA eplet mismatch assessment may refine current baseline immune-risk stratification and guide immunosuppression decision-making in kidney transplantation.

Cell therapy in transplantation: A comprehensive review of the current applications of cell therapy in transplant patients with the focus on Tregs, CAR Tregs, and Mesenchymal stem cells

Organ transplantation is a practical treatment for patients with end-stage organ failure. Despite the advances in short-term graft survival, long-term graft survival remains the main challenge considering the increased mortality and morbidity associated with chronic rejection and the toxicity of immunosuppressive drugs. Since a novel therapeutic strategy to induce allograft tolerance seems urgent, focusing on developing novel and safe approaches to prolong graft survival is one of the main goals of transplant investigators. Researchers in the field of organ transplantation are interested in suppressing or optimizing the immune responses by focusing on immune cells including mesenchymal stem cells (MSCs), polyclonal regulatory Tcells (Tregs), and antigen-specific Tregs engineered with chimeric antigen receptors (CAR Tregs). We review the mechanistic pathways, phenotypic and functional characteristics of these cells, and their promising application in organ transplantation.

Berberine Prolongs Mouse Heart Allograft Survival by Activating T Cell Apoptosis via the Mitochondrial Pathway

Berberine, which is a traditional Chinese medicine can inhibit tumorigenesis by inducing tumor cell apoptosis. However, the immunoregulatory of effects berberine on T cells remains poorly understood. Here, we first examined whether berberine can prolong allograft survival by regulating the recruitment and function of T cells. Using a major histocompatibility complex complete mismatch mouse heterotopic cardiac transplantation model, we found that the administration of moderate doses (5 mg/kg) of berberine significantly prolonged heart allograft survival to 19 days and elicited no obvious berberine-related toxicity. Compared to that with normal saline treatment, berberine treatment decreased alloreactive T cells in recipient splenocytes and lymph node cells. It also inhibited the activation, proliferation, and function of alloreactive T cells. Most importantly, berberine treatment protected myocardial cells by decreasing CD4⁺ and CD8⁺ T cell infiltration and by inhibiting T cell function in allografts. In vivo and in vitro assays revealed that berberine treatment eliminated alloreactive T lymphocytes via the mitochondrial apoptosis pathway, which was validated by transcriptome sequencing. Taken together, we demonstrated that berberine prolongs allograft survival by inducing apoptosis of alloreactive T cells. Thus, our study provides more evidence supporting the potential use of berberine in translational medicine.

Tissue-specific endothelial cell heterogeneity contributes to unequal inflammatory responses

Endothelial cells (EC) coordinate vascular homeostasis and inflammation. In organ transplantation, EC are a direct alloimmune target. We posited that tissue specific heterogeneity of vascular EC may partly underlie the disparate organ-specific alloimmune risk. We examined the vascular endothelial response to inflammation across six primary endothelial beds from four major transplanted organs: the heart, lung, kidney and liver. First, we reanalyzed a public dataset of cardiac allograft rejection and found that endothelial inflammatory response genes were elevated in human cardiac allograft biopsies undergoing rejection compared with stable grafts. Next, the inducible inflammatory phenotypes of EC from heart, lung, kidney, and liver were characterized in vitro, focused on expression of adhesion molecules and chemokines, and recruitment of allogeneic peripheral blood mononuclear immune cells. Large vessel cardiac EC most highly upregulated VCAM-1, particularly compared with hepatic EC, supported greater leukocyte adhesion and had distinct chemokine profiles after stimulation with cytokines and complement. Differentially expressed gene candidates that are known regulators of cytokine signaling and inflammatory programming were verified in publicly available datasets of organ-specific endothelial transcriptomes. In summary, differential baseline expression of immune regulating genes may contribute to differential vascular inflammatory responses depending on organ.

Research Advances on Health Effects of Edible Artemisia Species and Some Sesquiterpene Lactones Constituents

The genus Artemisia, often known collectively as "wormwood", has aroused great interest in the scientific community, pharmaceutical and food industries, generating many studies on the most varied aspects of these plants. In this review, the most recent evidence on health effects of edible Artemisia species and some of its constituents are presented and discussed, based on studies published until 2020, available in the Scopus, Web of Sciences and PubMed databases, related to food applications, nutritional and sesquiterpene lactones composition, and their therapeutic effects supported by in vivo and clinical studies. The analysis of more than 300 selected articles highlights the beneficial effect on health and the high clinical relevance of several Artemisia species besides some sesquiterpene lactones constituents and their derivatives. From an integrated perspective, as it includes therapeutic and nutritional properties, without ignoring some adverse effects described in the literature, this review shows the great potential of Artemisia plants and some of their constituents as dietary supplements, functional foods and as the source of new, more efficient, and safe medicines. Despite all the benefits demonstrated, some gaps need to be filled, mainly related to the use of raw Artemisia extracts, such as its standardization and clinical trials on adverse effects and its health care efficacy.

Repertoire-scale determination of class II MHC peptide binding via yeast display improves antigen prediction

CD4⁺ helper T cells contribute important functions to the immune response during pathogen infection and tumor formation by recognizing antigenic peptides presented by class II major histocompatibility complexes (MHC-II). While many computational algorithms for predicting peptide binding to MHC-II proteins have been reported, their performance varies greatly. Here we present a yeast-display-based platform that allows the identification of over an order of magnitude more unique MHC-II binders than comparable approaches. These peptides contain previously identified motifs, but also reveal new motifs that are validated by in vitro binding assays. Training of prediction algorithms with yeast-display library data improves the prediction of peptide-binding affinity and the identification of pathogen-associated and tumor-associated peptides. In summary, our yeast-display-based platform yields high-quality MHC-II-binding peptide datasets that can be used to improve the accuracy of MHC-II binding prediction algorithms, and potentially enhance our understanding of CD4⁺ T cell recognition.

Identifying peptides that can bind major histocompatibility complex II (MHC-II) is important for our understanding of T cell immunity and specificity. Here the authors present a yeast-display library screening approach that identifies more potential binders than various reported algorithms to help expand our understanding for antigen presentation.

Modulation of P2Y11-related purinergic signaling in inflammation and cardio-metabolic diseases

Chronic inflammation is the hallmark of cardiovascular pathologies with a major role in both disease progression and occurrence of long-term complications. The massive release of ATP during the inflammatory process activates various purinergic receptors, including P2Y11. This receptor is less studied but ubiquitously expressed in all cells relevant for cardiovascular pathology: cardiomyocytes, fibroblasts, endothelial and immune cells. While several studies suggested a potential pro-inflammatory role for P2Y11 receptors, recent literature data are supportive of an anti-inflammatory profile characterized by the immunosuppression of dendritic cells, inhibition of fibroblast proliferation and of cytokines and ATP secretion. Moreover, modulation of its activity appears to mediate the positive inotropic effect of ATP and mitigate endothelial dysfunction, thus rendering this receptor a promising therapeutic target in the cardiovascular disease armamentarium. The aim of the present review is to summarize the current available knowledge on P2Y11-related purinergic signaling in the setting of inflammation and cardio-metabolic diseases.

A Novel Immunosuppressant, Luteolin, Modulates Alloimmunity and Suppresses Murine Allograft Rejection

An allograft is rejected in the absence of any immunosuppressive treatment because of vigorous alloimmunity and thus requires extensive immunosuppression for its survival. Although there are many conventional immunosuppressants for clinical use, it is necessary to seek alternatives to existing drugs, especially in case of transplant patients with complicated conditions. Luteolin, a natural ingredient, exists in many plants. It exhibits multiple biological and pharmacological effects, including anti-inflammatory properties. In particular, luteolin has been shown to upregulate CD4⁺CD25⁺ regulatory T cells (Tregs) in the context of airway inflammation. However, it remains unknown whether luteolin regulates alloimmune responses. In this study, we demonstrated that luteolin significantly prolonged murine skin allograft survival, ameliorated cellular infiltration, and downregulated proinflammatory cytokine gene expression in skin allografts. Furthermore, luteolin increased the percentage of CD4⁺Foxp3⁺ Tregs while reducing frequency of mature dendritic cells and CD44^highCD62L^low effector CD4⁺/CD8⁺ T cells posttransplantation. It also suppressed the proliferation of T cells and their production of cytokines IFN-γ and IL-17A in vitro while increasing IL-10 level in the supernatant. Moreover, luteolin promoted CD4⁺Foxp3⁺ Treg generation from CD4⁺CD25^- T cells in vitro. Depleting Tregs largely, although not totally, reversed luteolin-mediated extension of allograft survival. More importantly, luteolin inhibited AKT/mTOR signaling in T cells. Thus, for the first time, to our knowledge, we found that luteolin is an emerging immunosuppressant as an mTOR inhibitor in allotransplantation. This finding could be important for the suppression of human allograft rejection, although it remains to be determined whether luteolin has an advantage over other conventional immunosuppressants in suppression of allograft rejection.

Transcriptional dissection of differentially expressed long non-coding RNAs and messenger RNAs reveals the potential molecular mechanism after kidney transplantation

Background

Kidney transplantation has given benefits to patients, although the associated genetic mechanisms are unclear. The present study aimed to understand the changes in gene expression and genetic pathways after kidney transplantation with the administration of immunosuppressive drugs.

Methods

The transcriptome data of blood samples from kidney transplantation recipients, obtained by RNA-seq, were reannotated to a more complete human genome (GRCh38/hg38). We compared the differentially expressed genes (DEGs) at pretransplant and 1 week, 3 months and 6 months posttransplant; researched the temporal variation of the DEGs; and constructed a long non-coding RNA (lncRNA)-messenger RNA (mRNA) network.

Results

We found that compared to that at pretransplantation, 1,766 genes and 3,530 genes were upregulated and downregulated, respectively, at 1 week after kidney transplantation, and the number of DEGs declined over time. These DEGs were separated into 16 clusters, and the temporal variation expression was established by the average expression of the DEGs. A pathway analysis suggested that the immune reaction was attenuated and that the expression of ribosome-related proteins was reduced.

Conclusions

The lncRNA-mRNA network had 235 connections between 138 lncRNAs and 170 mRNAs. This work generated a gene profile based on temporal variation and revealed a significantly altered lncRNA-mRNA axis contributing to molecular regulation, suggesting the potential gene mechanism of kidney transplantation and the effects of immunosuppressive drugs.

Pretransplant Donor-specific IFNγ ELISPOT as a Predictor of Graft Rejection: A Diagnostic Test Accuracy Meta-analysis

Supplemental Digital Content is available in the text.

Background.

Pretransplant interferon-γ enzyme-linked immunospot (IFN-γ ELISPOT) has been proposed as a tool to quantify alloreactive memory T cells and estimate the risk of acute rejection (AR) after kidney transplantation, but studies have been inconclusive so far. We performed a meta-analysis to evaluate the association between pretransplant IFN-γ ELISPOT and AR and assess its predictive accuracy at the individual level.

Methods.

We estimated the pooled summary of odds ratio for AR and the joined sensitivity and specificity for predicting AR using random-effects and hierarchical summary receiver-operating characteristic models. We used meta-regression models with the Monte Carlo permutation method to adjust for multiple tests to explain sensitivity and specificity heterogeneity across studies. The meta-analytic estimates of sensitivity and specificity were used to calculate positive and negative predictive values across studies.

Results.

The analysis included 12 studies and 1181 patients. IFN-γ ELISPOT was significantly associated with increased AR risk (odds ratio: 3.29; 95% confidence interval (CI), 2.34-4.60); hierarchical summary receiver operating characteristic jointly estimated sensitivity and specificity values were 64.9% (95% CI, 53.7%-74.6%) and 65.8% (95% CI, 57.4%-73.5%), respectively, with moderate heterogeneity across studies. After adjusting for multiple testing, meta-regression models showed that thymoglobulin induction, recipient black ethnicity, living versus deceased donors, and geographical location did not affect sensitivity or specificity. Because of the varying AR incidence of the studies, positive and negative predictive values ranged between 16%–60% and 70%–95%, respectively.

Conclusions.

Pretransplant IFN-γ ELISPOT is significantly associated with increased risk of AR but provides suboptimal predictive ability at an individual level. Prospective randomized clinical trials are warranted.

Shikonin Prolongs Allograft Survival via Induction of CD4+FoxP3+ Regulatory T Cells

A transplanted organ is usually rejected without any major immunosuppressive treatment because of vigorous alloimmune responsiveness. However, continuous global immunosuppression may cause severe side effects, including nephrotoxicity, tumors, and infections. Therefore, it is necessary to seek novel immunosuppressive agents, especially natural ingredients that may provide sufficient efficacy in immunosuppression with minimal side effects. Shikonin is a bioactive naphthoquinone pigment, an ingredient originally extracted from the root of Lithospermum erythrorhizon. Previous studies have shown that shikonin regulates immunity and exerts anti-inflammatory effects. In particular, it can ameliorate arthritis in animal models. However, it is unclear whether shikonin inhibits alloimmunity or allograft rejection. In this study and for the first time, we demonstrated that shikonin significantly prolonged the survival of skin allografts in wild-type mice. Shikonin increased the frequencies of CD4⁺Foxp3⁺ regulatory T cells (Tregs) post-transplantation and induced CD4⁺Foxp3⁺ Tregs in vitro as well. Importantly, depleting the Tregs abrogated the extension of skin allograft survival induced by shikonin. It also decreased the frequencies of CD8⁺CD44^highCD62L^low effector T cells and CD11c⁺CD80⁺/CD11c⁺CD86⁺ mature DCs after transplantation. Moreover, we found that shikonin inhibited the proliferation of T cells in vitro and suppressed their mTOR signaling. It also reduced the gene expression of pro-inflammatory cytokines, including IFNγ, IL-6, TNFα, and IL-17A, while increasing the gene expression of anti-inflammatory mediators IL-10, TGF-β1, and indoleamine-2, 3-dioxygenase (IDO) in skin allografts. Further, shikonin downregulated IDO protein expression in skin allografts and DCs in vitro. Taken together, shikonin inhibits allograft rejection via upregulating CD4⁺Foxp3⁺ Tregs. Thus, shikonin is a novel immunosuppressant that could be potentially used in clinical transplantation.

Transiently Activated Human Regulatory T Cells Upregulate BCL-XL Expression and Acquire a Functional Advantage in vivo

Regulatory T cells (Tregs) can control excessive or undesirable immune responses toward autoantigens, alloantigens, and pathogens. In transplantation, host immune responses against the allograft are suppressed through the use of immunosuppressive drugs, however this often results in life-threatening side effects including nephrotoxicity and an increased incidence of cancer and opportunistic infections. Tregs can control graft-vs.-host disease and transplant rejection in experimental models, providing impetus for the use of Tregs as a cellular therapy in clinical transplantation. One of the major barriers to the widespread use of Treg cellular therapy is the requirement to expand cells ex vivo to large numbers in order to alter the overall balance between regulatory and effector cells. Methods that enhance suppressive capacity thereby reducing the need for expansion are therefore of interest. Here, we have compared the function of freshly-isolated and ex vivo-manipulated human Tregs in a pre-clinical humanized mouse model of skin transplantation. Sorted human CD127^loCD25⁺CD4⁺ Tregs were assessed in three different conditions: freshly-isolated, following transient in vitro activation with antiCD3/antiCD28 beads or after ex vivo-expansion for 2 weeks in the presence of antiCD3/antiCD28 beads and recombinant human IL2. While ex vivo-expansion of human Tregs increased their suppressive function moderately, transient in vitro-activation of freshly isolated Tregs resulted in a powerful enhancement of Treg activity sufficient to promote long-term graft survival of all transplants in vivo. In order to investigate the mechanisms responsible for these effects, we measured the expression of Treg-associated markers and susceptibility to apoptosis in activated Tregs. Transiently activated Tregs displayed enhanced survival and proliferation in vitro and in vivo. On a molecular level, Treg activation resulted in an increased expression of anti-apoptotic BCL2L1 (encoding BCL-XL) which may be at least partially responsible for the observed enhancement in function. Our results suggest that in vitro activation of human Tregs arms them with superior proliferative and survival abilities, enabling them to more effectively control alloresponses. Importantly, this transient activation results in a rapid functional enhancement of freshly-isolated Tregs, thereby providing an opportunity to eliminate the need for in vitro expansion in select circumstances. A protocol employing this technique would therefore benefit from a reduced requirement for large cell numbers for effective therapy.

Allogeneic iPSC-Derived RPE Cell Graft Failure Following Transplantation Into the Subretinal Space in Nonhuman Primates

Purpose

To characterize the intraocular immune response following transplantation of iPS-derived allogeneic RPE cells into the subretinal space of non–immune-suppressed rhesus macaques.

Methods

GFP-labeled allogeneic iPS-derived RPE cells were transplanted into the subretinal space of one eye (n = 6), and into the contralateral eye 1 day to 4 weeks later, using a two-stage transretinal and transscleral approach. Retinas were examined pre- and post-surgery by color fundus photography, fundus autofluorescence, and optical coherence tomography (OCT) imaging. Animals were euthanized between 2 hours and 7 weeks following transplantation. T-cell (CD3), B-cell (CD20), and microglial (Iba1) responses were assessed immunohistochemically.

Results

Cells were delivered into the subretinal space in all eyes without leakage into the vitreous. Transplanted RPE cells were clearly visible at 4 days after surgery but were no longer detectable by 3 weeks. In localized areas within the bleb containing transplanted cells, T- and B-cell infiltrates and microglia were observed in the subretinal space and underlying choroid. A T-cell response predominated at 4 days, but converted to a B-cell response at 3 weeks. By 7 weeks, few infiltrates or microglia remained. Host RPE and choroid were disrupted in the immediate vicinity of the graft, with fibrosis in the subretinal space.

Conclusions

Engraftment of allogeneic RPE cells failed following transplantation into the subretinal space of rhesus macaques, likely due to rejection by the immune system. These data underscore the need for autologous cell sources and/or confirmation of adequate immune suppression to ensure survival of transplanted RPE cells.

Blimp-1 prolongs allograft survival without regimen via influencing T cell development in favor of regulatory T cells while suppressing Th1

BACKGROUND

B lymphocyte-induced maturation protein 1 (Blimp-1) transcription factor is expressed in multiple cell lineages and in particular, T cells. However, the role of Blimp-1 in T cell-mediated allograft tolerance is still unknown.

METHODS

This study is the first to investigate transplanted skin allograft survival using transgenic (Tg) mice with T cell overexpression of Blimp-1.

RESULTS

Without any immunosuppression, fully MHC-mismatched skin allografts on Tg(+) mice had a significantly prolonged survival rate and partial tolerance at 90 days. Allograft lymphocytic infiltration was decreased in Tg(+) mice and a dampened donor-stimulated alloimmune response was seen. An absolute cell number ratio of inflammatory Th1 and Th17 cells against anti-inflammatory regulatory T (Treg) and IL-10-producing T cells, as well as cytolytic proteins, were significantly decreased in lymphoid organs and allograft. Blimp-1 transgenic T cells displayed an increased Treg differentiation capability and enhanced suppression of T cell proliferation. Overexpression of Blimp-1 in T cells promoted the formation of an anti-inflammatory cell-cytokine composition, both systemically and locally via transcription factor modulation such as T-bet downregulation and FoxP3 upregulation.

DISCUSSION

As such, allograft survival was made possible due to Th1 suppression and Treg amplification with the creation of an 'allograft protective microenvironment'.

Emerging Roles of Vascular Cell Adhesion Molecule-1 (VCAM-1) in Immunological Disorders and Cancer

Tumor necrosis factor alpha (TNFα) is a pro-inflammatory cytokine that triggers the expression of inflammatory molecules, including other cytokines and cell adhesion molecules. TNFα induces the expression of intercellular cell adhesion molecule-1 and vascular cell adhesion molecule-1 (VCAM-1). VCAM-1 was originally identified as a cell adhesion molecule that helps regulate inflammation-associated vascular adhesion and the transendothelial migration of leukocytes, such as macrophages and T cells. Recent evidence suggests that VCAM-1 is closely associated with the progression of various immunological disorders, including rheumatoid arthritis, asthma, transplant rejection, and cancer. This review covers the role and relevance of VCAM-1 in inflammation, and also highlights the emerging potential of VCAM-1 as a novel therapeutic target in immunological disorders and cancer.

The rise and potential fall of pancreas transplantation

BACKGROUND

The aim of this review is to bring pancreatic transplantation out of the specialist realm, informing practitioners about this important procedure, so that they feel better equipped to refer suitable patients for transplantation and manage, counsel and support when encountering them within their own speciality.

SOURCES OF DATA

Narrative review conducted in May 2017. OVID interface searching EMBASE and MEDLINE databases, using Timeframe: Inception to June 1, 2017. Articles were assessed for clinical relevance and most up to date content with articles written in english as the only inclusion criteria. Other sources, used included conference proceedings/presentations, unpublished data from our institution (Oxford Transplant Centre).

AREAS OF AGREEMENT

Pancreas transplantation has evolved from an experimental procedure to the gold standard of care for patients with type 1 diabetes and uraemia. Currently, it remains the most effective method of establishing and maintaining euglycemia over the longer term, halting and potentially reversing many of the secondary complications associated with diabetes. Significant improvements to quality of life and better life expectancy make it in the longer term, a lifesaving procedure compared to waiting candidates.

AREAS OF CONTROVERSY

The future of solid organ pancreas transplantation remains uncertain, with extensive comorbidity and advances in alternative therapies makes the long-term growth of the procedure questionable.

GROWING POINTS AND AREAS TIMELY FOR DEVELOPING RESEARCH

Therapies to alleviate problems associated with ischaemia reperfusion injury, graft pancreatitis and more effective monitoring methods for detecting and treating organ rejection are the key areas of growth.

Therapeutic application of T regulatory cells in composite tissue allotransplantation

With growing number of cases in recent years, composite tissue allotransplantation (CTA) has been improving the quality of life of patient who seeks reconstruction and repair of damaged tissues. Composite tissue allografts are heterogeneous. They are composed of a variety of tissue types, including skin, muscle, vessel, bone, bone marrow, lymph nodes, nerve, and tendon. As a primary target of CTA, skin has high antigenicity with a rich repertoire of resident cells that play pivotal roles in immune surveillance. In this regard, understanding the molecular mechanisms involved in immune rejection in the skin would be essential to achieve successful CTA. Although scientific evidence has proved the necessity of immunosuppressive drugs to prevent rejection of allotransplanted tissues, there remains a lingering dilemma due to the lack of specificity of targeted immunosuppression and risks of side effects. A cumulative body of evidence has demonstrated T regulatory (Treg) cells have critical roles in induction of immune tolerance and immune homeostasis in preclinical and clinical studies. Presently, controlling immune susceptible characteristics of CTA with adoptive transfer of Treg cells is being considered promising and it has drawn great interests. This updated review will focus on a dominant form of Treg cells expressing CD4+CD25+ surface molecules and a forkhead box P3 transcription factor with immune tolerant and immune homeostasis activities. For future application of Treg cells as therapeutics in CTA, molecular and cellular characteristics of CTA and immune rejection, Treg cell development and phenotypes, Treg cell plasticity and stability, immune tolerant functions of Treg cells in CTA in preclinical studies, and protocols for therapeutic application of Treg cells in clinical settings are addressed in this review. Collectively, Treg cell therapy in CTA seems feasible with promising perspectives. However, the extreme high immunogenicity of CTA warrants caution.

Polyclonal and monoclonal antibodies for treating acute rejection episodes in kidney transplant recipients

BACKGROUND

Registry data shows that the incidence of acute rejection has been steadily falling. Approximately 10% to 35% of kidney recipients will undergo treatment for at least one episode of acute rejection within the first post-transplant year. Treatment options include pulsed steroid therapy, the use of an antibody preparation, the alteration of background immunosuppression, or combinations of these options. Over recent years, new treatment strategies have evolved, and in many parts of the world there has been an increase in use of tacrolimus and mycophenolate and a reduction in the use of cyclosporin and azathioprine use as baseline immunosuppression to prevent acute rejection. There are also global variations in use of polyclonal and monoclonal antibodies to treat acute rejection. This is an update of a review published in 2006.

OBJECTIVES

The aim of this systematic review was to: (1) to evaluate the relative and absolute effects of different classes of antibody preparation in preventing graft loss and resolving cellular or humoral rejection episodes when used as a treatment for first episode of rejection in kidney transplant recipients; (2) evaluate the relative and absolute effects of different classes of antibody preparation in preventing graft loss and resolving cellular or humoral rejection episodes when used as a treatment for steroid-resistant rejection in kidney transplant recipients; (3) determine how the benefits and adverse events vary for each type of antibody preparation; and (4) determine how the benefits and harms vary for different formulations of antibody within each type.

SEARCH METHODS

We searched the Cochrane Kidney and Transplant Specialised Register to 18 April 2017 through contact with the Information Specialist using search terms relevant to this review.

SELECTION CRITERIA

Randomised controlled trials (RCTs) in all languages comparing all mono- and polyclonal antibody preparations, given in combination with any other immunosuppressive agents, for the treatment of cellular or humoral graft rejection, when compared to any other treatment for acute rejection were eligible for inclusion.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the risk of bias of the included studies and extracted data. Statistical analyses were performed using a random-effects model and results expressed as risk ratio (RR) or mean difference (MD) with 95% confidence intervals (CI).

MAIN RESULTS

We included 11 new studies (18 reports, 346 participants) in this update, bring the total number of included studies to 31 (76 reports, 1680 participants). Studies were generally small, incompletely reported, especially for potential harms, and did not define outcome measures adequately. The risk of bias was inadequate or unclear risk for random sequence generation (81%), allocation concealment (87%) and other bias (87%). There were, however, a predominance of low risk of bias for blinding (75%) and incomplete outcome data (80%) across all the studies. Selective reporting had a mixture of low (58%), high (29%), and unclear (13%) risk of bias.Seventeen studies (1005 participants) compared therapies for first acute cellular rejection episodes. Antibody therapy was probably better than steroid in reversing acute cellular rejection (RR 0.50, 95% CI 0.30 to 0.82; moderate certainty) and preventing subsequent rejection (RR 0.70, 95% CI 0.50 to 0.99; moderate certainty), may be better for preventing graft loss (death censored: (RR 0.80, 95% CI 0.57 to 1.12; low certainty) but there was little or no difference in death at one year. Adverse effects of treatment (including fever, chills and malaise following drug administration) were probably reduced with steroid therapy (RR 23.88, 95% CI 5.10 to 111.86; I2 = 16%; moderate certainty).Twelve studies (576 patients) investigated antibody treatment for steroid-resistant rejection. There was little or no benefit of muromonab-CD3 over ATG or ALG in reversing rejection, preventing subsequent rejection, or preventing graft loss or death. Two studies compared the use of rituximab for treatment of acute humoral rejection (58 patients). Muromonab-CD3 treated patients suffered three times more than those receiving either ATG or T10B9, from a syndrome of fever, chills and malaise following drug administration (RR 3.12, 95% CI 1.87 to 5.21; I2 = 31%), and experienced more neurological side effects (RR 13.10 95% CI 1.43 to 120.05; I2 = 36%) (low certainty evidence).There was no evidence of additional benefit from rituximab in terms of either reversal of rejection (RR 0.94, 95% CI 0.54 to 1.64), or graft loss or death 12 months (RR 1.0, 95% CI 0.23 to 4.35). Rituximab plus steroids probably increases the risk of urinary tract infection/pyelonephritis (RR 5.73, 95% CI 1.80 to 18.21).

AUTHORS' CONCLUSIONS

In reversing first acute cellular rejection and preventing graft loss, any antibody is probably better than steroid, but there is little or no difference in subsequent rejection and patient survival. In reversing steroid-resistant rejection there was little or no difference between different antibodies over a period of 12 months, with limited data beyond that time frame. In treating acute humoral rejection, there was no evidence that the use of antibody therapy conferred additional benefit in terms of reversal of rejection, or death or graft loss.Although this is an updated review, the majority of newer included studies provide additional evidence from the cyclosporin/azathioprine era of kidney transplantation and therefore conclusions cannot necessarily be extrapolated to patients treated with more contemporary immunosuppressive regimens which include tacrolimus/mycophenolate or sirolimus. However, many kidney transplant centres around the world continue to use older immunosuppressive regimes and the findings of this review remain strongly relevant to their clinical practice.Larger studies with standardised reproducible outcome criteria are needed to investigate the outcomes and risks of antibody treatments for acute rejection in kidney transplant recipients receiving contemporary immunosuppressive regimes.

Vγ4 γδ T Cells Provide an Early Source of IL-17A and Accelerate Skin Graft Rejection

Activated γδ T cells have been shown to accelerate allograft rejection. However, the precise role of skin-resident γδ T cells and their subsets-Vγ5 (epidermis), Vγ1, and Vγ4 (dermis)-in skin graft rejection have not been identified. Here, using a male to female skin transplantation model, we demonstrated that Vγ4 T cells, rather than Vγ1 or Vγ5 T cells, accelerated skin graft rejection and that IL-17A was essential for Vγ4 T-cell-mediated skin graft rejection. Moreover, we found that Vγ4 T cells were required for early IL-17A production in the transplanted area, both in skin grafts and in the host epidermis around grafts. Additionally, the chemokine (C-C motif) ligand 20-chemokine receptor 6 pathway was essential for recruitment of Vγ4 T cells to the transplantation area, whereas both IL-1β and IL-23 induced IL-17A production from infiltrating cells. Lastly, Vγ4 T-cell-derived IL-17A promoted the accumulation of mature dendritic cells in draining lymph nodes to subsequently regulate αβ T-cell function after skin graft transplantation. Taken together, our data reveal that Vγ4 T cells accelerate skin graft rejection by providing an early source of IL-17A.

Blood biomarkers of kidney transplant rejection, an endless search?

INTRODUCTION

The tailoring of immunosuppressive treatment is recognized as a promising strategy to improve long-term kidney graft outcome. To guide the standard care of transplant recipients, physicians need objective biomarkers that can identify an ongoing pathology with the graft or low intensity signals that will be later evolved to accelerated transplant rejection. The early identification of 'high-risk /low-risk' patients enables the adjustment of standard of caring, including managing the frequency of clinical visits and the immunosuppression dosing. Given their ease of availability and the compatibility with a large technical array, blood-based biomarkers have been widely scrutinized for use as potential predictive and diagnostic biomarkers. Areas covered: Here, the authors report on non-invasive biomarkers, such as modification of immune cell subsets and mRNA and miRNA profiles, identified in the blood of kidney transplant recipients collected before or after transplantation. Expert commentary: Combined with functional tests, the identification of biomarkers will improve our understanding of pathological processes and will contribute to a global improvement in clinical management.

Upregulation of PIM2 by Underexpression of MicroRNA-135-5p Improves Survival Rates of Skin Allografts by Suppressing Apoptosis of Fibroblast Cells

BACKGROUND It has been reported that miR-135-5p is involved with many diseases. In this study, we aimed at define the relationship between miR-135-5p level and burn patient survival after skin transplantation. MATERIAL AND METHODS Expression of miR-135-5p and PIM2 was measured using real-time PCR and Western blot analysis in the skin samples collected from burn patients who received skin graft or in the fibroblast cells transfected with miR-135-5p mimics or inhibitors. The regulatory association between miR-135-5p and PIM2 was verified using bioinformatics analysis and luciferase assay. RESULTS The expression level of miR-135-5p was determined in 60 tissue samples divided into 2 groups based on the presence of rejection (long survival n=30, and short survival n=30). We found that miR-135-5p was substantially downregulated in the long survival group. We then searched the miRNA database online with the "seed sequence" located within the 3'-UTR of the target gene, and then validated PIM2 to be the direct gene via luciferase reporter assay system. We also established the negative regulatory relationship between miR-135-5p and PIM2 via studying the relative luciferase activity. We also conducted real-time PCR and Western blot analysis to study the mRNA and protein expression level of PIM2 among different groups (long survival n=30, short survival n=30) or cells treated with scramble control, miR-135-5p mimics, PIM2 siRNA, and miR-135-5p inhibitors, indicating the negative regulatory relationship between MiR-135-5p and PIM2. We also conducted experiments to investigate the influence of miR-135-5p and PIM2 on viability and apoptosis of cells. The results showed miR-135-5p reduced the viability of cells, while PIM2 negatively interfered with the viability of cells, and miR-135-5p inhibited apoptosis and PIM2 suppressed apoptosis. CONCLUSIONS MiR-135-5p is involved with the prognosis of burn patients after skin transplantation. PIM2 is a virtual target of miR-135-5p, and there is a negative regulatory relationship between miR-135-5p and PIM2. MiR-135-5p and PIM2 interfered with the viability and apoptosis in cells.

T- and B-cell immunosuppressive activity of novel α-santonin analogs with humoral and cellular immune response in Balb/c mice

In continuation of our endeavours to synthesize immunosuppressive agents from α-santonin, we report herein the design and synthesis of a new series of α-santonin derived O-aryl/aliphatic ether, ester and amide analogs and the evaluation of their immunosuppressive activities. The in vitro studies led to several analogs with significant immunosuppressive effects by inhibiting ConA and LPS stimulated T- and B-cell proliferation in a dose dependent manner. The more significant compounds 4d, 4e, 4f, 4h, 6a and 6b displayed potent inhibitory activity on the mitogen-induced T- and B-cell proliferation in comparison to α-santonin 1. Compound 4e displayed stupendous in vitro immunosuppressive effects with ∼80% suppression of B and ∼75% suppression of T lymphocyte proliferation, respectively. The in vivo investigation on BALB/c mice revealed that non-cytotoxic compound 4e suppresses both humoral and cellular immunity.