Myeloid-derived suppressor cells as cellular immunotherapy in transplantation and autoimmune diseases.

Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature myeloid cells, which have been characterized for their immunosuppressive capacity through multiple mechanisms. These cells have been extensively studied in the field of tumor immunity. Emerging evidence has highlighted its essential role in maintaining immune tolerance in transplantation and autoimmunity. Because of their robust immune inhibitory activities, there has been growing interest in MDSC-based cellular therapy. Various pre-clinical studies have demonstrated that the adoptive transfer of MDCS represented a promising therapeutic strategy for immune-related disorders. In this review, we summarize relevant studies of MDSC-based cell therapy in transplantation and autoimmune diseases and discuss the challenges and future directions for clinical application of MDSC-based cell therapy.

NK cells in antibody-mediated rejection - Key effector cells in microvascular graft damage.

Antibody-mediated rejection (ABMR) stands as the major limitation to long-term transplant outcome. The immunologic understanding of ABMR continues to progress and has identified natural killer (NK) cells as key effector cells promoting and coordinating the immune attack on the graft microvascular endothelium. This review discusses the current concepts outlining the different ways that allow for NK cell recognition of graft endothelial cells which includes antibody-dependent as well as independent processes.

Transplantation and immunosuppression: a review of novel transplant-related immunosuppressant drugs.

Immunosuppressive drugs used in the transplantation period are generally defined as induction and maintenance therapy. The use of immunosuppressants, which are particularly useful and have fewer side effects, decreased both mortality and morbidity. Many drugs such as steroids, calcineurin inhibitors (cyclosporine-A, tacrolimus), antimetabolites (mycophenolate mofetil, azathioprine), and mTOR inhibitors (sirolimus, everolimus) are used as immunosuppressive agents. Although immunosuppressant drugs cause many side effects such as hypertension, infection, and hyperlipidemia, they are the agents that should be used to prevent organ rejection. This shows the importance of individualized drug use. The optimal immunosuppressive therapy post-transplant is not established. Therefore, discovering less toxic but more potent new agents is of great importance, and new experimental and clinical studies are needed in this regard.Our review discussed the mechanism of immunosuppressants, new agents' discovery, and current therapeutic protocols in the transplantation.

Approaching treatment for immunological rejection of living-donor liver transplantation in rats.

BACKGROUND: The anti-immunological rejection therapy for small-for-size syndrome (SFSS) after live donor liver transplantation (LDLT) play a central role in keeping graft survival. The hepatocyte number and grafts function has undergone real-time changes with the proliferation and apoptosis of the grafts after reperfusion. Lacking an accurate and effective treatment regiments or indicators to guide the use of immunosuppressive drugs in SFS liver transplantation has made immunotherapy after SFS liver transplantation an urgent problem to be solved. Herein, we established small-for-size (SFS) and normal size liver transplantation model in rats to explore the effective indicators in guiding immunotherapy, to find an effective way for overcoming SFSS. METHODS: Lewis rats (donors) and BN rats (recipients) were used to mimic allograft liver transplantation and treated with tacrolimus. Local graft immune response was analyzed through haematoxylin and eosin and immunohistochemistry. Flow cytometry was used to assess the overall immune status of recipient. The pharmacokinetics mechanism of immunosuppressive drugs was explored through detecting CYP3A2 expression at mRNA level and protein levels. RESULTS: The results showed the local immune reaction of SFS grafts and systemic immune responses of recipient were significantly increased compared with those in normal size grafts and their recipient at four days after liver transplantation. Regression equation was used to regulate the tacrolimus dose which not only controlled tacrolimus serum concentration effectively but alleviated liver damage and improved survival rate. CONCLUSIONS: This study showed that AST level and tacrolimus serum concentrations are effective indicators in guiding immunotherapy. Regression equation (TD = - 0.494TC-0.0035AST + 260.487) based on AST and tacrolimus serum concentration can be used as a reference for adjustment of immunotherapy after SFS liver transplantation, which is applicable in clinical practice.

HLA-specific memory B-cell detection in kidney transplantation: Insights and future challenges.

Humoral alloimmunity mediated by anti-human leucocyte antigen (HLA) antibodies is a major challenge in kidney transplantation and impairs the longevity of the transplanted organ. The immunological risk of an individual patient is currently mainly assessed by detection of HLA antibodies in the serum, which are produced by long-lived bone marrow-residing plasma cells. However, humoral alloimmunity is complex, and alloreactive memory B cells constitute an additional factor in the interplay of immune cells. These recirculating "silent" cells are responsible for the immunological recall response by differentiating into antibody-producing cells upon antigen re-encounter. Historically, due to the lack of appropriate and routinely applicable assays to determine the presence and HLA specificity of alloreactive memory B cells, their contribution to the humoral alloimmune response has clinically often been suspected but could not be determined. In this review, we give an overview of recent advances in techniques to detect alloreactive memory B cells and discuss their strengths and limitations. Furthermore, we summarize experiences with these techniques in alloimmunized individuals and transplant recipients, thereby emphasizing unmet needs to be addressed in future studies.

The Leeds hand transplant programme: Review of the laboratory management of the first six cases.

The UK hand transplantation programme is hosted by the Department of Plastic and Reconstructive Surgery at Leeds Teaching Hospitals under the leadership of Professor Simon Kay. Since programme launch in 2013, ten procedures in six individuals have been performed involving unilateral or bilateral transplants. The multi-disciplinary team that delivers the programme includes the transplant immunology service. The laboratory experience in programme support is reported here.

Increased CD200 expression in post-transplant lymphoproliferative disorders correlates with an increased frequency of FoxP3(+) regulatory T cells.

CD200 is a membrane protein with immunosuppressive function and is expressed in many hematopoietic neoplasms, including acute myeloid leukemia (AML), plasma cell myeloma (PCM), and B-cell lymphoproliferative disorders, but is mostly negative in diffuse large cell lymphoma (DLBCL). CD200 has been shown to be a poor prognostic marker in AML and PCM; in AML, its immunomodulatory effect was linked to its ability to induce FoxP3(+) regulatory T cells (Tregs). Post-transplant lymphoproliferative disorders (PTLDs) arise in the setting of immune dysregulation, and tumor-infiltrating T cells, including Tregs, have been shown to correlate with outcome in these disorders. Because there is no literature data and CD200 is a potentially useful diagnostic and prognostic marker, we studied the expression of CD200 in a series of 38 PTLDs by immunohistochemistry (ICH), and found that 23.7% PTLDs were CD200(+) and showed strong membrane and cytoplasmic positivity in the neoplastic cells. All CD200(+) monomorphic PTLDs were DLBCLs and the median FoxP3(+) Treg count/hpf was higher in CD200(+) than in CD200(-) PTLDs: 22.6 vs. 0.30 (p < 0.001). These results indicated that almost a quarter of PTLDs in our series are CD200(+) by IHC, and CD200 expression correlates with the frequency of immunosuppressive Tregs. This is novel data and supports a pathophysiologic link between CD200 activity and Tregs. In our series, the 5-year overall survival was shorter in CD200(+) PTLDs, compared to CD200(-) patients, although this difference did not reach statistical significance. In addition, we find a higher proportion of CD200(+) monomorphic PTLD-DLBCLs (31.0%), as compared to de novo DLBCLs (7-8%, as found here and in other studies). This may indicate differential expression of CD200 in B-cell lymphomas arising in the setting of immune dysregulation, and raises the possibility of anti-CD200 immunotherapy for these cases.

Macrophage Proinflammatory Responses to Microorganisms and Transplanted Organs.

Tissue-resident macrophages and those conscripted from the blood/bone marrow are professional phagocytes. They play a role in tissue homeostasis, replacement, and healing, and are the first-line responders to microbial (viral, bacterial, and fungi) infections. Intrinsic ameboid-type motility allows non-resident macrophages to move to the site of inflammation or injury, where, in response to the inflammatory milieu they perform the anti-microbial and/or tissue repair functions. Depending on the need and the signaling from the surrounding tissue and other immune cells, macrophages acquire morphologically and functionally different phenotypes, which allow them to play either pro-inflammatory or anti-inflammatory functions. As such, the macrophages are also the major players in the rejection of the transplanted organs making an excellent target for the novel anti-rejection therapies in clinical transplantation. In this review, we describe some of the less covered aspects of macrophage response to microbial infection and organ transplantation.

The aging transplant population and immunobiology: any therapeutic implication?

PURPOSE OF REVIEW: The aim of this review is to describe the latest investigations into the immunobiology of aging and the potential impact on outcomes after mechanical circulatory support implantation and heart transplantation. This information is relevant given the growing numbers of older patients with heart failure undergoing evaluation for mechanical circulatory support device (MCSD) or heart transplantation. RECENT FINDINGS: A host of aging-associated aspects of immune dysfunction have been described in the general population including T-cell senescence, exhaustion, and terminal dedifferentiation, as well as impaired function of innate immune cells. Another important consequence of T-cell senescence is inflammation, which is known to have a strong relationship with both heart failure and frailty in older patients. Recent data on the association between T-cell and monocyte phenotypes as well as evaluation of gene expression and adverse outcomes after MCSD suggests the potential value of immunologic assessment of MCSD and heart transplant candidates and recipients. Measurement of physical frailty represents another avenue for patient evaluation that may complement immunologic assessment. Determination of immune dysfunction and frailty prior to transplantation may have implications for choice of induction and dosing of maintenance immunosuppression. SUMMARY: As the age of transplant and MCSD candidates and recipients continues to increase, it is important for providers to recognize the potential impact of aging-associated immune dysfunction and how it may influence candidate selection, postintervention monitoring, and adjustment of immunosuppression.

Precision transplant pathology.

PURPOSE OF REVIEW: Transplant pathology contributes substantially to personalized treatment of organ allograft recipients. Rapidly advancing next-generation human leukocyte antigen (HLA) sequencing and pathology are enhancing the abilities to improve donor/recipient matching and allograft monitoring. RECENT FINDINGS: The present review summarizes the workflow of a prototypical patient through a pathology practice, highlighting histocompatibility assessment and pathologic review of tissues as areas that are evolving to incorporate next-generation technologies while emphasizing critical needs of the field. SUMMARY: Successful organ transplantation starts with the most precise pratical donor-recipient histocompatibility matching. Next-generation sequencing provides the highest resolution donor-recipient matching and enables eplet mismatch scores and more precise monitoring of donor-specific antibodies (DSAs) that may arise after transplant. Multiplex labeling combined with hand-crafted machine learning is transforming traditional histopathology. The combination of traditional blood/body fluid laboratory tests, eplet and DSA analysis, traditional and next-generation histopathology, and -omics-based platforms enables risk stratification and identification of early subclinical molecular-based changes that precede a decline in allograft function. Needs include software integration of data derived from diverse platforms that can render the most accurate assessment of allograft health and needs for immunosuppression adjustments.

Erythropoietin, a multifaceted protein with innate and adaptive immune modulatory activity.

Erythropoietin (EPO) is a glycoprotein produced mainly by the adult kidney in response to hypoxia and is the crucial regulator of red blood cell production. EPO receptors (EPORs), however, are not confined to erythroid cells, but are expressed by many organs including the heart, brain, retina, pancreas, and kidney, where they mediate EPO-induced, erythropoiesis-independent, tissue-protective effects. Some of these tissues also produce and locally release small amounts of EPO in response to organ injury as a mechanism of self-repair. Growing evidence shows that EPO possesses also important immune-modulating effects. Monocytes can produce EPO, and autocrine EPO/EPOR signaling in these cells is crucial in maintaining immunologic self-tolerance. New data in mice and humans also indicate that EPO has a direct inhibitory effect on effector/memory T cells, while it promotes formation of regulatory T cells. This review examines the nonerythropoietic effects of EPO, with a special emphasis on its modulating activity on innate immune cells and T cells and on how it affects transplant outcomes.

Will donor-derived neoplasia be problematic after clinical pig organ or cell xenotransplantation?

There is an increased incidence of certain tumors and other neoplastic disease in organ allotransplant recipients receiving immunosuppressive therapy. Following clinical pig organ xenotransplantation, will there be a risk of the development of neoplasia in the pig graft or in other tissues transplanted with it, eg, lymph nodes? The incidence of neoplasia in young slaughterhouse pigs is very low (<0.005%), but in older pigs is largely unknown (as most pigs are killed within the first six months of life). However, lymphosarcoma, nephroblastoma, and melanoma have been reported in pigs. These tumors should be readily identified by ultrasound or direct inspection and palpation before an organ is excised for clinical xenotransplantation, and so transfer to the human recipient should be unlikely. Post-transplant lymphoproliferative disorder (PTLD) has been reported in pigs receiving intensive immunomodulatory therapy, particularly if this includes whole body irradiation, in an effort to induce mixed hematopoietic chimerism and immunological tolerance. However, the pigs used as sources of organs in xenotransplantation should be free of the porcine lymphotropic herpesvirus that is a key causative factor for PTLD in pigs, and so donor-derived PTLD should not occur. We conclude that the risk of a malignant tumor developing in a transplanted organ from a young pig is small.

The role of human CD46 in early xenoislet engraftment in a dual transplant model.

BACKGROUND: Membrane cofactor protein CD46 attenuates the complement cascade by facilitating cleavage of C3b and C4b. In solid organ xenotransplantation, organs expressing CD46 have been shown to resist hyperacute rejection. However, the incremental value of human CD46 expression for islet xenotransplantation remains poorly defined. METHODS: This study attempted to delineate the role of CD46 in early neonatal porcine islet engraftment by comparing Gal-knocked out (GKO) and hCD46-transgenic (GKO/CD46) islets in a dual transplant model. Seven rhesus macaques underwent dual transplant and were sacrificed at 1 hour (n = 4) or 24 hours (n = 3). Both hemilivers were recovered and fixed for immunohistochemistry (CD46, insulin, neutrophil elastase, platelet, IgM, IgG, C3d, C4d, CD68, Caspase 3). Quantitative immunohistochemical analysis was performed using the Aperio Imagescope. RESULTS: Within 1 hour of intraportal infusion of xenografts, no differences were observed between the two types of islets in terms of platelet, antibody, or complement deposition. Cellular infiltration and islet apoptotic activity were also similar at 1 hour. At 24 hours, GKO/CD46 islets demonstrated significantly less platelet deposition (P = 0.01) and neutrophil infiltration (P = 0.01) compared to GKO islets. In contrast, C3d (P = 0.38) and C4d (P = 0.45) deposition was equal between the two genotypes. CONCLUSIONS: Our findings suggest that expression of hCD46 on NPIs potentially provides a measurable incremental survival advantage in vivo by reducing early thrombo-inflammatory events associated with instant blood-mediated inflammatory reaction (IBMIR) following intraportal islet infusion.

Auxiliary xenotransplantation as an in vivo bioreactor-Development of a transplantable liver graft from a tiny partial liver.

BACKGROUND: We established a completely novel method of auxiliary xenogeneic partial liver transplantation and examined whether liver grafts procured from Syrian hamsters regenerated in nude rats, which were used as in vivo bioreactors. METHODS: The hamsters and the rats were all males (n = 10). Partial liver grafts from hamsters were transplanted into nude rats in an auxiliary manner. We evaluated liver graft injury, rejection, and regeneration during 7 days after auxiliary xenogeneic partial liver transplantation. RESULTS: All rats survived until sacrifice on post-operative day (POD) 1, 3, and 7. HE-staining showed normal at POD1, mild periportal edema, and slight bile duct and venous endothelial inflammation at POD3, and moderate acute cellular rejection at POD7 without parenchymal necrosis. The liver regeneration rates at POD3 and 7 were 1.54 ± 0.23 and 2.54 ± 0.43, respectively. The Ki-67 labeling index was also elevated at POD3 (27.5 ± 4.1%). Serum HGF and VEGF were elevated at POD1 and 3. ATP levels of liver grafts recovered at POD7. CONCLUSIONS: These results revealed that with appropriate immunosuppressive therapy, partial liver graft regeneration occurred in a xenogeneic animal, which suggests liver grafts regenerated in xenogeneic environments, such as an in vivo bioreactor, have potential to be transplantable liver grafts for humans.

A transplant "immunome" screening platform defines a targetable epitope fingerprint of multiple myeloma.

Multiple myeloma (MM) is a hematological cancer for which immune-based treatments are currently in development. Many of these rely on the identification of highly disease-specific, strongly and stably expressed antigens. Here, we profiled the myeloma B-cell immunome both to explore its predictive role in the context of autologous and allogeneic hematopoietic stem cell transplantation (HSCT) and to identify novel immunotherapeutic targets. We used random peptide phage display, reverse immunization, and next-generation sequencing-assisted antibody phage display to establish a highly myeloma-specific epitope fingerprint targeted by B-cell responses of 18 patients in clinical remission. We found that allogeneic HSCT more efficiently allowed production of myeloma-specific antibodies compared with autologous HSCT and that a highly reactive epitope recognition signature correlated with superior response to treatment. Next, we performed myeloma cell surface screenings of phage-displayed patient transplant immunomes. Although some of the screenings yielded clear-cut surface binders, the majority of screenings did not, suggesting that many of the targeted antigens may in fact not be accessible to the B-cell immune system in untreated myeloma cells. This fit well with the identification of heat-shock proteins as a class of antigens that showed overall the broadest reactivity with myeloma patient sera after allogeneic HSCT and that may be significantly translocated to the cell surface upon treatment as a result of immunogenic cell death. Our data reveal a disease-specific epitope signature of MM that is predictive for response to treatment. Mining of transplant immunomes for strong myeloma surface binders may open up avenues for myeloma immunotherapy.

Accommodation in ABO-incompatible organ transplants.

Accommodation refers to a condition in which a transplant (or any tissue) appears to resist immune-mediated injury and loss of function. Accommodation was discovered and has been explored most thoroughly in ABO-incompatible kidney transplantation. In this setting, kidney transplants bearing blood group A or B antigens often are found to function normally in recipients who lack and hence produce antibodies directed against the corresponding antigens. Whether accommodation is owed to changes in anti-blood group antibodies, changes in antigen or a change in the response of the transplant to antibody binding are critically reviewed and a new working model that allows for the kinetics of development of accommodation is put forth. Regardless of how accommodation develops, observations on the fate of ABO-incompatible transplants offer lessons applicable more broadly in transplantation and in other fields.

Update on cellular encapsulation.

There is currently a significant disparity between the number of patients who need lifesaving transplants and the number of donated human organs. Xenotransplantation is a way to address this disparity and attempts to enable the use of xenogeneic tissues have persisted for centuries. While immunologic incompatibilities have presented a persistent impediment to their use, encapsulation may represent a way forward for the use of cell-based xenogeneic therapeutics without the need for immunosuppression. In conjunction with modern innovations such as the use of bioprinting, incorporation of immune modulating molecules into capsule membranes, and genetic engineering, the application of xenogeneic cells to treat disorders ranging from pain to liver failure is becoming increasingly realistic. The present review discusses encapsulation in the context of xenotransplantation, focusing on the current status of clinical trials, persistent issues such as antigen shedding, oxygen availability, and donor selection, and recent developments that may address these limitations.

GalT-KO pig lungs are highly susceptible to acute vascular rejection in baboons, which may be mitigated by transgenic expression of hCD47 on porcine blood vessels.

BACKGROUND: Despite recent progress in survival times of xenografts in non-human primates, there are no reports of survival beyond 5 days of histologically well-aerated porcine lung grafts in baboons. Here, we report our initial results of pig-to-baboon xeno-lung transplantation (XLTx). METHODS: Eleven baboons received genetically modified porcine left lungs from either GalT-KO alone (n = 3), GalT-KO/humanCD47(hCD47)/hCD55 (n = 3), GalT-KO/hD47/hCD46 (n = 4), or GalT-KO/hCD39/hCD46/hCD55/TBM/EPCR (n = 1) swine. The first 2 XLTx procedures were performed under a non-survival protocol that allowed a 72-hour follow-up of the recipients with general anesthesia, while the remaining 9 underwent a survival protocol with the intention of weaning from ventilation. RESULTS: Lung graft survivals in the 2 non-survival animals were 48 and >72 hours, while survivals in the other 9 were 25 and 28 hours, at 5, 5, 6, 7, >7, 9, and 10 days. One baboon with graft survival >7 days, whose entire lung graft remained well aerated, was euthanized on POD 7 due to malfunction of femoral catheters. hCD47 expression of donor lungs was detected in both alveoli and vessels only in the 3 grafts surviving >7, 9, and 10 days. All other grafts lacked hCD47 expression in endothelial cells and were completely rejected with diffuse hemorrhagic changes and antibody/complement deposition detected in association with early graft loss. CONCLUSIONS: To our knowledge, this is the first evidence of histologically viable porcine lung grafts beyond 7 days in baboons. Our results indicate that GalT-KO pig lungs are highly susceptible to acute humoral rejection and that this may be mitigated by transgenic expression of hCD47.

The feasibility and efficacy of preparing porcine Descemet's membrane endothelial keratoplasty (DMEK) grafts by two techniques: An ex-vivo investigation for future xeno-DMEK.

BACKGROUND: Descemet's membrane endothelial keratoplasty (DMEK) might be a promising technique for future xeno-corneal transplantation due to its ultrathin graft, extremely low rejection occurrence, suture-free graft fixation, and minimal immunosuppressive regime usage. The aim of this study is to explore the feasibility and efficacy of preparing porcine DMEK grafts by 2 techniques and investigate the graft ultrastructure. METHODS: Two mainstream techniques, mechanical stripping technique and liquid bubble technique, were modified to prepare the porcine DMEK grafts. In all, 40 corneas harvested from WZS-pigs (aged 10-12 months) were subjected to the techniques (20 corneas for each technique). The success rate, time consumption, and endothelial cell density (ECD) before and after preparation were recorded and compared between the 2 techniques. And the ultrastructure of the porcine DEMK graft was investigated by transmission electron microscope. In addition, 9 WZS-pigs with different ages were sacrificed to explore the correlation between the thickness of Descemet's membrane and porcine age. RESULTS: After modifying several technical details, the porcine DMEK grafts were successfully prepared by either mechanical stripping technique or liquid bubble technique, and the mark technique to distinguish the 2 sides of the graft was also explored. In all, 13 DMEK grafts (65%) were prepared successfully by the mechanical stripping technique, whereas 14 successful cases (70%) were prepared by the liquid bubble technique. The success rates between the 2 techniques showed no significant difference (P = .847). However, the mechanical stripping technique was significantly time-consuming when compared with the liquid bubble technique (P < .0001). The ECDs reduced significantly after preparation no matter what techniques were used (P < .0001), but the ECD after the liquid bubble preparation was significantly higher than the ECD after mechanical stripping (P = .032). The ECD reduction positively correlated to the time consumption for both mechanical stripping technique (P = .0014, R2  = 0.621) and liquid bubble technique (P = .013, R2  = 0.412). The ultrastructure showed the graft was comprised of stromal residuals, non-banded layer, and endothelial layer. Unlike human Descemet's membrane (DM), anterior banded layer was not observed. The thickness of porcine DM increased with the age, and a significant positive correlation between them was found (P < .0001, R2  = 0.949), and the predict equation was Y = 0.3764*X + 7.378 (Y indicates the thickness, whereas X indicates the age). CONCLUSIONS: Porcine DMEK grafts could be prepared either by mechanical stripping technique or liquid bubble technique, and the liquid bubble technique seems superior over the mechanical stripping technique regarding time consumption and ECD preservation. Although there are several technical barriers to overcome, xeno-DMEK might be a promising direction for future xeno-corneal transplantation.

The value of glycated albumin for the prediction of graft outcome in the non-human primate porcine islet transplantation model.

BACKGROUND: The development of a precise and easy-to-use tool for monitoring islet graft function is important in clarifying the causes of graft loss, identifying appropriate therapy, and ensuring graft survival in the nonhuman primate (NHP) model of porcine islet transplantation (PITx). Glycated albumin (GA) is an indicator of intermediate-term changes in blood glucose control and is useful in clinical diabetes management. The validity of GA for monitoring graft function in NHP recipients of PITx was evaluated using a retrospective analysis of cohort samples. METHODS: Data from a total of 23 PITxs performed in 20 recipients (3 were retransplanted) were included in this study. Islet clusters purified from adult wild-type pigs were transplanted via the intraportal route into streptozotocin-induced diabetic rhesus monkeys with immune suppression. Blood samples were obtained once per week from the recipients until they lost insulin-independence. Blood samples were also obtained from 69 non-diabetic monkeys that served as a control group. The levels of GA and albumin in stored plasma aliquots were measured using each enzymatic method, and the GA result was expressed as the percentage of GA level to the total albumin level. RESULTS: The median level of GA in the recipients on the day of PITx (median 18.6%, 95% confidence interval [CI] 16.7%-20.4%) was significantly higher than that of healthy controls (median 9.14%, 95% CI 9.0%-9.3%, P < .0001). However, the level decreased after PITx and remained low or increased depending on the extent of residual graft function. The GA level at a nadir (median 11.6%, 95% CI 10.8%-13.0%) and the time to reach a nadir (median 43 days, 95% CI 21.7-69.3 days) both correlated with the duration of insulin-independence (rho [ρ] = -.605, P = .0028 and ρ = .662, P = .0008, respectively). The GA level strongly correlated with KG , the glucose disappearance rate during intravenous glucose tolerance testing (ρ = -.76, P < .0001). At post-transplant week (PTW) 3 and at PTW 4, the GA levels in recipients with long-term insulin-independence (>90 days) were significantly lower than those with short-term insulin-independence, which revealed the excellent performance for the prediction of long-term insulin-independence that is comparable to that of porcine C-peptide (historic data). CONCLUSIONS: As a surrogate indicator for graft function, serial measurement of GA may provide Supporting Information to that obtained from conventional monitoring techniques of graft function for assessing porcine islet grafts in NHP models.