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Background: Transplantation is the treatment of choice for many patients with end-stage organ disease. Despite advances in immunosuppression, long-term outcomes remain suboptimal, hampered by drug toxicity and immune-mediated injury, the leading cause of late graft loss. The development of therapies that promote regulation while suppressing effector immunity is imperative to improve graft survival and minimize conventional immunosuppression. Notch signaling is a highly conserved pathway pivotal to T-cell differentiation and function, rendering it a target of interest in efforts to manipulate T cell–mediated immunity. Methods: We investigated the pattern of Notch-1 expression in effector and regulatory T cells (Tregs) in both murine and human recipients of a solid-organ transplant. Using a selective human anti-Notch-1 antibody (aNotch-1), we examined the effect of Notch-1 receptor inhibition in full major histocompatibility complex–mismatch murine cardiac and lung transplant models, and in a humanized skin transplant model. On the basis of our findings, we further used a genetic approach to investigate the effect of selective Notch-1 inhibition in Tregs. Results: We observed an increased proportion of Tregs expressing surface and intracellular (activated) Notch-1 in comparison with conventional T cells, both in mice with transplants and in the peripheral blood of patients with transplants. In the murine cardiac transplant model, peritransplant administration of aNotch-1 (days 0, 2, 4, 6, 8, and 10) significantly prolonged allograft survival in comparison with immunoglobulin G–treated controls. Similarly, aNotch-1 treatment improved both histological and functional outcomes in the murine lung transplant model. The use of aNotch-1 resulted in a reduced proportion of both splenic and intragraft conventional T cells, while increasing the proportion of Tregs. Furthermore, Tregs isolated from aNotch-1–treated mice showed enhanced suppressive function on a per-cell basis, confirmed with selective Notch-1 deletion in Tregs (Foxp3 EGFPCre Notch1 fl/fl ). Notch-1 blockade inhibited the mammalian target of rapamycin pathway and increased the phosphorylation of STAT5 (signal transducer and activator of transcription 5) in murine Tregs. Notch-1 low Tregs isolated from human peripheral blood exhibited more potent suppressive capacity than Notch-1 high Tregs. Last, the combination of aNotch-1 with costimulation blockade induced long-term tolerance in a cardiac transplant model, and this tolerance was dependent on CTLA-4 (cytotoxic T-lymphocyte–associated antigen-4) signaling. Conclusions: Our data reveal a promising, clinically relevant approach for immune modulation in transplantation by selectively targeting Notch-1.

Early immunological biomarkers that predict rejection and chronic allograft loss are needed to inform preemptive therapy and improve long-term outcomes. Here, we prospectively examined the ratio of interleukin-10 (IL-10) to tumor necrosis factor-α (TNFα) produced by transitional-1 B cells (T1B) 3 months after transplantation as a predictive biomarker for clinical and subclinical renal allograft rejection and subsequent clinical course. In both Training (n = 162) and Internal Validation (n = 82) Sets, the T1B IL-10/TNFα ratio 3 months after transplantation predicted both clinical and subclinical rejection anytime in the first year. The biomarker also predicted subsequent late rejection with a lead time averaging 8 months. Among biomarker high-risk patients, 60% had early rejection, of which 48% recurred later in the first posttransplant year. Among high-risk patients without early rejection, 74% developed rejection later in the first year. In contrast, only 5% of low-risk patients had early and 5% late rejection. The biomarker also predicted rejection in an External Validation Set (n = 95) and in key patient subgroups, confirming generalizability. Biomarker high-risk patients exhibited progressively worse renal function and decreased 5-year graft survival compared to low-risk patients. Treatment of B cells with anti-TNFα in vitro augmented the IL-10/TNFα ratio, restored regulatory activity, and inhibited plasmablast differentiation. To conclude, the T1B IL-10/TNFα ratio was validated as a strong predictive biomarker of renal allograft outcomes and provides a rationale for preemptive therapeutic intervention with TNF blockade.

Purpose of review Improved long-term kidney allograft survival remains a critical goal in transplantation; the achievement of this, however, is highly dependent on the identification of biomarkers that can either predict or allow advance detection of patients at risk of allograft injury. The present review outlines the commonly used biomarkers in kidney transplantation, while also highlighting those currently under investigation, discussing their advantages and limitations. Recent findings Most of the approved biomarkers currently used in kidney transplantation capture antigen recognition or alloantibody production. However, tremendous progress has recently been made in the development of markers of other signaling pathways pertinent to the alloimmune response. Microarray gene sets that predict rejection or poor prognostic phenotypes have been identified in kidney biopsies (the 'molecular microscope diagnostic system' and the 'genomics of chronic allograft rejection' scores), peripheral blood (the 'kidney solid organ response test'), and urine (the '3-genes signature'). Strategies targeting serial measurements of urinary chemokines such as CXCL9 and CXCL10 also appear promising. Summary Although the range of biomarkers in current use is limited, there are many assays in the development and validation pipeline that appear promising but that have yet to reach mainstream clinical transplantation. The 'ideal biomarker' may eventually transpire to be the combination of several assays.

The development of de novo anti-HLA donor-specific antibodies (dnDSA) is associated with poorer outcomes in kidney transplant recipients. Despite this, antibody screening post-transplant is not widespread, largely because the optimal management of patients with dnDSA remains undetermined. We hypothesized that in this population, calcineurin inhibitor blood levels would be an independent predictor of graft loss. We analyzed a cohort of unsensitized patients for whom anti-HLA antibody screening was performed prospectively post-transplant. During the screening period between January 2005 and April 2016, 42 patients developed dnDSA. There was no difference in the clinical characteristics or the histological scores of patients biopsied for clinical indication versus those biopsied solely due to detection of dnDSA. Cox modeling revealed a strong relationship between mean tacrolimus levels following dnDSA detection and graft loss, with a hazard ratio of 0.49 (95% CI, 0.33-0.75), which persisted following adjustment for established independent predictors (HR, 0.52, 95% CI, 0.30-0.89). Kaplan-Meier analysis by tertiles of tacrolimus levels and receiver operating curve analysis concurred to show that a threshold of 5.3 ng/ml could be predictive of graft loss. These data suggest that anti-HLA antibody monitoring post-transplant could guide maintenance immunosuppression and improve graft outcomes.

Commonly available clinical parameters fail to predict early acute cellular rejection (EAR, occurring within 6 months after transplant), a major risk factor for graft loss after kidney transplantation. We performed whole-blood RNA sequencing at the time of transplant in 235 kidney transplant recipients enrolled in a prospective cohort study (Genomics of Chronic Allograft Rejection [GoCAR]) and evaluated the relationship of pretransplant transcriptomic profiles with EAR. EAR was associated with downregulation of NK and CD8(+) T cell gene signatures in pretransplant blood. We identified a 23-gene set that predicted EAR in the discovery (n = 81, and AUC = 0.80) and validation (n = 74, and AUC = 0.74) sets. Exclusion of recipients with 5 or 6 HLA donor mismatches increased the AUC to 0.89. The risk score derived from the gene set was also significantly associated with acute cellular rejection after 6 months, antibody-mediated rejection and/or de novo donor-specific antibodies, and graft loss in a cohort of 154 patients, combining the validation set and additional GoCAR patients with surveillance biopsies between 6 and 24 months (n = 80) posttransplant. This 23-gene set is a potentially important new tool for determination of the recipient’s immunological risk before kidney transplantation, and facilitation of an individualized approach to immunosuppressive therapy.

Notch receptors are a family of highly conserved transmembrane receptors crucial to cell development and fate: Notch-1 plays a critical role in normal T cell development, and is further involved in T cell activation and differentiation, while Notch-2 is known to be important to B cell development. The ability to influence T and B cell fate is of great interest in the field of transplantation; however, limited data exist on the importance of Notch-1 and Notch-2 in immune regulation. The primary aim of this study was to investigate the role of Notch-1 and Notch-2 in the alloimmune response using an in vivo mouse model of solid organ transplantation and selective human anti-Notch-1 (aNotch-1) and anti-Notch-2 (aNotch-2) antibodies, with particular reference to their roles in T and B cell development and behaviour, respectively. Inhibition of Notch-1 prolonged cardiac graft survival, primarily by expanding natural regulatory T cells (Tregs), but also by reducing effector T cells; use of aNotch-1 decreased Treg apoptosis whilst increasing Treg proliferation and suppressive function. The protective effect of aNotch-1 was abrogated by Treg depletion but not by prior thymectomy, indicating a principal effect on peripheral T cells. Furthermore, selective genetic deletion of Notch-1 on Tregs increased the proportion, proliferation and suppressive function of Tregs in vitro and in vivo. Lastly, transient Notch-1 inhibition combined with single-dose CTLA4-Ig induced long-term graft tolerance. Notch-2 blockade also prolonged cardiac allograft survival, an effect that was associated both with a reduction in T effector cells and, most strikingly, marked changes in the B cell subsets. Near-complete loss of the marginal zone B cell subset and reduction in the plasma cell population resulted in a highly significant reduction in the levels of donor-specific antibodies. These data reveal a promising, novel approach for immune modulation in transplantation by selectively targeting Notch-1 and Notch-2.

Background In kidney transplant recipients, surveillance biopsies can reveal, despite stable graft function, histologic features of acute rejection and borderline changes that are associated with undesirable graft outcomes. Noninvasive biomarkers of subclinical acute rejection are needed to avoid the risks and costs associated with repeated biopsies. Methods We examined subclinical histologic and functional changes in kidney transplant recipients from the prospective Genomics of Chronic Allograft Rejection (GoCAR) study who underwent surveillance biopsies over 2 years, identifying those with subclinical or borderline acute cellular rejection (ACR) at 3 months (ACR-3) post-transplant. We performed RNA sequencing on whole blood collected from 88 individuals at the time of 3-month surveillance biopsy to identify transcripts associated with ACR-3, developed a novel sequencing-based targeted expression assay, and validated this gene signature in an independent cohort. Results Study participants with ACR-3 had significantly higher risk than those without ACR-3 of subsequent clinical acute rejection at 12 and 24 months, faster decline in graft function, and decreased graft survival in adjusted Cox analysis. We identified a 17-gene signature in peripheral blood that accurately diagnosed ACR-3, and validated it using microarray expression profiles of blood samples from 65 transplant recipients in the GoCAR cohort and three public microarray datasets. In an independent cohort of 110 transplant recipients, tests of the targeted expression assay on the basis of the 17-gene set showed that it identified individuals at higher risk of ongoing acute rejection and future graft loss. Conclusions Our targeted expression assay enabled noninvasive diagnosis of subclinical acute rejection and inflammation in the graft and may represent a useful tool to risk-stratify kidney transplant recipients.

BK polyomavirus (BKV) is an important cause of graft loss in renal transplant recipients that continues to pose a significant challenge to clinicians due to its frequently unpredictable onset, persistence, and the lack of effective antiviral agents or prevention strategies. This review covers our current understanding of epidemiology, viral transmission and disease progression, and treatment and prevention strategies that have been used to manage this disease.

Regulatory T cells (Tregs) play a pivotal role in the maintenance of immune tolerance and hold great promise as cell therapy for a variety of immune-mediated diseases. However, the cellular mechanisms that regulate Treg maintenance and homeostasis have yet to be fully explored. Although Tregs express granzyme-B (GrB) to suppress effector T cells via direct killing, the mechanisms by which they protect themselves from GrB-mediated self-inflicted damage are unknown. To our knowledge, we show for the first time that both induced Tregs and natural Tregs (nTregs) increase their intracellular expression of GrB and its endogenous inhibitor, serine protease inhibitor 6 (Spi6) upon activation. Subcellular fractionation and measurement of GrB activity in the cytoplasm of Tregs show that activated Spi6−/− Tregs had significantly higher cytoplasmic GrB activity. We observed an increase in GrB-mediated apoptosis in Spi6−/− nTregs and impaired suppression of alloreactive T cells in vitro. Spi6−/− Tregs were rescued from apoptosis by the addition of a GrB inhibitor (Z-AAD-CMK) in vitro. Furthermore, adoptive transfer experiments showed that Spi6−/− nTregs were less effective than wild type nTregs in suppressing graft-versus-host disease because of their impaired survival, as shown in our in vivo bioluminescence imaging. Finally, Spi6-deficient recipients rejected MHC class II-mismatch heart allografts at a much faster rate and showed a higher rate of apoptosis among Tregs, as compared with wild type recipients. To our knowledge, our data demonstrate, for the first time, a novel role for Spi6 in Treg homeostasis by protecting activated Tregs from GrB-mediated injury. These data could have significant clinical implications for Treg-based therapy in immune-mediated diseases.

The Notch pathway is an important intercellular signaling pathway that plays a major role in controlling cell fate. Accumulating evidence indicates that Notch and its ligands present on antigen-presenting cells might be important mediators of T helper cell differentiation. In this study, we investigated the role of Jagged2 in murine cardiac transplantation by using a signaling Jagged2 mAb (Jag2) that activates recombinant signal-binding protein-Jκ. While administration of Jag2 mAb had little effect on graft survival in the fully allogeneic mismatched model BALB/c→B6, it hastened rejection in CD28-deficient recipients. Similarly, Jag2 precipitated rejection in the bm12→B6 model. In this MHC class II-mismatched model, allografts spontaneously survive for >56 days due to the emergence of Treg cells that inhibit the expansion of alloreactive T cells. The accelerated rejection was associated with upregulation of Th2 cytokines and proinflammatory cytokine IL-6, despite expansion of Treg cells. Incubation of Treg cells with recombinant IL-6 abrogated their inhibitory effects in vitro. Furthermore, neutralization of IL-6 in vivo protected Jag2-treated recipients from rejection and Jagged2 signaling was unable to further accelerate rejection in the absence of Treg cells. Our findings therefore suggest that Jagged2 signaling can affect graft acceptance by upregulation of IL-6 and consequent resistance to Treg-cell suppression.

Co-stimulatory molecules are a heterogenous group of cell surface molecules that act to amplify or counteract the initial activating signals provided to T cells from the T cell receptor (TCR) following its interaction with an antigen/major histocompatibility complex (MHC), thereby influencing T cell differentiation and fate. While co-stimulation was previously thought to be indispensable for T cell activation at all stages of development, it is now known that the requirements for co-stimulation, and co-stimulatory molecules involved, vary according to the stage of T cell differentiation. The ability to influence T cell fate is of paramount interest in the field of transplantation as we seek therapeutic options that inhibit detrimental alloimmune responses whilst simultaneously promoting allograft tolerance. As with many immune mechanisms, there is a degree of functional overlap between certain co-stimulatory molecules, while some have diametrically opposite effects on different T cell subsets despite sharing common ligands. This is a critical point when considering these molecules as therapeutic targets in transplantation, as blockade of a co-stimulatory pathway, while desirable in itself, may prevent the ligation of an essential regulatory co-inhibitory molecule. This review discusses the T helper cell lineages pertinent to transplantation and the co-stimulatory molecules involved in their differentiation.

Ligands of the B7 family provide both positive and negative costimulatory signals to the CD28 family of receptors on T lymphocytes, the balance of which determines the immune response. B7-H3 is a member of the B7 family whose function in T-cell activation has been the subject of some controversy: in autoimmunity and tumor immunity, it has been described as both costimulatory and coinhibitory, while in transplantation, B7-H3 signaling is thought to contribute to graft rejection. However, we now demonstrate results to the contrary. Signaling through a putative B7-H3 receptor prolonged allograft survival in a fully MHC-mismatched cardiac model and promoted a shift toward a Th2 milieu; conversely, B7-H3 blockade, achieved by use of a blocking antibody, resulted in accelerated rejection, an effect associated with enhanced IFN-γ production. Finally, graft prolongation achieved by CTLA4 Ig was shortened both by B7-H3 blockade and the absence of recipient B7-H3. These findings suggest a coinhibitory role for B7-H3. However, experience with other CD28/B7 family members suggests that immune redundancy plays a crucial role in determining the functions of various pathways. Given the abundance of conflicting data, it is plausible that, under differing conditions, B7-H3 may have both positive and negative costimulatory functions.

The addition of low, nondepleting doses of rabbit antithymocyte globulin (ATG) to human peripheral blood mononuclear cells has been shown to expand functional CD4(+) CD25(+) FoxP3(+) regulatory T cells (Tregs) in vitro. This report is the first to elucidate the exact cellular mechanisms of ATG-mediated Treg expansion. CD4(+) T cells require monocytes, but not other antigen presenting cell subsets, to be present in coculture to expand Tregs. However, T cells do not require direct cell-cell contact with monocytes, suggesting the importance of soluble factors. Moreover, ATG initially "reprograms" CD4(+) T cells, but not monocytes, and induces STAT3 and STAT5 signaling in CD4(+) cells. These reprogrammed CD4(+) T cells subsequently secrete GM-CSF and IL-10 only in case of intact STAT3 signaling, which in turn promote the generation of tolerogenic CD14(+) CD11c(+) dendritic cells characterized by enhanced IL-10 and decreased IL-12 production. Treg expansion following ATG treatment is accompanied by enhanced gene expression of both GM-CSF and Bcl-2, but not TGF-β, in peripheral blood mononuclear cells. These results demonstrate that ex vivo expansion of human Tregs by ATG is due to its ability to reprogram CD4(+) T cells in a STAT3-dependent but TGF-β-independent manner, leading to the generation of monocyte-derived dendritic cells with a tolerogenic cytokine profile.

The incidence of developing circulating anti-human leukocyte antigen antibodies and the kinetics of T cell depletion and recovery among pediatric renal transplant recipients who receive alemtuzumab induction therapy are unknown. In a collaborative endeavor to minimize maintenance immunosuppression in pediatric renal transplant recipients, we enrolled 35 participants from four centers and treated them with alemtuzumab induction therapy and a steroid-free, calcineurin-inhibitor-withdrawal maintenance regimen. At 3 months after transplant, there was greater depletion of CD4(+) than CD8(+) T cells within the total, naive, memory, and effector memory subsets, although depletion of the central memory subset was similar for CD4(+) and CD8(+) cells. Although CD8(+) T cells recovered faster than CD4(+) subsets overall, they failed to return to pretransplant levels by 24 months after transplant. There was no evidence for greater recovery of either CD4(+) or CD8(+) memory cells than naïve cells. Alemtuzumab relatively spared CD4(+)CD25(+)FoxP3(+) regulatory T cells, resulting in a rise in their numbers relative to total CD4(+) cells and a ratio that remained at least at pretransplant levels throughout the study period. Seven participants (20%) developed anti-human leukocyte antigen antibodies without adversely affecting allograft function or histology on 2-year biopsies. Long-term follow-up is underway to assess the potential benefits of this regimen in children.

PURPOSE OF REVIEW The Notch signaling pathway is known to play a pivotal role in T- and B-cell development and fate, presenting it as an attractive therapeutic target in alloimmunity. This review provides an overview of the mechanisms of Notch signaling, focusing on new insights into its diverse functions in T-cell activation, differentiation and memory subset formation, and the consequences thereof in transplantation. RECENT FINDINGS Recent evidence has shown that while not critical for early antigen-specific CD4 T-cell activation, Notch signaling regulates the survival of memory CD4 T cells via control of glycolytic metabolism; in contrast, Notch signaling is critical for the generation of short-lived CD8 effector T cells, but not memory CD8 cells. Transient, selective inhibition of various Notch receptors and ligands in models of solid organ transplantation has been shown to successfully modulate the alloimmune response, affecting the balance between effector and regulatory cells, with particular influence on the natural regulatory T-cell population. SUMMARY These studies reveal diverse roles for individual Notch receptors and ligands in peripheral immunity and indicate that selective targeting of the Notch pathway is a promising, novel approach for immune modulation in transplantation; the advent of therapeutic human antibodies to neutralize both the Notch ligands and the individual Notch receptors suggests that this approach could be efficiently developed.

Rhabdomyolysis is a known complication of statin therapy and may be triggered by a pharmacokinetic interaction between a statin and a second medication. Fatal statin-induced rhabdomyolysis has an incidence of 0.15 deaths/million prescriptions. We describe 4 cases of severe rhabdomyolysis with the common feature of atorvastatin use and coadministration of fusidic acid. All cases involved long-term therapy with atorvastatin; fusidic acid was introduced for treatment of osteomyelitis or septic arthritis. Three cases occurred in the setting of diabetes mellitus, with 2 in patients with end-stage renal disease, suggesting increased susceptibility to atorvastatin-fusidic acid-induced rhabdomyolysis in these patient populations. Of the 4 patients in this series, 3 died. Fusidic acid is a unique bacteriostatic antimicrobial agent with principal antistaphylococcal activity. There have been isolated reports of rhabdomyolysis attributed to the interaction of statins and fusidic acid, the cause of which is unclear. Fusidic acid does not inhibit the cytochrome P450 3A4 isoenzyme responsible for atorvastatin metabolism; increased atorvastatin levels due to inhibition of the glucuronidation pathway may be responsible. Considering the low frequency of fusidic acid use, the appearance of 4 such cases within a short time and in a small population suggests the probability that development of this potentially fatal complication may be relatively high.

B7 ligands deliver both costimulatory and coinhibitory signals to the CD28 family of receptors on T lymphocytes, the balance between which determines the ultimate immune response. Although B7-H4, a recently discovered member of the B7 family, is known to negatively regulate T cell immunity in autoimmunity and cancer, its role in solid organ allograft rejection and tolerance has not been established. Targeting the B7-H4 molecule by a blocking antibody or use of B7-H4(-/-) mice as recipients of fully MHC-mismatched cardiac allografts did not affect graft survival. However, B7-H4 blockade resulted in accelerated allograft rejection in CD28-deficient recipients. B7-1/B7-2-double-deficient recipients are truly independent of CD28/CTLA-4:B7 signals and usually accept MHC-mismatched heart allografts. Blockade of B7-H4 in these mice also precipitated rejection, demonstrating regulatory function of this molecule independent of an intact CD28/CTLA-4:B7 costimulatory pathway. Accelerated allograft rejection was always accompanied by increased frequencies of alloreactive IFN-γ-, IL-4- and Granzyme B-producing splenocytes. Finally, intact recipient, but not donor, B7-H4 is essential for prolongation of allograft survival by blocking CD28/CTLA4:B7 pathway using CTLA4-Ig. These data are the first to provide evidence of the regulatory effects of B7-H4 in alloimmune responses in a murine model of solid organ transplantation.

A high-salt diet (HSD) in humans is linked to a number of complications, including hypertension and cardiovascular events. Whether a HSD affects the immune response in transplantation is unknown. Using a murine transplantation model, we investigated the effect of NaCl on the alloimmune response in vitro and in vivo. Incremental NaCl concentrations in vitro augmented T cell proliferation in the settings of both polyclonal and allospecific stimulation. Feeding a HSD to C57BL/6 wild-type recipients of bm12 allografts led to accelerated cardiac allograft rejection, despite similar mean BP and serum sodium levels in HSD and normal salt diet (NSD) groups. The accelerated rejection was associated with a reduction in the proportion of CD4(+)Foxp3(+) regulatory T cells (Tregs) and a significant decrease in Treg proliferation, leading to an increased ratio of antigen-experienced CD4(+) T cells to Tregs in mice recipients of a HSD compared with mice recipients of a NSD. Because serum- and glucocorticoid-regulated kinase-1 (SGK1) has been proposed as a potential target of salt in immune cells, we fed a HSD to CD4(Cre)SGK1(fl/fl) B6-transplanted recipients and observed abrogation of the deleterious effect of a HSD in the absence of SGK1 on CD4(+) cells. In summary, we show that NaCl negatively affects the regulatory balance of T cells in transplantation and precipitates rejection in an SGK1-dependent manner.

Cystic fibrosis (CF) is a multisystemic disease but without a classical disease-specific renal phenotype. A 32-year-old male patient with CF (ΔF508/ΔF508) presented with a nephrotic syndrome. Renal biopsy revealed nodular glomerulosclerosis (NGS) occurring in the absence of diabetes mellitus, amyloidosis and any other known common cause of NGS. He had a progressive decline in estimated glomerular filtration rate (eGFR) to chronic kidney disease stage V (eGFR

Regulatory T cells (Tregs) are amongst the most widely studied cells in a variety of immune-mediated conditions, including transplantation and Graft Versus Host Disease (GVHD), cancer and autoimmunity; indeed, there is great interest in the tolerogenic potential of Treg-based therapy. Consequently, the need to establish the mechanisms that determine Treg survival and longevity, in addition to developing new tools to monitor these parameters, is paramount. Using both a mouse model of GVHD and a mouse model of Type 1 Diabetes (T1D), we describe herein a dual reporter system based on Gluc and multiplexed with SEAP and non-secreted Firefly luciferase (Fluc), which permits simultaneous imaging and noninvasive tracking of two different T-cell populations (CD4(+)CD25(+) Tregs and CD4(+)CD25(-) Tcon cells) in vivo by transducing the cells with different lentiviruses bearing distinct color signatures. This new technology promises to overcome the limitations of the conventional methods currently available to study lymphocyte survival in vivo. Furthermore, this novel technique has applications not only in autoimmunity and alloimmunity, but also in the wider field of immunology.

Regulatory T cells (Tregs) are amongst the most widely studied cells in a variety of immune-mediated conditions, including transplantation and Graft Versus Host Disease (GVHD), cancer and autoimmunity; indeed, there is great interest in the tolerogenic potential of Treg-based therapy. Consequently, the need to establish the mechanisms that determine Treg survival and longevity, in addition to developing new tools to monitor these parameters, is paramount. Using both a mouse model of GVHD and a mouse model of Type 1 Diabetes (T1D), we describe herein a dual reporter system based on Gluc and multiplexed with SEAP and non-secreted Firefly luciferase (Fluc), which permits simultaneous imaging and noninvasive tracking of two different T-cell populations (CD4(+)CD25(+) Tregs and CD4(+)CD25(-) Tcon cells) in vivo by transducing the cells with different lentiviruses bearing distinct color signatures. This new technology promises to overcome the limitations of the conventional methods currently available to study lymphocyte survival in vivo. Furthermore, this novel technique has applications not only in autoimmunity and alloimmunity, but also in the wider field of immunology.

Background Despite significant nephrotoxicity, calcineurin inhibitors (CNIs) remain the cornerstone of immunosuppression in solid organ transplantation. We, along with others, have reported tolerogenic properties of anti-thymocyte globulin (ATG, Thymoglobulin®), evinced by its ability both to spare Tregs from depletion in vivo and, when administered at low, non-depleting doses, to expand Tregs ex vivo. Clinical trials investigating B7/CD28 blockade (LEA29Y, Belatacept) in kidney transplant recipients have proven that the replacement of toxic CNI use is feasible in selected populations. Methods Rabbit polyclonal anti-murine thymocyte globulin (mATG) was administered as induction and/or prolonged, low-dose therapy, in combination with CTLA4-Ig, in a stringent, fully MHC-mismatched murine skin transplant model to assess graft survival and mechanisms of action. Results Prolonged, low-dose mATG, combined with CTLA4-Ig, effectively promotes engraftment in a stringent transplant model. Our data demonstrate that mATG achieves graft acceptance primarily by promoting Tregs, while CTLA4-Ig enhances mATG function by limiting activation of the effector T cell pool in the early stages of treatment, and by inhibiting production of anti-rabbit antibodies in the maintenance phase, thereby promoting regulation of alloreactivity. Conclusion These data provide the rationale for development of novel, CNI-free clinical protocols in human transplant recipients.

The Notch pathway is an important intercellular signaling pathway that plays a major role in controlling cell fate. Accumulating evidence indicates that Notch and its ligands present on antigen-presenting cells might be important mediators of T helper cell differentiation. In this study, we investigated the role of Jagged2 in murine cardiac transplantation by using a signaling Jagged2 mAb (Jag2) that activates recombinant signal-binding protein-Jκ. While administration of Jag2 mAb had little effect on graft survival in the fully allogeneic mismatched model BALB/c→B6, it hastened rejection in CD28-deficient recipients. Similarly, Jag2 precipitated rejection in the bm12→B6 model. In this MHC class II-mismatched model, allografts spontaneously survive for56 days due to the emergence of Treg cells that inhibit the expansion of alloreactive T cells. The accelerated rejection was associated with upregulation of Th2 cytokines and proinflammatory cytokine IL-6, despite expansion of Treg cells. Incubation of Treg cells with recombinant IL-6 abrogated their inhibitory effects in vitro. Furthermore, neutralization of IL-6 in vivo protected Jag2-treated recipients from rejection and Jagged2 signaling was unable to further accelerate rejection in the absence of Treg cells. Our findings therefore suggest that Jagged2 signaling can affect graft acceptance by upregulation of IL-6 and consequent resistance to Treg-cell suppression.

Summary Background and objectives Acute rejection remains a problem in renal transplantation. This study sought to determine the utility of a noninvasive cytokine assay in screening of acute rejection. Design, setting, participants, & measurements In this observational cross-sectional study, 64 patients from two centers were recruited upon admission for allograft biopsy to investigate acute graft dysfunction. Blood was collected before biopsy and assayed for a panel of 21 cytokines secreted by PBMCs. Patients were classified as acute rejectors or nonrejectors according to a classification rule derived from an initial set of 32 patients (training cohort) and subsequently validated in the remaining patients (validation cohort). Results Although six cytokines (IL-1β, IL-6, TNF-α, IL-4, GM-CSF, and monocyte chemoattractant protein-1) distinguished acute rejectors in the training cohort, logistic regression modeling identified a single cytokine, IL-6, as the best predictor. In the validation cohort, IL-6 was consistently the most accurate cytokine (area under the receiver-operating characteristic curve, 0.85; P =0.006), whereas the application of a prespecified cutoff level, as determined from the training cohort, resulted in a sensitivity and specificity of 92% and 63%, respectively. Secondary analyses revealed a strong association between IL-6 levels and acute rejection after multivariate adjustment for clinical characteristics ( P Conclusions In this pilot study, the measurement of a single cytokine can exclude acute rejection with a sensitivity of 92% in renal transplant recipients presenting with acute graft dysfunction. Prospective studies are needed to determine the utility of this simple assay, particularly for low-risk or remote patients.

Background. Although there is ample evidence about the role of adaptive immunity in the development of chroni allograft dysfunction, little is known about the contribution of innate immunity to this process. Herein, we studied th relationship between inflammation, chronic biopsy scores, and anti-human leukocyte antigen (HLA) circulating a] loantibodies in a cohort of 57 patients recruited at our center. Methods. Available biopsies (n=27) were graded for chronic lesion scores according to Banff criteria. The production on cytokines by peripheral blood mononuclear cells after 48 hr of culture under resting conditions was quantified by Lumineux Tumor necrosis factor (TNF)-α secretion assay and depletion studies were used to identify the source of these cytokines. Results. There was a high correlation between the levels of interleukin (IL)-1β, IL-6, and TNF-α (r>0.8, P

Gitelman's syndrome (GS), a rare renal disorder, results in hypokalaemia, hypomagnesaemia, hypocalciuria and a metabolic alkalosis. It is unclear if an alteration in management is necessary or beneficial during pregnancy. A 32-year-old woman with GS was managed in her second pregnancy. Antenatally, the patient required 39 (principally day case) admissions to the hospital for intravenous (IV) therapy and received a cumulative total of 47 l of IV 0.9% saline solution, 47 doses of 20 mmol magnesium chloride and 46 doses of 80 mmol potassium chloride. She delivered a 2940-g female infant in excellent condition by caesarean section. We would suggest that close attention to maternal weight gain during pregnancy is an easily available clinical tool to assess adequacy of fluid and electrolyte repletion in this condition.