Although outcomes for small intestine transplantation (SIT) have improved in recent years, allograft rejection rates remain among the highest of solid organ grafts. The high load of commensal ...bacteria in the small intestine may contribute through activation of the toll-like receptor (TLR) pathway. In this study, we examine the participation of TLR4 in acute allograft rejection in an orthotopic mouse model of SIT.
Wild-type C57Bl/6 (H-2b) or TLR49(-/-) (H-2b) mice were transplanted with syngeneic (C57Bl/6), allogeneic (BALB/c; H-2d), or F1 (BALB/cxC57Bl/6; H-2d/b) vascularized, orthotopic small intestine grafts. Graft recipients were killed on days 2 to 6 posttransplant. Serum cytokines were measured by Luminex, and tissue was obtained for histology and quantitative real-time polymerase chain reaction.
BALB/c grafts transplanted into C57Bl/6 recipients exhibited mixed inflammatory infiltrates, destruction of the mucosa, and significant apoptosis. TLR2 and TLR4 transcripts were modestly increased in syngeneic grafts on days 2 and 6 compared with native bowel, whereas TLR2 and TLR4 were significantly increased on days 2 and 6 in allogeneic grafts. Although fully mismatched and F1 grafts were rejected by C57Bl/6 recipients (mean survival time=8.2 and 9.3 days, respectively), graft survival was significantly prolonged in TLR4(-/-) recipients (mean survival time=10.6 and 14.3 days, respectively). Proinflammatory cytokines were markedly reduced in TLR4(-/-) graft recipients.
Small intestine graft survival is prolonged in the absence of TLR4, suggesting that gut flora associated with the graft may augment alloimmune responses through TLR4. Thus, the TLR pathway may be a novel therapeutic target for improving SIT allograft survival.
Natural killer (NK) cells control viral infection through the interaction between inhibitory receptors and human leukocyte antigen (HLA) ligands and bound peptide. NK cells expressing the inhibitory ...receptor NKG2A/CD94 recognize and respond to autologous B cells latently infected with Epstein-Barr virus (EBV). The mechanism is not yet understood, thus we investigated peptides derived from seven latent proteins of EBV in the interaction of NKG2A and its ligand HLA-E. Functional analysis demonstrated that EBV peptides can bind to HLA-E and block inhibition of NK cell effector function. Moreover, analysis of DNA from 79 subjects showed sequence variations in the latent protein, LMP1, which alters NK responses to EBV. We provide evidence that peptides derived from EBV latent cycle proteins can impair the recognition of NKG2A despite being presented by HLA-E, resulting in NK cell activation.
We used positron emission tomography (PET) to measure movement set-related changes in regional cerebral blood flow (rCBF) when human subjects were asked to copy hand movements. Movement set-related ...activity in the brain is thought to reflect the processes of movement selection, preparation and inhibition. Four conditions were used. In the first condition, prepare and execute (PE), the hand stimulus to be copied was shown to subjects 3 s before an auditory "go"-cue instructed subjects to execute the movement; a large part of the scanning time was therefore spent in preparing to move. In the immediate execution condition (E), the hand stimulus and the go cue were presented simultaneously. The prepare-only condition (P) was similar to PE, except subjects only prepared to make the movement and did not actually execute any movement when they heard the auditory go-cue. The same stimuli were presented in a baseline condition (B), but the subjects were instructed to neither prepare nor execute movements. There were 5 principle findings: (1) In contrast to a previous study of human set-related activity in which movements were instructed by an arbitrary pattern of LEDs, preparing to make a copied movement causes rCBF changes in area 44 in posterior Broca's area; (2) set-related activity can be recorded in the cerebellar hemispheres and midline; (3) we confirmed that the supramarginal gyrus has a general role in preparing movements - there was more rCBF in the P than the E condition; (4) the cerebellar nuclei and the basal ganglia may be particularly involved in the initiation and execution of a planned movement; these regions were more active in the PE condition than the P condition; (5) the ventrolateral prefrontal cortex and a left anterior cingulate area are part of a distributed system involved in the suppression of a motor response; these areas were significantly more active in the P than the PE condition.
Epstein-Barr virus (EBV)–positive posttransplant lymphoproliferative disorder (PTLD) results in significant morbidity and mortality in pediatric transplant recipients. Identifying individuals at an ...increased risk of EBV-positive PTLD could influence clinical management of immunosuppression and other therapies, improving posttransplant outcomes. A 7-center prospective, observational clinical trial of 872 pediatric transplant recipients evaluated the presence of mutations at positions 212 and 366 of EBV latent membrane protein 1 (LMP1) as an indicator of risk of EBV-positive PTLD (clinical trials: NCT02182986). DNA was isolated from peripheral blood of EBV-positive PTLD case patients and matched controls (1:2 nested case:control), and the cytoplasmic tail of LMP1 was sequenced. Thirty-four participants reached the primary endpoint of biopsy-proven EBV-positive PTLD. DNA was sequenced from 32 PTLD case patients and 62 matched controls. Both LMP1 mutations were present in 31 of 32 PTLD cases (96.9%) and in 45 of 62 matched controls (72.6%) (P = .005; OR = 11.7; 95% confidence interval, 1.5, 92.6). The presence of both G212S and S366T carries a nearly 12-fold increased risk of development of EBV-positive PTLD. Conversely, transplant recipients without both LMP1 mutations carry a very low risk of PTLD. Analysis of mutations at positions 212 and 366 of LMP1 can be informative in stratifying patients for risk of EBV-positive PTLD.
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Abstract Aim Liver fibrosis, heralding the potential progression to cirrhosis and hepatocellular carcinoma (HCC), compromises patient survival and augments post‐hepatectomy recurrence. This study ...examined the detrimental effects of liver fibrosis on the antitumor functions of liver natural killer (NK) cells and the interleukin‐33 (IL‐33) signaling pathway. Methods Our investigation, anchored in both human physiologies using living and deceased donor livers and the carbon tetrachloride (CCl 4 )‐induced mouse fibrosis model, aimed to show a troubling interface between liver fibrosis and weakened hepatic immunity. Results The Fibrosis‐4 (FIB‐4) index emerged as a salient, non‐invasive prognostic marker, and its elevation correlated with reduced survival and heightened recurrence after HCC surgery even after propensity matching ( n = 385). We established a strong correlation between liver fibrosis and liver NK cell dysfunction by developing a method for extracting liver NK cells from the liver graft perfusate. Furthermore, liver fibrosis ostensibly disrupted chemokines and promoted IL‐33 expression, impeding liver NK cell antitumor activities, as evidenced in mouse models. Intriguingly, our results implicated IL‐33 in diminishing the antitumor responses of NK cells. This interrelation, consistent across both mouse and human studies, coincides with clinical data suggesting that liver fibrosis predisposes patients to an increased risk of HCC recurrence. Conclusion Our study revealed a critical relationship between liver fibrosis and compromised tumor immunity, emphasizing the potential interference of IL‐33 with NK cell function. These insights advocate for advanced immunostimulatory therapies targeting cytokines, such as IL‐33, aiming to bolster the hepatic immune response against HCC in the context of liver fibrosis.
Alloimmune responses in acute rejection are complex, involving multiple interacting cell types and pathways. Deep profiling of these cell types has been limited by technology that lacks the capacity ...to resolve this high dimensionality. Single-cell mass cytometry is used to characterize the alloimmune response in early acute rejection, measuring 37 parameters simultaneously, across multiple time points in two models: a murine cardiac and vascularized composite allotransplant (VCA). Semi-supervised hierarchical clustering is used to group related cell types defined by combinatorial expression of surface and intracellular proteins, along with markers of effector function and activation. This expression profile is mapped to visualize changes in antigen composition across cell types, revealing phenotypic signatures in alloimmune T cells, natural killer (NK) cells, and myeloid subsets that are conserved and that firmly distinguish rejecting from non-rejecting grafts. These data provide a comprehensive, high-dimensional profile of cellular rejection after allograft transplantation.
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•High-dimensional analysis reveals an alloimmune profile by day 5 post-transplant•MHC class I and CCR6 global upregulation is a hallmark of allograft rejection•Unbiased clustering exposes multiple phenotypically distinct alloimmune populations•Alloimmune signature is conserved across two models of transplantation
Harden et al. show that unsupervised high-dimensional CyTOF analysis identifies an alloimmune signature that specifically distinguishes rejecting from non-rejecting transplants. This signature is revealed by day 5 post-transplant and is conserved across two murine models of transplantation.
The mouse is the most widely used animal for establishing in vivo models in transplant research. However, because of the advanced microsurgical skills required for these operations, the vascularized ...composite transplantation model in mouse has proven to be technically challenging. The purpose of this report is to describe novel modifications in surgical techniques to establish a consistent and reliable mouse model of hind limb transplantation.
Forty C57BL/6 male mice, half as donors and half as recipients, were used in this study. The donor hind limb was harvested and transplanted into the recipient’s ipsilateral cervical region by anastomosing the donor femoral artery to the recipient common carotid artery with a modified sleeve technique. The donor femoral vein was mounted with a modified cuff and inserted into the recipient external jugular vein. The graft was evaluated at 2 weeks postoperatively.
The modified cuff and modified sleeve technique facilitated anastomoses. The time spent on either of the donor operation and recipient operation was about 45 minutes. The graft survival rate was 80% (16 of 20) at 2 weeks after transplant. There was minimal blood loss and no infections were noted.
Revised surgical techniques using a modified cuff proved to be a safe, reliable, and reproducible strategy in establishing a mouse model of hind limb heterotopic transplantation. The consistent graft survival in this syngeneic study demonstrates that this model can serve as a useful tool for further studies in vascularized composite transplantation.
Background
Epstein–Barr virus (EBV)‐associated post‐transplant lymphoproliferative disorders (PTLD) is the most common malignancy in children after transplant; however, difficulties for early ...detection may worsen the prognosis.
Methods
The prospective, multicenter, study enrolled 944 children (≤21 years of age). Of these, 872 received liver, heart, kidney, intestinal, or multivisceral transplants in seven US centers between 2014 and 2019 (NCT02182986). In total, 34 pediatric EBV+ PTLD (3.9%) were identified by biopsy. Variables included sex, age, race, ethnicity, transplanted organ, EBV viral load, pre‐transplant EBV serology, immunosuppression, response to chemotherapy and rituximab, and histopathological diagnosis.
Results
The uni−/multivariable competing risk analyses revealed the combination of EBV‐seropositive donor and EBV‐naïve recipient (D+R−) was a significant risk factor for PTLD development (sub‐hazard ratio: 2.79 1.34–5.78, p = .006) and EBV DNAemia (2.65 1.72–4.09, p < .001). Patients with D+R− were significantly more associated with monomorphic/polymorphic PTLD than those with the other combinations (p = .02). Patients with monomorphic/polymorphic PTLD (n = 21) had significantly more EBV DNAemia than non‐PTLD patients (p < .001) and an earlier clinical presentation of PTLD than patients with hyperplasias (p < .001), within 6‐month post‐transplant. Among non‐liver transplant recipients, monomorphic/polymorphic PTLD were significantly more frequent than hyperplasias in patients ≥5 years of age at transplant (p = .01).
Conclusions
D+R− is a risk factor for PTLD and EBV DNAemia and associated with the incidence of monomorphic/polymorphic PTLD. Intensive follow‐up of EBV viral load within 6‐month post‐transplant, especially for patients with D+R− and/or non‐liver transplant recipients ≥5 years of age at transplant, may help detect monomorphic/polymorphic PTLD early in pediatric transplant.
D+R− serostatus is significantly associated with the development of monomorphic/polymorphic PTLD. Intensive follow‐up of EBV viral load within 6‐month post‐transplant, especially for patients with D+R− and/or non‐liver transplant recipients ≥5 years of age at transplant, may help detect monomorphic/polymorphic PTLD early in pediatric transplant.
Epstein–Barr virus (EBV) is a γ‐herpesvirus that is linked to the development of posttransplant lymphoproliferative disorder (PTLD) in solid organ recipients. We previously demonstrated that EBV+ B ...cell lymphoma cell lines isolated from patients with PTLD produce human IL‐10 as an autocrine growth factor. However, little is known regarding IL‐10 regulation in B cells. Here we show that EBV infection markedly alters the expression of host B cell microRNA, a class of small noncoding RNA that is an important regulator of transcriptional and posttranscriptional gene expression. Gene arrays reveal unique microRNA profiles in EBV+ B cell lymphoma lines from patients with PTLD, compared to normal B cells or in vitro generated EBV+ lymphoblastoid cell lines. We show that microRNA‐194 expression is uniquely suppressed in EBV+ B cell lines from PTLD patients and that the 3'untranslated region of IL‐10 is targeted by microRNA‐194. Overexpression of microRNA‐194 attenuates IL‐10 production and increases apoptosis of EBV+ B cell lymphoma lines. Together, these data indicate that EBV co‐opts the host B cell microRNA network and specifically suppresses microRNA‐194 to override control of IL‐10 expression. Thus, modulation of microRNA‐194 may constitute a novel approach to inhibiting proliferation of EBV+ B cell lymphomas in PTLD.
Epstein‐Barr virus modulates B cell microRNA‐194 expression during latent infection to promote the production of IL‐10, an important autocrine growth factor for EBV+ B cell lymphomas in posttransplant lymphoproliferative disorder.
Abstract Although outcomes after intestinal transplantation have steadily improved owing to advances in immunosuppressive therapy, operative techniques, and postoperative medical management, ...rejection of the intestinal allograft continues to be a major clinical problem and constitutes the primary reason for graft loss. Although the adaptive immune system has been the major focus of investigation regarding regulation of rejection of the intestinal allograft, the role of the innate immune system has recently become of increased interest. We hypothesized that microbial products of the microflora associated with the intestinal allograft may engage the Toll-like receptor pathway of the innate immune system to potentiate alloimmune responses and rejection of the allograft. To investigate this, we established a murine model for orthotopic intestinal transplantation and allograft rejection. Using this model, we show that the expression of Toll-like receptor 2 is increased 50-fold and the expression of Toll-like receptor 4 is increased 200-fold during rejection of the allograft. We then performed survival studies that showed increased survival of mice, which had the Toll-like receptor knocked out. These preliminary studies suggest an important role for in innate immune system in acute rejection of the small intestinal allografts, and as such represents an emerging and promising area of investigation.
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