Patterns of graft infiltration and cytokine gene expression during the first 10 days of kidney transplantation

An agent-based model of cardiac allograft vasculopathy: toward a better understanding of chronic rejection dynamics

Cardiac allograft vasculopathy (CAV) is a coronary artery disease affecting 50% of heart transplant (HTx) recipients, and it is the major cause of graft loss. CAV is driven by the interplay of immunological and non-immunological factors, setting off a cascade of events promoting endothelial damage and vascular dysfunction. The etiology and evolution of tissue pathology are largely unknown, making disease management challenging. So far, in vivo models, mostly mouse-based, have been widely used to study CAV, but they are resource-consuming, pose many ethical issues, and allow limited investigation of time points and important biomechanical measurements. Recently, agent-based models (ABMs) proved to be valid computational tools for deciphering mechanobiological mechanisms driving vascular adaptation processes at the cell/tissue level, augmenting cost-effective in vivo lab-based experiments, at the same time guaranteeing richness in observation time points and low consumption of resources. We hypothesize that integrating ABMs with lab-based experiments can aid in vivo research by overcoming those limitations. Accordingly, this work proposes a bidimensional ABM of CAV in a mouse coronary artery cross-section, simulating the arterial wall response to two distinct stimuli: inflammation and hemodynamic disturbances, the latter considered in terms of low wall shear stress (WSS). These stimuli trigger i) inflammatory cell activation and ii) exacerbated vascular cell activities. Moreover, an extensive analysis was performed to investigate the ABM sensitivity to the driving parameters and inputs and gain insights into the ABM working mechanisms. The ABM was able to effectively replicate a 4-week CAV initiation and progression, characterized by lumen area decrease due to progressive intimal thickening in regions exposed to high inflammation and low WSS. Moreover, the parameter and input sensitivity analysis highlighted that the inflammatory-related events rather than the WSS predominantly drive CAV, corroborating the inflammatory nature of the vasculopathy. The proof-of-concept model proposed herein demonstrated its potential in deepening the pathology knowledge and supporting the in vivo analysis of CAV.

Multiple Shades of Gray-Macrophages in Acute Allograft Rejection

Long-term results following solid organ transplantation do not mirror the excellent short-term results achieved in recent decades. It is therefore clear that current immunosuppressive maintenance protocols primarily addressing the adaptive immune system no longer meet the required clinical need. Identification of novel targets addressing this shortcoming is urgently needed. There is a growing interest in better understanding the role of the innate immune system in this context. In this review, we focus on macrophages, which are known to prominently infiltrate allografts and, during allograft rejection, to be involved in the surge of the adaptive immune response by expression of pro-inflammatory cytokines and direct cytotoxicity. However, this active participation is janus-faced and unspecific targeting of macrophages may not consider the different subtypes involved. Under this premise, we give an overview on macrophages, including their origins, plasticity, and important markers. We then briefly describe their role in acute allograft rejection, which ranges from sustaining injury to promoting tolerance, as well as the impact of maintenance immunosuppressants on macrophages. Finally, we discuss the observed immunosuppressive role of the vitamin-like compound tetrahydrobiopterin and the recent findings that suggest the innate immune system, particularly macrophages, as its target.

A novel phosphocholine-mimetic inhibits a pro-inflammatory conformational change in C-reactive protein

C-reactive protein (CRP) is an early-stage acute phase protein and highly upregulated in response to inflammatory reactions. We recently identified a novel mechanism that leads to a conformational change from the native, functionally relatively inert, pentameric CRP (pCRP) structure to a pentameric CRP intermediate (pCRP*) and ultimately to the monomeric CRP (mCRP) form, both exhibiting highly pro-inflammatory effects. This transition in the inflammatory profile of CRP is mediated by binding of pCRP to activated/damaged cell membranes via exposed phosphocholine lipid head groups. We designed a tool compound as a low molecular weight CRP inhibitor using the structure of phosphocholine as a template. X-ray crystallography revealed specific binding to the phosphocholine binding pockets of pCRP. We provide in vitro and in vivo proof-of-concept data demonstrating that the low molecular weight tool compound inhibits CRP-driven exacerbation of local inflammatory responses, while potentially preserving pathogen-defense functions of CRP. The inhibition of the conformational change generating pro-inflammatory CRP isoforms via phosphocholine-mimicking compounds represents a promising, potentially broadly applicable anti-inflammatory therapy.

Myeloid and Mesenchymal Stem Cell Therapies for Solid Organ Transplant Tolerance

Transplantation is now performed globally as a routine procedure. However, the increased demand for donor organs and consequent expansion of donor criteria has created an imperative to maximize the quality of these gains. The goal is to balance preservation of allograft function against patient quality-of-life, despite exposure to long-term immunosuppression. Elimination of immunosuppressive therapy to avoid drug toxicity, with concurrent acceptance of the allograft-so-called operational tolerance-has proven elusive. The lack of recent advances in immunomodulatory drug development, together with advances in immunotherapy in oncology, has prompted interest in cell-based therapies to control the alloimmune response. Extensive experimental work in animals has characterized regulatory immune cell populations that can induce and maintain tolerance, demonstrating that their adoptive transfer can promote donor-specific tolerance. An extension of this large body of work has resulted in protocols for manufacture, as well as early-phase safety and feasibility trials for many regulatory cell types. Despite the excitement generated by early clinical trials in autoimmune diseases and organ transplantation, there is as yet no clinically validated, approved regulatory cell therapy for transplantation. In this review, we summarize recent advances in this field, with a focus on myeloid and mesenchymal cell therapies, including current understanding of the mechanisms of action of regulatory immune cells, and clinical trials in organ transplantation using these cells as therapeutics.

Macrophages in Organ Transplantation

Current immunosuppressive therapy has led to excellent short-term survival rates in organ transplantation. However, long-term graft survival rates are suboptimal, and a vast number of allografts are gradually lost in the clinic. An increasing number of animal and clinical studies have demonstrated that monocytes and macrophages play a pivotal role in graft rejection, as these mononuclear phagocytic cells recognize alloantigens and trigger an inflammatory cascade that activate the adaptive immune response. Moreover, recent studies suggest that monocytes acquire a feature of memory recall response that is associated with a potent immune response. This form of memory is called “trained immunity,” and it is retained by mechanisms of epigenetic and metabolic changes in innate immune cells after exposure to particular ligands, which have a direct impact in allograft rejection. In this review article, we highlight the role of monocytes and macrophages in organ transplantation and summarize therapeutic approaches to promote tolerance through manipulation of monocytes and macrophages. These strategies may open new therapeutic opportunities to increase long-term transplant survival rates in the clinic.

The Mononuclear Phagocyte System in Organ Transplantation

The mononuclear phagocyte system (MPS) comprises monocytes, macrophages and dendritic cells (DCs). Over the past few decades, classification of the cells of the MPS has generated considerable controversy. Recent studies into the origin, developmental requirements and function of MPS cells are beginning to solve this problem in an objective manner. Using high-resolution genetic analyses and fate-mapping studies, three main mononuclear phagocyte lineages have been defined, namely, macrophage populations established during embryogenesis, monocyte-derived cells that develop during adult life and DCs. These subsets and their diverse subsets have specialized functions that are largely conserved between species, justifying the introduction of a new, universal scheme of nomenclature and providing the framework for therapeutic manipulation of immune responses in the clinic. In this review, we have commented on the implications of this novel MPS classification in solid organ transplantation.

Down-regulated expression of monocyte/macrophage major histocompatibility complex receptors in human and mouse monocytes by expression of their ligands

Mouse monocyte/macrophage major histocompatibility complex (MHC) receptor 1 (MMR1; or MMR2) specific for H-2D(d) (or H-2K(d) ) molecules is expressed on monocytes from non-H-2D(d) (or non-H-2K(d) ), but not those from H-2D(d) (or H-2K(d) ), inbred mice. The MMR1 and/or MMR2 is essential for the rejection of H-2D(d) - and/or H-2K(d) -transgenic mouse skin onto C57BL/6 (H-2D(b) K(b) ) mice. Recently, we found that human leucocyte antigen (HLA)-B44 was the sole ligand of human MMR1 using microbeads that had been conjugated with 80 types of HLA class I molecules covering 94·2% (or 99·4%) and 92·4% (or 96·2%) of HLA-A and B molecules of Native Americans (or Japanese), respectively. In the present study, we also explored the ligand specificity of human MMR2 using microbeads. Microbeads coated with HLA-A32, HLA-B13 or HLA-B62 antigens bound specifically to human embryonic kidney (HEK)293T or EL-4 cells expressing human MMR2 and to the solubilized MMR2-green fluorescent protein (GFP) fusion protein; and MMR2(+) monocytes from a volunteer bound HLA-B62 molecules with a Kd of 8·7 × 10(-9)  M, implying a three times down-regulation of MMR2 expression by the ligand expression. H-2K(d) (or H-2D(d) ) transgene into C57BL/6 mice down-regulated not only MMR2 (or MMR1) but also MMR1 (or MMR2) expression, leading to further down-regulation of MMR expression. In fact, monocytes from two (i.e. MMR1(+) /MMR2(+) and MMR1(-) /MMR2(-) ) volunteers bound seven to nine types of microbeads among 80, indicating ≤ 10 types of MMR expression on monocytes. The physiological role of constitutive MMRs on monocytes possibly towards allogeneic (e.g. fetal) cells in the blood appears to be distinct from that of inducible MMRs on macrophages toward allografts in tissue.

Microarray analysis of long non-coding RNA expression in human acute rejection biopsy samples following renal transplantation

Rejection is still a major obstacle in long-term allograft survival of renal transplant recipients. Long non‑coding RNAs (lncRNAs) are an important class of pervasive RNAs involved in a variety of biological functions, and which are often found to be differentially expressed between healthy and pathological conditions. The aim of this study was to compare the expression profiles of lncRNAs between samples from acute rejection following kidney transplantation and control samples. Three patients were enrolled, diagnosed by renal biopsy with acute rejection upon kidney transplantation. We used lncRNA microarrays to study the lncRNA expression profiles in the kidney biopsies of these patients and in kidneys from healthy donors. Reverse transcription‑quantitative polymerase chain reaction (RT-qPCR) was used to validate the microarray results. In addition, potential functions of the identified lncRNAs were further explored by searching the UCSC, RNAdb, RefSeq and NRED databases. Five candidate lncRNAs displaying differential expression in acute rejection samples were validated by RT-qPCR. The results were in agreement with the microarray data. Among the identified lncRNAs, certain have been previously identified in relevant conditions, thereby supporting previous evidence, but certain may constitute novel biomarker candidates. This is the first report to date using lncRNA microarrays to identify unique expression signatures of acute rejection in transplant biopsies. Our data indicate that lncRNAs are potentially involved in the pathogenesis of acute rejection. Our results may have important implications in the identification of diagnostic biomarkers, as well as in the understanding and treatment of acute rejection following renal transplantation.

Macrophages in renal transplantation: Roles and therapeutic implications

The presence of macrophages within transplanted renal allografts has been appreciated for some time, whereby macrophages were viewed primarily as participants in the process of cell-mediated allograft rejection. Recent insights into macrophage biology have greatly expanded our conceptual understanding of the multiple roles of macrophages within the allograft. Distinct macrophage subsets are present within the kidney and these sub-serve discrete functions in promoting and attenuating inflammation, immune modulation and tissue repair. Unraveling the complex roles macrophages play in transplantation will allow identification of potential therapeutic targets to prevent and treat allograft rejection and maximize graft longevity.

Regulatory macrophages as therapeutic targets and therapeutic agents in solid organ transplantation

PURPOSE OF REVIEW

This review aims to provide a basic introduction to human macrophage biology and an appreciation of the diverse roles played by macrophage subsets in allograft damage and repair. Current and future strategies for therapeutically manipulating macrophage behaviour are discussed.

RECENT FINDINGS

Macrophages are extremely versatile effector cells that exert both immunostimulatory and immunosuppressive effects. This adaptability cannot be explained by differentiation into committed sublineages, but instead reflects the ability of macrophages to rapidly transition between states of functional polarisation. Consequently, categorisation of macrophage subpopulations is not straightforward and this, in turn, creates difficulties in studying their pathophysiology. Nevertheless, particular macrophage subpopulations have been implicated in exacerbating or attenuating ischaemia-reperfusion injury, rejection reactions and allograft fibrosis. Three general strategies for therapeutically targeting macrophages can be envisaged, namely, depletional approaches, in-situ repolarisation towards a regulatory or tissue-reparative phenotype, and ex-vivo generation of regulatory macrophages (M reg) as a cell-based therapy.

SUMMARY

As critical determinants of the local and systemic immune response to solid organ allografts, macrophage subpopulations represent attractive therapeutic targets. Rapid progress is being made in the implementation of novel macrophage-targeted therapies, particularly in the use of ex-vivo-generated M regs as a cell-based medicinal product.

The role of macrophage lineage cells in kidney graft rejection and survival

Large numbers of macrophage lineage cells are present in transplants undergoing ischemia-reperfusion injury and rejection, and their presence correlates with a high probability of rejection. However, the extent to which monocytes and macrophages contribute to kidney graft rejection is poorly understood. The heterogeneity of the monocyte/macrophage lineage cells could be one of the reasons why these cells have been neglected up to now. Circulating monocytes can be divided into various subsets, which are able to give rise to tissue macrophages and dendritic cells. Macrophages are believed to be highly plastic cells that can respond to environmental signals by changing their phenotype and function. Macrophages have established roles in early and late kidney graft inflammation, tissue homeostasis, remodeling, and repair. In kidney transplantation, macrophages are believed to play a role in both damage and repair of the graft, depending on the type of macrophages involved, the environmental drive, and the time after transplantation. The heterogeneity and plasticity of monocytes and macrophages are obstacles to translating the functional relevance of this cell lineage to diagnostic and prognostic clinical parameters and to defining specific, macrophage-related, therapeutic targets. Recent evidence has indicated an immunomodulatory role for the so-called regulatory macrophages in induction of tolerance in kidney transplant recipients. In this article, we summarize current views on monocyte/macrophage immunobiology in kidney transplantation. Key issues for ongoing research are discussed.

Blocking of CCR5 and CXCR3 suppresses the infiltration of macrophages in acute renal allograft rejection

BACKGROUND

The chemokine receptors CCR5 and CXCR3 are expressed by T cells and macrophages. We examined effects of a CCR5/CXCR3 antagonist (TAK), with a particular focus on the role of macrophages, in a rat kidney transplant model.

METHODS

Dark Agouti rat kidneys were transplanted into Lewis rats. The recipients were treated daily with a 10 mg/kg TAK on posttransplant days 0 to 14 and/or 2 mg/kg of cyclosporine A (CsA) on days 0 to 5. Graft survival, histological changes, and the expression of chemokines and chemokine receptors on T cells and macrophages were studied.

RESULTS

Treatment with TAK alone suppressed CD4+T cell infiltration and slightly prolonged graft survival. The expressions of both CCR5 and CXCR3, and activated macrophage-associated cytokines and chemokines, were significantly increased on macrophages that had been separated from rejecting kidneys, compared with those from spleens. However, these upregulations were decreased in macrophages from kidneys that had been treated with TAK. Immunohistochemistry also showed that macrophages infiltrating tubules of rejecting kidney expressed both receptors. In the CsA alone group, macrophages were the dominant infiltrating cells, and all allografts were rejected within 10 days. A combined therapy involving CsA and TAK resulted in decreased macrophage infiltration, and graft survival was substantially prolonged. The levels of activated macrophage-associated cytokines and chemokines were also decreased.

CONCLUSION

The dual blocking of CCR5/CXCR3 can be useful in decreasing rejection, with or without CsA. This mechanism acts, not only to block T-cell recruitment to a kidney graft but to suppress the infiltration of macrophages as well.

Novel gene markers of immunosuppressive chemicals in mouse lymph node assay

The murine local lymph node assay (LLNA) is an immunologically based test of the sensitizing potential of immunotoxicants, but also evaluates immunosuppressive potential with good sensitivity and specificity. We conducted the LLNA with calcineurin inhibitors (tacrolimus and cyclosporin A), antimetabolites (methotrexate and azathioprine), steroids (dexamethasone and prednisolone), and an alkylator (cyclophosphamide). We performed a comprehensive analysis of results of gene expression in lymph nodes obtained in the LLNA using a highly sensitive DNA chip, 3D-Gene™, and the quantitative reverse transcription-polymerase chain reaction (qPCR). Zfp459 expression increased in all animals treated with immunosuppressive chemicals. Ltf, Cbll1 and Lias expression changed specifically in response to the calcineurin inhibitors, Fmo2 and 9630033F20Rik in response to the antimetabolites, Krt8, Gjb1, Hmha1 and Sfrs7 in response to the steroids, and Gbp1 and Mup5 in response to the alkylator. Therefore, these genes were considered novel markers for immunosuppression and their expression could be used to evaluate the mechanism of action of immunosuppressive chemicals.

Diagnostic Tools for Monitoring Kidney Transplant Recipients

Recent advancements in immunobiology have introduced several new diagnostic tools for monitoring kidney transplant recipients. These have been added to more established tests that, although imperfect, remain important benchmarks of diagnostic utility. Both new and old tests can be characterized with regard to their practicality, and as to whether they detect aberrant function or define the cause of dysfunction. Unfortunately, no current test is both practical and specific to a particular disease entity. Accordingly, the diagnosis of graft dysfunction remains dependent on the proper use and interpretation of many studies. This article reviews the current assays that have been evaluated in the clinic for the diagnosis of renal allograft-related diseases. These are limited to assays based on routinely obtainable samples such as blood, biopsy tissue, and urine. Newer studies are presented, along with more mundane assays, to highlight the practical use of studies regardless of their degree of mechanistic sophistication.

Human monocytes as intermediaries between allogeneic endothelial cells and allospecific T cells: a role for direct scavenger receptor-mediated endothelial membrane uptake in the initiation of alloimmunity

Recipient monocytes, T cells, and donor endothelial cells (ECs) are recognized as critical components of allograft rejection. We have recently shown that human monocytes infiltrate vascularized allografts before clinical rejection and have thus hypothesized that monocytes, rather than costimulation-poor ECs, initiate an alloimmune response. However, the nature of the interactions between ECs, monocytes, and T cells has been incompletely defined. Specifically, it is not clear whether these cells interact in a hierarchical manner, nor is it apparent what constitutes an interaction. We therefore studied human ECs, monocytes, and T cells in various isolated in vitro combinations to define the salient features of their contact and to determine whether their interactions were sequential in nature. We find that T cells proliferate poorly to allogeneic ECs and autologous monocytes but well to autologous monocytes following allogeneic EC contact. We show that monocytes gain their stimulatory capacity by phagocytizing allogeneic but not autologous EC membranes in a process governed by scavenger receptors. This process facilitates the subsequent presentation of intact donor HLA molecules to T cells (semidirect presentation). Moreover, monocytes are receptive to T cell help only after exposure to ECs and require CD4+ T cells to optimally express costimulatory molecules and foster Ag presentation. Our results indicate that monocytes engage allogeneic ECs through scavenger receptors and are then primed to facilitate T cell activation in a codependent manner. This reciprocal codependence allows for monocytes to serve as a regulated bridge between the allograft and T cells.

Differences in lymphocyte gene expression between tolerant and syngeneic liver grafted rats

Induction of tolerance to allogeneic donor grafts is a clinically desirable goal in bone marrow and solid organ transplantation. We have taken the advantage of DNA microarray technology to investigate gene expression mechanism in regulatory cells. In the present study, using a tacrolimus (FK506) induced tolerance of the fully mismatched liver allograft rat model, we demonstrated that, in contrast with peripheral blood lymphocytes (PBLs) from syngeneic recipients, PBLs taken from tolerant recipients 100 days after transplantation were able to suppress the in vitro proliferation of allogeneic PBLs and to prolong the survival of second syngeneic recipients. We also compared messenger RNA profiles in PBLs from tolerant recipients with those from syngeneic recipients using a DNA microarray with probe sets corresponding to more than 8000 rat genes. There were 96 up-regulated and 103 down-regulated genes in the tolerant recipients. In the up-regulated group, there were 76 known genes and 20 expressed sequence tags (ESTs). In the down-regulated groups, there were 87 known genes and 16 ESTs. Our data indicated that FK506 treatment induced tolerance and expansion of regulatory cells and the DNA microarray technology was useful for this application and provided many informative insights into the mechanism of lymphocyte regulation.

Tubulitis in renal allograft rejection: role of transforming growth factor-beta and interleukin-15 in development and maintenance of CD103+ intraepithelial T cells

BACKGROUND

Renal tubules normally show no lymphocyte infiltration, but tubulitis is a feature of renal allograft rejection with many intratubular T cells expressing CD8 and CD103 (the alphaEbeta7 integrin). We investigated the development and maintenance of allospecific CD103 T cells within the tubular microenvironment.

METHODS

Mixed lymphocyte cultures were supplemented with transforming growth factor (TGF)-beta1 to model the expression and function of CD103 observed in situ on intratubular lymphocytes. Immunocytochemical techniques were used to identify cells coexpressing CD8 and interleukin (IL)-15Ralpha, to enumerate proliferating intratubular T cells, and to quantify IL-15 expression within the tubules of control and rejection-graded transplant biopsy specimens. These results were compared with a parallel analysis of the phenotype and proliferation of allospecific T cells expanded in vitro in the presence of TGF-beta1 and IL-15.

RESULTS

TGF-beta1 only induced the expression of adhesive CD103 after at least one cycle of alloantigen-specific cell division in vitro. In the renal allograft, a similar proportion of intratubular T cells was observed to proliferate during and after acute rejection. Tubular epithelial cells expressed IL-15 constitutively, whereas intratubular CD8 T cells expressed IL-15 receptor alpha. IL-15 and TGF-beta1 synergized to promote expansion and survival of allospecific CD8 CD103 T cells in vitro, but IL-15 down-regulated perforin expression.

CONCLUSIONS

These results suggest that activated, allospecific CD8 T cells are recruited to tubules during acute rejection where they encounter TGF-beta, up-regulate CD103 expression, and bind E-cadherin. A proportion of these cells proliferates and is maintained in a state of low perforin expression by the combined action of TGF-beta and IL-15.

Post-transplant renal tubulitis: the recruitment, differentiation and persistence of intra-epithelial T cells

Tubulitis is used by the Banff protocol as a major criterion to grade acute renal allograft rejection. This review integrates results from in vitro and in vivo studies to develop a chronological model to explain the development and functions of tubular inflammation during the rejection process. Proteoglycan-immobilized chemokines are the primary motivators for the vectorial recruitment of specific immune cell populations from the blood, through the endothelium and interstitial tissues to the renal tubules. After penetration of the basement membrane, T cells encounter TGF-beta that can induce expression of the alphaEbeta7 integrin on proliferating cells. This allows adhesion to E-cadherin on the baso-lateral surfaces of tubular epithelial cells and provides an explanation for the epithelial-specific cytotoxicity observed during acute rejection. Tubular epithelium is also a rich source of IL-15 that can stimulate IL-15 receptor-expressing intratubular CD8+ T cells. This anti-apoptotic microenvironment may explain the long-term persistence of cycling T cells within intact tubules after episodes of acute rejection. These memory-like T cells may have local immunoregulatory properties, including the production of additional TGF-beta, but could also modify normal tubular homeostasis resulting in epithelial to mesenchymal transdifferentiation, tubulointerstitial fibrosis and, ultimately, graft failure.

Differential allograft gene expression in acute cellular rejection and recurrence of hepatitis C after liver transplantation

Treatment of acute cellular rejection (ACR) is associated with increased viral load, more severe histologic recurrence, and diminished patient and graft survival after liver transplantation for hepatitis C virus (HCV). Recurrence of HCV may be difficult to distinguish histologically from ACR. Because the immunologic mechanisms of ACR and HCV recurrence are likely to differ, we hypothesized that ACR is associated with the expression of a specific subset of immune activation genes that may serve as a diagnostic indicator of ACR and provide mechanistic insight into the pathophysiology of ACR and recurrence of HCV. The goal of the study was to study intragraft gene expression patterns in ACR and during recurrence of HCV in HCV-infected recipients. High-density microarrays were used to determine relative intragraft gene expression in two groups of HCV-infected liver transplant recipients: four with steroid responsive ACR by Banff criteria and four age- and gender-matched HCV-infected recipients with similar necroinflammatory activity but without histological criteria for rejection (no cholangitis or endotheliitis). Immunosuppression was similar in both groups. Other etiologies of graft dysfunction were excluded by ultrasound, cholangiography, and cultures. High-quality total RNA was extracted from snap frozen liver biopsies, reverse transcribed, labeled with biotin, and fragmented according to established protocol. Twenty-five genes were relatively overexpressed, and 15 were relatively underexpressed by > or = twofold in the ACR when compared with the HCV group. ACR was most notably associated with the relative overexpression of genes associated with major histocompatibility complex I and II, insulin-like growth factor-1 expression, apoptosis induction, and T-cell activation. In HCV-infected liver transplant recipients, ACR is associated with an intragraft gene expression profile that is distinct from that seen during recurrence of HCV. These experiments provide evidence that alloimmunity, as indicated by expression of T-cell activation and apoptosis-inducing genes, is less important in recurrence of HCV than in ACR. Further studies are required to determine whether gene expression profiles, either intragraft or in serum, can be used for the diagnosis and differentiation of ACR from recurrence of HCV.

Genetic polymorphisms influencing therapy and susceptibility to rejection in organ allograft recipients

Solid organ transplantation during the past 30 years has developed from an experimental procedure into routine clinical practice. The current repertoire of immunosuppressive agents has made a major contribution to transplant survival; however, problems in different areas still need to be overcome. Several gene polymorphisms are supposed to influence immunosuppressive therapy and susceptibility to rejection. Therefore, a priority of transplant biologists is to estimate individual patient risk and to characterise the genetic profile of patients in need of a transplant in order to optimise the use of a scarce resource such as organs from cadaver donors, and to avoid serious drug-induced adverse effects. Polymorphisms in genes encoding tumour necrosis factor-alpha (TNFalpha), interleukin (IL)-6, IL-10, interferon-gamma (IFNgamma), transforming growth factor-beta (TGFbeta) and thiopurine S-methyltransferase (TPMT) can have significant effects on an individual's risk of rejection, as well as their ability to tolerate immunosuppressive therapy. Genotyping of known polymorphisms in these genes may in the future contribute to our ability to individualise immunosuppressive therapy in organ transplant recipients.

Repuncturing the renal biopsy: strategies for molecular diagnosis in nephrology

As has been exemplified by recent progress in the classification of cancer, future approaches to enhance the clinical diagnostic power of tissue biopsies may be based on gene expression profiles. A series of strategies to translate these approaches to the diagnosis of renal disease is here proposed. The theoretical and technical problems resulting from the small amount of starting material available from renal biopsies will be specifically addressed. A preliminary study with cDNA array-based expression data obtained from kidneys with tubulointerstitial inflammation and fibrosis suggests the feasibility of distinguishing molecular categories of renal disease. Finally, a combined conventional and molecular work-up of renal biopsies will be suggested. These approaches should add a new dimension to biopsy interpretation and provide novel information concerning renal pathogenesis, diagnosis, prognosis, and differential therapy. A coordinated effort from nephrologists and pathologists in large multicenter trials will be required to achieve this goal. It is hoped that this outlook will lead to stimulating discussions and the implementation of these innovative ideas in nephrology.

Costimulatory blockade prevents early rejection, promotes lymphocyte apoptosis, and inhibits the upregulation of intragraft interleukin-6 in an orthotopic liver transplant model in the rat

Costimulatory pathways have a pivotal role in the T-cell response to alloantigen. The role of costimulatory blockade with anti-CD154 in orthotopic liver transplantation (OLT) has not been examined previously. This study aims to investigate effects of anti-CD154 and CTLA4-immunoglobulin (Ig) in the early post-OLT period using a major histocompatibility complex-disparate fully arterialized OLT model in the rat. Lewis rats underwent OLT with Dark Agouti liver allografts. Recipients were randomized to receive (1) isotype control, (2) anti-CD154, (3) CTLA4-Ig, or (4) cyclosporine A (CyA). Rats were killed day 8, and specimens were obtained for histological examination, terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick end labeling, immunohistochemistry, and quantitative reverse-transcriptase polymerase chain reaction. An additional five transplant recipients were treated with anti-CD154 for 14 days postoperatively to assess long-term allograft survival. All isotype control animals died on or before day 6 of acute rejection. Apart from four deaths caused by nonimmunologic causes, all treated recipients survived to day 8. The median survival of rats treated for 14 days with anti-CD154 was greater than 150 days. Serum aspartate aminotransferase and bilirubin levels normalized by day 3 in the CyA group and day 5 in transplant recipients treated with costimulatory blockade. Histologically, there was no difference between isotype controls and CTLA4-Ig-treated animals, whereas anti-CD154-treated transplant recipients had a lower Banff score. CD4+ and CD8+ T-cell infiltrates were prominent in transplant recipients treated with costimulatory blockade. Intragraft analysis showed an increase in lymphocyte apoptosis, Fas ligand messenger RNA expression, and reduction in interleukin-6 gene expression in transplant recipients treated with costimulatory blockade. Costimulatory blockade did not alter intragraft gene expression of other mediators of T-cell priming, differentiation, and effector function compared with isotype control animals. In conclusion, costimulatory blockade prevented acute rejection, enabled long-term survival, and increased intragraft lymphocyte apoptosis in a high-responding rat OLT model.

The role of cytokine polymorphisms in rejection after solid organ transplantation

The importance of cytokines to the immune response is irrefutable. Their role in the biology of solid organ transplantation per se is also assured. Thus it is likely that subtle differences in cytokine composition, particularly at the initiation of an immune response, may have a major effect on the outcome of that response. This may be particularly relevant in solid organ transplantation, where it is possible that genetic polymorphisms which influence cytokine production may determine the outcome of a transplant. Indeed, it has been suggested that immunosuppression may be individualised on the basis of recipient or donor genotype. However, much of the early data regarding the importance of specific cytokine polymorphisms has not been reproduced, and the significance of this field remains controversial. Nonetheless, with the experience gained from earlier studies, some clear patterns for future studies are emerging.

Gene expression analysis in human renal allograft biopsy samples using high-density oligoarray technology

BACKGROUND

High-density oligoarray technology is a novel method for screening the expression of thousands of genes in a small tissue sample. Oligoarray analysis of genes expressed during human renal allograft rejection has not been reported previously.

METHODS

Seven human renal allograft biopsies with histologic evidence of acute cellular rejection and three renal allograft biopsies without evidence of rejection (control) were analyzed for the expression of 6800 human genes using high-density oligoarrays (GeneChip, Affymetrix, Santa Clara, CA). Quantitative expression of gene transcripts was determined and a comparison analysis between acute rejection and control biopsy samples was performed. Up-regulation of a specific gene transcript during acute rejection was considered to be significant if transcript abundance increased fourfold or more relative to control biopsy samples.

RESULTS

Comparison analysis revealed that between 32 and 219 gene transcripts are up-regulated (>fourfold) during acute rejection. Of these transcripts, only four (human monokine induced by interferon-gamma, T-cell receptor active beta-chain protein, interleukin-2 stimulated phosphoprotein, and RING4 (a transporter involved in antigen presentation)) were consistently up-regulated in each acute rejection sample relative to at least two of three control biopsy samples. Six other genes were up-regulated in six of seven acute rejection samples. These were interferon-stimulated growth factor-3, complement factor 3, nicotinamide N-methyltransferase, macrophage inflammatory protein-3beta, myeloid differentiation protein, and CD18. Only two gene transcripts were down-regulated in five of seven acute rejection samples. Significant up-regulation of cytotoxic T-cell effector molecules, previously reported as markers of acute renal rejection in humans, was not detected.

CONCLUSIONS

High-density oligoarray technology is useful for screening gene expression in transplanted tissues undergoing acute rejection. Because this method does not rely on a priori knowledge of which genes are involved in acute rejection, it is likely to yield novel insights into the mechanisms and diagnosis of rejection.

Immunohistochemical model to predict risk for coronary artery disease and failure in heart transplant patients

Transplant coronary artery disease is the leading cause of long-term morbidity and mortality in cardiac transplantation. We developed a model for early identification of patients who subsequently develop coronary artery disease and graft failure. Serial biopsies obtained from 141 cardiac allografts (5.5 +/- 0.1 biopsies/patient) during the first 3 months post-transplant were evaluated immunohistochemically for deposition of myocardial fibrin, depletion of arteriolar tissue plasminogen activator, presence of arterial/arteriolar endothelial activation markers, and changes in vascular antithrombin. An immunohistochemical risk score was developed with a minimum value of 0 (normal) and a maximum value of 4 (most abnormal). Scores of 0 (low risk), 0.5-3.0 (moderate risk), and 3.5-4.0 (high risk) were analyzed for association with graft failure and development, severity, and progression of coronary artery disease detected using serial coronary angiograms (3.9 +/- 0.2/patient). Allografts with high immunohistochemical risk scores in the first 3months post-transplant developed more coronary artery disease (p<0.001), developed coronary artery disease earlier (p<0.001), developed more severe disease (p<0.001), and showed more disease progression (p<0.001) than allografts with moderate or low scores. Allografts with high immunohistochemical risk scores in the first 3 months post-transplant failed more (p<0.001) and failed earlier (p<0.001) than allografts with moderate or low scores. The present study demonstrates that early changes in the microvasculature are associated with impending coronary artery disease and graft failure in cardiac allograft recipients and suggests that treatment needs to be instituted early after transplantation in order to improve outcome.

Sequential monitoring of peripheral T-lymphocyte cytokine gene expression in the early post renal allograft period

BACKGROUND

Despite numerous studies, the precise role of cytokines in acute renal allograft rejection remains unclear. In this study we have monitored sequential changes in peripheral T cell cytokine gene expression, correlating the changes with clinical events after adult renal transplantation, to provide a deeper insight of the role of cytokines in allograft rejection.

METHODS

Sequential changes in peripheral Th-1 [interleukin- (IL) 2 and interferon-gamma] and Th-2 (IL-4, IL-5, IL-10, and IL-13) cytokine gene expression in 43 patients with (n=15) and without (n=28) episodes of biopsy-proven rejection was monitored in the first 6 weeks after renal transplantation using a sensitive, semi-quantitative reverse-transcriptase polymerase chain reaction ELISA approach.

RESULTS

Th-2 cytokines: IL-5 and IL13 expression increased before and during acute rejection, and decreased after successful antirejection therapy. A significant fall in IL-4 expression after transplantation and subsequent return to its baseline level of expression was observed in both nonrejectors and rejectors. IL-10 showed persistently high expression in nonrejectors, but in rejectors the expression fell during acute rejection, with a subsequent rise after antirejection therapy. Th-1 cytokines: IL-2 and IFN-gamma decreased in expression in the first week posttransplant in the rejectors, at the time of acute rejection (IL-2 only) and immediately after completion of antirejection therapy.

CONCLUSIONS

Sequential monitoring of peripheral T cell cytokine gene expression after renal transplantation detected changes in expression that correlated with episodes of acute rejection and response to antirejection therapy. This approach may be applicable in the clinical laboratory for monitoring posttransplant changes in T cell alloreactivity and immunosuppression.

The clinical relevance of molecular staging for melanoma

The presence of metastatic disease in the regional nodal basin is the most important prognostic indicator for patients with malignant melanoma. The metastatic status of the sentinel lymph node (SLN), defined as the first node in the basin to drain a primary tumor, has been shown to represent that of the entire basin. Since routine histologic examination of lymph nodes often underestimates the presence of micrometastatic disease, a more sensitive assay for detecting tumor cells is needed. We have previously shown that a molecular assay based on the reverse transcriptase polymerase chain reaction (RT-PCR) was able to define a population of patients at higher risk for both recurrence and death, compared with routine H&E histology. Recently, we have compared "molecular staging" of patients by RT-PCR with conventional S-100 immunohistochemistry (IHC) staining of the SLNs. In these studies, SLN specimens were bivaled, and half of each specimen was examined by routine histology, including both H&E and S-100 IHC. The other half of each specimen was analyzed by a nested RT-PCR assay. H&E histology alone detected metastatic disease in 36 of 233 (16%) patients tested. Serial sectioning and IHC detected micrometastatic disease in another 16 patients, thus increasing the proportion of patients with nodal disease to 22%. RT-PCR detected micrometastatic disease in 114 of 181 patients who were negative by conventional methods, further increasing the proportion of patients with evidence of nodal disease to 70% overall. The clinical significance of these findings is still uncertain. The value of additional therapy (including elective lymph node dissection and interferon therapy) for patients who are positive only by the molecular method is currently being investigated by the national multi-center Sunbelt Melanoma Trial.

Fine needle aspiration biopsy and cytology in renal transplantation

Fine needle aspiration biopsy with cytology provides a useful and easily repeated method of obtaining cell samples from a grafted kidney, enabling a more accurate diagnosis of rejection. The technique is simple to perform and is minimally invasive. It is easily repeated, daily if necessary, to evaluate events within the graft and the response to therapy. In addition to the findings of rejection (high total corrected incremental score and activated lymphocytes), both cyclosporin toxicity and acute tubular necrosis can be diagnosed. In the patient with a non-functioning graft with acute tubular necrosis, repeated fine needle aspiration biopsy may reveal early rejection. In rare cases, unusual graft infections have also been diagnosed by means of fine needle aspiration biopsy.

Ischemia-reperfusion injury in renal transplantation is independent of the immunologic background

BACKGROUND

Adhesion molecule expression is important to early transplant failure. However, whether or not adhesion molecule-facilitated inflammation is antigen-dependent is unknown. We tested this hypothesis.

METHODS

Rat renal grafts were four-hours cold-preserved in University of Wisconsin (UW) solution, transplanted to syngeneic or allogeneic recipients, and harvested after 2, 6, 12, 24, and 48 hours and after 1 week. The first allogeneic group receive no immunosuppression; two additional groups received either low (1.5 mg/kg) or standard (5 mg/kg) cyclosporine A (CsA). Renal function and morphology were determined; frozen sections were immunostained for P-selectin, L-selectin, intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), platelet endothelial cell adhesion molecule-1 (PECAM-1), leukocyte function associated molecule-1 (LFA-1), very late antigen-4 (VLA-4), as well as for neutrophils and monocytes.

RESULTS

Selectins increased rapidly at 2 hours and quickly decreased by 12 hours. While P-selectin was expressed on vasculature, L-selectin was found on inflammatory cells. Neutrophil influx and that of LFA-1-positive cells occurred early, peaked between 12 and 24 hours, and paralleled the maximal impairment in renal function. ICAM-1 and PECAM-1 showed similar kinetics and a diffuse distribution. VCAM-1 increased more slowly after 12 hours, peaked at 24 hours, and was localized predominantly on the endothelium of elastic vessels. Between 24 hours and 1 week, all grafts progressively developed dense VLA-4-positive monocytic infiltrates adjacent to vessels expressing VCAM-1. Functional, morphological, and immunohistochemical parameters did not differ between isografts and allografts at one week. However, by day 10, allografts showed severe vascular and cellular rejection, while injury in isografts resolved. Immunosuppression with CsA did not reverse the inflammation induced by ischemia-reperfusion injury.

CONCLUSIONS

The early inflammation after ischemia-reperfusion injury is largely independent of the immunologic background. We suggest that initial injury prevention should receive the highest priority.

Granulomatous tubulointerstitial nephritis in the renal allograft

Granulomatous tubulointerstitial nephritis has rarely been described in renal allografts. Of 1,574 renal allograft tissue specimens obtained from 514 patients in the period 1993 to 1998, we report three cases (0.6%) with interstitial nephritis containing multiple noncaseating granulomas. Biopsy specimen 1 was obtained from a 44-year-old woman with a 6-day history of systemic Candida albicans infection and showed multiple granulomas containing budding yeasts. Biopsy specimen 2 was from a 33-year-old man who presented with miliary spread of Mycobacterium tuberculosis 12 days before the allograft biopsy. Biopsy specimen 3 was from a 23-year-old woman who presented with Escherichia coli urinary infection and bacteremia that was treated with antibiotics for 10 days before the biopsy. Granulomatous inflammation in reponse to infectious agents or drugs in immunosuppressed kidney transplant recipients can rarely give rise to allograft interstitial nephritis that is distinct from acute rejection. To our knowledge, there are no prior reports of granulomatous tubulointerstitial nephritis associated with C albicans and E coli infection or antibiotic therapy in human renal allografts.

Increased accuracy of renal allograft rejection diagnosis using combined perforin, granzyme B, and Fas ligand fine-needle aspiration immunocytology

BACKGROUND

Two major routes by which cytotoxic T lymphocytes induce apoptosis in target cells are the perforin-granzyme and the Fas ligand/Fas pathways. Intragraft expression of message for these immune activation genes has been shown to correlate very closely with clinical rejection. We have immunolabeled fine-needle aspiration biopsy samples using a panel of cytotoxic T-cell activation markers to evaluate the immunocytochemical identification of the protein products of these genes in the verification of human renal allograft rejection.

METHODS

In this retrospective pilot study, 140 fine-needle aspiration biopsy samples from 50 human renal allografts were labeled using alkaline phosphatase/ anti-alkaline phosphatase immunocytochemistry incorporating monoclonal antibodies to perforin, granzyme B, and Fas ligand. Levels of positive labeling for these markers were compared with the original clinical diagnosis of rejection.

RESULTS

An excellent correlation with clinical rejection was obtained when all three antibodies were positive. The false positive rate for each antibody was sufficient to make any one alone or in combination with one other unreliable for diagnosing rejection. When all three antibodies gave positive labeling, agreement with clinical rejection status was superior to using conventional morphological cytology.

CONCLUSIONS

In addition to providing valuable morphological information regarding the composition of inflammatory leukocyte populations and the preservation status of renal parenchymal cells, fine-needle aspiration biopsy samples may be labeled using combined perforin, granzyme B, and Fas ligand immunocytochemistry to offer a safe and reliable method for diagnosing rejection with an excellent level of accuracy.

Prolongation of allograft survival by Nippostrongylus brasiliensis is associated with decreased allospecific cytotoxic T lymphocyte activity and development of T cytotoxic cell type 2 cells

BACKGROUND

We have demonstrated that infection with Nippostrongylus brasiliensis (Nb), which induces strong type 2 responses, prolongs kidney allograft survival in rats. Here, we confirm that this effect is not species-specific and address immune modulation in allospecific T-cell responses mediated by nematode infection.

METHODS

C57BL/6 mice were injected with Nb or phosphate-buffered saline. Four days later, mice were transplanted with BALB/c hearts and graft survival was assessed. In other experiments, Nb-infected mice were immunized with BALB/c spleen cells and allospecific T-cell responses were determined in vitro.

RESULTS

In this study, we show that Nb prolongs cardiac allograft survival in mice. Further, spleen T cells from Nb-infected, allo-immunized mice exhibit reduced allospecific cytotoxic T-lymphocyte activity. In contrast, allospecific proliferation of T cells in the mixed lymphocyte reaction was not reduced by Nb, ruling out immunosuppression as the mechanism of Nb-induced allograft survival. Nb infection induced IL-4 and IL-6 and inhibited IFN-gamma production by T cells in response to allo-antigen. Furthermore, anti-IL-4 treatment reduced allospecific T-cell proliferation from Nb-infected but not control mice, indicating that type 2 allospecific T cells develop in the presence of Nb. We also double-stained T cells for CD8 and IL-4 and showed that Nb induces an 8-fold increase in Tc2 cell numbers.

CONCLUSIONS

These results are consistent with a hypothesis that Nb mediates prolongation of allograft survival through induction of type 2 immunity, including the development of regulatory Tc2 cells, and subsequent inhibition of allospecific cytotoxic T-lymphocyte activity.

Effect of tacrolimus (FK506) and sirolimus (rapamycin) mono- and combination therapy in prolongation of renal allograft survival in the monkey

BACKGROUND

Our previous studies confirmed that tacrolimus (FK506) and sirolimus [rapamycin (RAPA)], in combination, are not antagonistic but are synergistic in the prolongation of heart and small bowel grafts in the rodent. The aim of this study was to confirm further the synergistic effect of combined FK506 and RAPA in the more clinically relevant model, kidney transplantation in monkeys.

METHODS

A total of 60 male Vervet monkeys were randomly assigned to 10 groups (n> or =5). Monkeys with renal allografts were treated with different doses of FK506 and/or RAPA orally for 60 days. Graft survival, body weight, clinical biochemistry determinations, oral glucose tolerance test, trough levels of the two drugs, and histopathology were investigated.

RESULTS

Low doses of FK506 (1 or 4 mg/kg) combined with RAPA (0.5 mg/kg) produced synergistic effect in the prolongation of renal graft survival [combination index (CI) = 0.292, 0.565]. There were no additive or synergistic drug-associated toxicities such as hyperglycemia, nephrotoxicity, and hyperlipidemia. There also was no pharmacological antagonism.

CONCLUSION

Concomitant therapy of low-dose (drug-optimal) FK506 and RAPA produced a synergistic effect in the prolongation of kidney allograft survival in Vervet monkeys without additive drug-associated toxicities.

Improved techniques for kidney transplantation in the monkey

Improved microsurgical techniques for kidney transplantation in the monkey are described. The left graft kidney is transplanted to the lower part of abdomen with end-to-side anastomoses of renal artery to aorta without a patch of aorta, renal vein to inferior vena cava, and end-to-end anastomosis of donor and recipient ureter with 8-0 nylon sutures in a bilateral nephrectomized recipient monkey. We recently performed 60 kidney transplantations in Vervet monkeys. None died of surgery or surgical complications. This reproducible model provides a useful tool to test new immunosuppressants and to investigate the mechanism of drug-induced tolerance and xenotransplantation in primates as a support to clinical trial.

A study of cytokine protein secretion, frequencies of cytokine expressing cells and IFN-G gene polymorphisms in normal individuals

BACKGROUND

Cytokines are major regulators of immune responses, and there is evidence that they play a role in allograft rejection. Before embarking on a detailed study of pretransplant cytokine profiles in renal allograft recipients, we wished to investigate variations in cytokine protein secretion, numbers of cytokine expressing T cells, and cytokine gene polymorphisms in normal volunteers.

METHODS

Twenty normal healthy volunteers were studied. Cytokine protein secretion [interleukin- (IL) 2, IL-4, IL-10, and interferon- (IFN) y] and numbers of cytokine expressing CD3+ T cells (IL-2, IL-4, IL-10, and IFN-gamma) were quantified by means of enzyme-linked immunosorbent assay and two-color flow cytometry respectively. IFN-gamma gene polymorphisms were determined by polymerase chain reaction and autoradio graphy.

RESULTS

Large interindividual variations in both the quantity of IL-2, IL-4, IL-10, and IFN-gamma cytokine protein secreted and numbers of IL-2 and IFN-gamma expressing T cells were demonstrated. However, numbers of IL-4 and IL-10 expressing cells were found to be below detectable limits by flow cytometry. In the case of IFN-gamma, a bi-modal distribution was seen for the quantity of protein secreted. In addition, correlations were observed between IL-2 protein and frequency of IL-2 expressing T cells. However, no relationship was found between IFN-gamma protein levels, numbers of IFN-gamma expressing cells and IFN-gamma gene polymorphisms.

CONCLUSIONS

We have demonstrated large differences in both numbers of T helper 1 cytokine expressing cells and the quantity of T helper 1 and T helper 2 cytokine protein secreted between normal individuals. Although the amount of IL-2 protein secreted appeared to be determined by the frequency of IL-2 expressing cells, this was not the case for IFN-gamma.

Resistance of Rheumatoid Synovial Dendritic Cells to the Immunosuppressive Effects of IL-10

IL-10 down-regulates the APC function of many dendritic cells (DC), including human peripheral blood (PB) DC. In rheumatoid arthritis (RA), synovial fluid (SF) DC express markers of differentiation and are effective APC despite abundant synovial IL-10. The regulation of DC responsiveness to IL-10 was therefore examined by comparing the effect of IL-10 on normal PB and RA SF DC. Whereas IL-10 down-modulated APC function and MHC class II and B7 expression of PB DC, IL-10 had no such effect on SF DC. Since SF DC have differentiated in vivo in the presence of proinflammatory cytokines, PB DC were cocultured in the presence of IL-10 and either GM-CSF, IL-1β, TNF-α, IL-6, or TGF-β. GM-CSF, IL-1β, and TNF-α were all able to restore APC function. Whereas the effects of IL-10 on PB DC were shown to be mediated by IL-10R1, neither PB nor RA SF DC constitutively expressed IL-10R1 mRNA or detectable surface protein. In contrast, IL-10R1 protein was demonstrated in PB and SF DC whole cell lysates, suggestive of predominant intracellular localization of the receptor. Thus, DC responsiveness to IL-10 may be regulated through modulation of cell surface IL-10R1 expression or signaling.

CD8+ T cells produce RANTES during acute rejection of murine allogeneic skin grafts

BACKGROUND

Based on their chemoattractant properties, it is likely that chemokines play a role in recruiting alloantigen-primed T cells to allografts and in amplifying inflammation within the graft. The graft-infiltrating leukocytes producing specific chemokines remain largely unknown.

METHODS

We tested the intragraft RNA expression of the chemokine RANTES (regulated on activation normal T expressed and secreted) and granzyme B during rejection of full thickness, allogeneic skin grafts by C57BL/6 mice. Grafts with different immunogenetic disparities were chosen to test expression when rejection was mediated by CD4+, CD8+, or both CD4+ and CD8+ T cells. RNA expression was also tested in purified CD4+ and CD8+ T cell populations from skin graft recipients. Immunohistology was performed on graft sections to test colocalization of RANTES protein and graft-infiltrating CD4+ and CD8+ T cells.

RESULTS

Intra-allograft RANTES RNA expression was not observed during CD4+ T cell-mediated rejection. Expression of RANTES and granzyme B RNA was observed at low levels in purified populations of CD8+, but not CD4+, T cells from the spleen and lymph nodes of graft recipients beginning at day 7 after transplantation and increased thereafter. Intra-allograft RANTES protein was associated with a small number of graft-infiltrating CD8+ T cells but was also associated with endothelial cells and with many graft-infiltrating CD4+ T cells.

CONCLUSIONS

CD8+ T cells produce RANTES during allogeneic skin graft rejection. In the allograft, the chemokine also colocalizes with CD4+ T cells that do not produce RANTES.

Evidence for Immune Regulation in the Induction of Transplantation Tolerance: A Conditional but Limited Role for IL-4

Most experimental models of allograft tolerance depend on manipulation of immune responses at the time of transplant. In such systems, the graft itself probably plays an important role in the induction of unresponsiveness but as a consequence may suffer immune mediated damage. Ideally, recipients would be made specifically unresponsive before transplant such that the graft is protected from the outset. In this report, we demonstrate that CBA mice pretreated with donor-specific transfusion plus anti-CD4 Ab 28 days before transplant accept cardiac allografts indefinitely without further intervention. Adoptive transfer of spleen cells from mice with long term surviving grafts results in donor-specific graft acceptance in naive secondary recipients, indicating that tolerance in this system involves immuneregulation. Regulation develops as a result of the pretreatment protocol alone, since transfer of cells from pretreated but untransplanted mice to naive recipients also leads to prolonged allograft survival without additional therapy. Neutralizing IL-4 at the time of tolerance induction had no effect on graft outcome in primary recipients. However, removal of IL-4 from the adoptive transfer donors at the time of tolerance induction prevented long term engraftment in the majority of secondary recipients. Our data demonstrate that pretreatment of transplant recipients can establish immune regulation powerful enough to override the responses of an intact immune repertoire and that under stringent conditions at least, development of this regulatory population may in part be dependent on IL-4.

Intragraft cytokine expression in tolerant rat renal allografts with rapamycin and cyclosporin immunosuppression

The Th-1/Th-2 paradigm proposes clonal expansion of Th-2 lymphocytes as the basis of tolerance towards allografts. Intragraft cytokine expression was evaluated in a highly stringent model of renal transplantation. ACI and Lewis rats were used as donors and recipients, respectively, for heterotopic renal transplantation. Group A (n = 8) received a single dose of rapamycin and cyclosporin 12 h prior to engraftment, followed by 7 d of cyclosporin post-operatively. Isografts (Group B, n = 5) and control allografts (Group C, n = 4) received no immunosuppression. Sacrifice was performed after 120 d. Intragraft expression of IL-10, IL-4, and IFN-gamma was determined using qualitative reverse transcriptase-polymerase chain reaction (RT-PCR). All groups had functionally normal grafts at sacrifice, with 50% histological tolerance among Group A animals. No isografts showed evidence of cellular infiltrate, and all control allografts showed severe rejection. IL-10 was only detected in the tolerant animals (p < 0.001). Similarly, IL-4 was detected predominantly in the tolerant allografts (p < 0.05). IFN-gamma was only isolated in rejected allografts, whether treated or untreated (p < 0.001). We conclude that the expansion of Th-2 cells is associated with tolerance, while the expansion of Th-1 cell is associated with acute cellular rejection.

Intragraft cytokine expression and tolerance induction in rat renal allografts

BACKGROUND

Intragraft cytokine expression was evaluated in a model of renal transplantation. ACI and Lewis rats were used as donors and recipients, respectively, for heterotopic renal transplantation.

METHODS

Treated allograft rats (n=10) received a preoperative dose of rapamycin and cyclosporine, followed by 7 days of cyclosporine postoperatively. Isograft rats (n=5) and control allograft rats (n=4) received no immunosuppression. Sacrifice was performed after 120 days. Expression of interleukin (IL)-4, IL-10, and interferon-gamma (IFN-gamma) transcripts was determined with semiquantitative reverse transcriptase-polymerase chain reaction.

RESULTS

All treated allograft rats had normal function with 50% histologic rejection. All isografts had normal function. IL-4 and IL-10 were in greater density in allografts with normal histology, whereas IFN-gamma was only seen in allografts with cellular rejection. No IL-10 was seen in isografts, but IL-4 was detected in 3/5 isografts.

CONCLUSIONS

We conclude that the lymphocyte population's elaboration of IL-4 and IL-10 is associated with tolerance, whereas the production of IFN-gamma and absence of IL-4 is associated with histology suggestive of acute cellular rejection.