Can Gene Expression Analysis in Zero-Time Biopsies Predict Kidney Transplant Rejection?

Zero-time biopsies are taken to determine the quality of the donor organ at the time of transplantation. Histological analyses alone have so far not been able to identify parameters that allow the prediction of subsequent rejection episodes or graft survival. This study investigated whether gene expression analyses of zero-time biopsies might support this prediction. Using a well-characterized cohort of 26 zero-time biopsies from renal transplant patients that include 4 living donor (LD) and 22 deceased donor (DD) biopsies that later developed no rejection (Ctrl, n = 7), delayed graft function (DGF, n = 4), cellular (T-cell mediated rejection; TCMR, n = 8), or antibody-mediated rejection (ABMR, n = 7), we analyzed gene expression profiles for different types of subsequent renal transplant complication. To this end, RNA was isolated from formalin-fixed, paraffin-embedded (FFPE) sections and gene expression profiles were quantified. Results were correlated with transplant data and B-cell, and plasma cell infiltration was assessed by immunofluorescence microscopy. Both principal component analysis and clustering analysis of gene expression data revealed marked separation between LDs and DDs. Differential expression analysis identified 185 significant differentially expressed genes (adjusted p < 0.05). The expression of 68% of these genes significantly correlated with cold ischemia time (CIT). Furthermore, immunoglobulins were differentially expressed in zero-time biopsies from transplants later developing rejection (TCMR + ABMR) compared to non-rejected (Ctrl + DGF) transplants. In addition, immunoglobulin expression did not correlate with CIT but was increased in transplants with previous acute renal failure (ARF). In conclusion, gene expression profiles in zero-time biopsies derived from LDs are markedly different from those of DDs. Pre-transplant ARF increased immunoglobulin expression, which might be involved in triggering later rejection events. However, these findings must be confirmed in larger cohorts and the role of early immunoglobulin upregulation in zero-biopsies needs further clarification.

Association of high HLA-E expression during acute cellular rejection and numbers of HLA class I leader peptide mismatches with reduced renal allograft survival

Non-classical Human Leukocyte Antigen (HLA)-E preferentially presents leader peptides derived from classical HLA-class I molecules. HLA-E can trigger opposed immune responses by interacting with inhibitory NKG2A or by activating NKG2C receptors on NK and T-cells. We studied the impact of HLA-E on renal allograft survival during acute cellular rejection. HLA-E expression was up-regulated in acute cellular rejection (ACR) biopsies (n=12) compared to biopsies from 13 renal allografts with no rejection-signs. HLA-E up-regulation was correlated with numbers of HLA-class I leader peptide mismatches (p=0.04). CD8+ and CD56+ infiltrating cells correlated with HLA-E expression (p<0.0001 and p=0.0009, respectively). Activating NKG2C receptor dominated on effector cells in biopsies and peripheral blood during ACR potentially allowing HLA-E-mediated immune activation. Moreover, HLA-E expression correlated with deterioration in renal allograft function (p<0.008) and reduced allograft survival (p=0.002). Our findings provide evidence that during renal allograft rejection HLA-E along with high numbers of mismatched HLA-class I leader peptides might represent additional targets for immune-activating responses.

Molecular landscape of T cell-mediated rejection in human kidney transplants: prominence of CTLA4 and PD ligands

We used expression microarrays to characterize the changes most specific for pure T cell-mediated rejection (TCMR) compared to other diseases including antibody-mediated rejection in 703 human kidney transplant biopsies, using a Discovery Set-Validation Set approach. The expression of thousands of transcripts--fold change and association strength--changed in a pattern that was highly conserved between the Discovery and Validation sets, reflecting a hierarchy of T cell signaling, costimulation, antigen-presenting cell (APC) activation and interferon-gamma (IFNG) expression and effects, with weaker associations for inflammasome activation, innate immunity, cytotoxic molecules and parenchymal injury. In cell lines, the transcripts most specific for TCMR were expressed most strongly in effector T cells (e.g. CTLA4, CD28, IFNG), macrophages (e.g. PDL1, CD86, SLAMF8, ADAMDEC1), B cells (e.g. CD72, BTLA) and IFNG-treated macrophages (e.g. ANKRD22, AIM2). In pathway analysis, the top pathways included T cell receptor signaling and CTLA4 costimulation. These results suggest a model in which TCMR creates an inflammatory compartment with a rigorous hierarchy dominated by the proximal aspects of cognate engagement of effector T cell receptor and costimulator triggering by APCs. The prominence of inhibitors like CTLA4 and PDL1 raises the possibility of active negative controls within the rejecting tissue.

Gene expression profiling in acute allograft rejection: challenging the immunologic constant of rejection hypothesis

In humans, the role and relationship between molecular pathways that lead to tissue destruction during acute allograft rejection are not fully understood. Based on studies conducted in humans, we recently hypothesized that different immune-mediated tissue destruction processes (i.e. cancer, infection, autoimmunity) share common convergent final mechanisms. We called this phenomenon the "Immunologic Constant of Rejection (ICR)." The elements of the ICR include molecular pathways that are consistently described through different immune-mediated tissue destruction processes and demonstrate the activation of interferon-stimulated genes (ISGs), the recruitment of cytotoxic immune cells (primarily through CXCR3/CCR5 ligand pathways), and the activation of immune effector function genes (IEF genes; granzymes A/B, perforin, etc.). Here, we challenge the ICR hypothesis by using a meta-analytical approach and systematically reviewing microarray studies evaluating gene expression on tissue biopsies during acute allograft rejection. We found the pillars of the ICR consistently present among the studies reviewed, despite implicit heterogeneity. Additionally, we provide a descriptive mechanistic overview of acute allograft rejection by describing those molecular pathways most frequently encountered and thereby thought to be most significant. The biological role of the following molecular pathways is described: IFN-γ, CXCR3/CCR5 ligand, IEF genes, TNF-α, IL-10, IRF-1/STAT-1, and complement pathways. The role of NK cell, B cell and T-regulatory cell signatures are also addressed.

Renal tubular PD-L1 (CD274) suppresses alloreactive human T-cell responses

Renal proximal tubular epithelial cells, a target of infiltrating T cells during renal allograft rejection, may be protected from this injury by the cell surface protein CD274 (also termed PD-L1 for programmed death ligand 1). The co-inhibitory molecules PD-L1 (CD274) and PD-L2 (CD273) are ligands of PD-1 (programmed death 1; CD279). Here we determine the functional role of PD-1/PD-L pathways in human renal allograft rejection. Treatment of human primary tubular epithelial cells with interferon-beta and -gamma caused a dose-dependent and synergistic increase of PD-L1 and PD-L2 expression. Blockade of surface PD-L1, but not PD-L2, on interferon-treated tubular epithelial cells resulted in a significant increase in CD4+ T-cell proliferation and cytokine production by CD4+ and CD8+ T cells. The expression of PD-L1, PD-L2, and PD-1 mRNA and protein was upregulated in biopsies of patients with renal allograft rejection compared to the respective levels found in the pre-transplant biopsies. Induction of PD-L1 was significantly associated with acute vascular rejection. Our study suggests that the renal epithelial PD-1/PD-L1 pathway exerts an inhibitory effect of on alloreactive T-cell responses. The upregulation of PD-L1 on proximal tubular epithelial cells in patients with acute allograft rejection may reduce T-cell-mediated injury.

The early course of kidney allograft rejection: defining the time when rejection begins

We studied the early events in mouse kidney allografts and isografts to define when allorecognition begins and when alloimmune tissue injury begins. Allografts but not isografts showed T-cell infiltration in perivascular areas from day 1, but tubulitis and arteritis did not develop until day 7. Flow cytometry confirmed the early allospecific CD3(+)CD8(+) T-cell infiltrate. At day 1, both allografts and isografts showed extensive transcriptome changes, reflecting the response to surgery, but only allografts showed expression of interferon-gamma (IFN-gamma)-inducible transcripts and T-cell-associated transcripts. Although the number of CD68(+) myeloid cell numbers did not increase in day 1 isografts or allografts, mRNA expression for myeloid markers was increased in isografts and allografts, suggesting activation of resident cells of the macrophage-dendritic cell series (MMDCs) in response to injury, followed by increased CD68(+) cell numbers from day 2. By day 3, an interstitial T-cell and MMDC infiltrate was established in allografts, corresponding with the emergence of allospecific tissue injury, as reflected by decreased parenchymal transcripts. Thus, in renal allografts, allorecognition by T cells occurs in perivascular sites by day 1, but alloimmune parenchymal damage begins at day 3, coinciding with the emergence of the interstitial T-cell-MMDC infiltrate.

The transcriptome of human cytotoxic T cells: measuring the burden of CTL-associated transcripts in human kidney transplants

Having defined CTL-associated transcripts (CATs) in CTL in vitro, we used microarrays to quantify the burden of CAT sets compared with individual transcripts in human renal transplant biopsies with T-cell mediated rejection (TCMR). CAT sets in TCMR resembled diluted CTL RNA, maintaining overall hierarchy of expression relative to CTL in vitro. NK selective sets were not detected in TCMR, indicating the CATs mainly reflect T cells. We selected 25 highly expressed CATs that diluted quantitatively in kidney RNA (QCATs) and remained detectable after 32-fold dilution. QCAT burden in 14 kidneys with TCMR was 3 to 15% of CTL RNA, correlating with infiltration. One biopsy diagnosed as TCMR only by endothelialitis had little interstitial infiltrate and lowest CAT burden. CAT sets were more consistent than individual CATs such as perforin or granzyme B, which showed heterogeneity. In luster and principal component analysis, QCATs grouped biopsies with TCMR together, in close relationship to in vitro CTL. Thus QCAT sets robustly measure the burden of CTL and effector memory T cells in biopsies as %CTL RNA, in a manner not achieved by measurement of individual transcripts.

The transcriptome of human cytotoxic T cells: similarities and disparities among allostimulated CD4(+) CTL, CD8(+) CTL and NK cells

Transcripts expressed in cytotoxic T lymphocytes (CTL) have mechanistic and diagnostic importance in transplantation. We used microarrays to select CTL-associated transcripts (CATs) expressed in human CD4(+) CTL, CD8(+) CTL and NK cells, excluding transcripts expressed in B cells, monocytes and kidney. This generated three transcript sets: CD4(+)-associated, CD8(+)-associated and NK-associated. Surprisingly, many CATs were expressed in effector memory cells e.g. granzyme B/GZMB, interferon-gamma/IFNG. Transcript expression was very similar between CD4(+) and CD8(+) CTL. There were no transcripts highly selective for CD4(+) CTL or CD8(+) CTL: for example, cytotoxic molecule transcripts (perforin, granzymes, granulysin) were shared between CD8(+) CTL and CD4(+) CTL although expression remained higher in CD8(+) CTL. Transcripts that differentiated between CD8(+) CTL and CD4(+) CTL were primarily those shared between CD8(+) CTL and NK cells (e.g. NK receptors KLRC1, KLRC3, KLRD1, KLRK1). No transcripts could differentiate CD4(+) CTL from CD8(+) CTL but NK cell-associated transcripts could differentiate NK cells from CTL. This study serves as a foundation for the interpretation of CATs in rejecting allografts and highlights the extensive sharing of CATs among CD4(+) CTL, CD8(+) CTL and effector memory T cells.

IFN-gamma prevents early perforin-granzyme-mediated destruction of kidney allografts by inducing donor class I products in the kidney

Interferon-gamma (Ifng) protects organ allografts: mouse kidney allografts lacking Ifng receptors rapidly fail with massive ischemic necrosis around days 5 to 7, reflecting microcirculation failure. We hypothesized that Ifng protects the graft by preventing perforin-granzyme-mediated cytotoxic damage to the microcirculation by inducing class Ia and/or Ib products. We transplanted kidney allografts lacking Ifng receptors into various knockout hosts. The necrosis/congestion phenotype did not require host B cells or IL-4 and IL-13 receptors, but required the T-cell alloresponse: it did not occur if the hosts were syngeneic or T-cell deficient. However, host perforin-granzyme mechanisms were required: no necrosis developed if hosts lacked either perforin or granzymes A and B. The ability of Ifng to protect the allograft required donor class I products: allografts lacking class I products due to Tap1 or beta2 microglobulin deficiency developed a similar necrosis-congestion phenotype at day 7 despite Ifng receptors being present. Thus when host cytotoxic T cells infiltrate organ allografts, Ifng prevents their perforin-granzyme mechanism from compromising the microcirculation by a mechanism requiring donor class Ia or Ib products. We propose that donor class Ia or Ib products are needed to trigger inhibitory receptors on effector T cells.

Plasma Cell-Rich Rejection Processes in Renal Transplantation: Morphology and Prognostic Relevance

BACKGROUND

Renal transplantation is the most effective therapy in end-stage renal disease. The prognosis of transplant survival is still determined by rejection. Morphologically, this involves interstitial rejection with potential development of vascular rejection (VR) and/or glomerular rejection processes, designated as transplant glomerulopathy (TGP). The cellular infiltrates are usually dominated by lymphocytes and macrophages in differing quantity, characterizing the severity of the rejection processes.

METHODS

In 14% of the renal transplant biopsies and explants in our investigation (n = 399) plasma cells (PR) predominate in the cellular infiltrate. To determine whether the enrichment of PR has an impact on graft function or could even constitute an independent parameter for transplant survival, we analyzed 109 cases of transplanted patients matched for AR and CR and divided them into those rich and those nonrich in PR.

RESULTS

In the group rich in PR, PR comprised 30% of all infiltrates in comparison to 5% in the group non-rich in PR. VR and TGP appeared significantly more often in PR-rich rejections (P = 0.0044). The group rich in PR had a significantly more adverse prognosis (P = 0.0024), especially if PR enrichment was observed in the chronic rejection processes (P = 0.0148). In the Cox proportional hazard model the occurrence of VR was the only independent factor.

CONCLUSION

In itself, plasma-cell enrichment is not a prognostic marker, but it is an indicator of a more adverse outcome because it is often accompanied by the appearance or subsequent development of VR +/- TGP. The detection of PR-rich rejection processes should therefore encourage the clinician to intensify the immunosuppressive schedule.

FK506 suppresses E-selectin, ICAM-1 and VCAM-1 expression on vascular endothelial cells by inhibiting tumor necrosis factor alpha secretion from peripheral blood mononuclear cells

FK506 suppresses activation of T cells; however, it down-regulates E-selectin, ICAM-1 and VCAM-1 expression in inflamed tissues. In this study, we investigated the effect of FK506 on expression of those adhesion molecules on human vascular endothelial cells (HMVEC). Culture supernatant from peripheral blood mononuclear cells (PBMC) stimulated with anti-CD3 plus anti-CD2 antibodies effectively induced the expression of E-selectin, ICAM-1 and VCAM-1 on HMVEC, and treatment with FK506 down-regulated their expression. Culture supernatant contained tumor necrosis factor (TNF) alpha and interleukin (IL)-1beta, which effectively induced adhesion molecules, and FK506 suppressed both cytokine secretions. TNFalpha content in culture supernatant was parallel to the induction of adhesion molecules by the culture supernatant. IL-1beta content was not enough to induce those adhesion molecules. Anti-TNFalpha antibody completely inhibited those expressions. FK506 did not inhibit either TNFalpha- or IL-1beta-induced expression of adhesion molecules, or viability of HMVEC. These results indicate that FK506 suppresses migration of inflammatory cells through the inhibition of TNFalpha secretion from leukocytes.

Prevalence and immunohistochemical findings of subclinical kidney allograft rejection and its association with graft outcome

Subclinical acute rejection (SAR) occurs in about 30% of stable renal transplant patients and may be a risk factor for a poor allograft outcome. In the present study, the prevalence and clinical features of subclinical rejection, and the expression of immune activation markers in surveillance graft biopsies were assessed and correlated with late graft outcomes. Protocol biopsies were obtained at 2 and 12 months post-transplant in 32 and 26 patients, respectively, with stable renal function. The Banff 1997 criteria were used for histological diagnosis. Graft function and survival and proteinuria were assessed during the 36 months of follow-up. Immunohistochemical evaluation of cell subpopulations and immunoactivation markers were performed on protocol biopsies. The prevalence of SAR at 2 months and of chronic allograft nephropathy (CAN) at 12 months in representative biopsies was 55 and 50%, respectively. Patients with SAR presented mononuclear cell infiltration with an increased expression of CD3, CD4, CD68, IL-2R and granzyme B. Kidney graft function was significantly worse in patients with SAR at 2 months who had chronic rejection on biopsy at 12 months, but SAR was not associated with a worse graft function, greater proteinuria or a lower graft survival in 3 yr of follow-up. In conclusion, we found an elevated prevalence of SAR at 2 months after transplantation with an increased expression of activation markers. Although an association of SAR with poor graft outcome was not observed, our results suggest that SAR is an immunologically active process and underscore the importance of protocol biopsies in the surveillance of transplanted kidneys.

Is “zero-hour” biopsy of the transplanted kidney risky?

"Zero-hour" renal allograft biopsy provides valuable diagnostic information for comparison to subsequent kidney material. However, the invasive nature of the biopsy procedure tends to limit its widespread use in many centers. We undertook this retrospective study to examine the rate and clinical importance of complications in our series of patients routinely undergoing zero-hour biopsies performed between 1994 and 2001. Two hundred thirty-six zero-hour biopsies included only one sample performed with a 14G needle from lower posterior part of kidney by using a manual tru-cut technique. Doppler ultrasonography was performed after first 5 days. An average of 34 +/- 19 glomeruli were obtained in the biopsies. The biopsy specimens were adequate for diagnosis in 77% of the procedures. Ten (4%) patients experienced complications of intraparenchymal arteriovenous fistula (n = 4), which regressed spontaneously; perirenal hematoma (n = 4); intraparenchymal hematoma (n = 2); and a minimal perirenal collection (n = 41). We conclude that zero-hour biopsy is a safe diagnostic method. The rate of complications is low, as well as generally mild and self-limiting.

Preexisting crescentic glomerulonephritis in the renal allograft

Two patients who received cadaveric renal transplants from the same donor were found to have similar diffuse proliferative glomerular lesions on renal biopsies performed for delayed graft function. The donor had no known disease, but had subtle abnormalities on preprocurement urinalysis. In retrospect, lupus nephritis is suspected in the donor. The authors detail the course of these 2 patients, review the literature on preexisting glomerular lesions, and address issues with regard to donor selection.

Pre-transplant Th1 and post-transplant Th2 cytokine patterns are associated with early acute rejection in renal transplant recipients

In this retrospective study, we tried to define pre- and post-transplant immunological parameters that identify patients at risk for early acute rejection. Lymphocyte subpopulations and plasma levels of cytokines and neopterin were determined pre- and post-transplant in 32 renal transplant recipients with biopsy-proven early acute graft rejection. Recipients without early acute rejection served as controls. High pre-transplant interferon-gamma (IFN-gamma) plasma levels (p = 0.006), consistently high levels of neopterin early post-transplant (p = 0.008), a post-transplant switch from a Th1 to a Th2 cytokine pattern with decreasing IFN-gamma (p = 0.02), low CD8+ lymphocyte counts (p = 0.006) and consistently high CD19+ B lymphocyte counts were associated with acute rejection. Our data suggest that patients with a pre-transplant Th1 and an early post-transplant Th2 cytokine pattern are pre-disposed for early acute rejection.

Long-term culture of islets abrogates cytokine-induced or lymphocyte-induced increase of antigen expression on beta cells

BACKGROUND

Immunogenicity of a graft depends on its expression of major histocompatability complex (MHC) antigens and adhesion molecules and on the amount of intragraft leukocytes, the so-called passenger leukocytes. Although long-term culture reduces passenger leukocytes, permanent acceptance is not necessarily observed after allogeneic transplantation. Because little is known about antigen expression on the surface of islet cells after long-term culture of islets, we investigated whether antigen expression of pancreatic beta cells is influenced by long-term culture and whether long-term culture can counteract the increase of antigen expression induced by cytokines or by allogeneic lymphocytes. We also investigated whether long-term cultured islets were able to stimulate allogeneic lymphocytes to produce cytokines.

METHODS

Isolated LEW.1A (RT1a) rat islets of Langerhans were cultured for 14 and 28 days. Precultured and freshly-isolated islets were then incubated for 2 days with rat recombinant interferon (rIFN)-gamma (1,000 IU/mL), or were co-cultured for 4 days with LEW.1W (RT1u) splenic lymphocytes.

RESULTS

Long-term culture significantly reduced CD45 leukocytes within the islets and decreased the amount of beta cells expressing intercellular adhesion molecule (ICAM)-1, whereas MHC antigen expression remained unchanged. After incubation of freshly isolated islets with IFN-gamma induction of MHC class II antigens on beta cells, an increase of MHC class I antigen density and an enhancement of ICAM-1+ beta cells were observed. Similar results were found after co-culturing with allogeneic lymphocytes. Using precultured islets, the induction of MHC class II on beta cells by IFN-gamma was still present but significantly lower and was absent after co-culture with allogeneic lymphocytes. Enhancement of ICAM-1+ beta cells by IFN-gamma or by allogeneic lymphocytes was markedly lowered because of preculturing. The proportion of MHC class I beta cells remained unchanged; however, antigen density of long-term cultured islets (28 days) could not be enhanced by allogeneic lymphocytes. Precultured islets were not able to stimulate allogeneic lymphocytes to produce and release normal amounts of cytokines (IFN-gamma or interleukin [IL]-2).

CONCLUSIONS

In conclusion, in addition to reduction-depletion of passenger leukocytes, long-term culturing of islets also is able to counteract the IFN-gamma-induced or allogeneic lymphocyte-induced increase of antigen expression. Therefore, initiation of rejection and generation of cytotoxic cells might be altered or timely delayed when long-term cultured islets are transplanted. The variable and conflicting in vivo results after transplantation of long-term cultured islets might be explained by the possible indirect antigen presentation, which is not influenced by islet preculture.

Fractalkine expression on human renal tubular epithelial cells: potential role in mononuclear cell adhesion

Fractalkine (CX3CL1) is a transmembrane molecule with a CX3C chemokine domain attached to an extracellular mucin stalk which can induce both adhesion and migration of leucocytes. Mononuclear cell infiltration at renal tubular sites and associated tubular epithelial cell damage are key events during acute renal inflammation following renal allograft transplantation. Using northern and Western blot analysis, we have demonstrated the expression of fractalkine message and protein by renal tubular epithelial cells in vitro. The expression was up-regulated by TNF-alpha, a key proinflammatory cytokine in acute rejection. Investigation of surface expression of fractalkine on cultured proximal tubular epithelial cells revealed only a subpopulation of positively staining cells. Immunohistochemistry revealed that only a proportion of tubules in renal allograft biopsies showed induction of fractalkine expression. Studies using a static model of adhesion demonstrated CX3CR1/fractalkine interactions accounted for 26% of monocytic THP-1 cell and 17% of peripheral blood natural killer cell adhesion to tubular epithelial cells, suggesting that fractalkine may have a functional role in leucocyte adhesion and retention, at selected tubular sites in acute renal inflammation. Thus, fractalkine blockade strategies could reduce mononuclear cell mediated tubular damage and improve graft survival following kidney transplantation.

Cyclosporine microemulsion- and mycophenolate mofetil-related lymphoid aggregates are not associated with acute rejection

BACKGROUND

Microemulsion cyclosporine, mycophenolate mofetil, and prednisone have become a common immunosuppressive protocol in renal transplantation. We identified lymphocytic infiltrates in transplant fine-needle aspirates and core biopsies from patients on this regimen without acute rejection clinically or by standardized morphological criteria and investigated this inflammatory response.

METHODS

Twenty-eight aspirates from 21 patients were included and assessed in the standard fashion. Nine core biopsies showing interstitial lymphocytic infiltration were evaluated with antibodies against CD3, CD4, CD8, CD20, CD30, CD56, KP1, and epithelial membrane antigen (EMA). Aspirates and biopsies were assessed for tubular cell major histocompatibility complex (MHC) class II antigen and for gamma-interferon (gamma-IFN), interleukin-4 (IL-4), and IL-10 mRNAs by reverse transcription-polymerase chain reaction.

RESULTS

Fifteen aspirates showed immune activation solely due to mature lymphocytes and monocytes; 13 had no immune activation. All aspirates were negative for MHC class II antigens. Of 6 activated aspirates assessed for gamma-IFN mRNA, 5 were negative. All 21 patients had similar clinical characteristics and recovered renal function without rejection treatment. The core biopsies had lymphocytes in 5-30% of the interstitium. The cells were 70-85% CD3+, with 50-85% CD4+, 3-10% KP1+, and rare cells CD56+. No T-cell activation was present (EMA- and CD30-). Seven biopsies were assessed and were negative for gamma-IFN mRNA; only one biopsy had weakly positive MHC class II staining. Two activated aspirates were negative for IL-4 and IL-10 mRNA, while three biopsies each contained IL-4 and IL-10 mRNAs.

CONCLUSIONS

Inactive interstitial lymphoid infiltrates are frequent in patients on this drug regimen and should not be interpreted as acute rejection, particularly in aspirate samples. These lymphocytes may play a role in long-term allograft acceptance.

The contribution of adhesion molecule expression in donor kidney biopsies to early allograft dysfunction

BACKGROUND

Renal allograft rejection is associated with the expression of adhesion molecules on vascular endothelial and tubular epithelial cells.

METHODS

To assess whether the number of cell adhesion molecules expressed in donor kidneys can predict early rejection or delayed graft function, kidney biopsies from 20 living and 53 cadaveric kidney donors were obtained before engraftment into the recipients and the expression of the cell adhesion molecules intercellular adhesion molecule 1 (ICAM-1), vascular cell adhesion molecule 1 (VCAM-1), and endothelial leukocyte adhesion molecule (E-selectin) were determined by immunohistochemistry.

RESULTS

All biopsies from living donors showed significantly lower expression of ICAM-1 and VCAM-1 compared to biopsies from cadaveric donors. There was no difference in the expression of adhesion molecules on tubular cells between transplants with primary function compared to allografts with early rejection in living donated kidneys (ICAM-1: 2+/-8 vs. 3+/-8%; VCAM-1: 9+/-7 vs. 1+/-1%), as well as in cadaveric kidneys (ICAM-1: 38+/-29 vs. 39+/-38%; VCAM-1: 55+/-27 vs. 48+/-29%). The expression of ICAM-1 molecules on tubular cells was determined to be a predictor for the occurrence of delayed graft function in cadaveric kidneys (ICAM-1: 65+/-24* vs. 38+/-29% delayed graft versus primary graft function). No delayed graft function occurred in recipients of living donated kidneys.

CONCLUSIONS

These data suggest that adhesion molecule expression in donor biopsies is not a predictor for early allograft rejection, but can be used as a marker for the development of postischemic acute renal allograft failure.

Recognition of islet-directed peripheral blood lymphocytes in vitro before rejection of allogeneic grafted islets

A co-culture of splenic lymphocytes with allogeneic pancreatic islets [i.e., mixed lymphocyte islet co-culture (MLIC)] for 96 hr leads to reduction of beta-cells and to an allospecific induction of major histocompatibility complex (MHC) class II antigens on beta-cells. The intent of our investigation was to determine whether peripheral blood lymphocytes (PBL) obtained from allogeneic islet-grafted BB/OK rats (=sensitization in vivo) cause similar alterations to donor-specific islet cells. PBL prepared before transplantation, before (at day 7) and after islet rejection were co-cultured for 24 hr with donor-specific islets. PBL obtained at any time before and after transplantation caused reduction of beta-cells and enhancement of intercellular adhesion molecule-1(+)/beta-cells. Induction of MHC class II+ beta-cells was most pronounced with PBL obtained before rejection. Down-regulation of major histocompatibility complex class I+ beta-cells was caused by PBL that had been obtained from grafted animals only; it was most pronounced before islet rejection and has never been observed with lymphocytes from nongrafted normoglycemic rats. The 24-hr MLIC is capable of recognizing functionally active, donor-specific lymphocytes and is able to distinguish between the effects of sensitized and nonsensitized lymphocytes.

Suppression of hepatic lesions in a murine graft-versus-host reaction by antibodies against adhesion molecules

BACKGROUND/AIMS

The injection of parental CD4+ T cells into major histocompatibility complex (MHC) class II disparate F1 hybrid mice induced an autoimmune graft-versus-host reaction (GVHR) which is analogous to autoimmune liver diseases. The interaction of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) and very late antigen-4 (VLA-4) has been known to be profoundly involved in the trafficking of lymphocytes into the inflammatory tissues. The aim of this study was to clarify the role of VLA4 or VCAM-1 in the development of GVHR-induced hepatic lesions in our model.

METHODS

B6 T spleen cells were injected into (B6.C-H-2bm12xB6) F1 mice intravenously. Anti-VLA-4 mAbs and/or anti-VCAM-1 mAbs were injected intraperitoneally at a dose of 2.5 mg/kg of each mAbs per body weight of mouse. We examined the changes in GVHR-induced hepatic lesions, serum levels of antimitochondrial antibodies (AMA) and cytokine mRNA expressions of liver-infiltrating lymphocytes using H.E. and immunohistochemical staining, enzyme-linked immunosorbent assay (ELISA), and reverse transcription-polymerase chain reaction (RT-PCR), respectively.

RESULTS

Hepatic lesions of anti-VLA-4 mAbs-treated mice were inhibited compared with those of GVHR mice. However, the administration of mAbs did not interfere with the induction of splenomegaly, the invasion of CD4+, CD8+, B220+, or Mac-1+ cells around bile ducts, nor the production of AMA. Liver-infiltrating CD4+ T cells obtained from these treated mice did not alter the expression of T helper (Th)1 and Th2 cytokine mRNA.

CONCLUSION

The results suggest that treatment with antibodies against these adhesion molecules could inhibit the infiltration of lymphocytes without affecting the Th1/Th2 balance. The blockade of VLA-4-mediated cell infiltration into the liver in this model may have a possible novel therapeutic role of VLA-4 mAbs.

T lymphocyte adhesion mechanisms within inflamed human kidney: studies with a Stamper-Woodruff assay

Renal inflammatory conditions are characterized by mononuclear cell recruitment to sites of inflammation. We have developed a modified Stamper-Woodruff assay system to analyze mechanisms of functional T cell adhesion to cryostat sections of renal biopsy material from patients with vasculitic glomerulonephritis (GN) and acute allograft rejection. Peripheral blood T cells adhered to intraglomerular, periglomerular, and tubulointerstitial regions of the cortex. Blocking monoclonal antibodies against tissue expressed ICAM-1, VCAM-1, and the CS-1 domain of fibronectin (CS-1Fn) differentially attenuated T cell adhesion. Glomerular adhesion in vasculitic GN and tubulointerstitial adhesion in acute rejection were particularly sensitive to both anti-ICAM-1 and anti-VCAM-1 antibodies, indicating a prominent role for ICAM-1 and VCAM-1 at glomerular sites in vasculitis and at tubulointerstitial sites in rejection. Furthermore, using KL/4 cells (LFA-1 expressing) and Jurkat cells (VLA-4 expressing), we demonstrated specific LFA-1/ICAM-1- and VLA-4/VCAM-1-mediated interactions within glomerular and tubulointerstitial compartments. Jurkat cells also adhered to VCAM-1-free sites, and binding was inhibitable by anti-CS-1Fn antibody, thereby demonstrating a role for VLA-4/fibronectin interactions especially at intraglomerular sites in acute rejection where VCAM-1 is notably absent. We therefore propose a prominent functional role for ICAM-1, VCAM-1, and CS-1 domain fibronectin in T cell recruitment to the inflamed kidney.

Co-culture of pancreatic islets and allogeneic lymphocytes: alterations of responder and stimulator cells

Mixed lymphocyte cultures have been used, e.g., in clinical transplantation, for donor-recipient selections. In experimental research, the mixed lymphocyte culture is valuable in studying several aspects of lymphocyte activation by allogeneic major histocompatibility complex (MHC) antigens and, therefore, in proving new strategies of interrupting lymphocyte activation and proliferation. However, this in vitro model is donor-specific but not antigen-specific. Therefore, we used islets of Langerhans, the donor tissue for grafting diabetic recipients, to stimulate allogeneic mononuclear cells prepared from spleens of healthy LEW.1A, LEW.1W, or WF rats and from diabetes-prone normoglycemic BB/OK rats. The considerable advantage of the mixed lymphocyte islet culture is not only the antigen specificity but also the possibility to separate lymphocytes from islets after the co-culture. In addition to lymphocyte activation, we investigated cytokine secretion and changes of antigen expression on the stimulatory islet cells. After allogeneic co-culture, lymphocyte activation was found by an increased release of the cytokines interferon-gamma, interleukin 2, and macrophage inflammatory protein 2, as well as by an enhanced expression of the interleukin 2 receptor on CD4+ T and CD8+ T cells. We also demonstrated changes in antigen expression on the surface of stimulatory islet cells after co-culture with allogeneic lymphocytes. These changes comprised not only the enhancement of MHC class I and intercellular adhesion molecule 1 but also the induction of MHC class II antigens on pancreatic beta cells. Activation of responding lymphocytes, cytokine secretion, and changes in islet cell antigen expression were time dependent. We did not find major differences in the effects induced by allogeneic lymphocytes obtained from the different donor rat strains. In a syngeneic control mixed lymphocyte islet culture, lymphocytes were not activated and no induction of MHC class II antigens on beta cells was observed. However, up-regulation of intercellular adhesion molecule 1 was found. The enhancement and induction of MHC antigens and an adhesion molecule improve the binding of effector and target cells supporting our hypothesis that the change of antigen expression on target cells induced by allogeneic lymphocytes might contribute to their destruction. Since lymphocytes obtained from healthy or diabetes-prone rats induce very similar effects, we conclude that the results described are of general importance.

Demonstration of the proliferation marker Ki-67 in renal biopsies: correlation to clinical findings

Assessment of cell proliferation in renal biopsy samples is a potentially promising analytical tool to evaluate disease activity. So far no information is available on the correlation between proliferative activity in different anatomic compartments of the kidney and clinical symptoms. To elucidate this issue, we examined renal biopsy specimens from 20 patients with systemic vasculitis (15 Wegener's granulomatosis, five microscopic polyangiitis), 20 patients with immunoglobulin (Ig) A nephropathy (IgAN), 13 patients with minimal-change disease (MCD), 11 patients with tubulointerstitial nephritis, and five patients with diabetes mellitus. The streptavidin-biotin-peroxidase complex technique was applied to autoclave-pretreated, formalin-fixed, paraffin-embedded tissue sections to label different cell types with the antibody MIB1 directed against the Ki-67 antigen. Proliferation index (PI) was estimated as the number of positively stained nuclei per glomerular cross-section or per square millimeter section area. The interstitial cells were discriminated by additional staining of Ki-67-processed samples with specific immune markers. In patients with vasculitis, PI was considerably elevated in the extracapillary glomerular compartment (0.86), in proximal tubules (6.24), and in the interstitium (8.62). High proliferative activity was also noted in interstitium (3.98) and proximal tubules (1.35) of patients with IgAN. Of particular interest was the increased interstitial proliferative activity (15.0) in diabetic patients. Resident renal cells, but not infiltrating cells, seemed to constitute the majority of the proliferating cell population in the interstitium. In systemic vasculitis, clinical disease activity was significantly correlated to endocapillary (r(s) = 0.58), extracapillary (r(s) = 0.67), proximal tubular (r(s) = 0.67), and interstitial PI (r(s) = 0.61). By multiple linear regression analysis, proximal tubular PI was correlated to the presence of hematuria (beta = 0.72) and to interstitial fibrosis score (beta = 0.59). Interstitial PI was independently correlated to antineutrophil cytoplasmic antibodies (ANCA) titer (beta = 0.7) and interstitial fibrosis score (beta = 0.55), and it was the only one PI correlated to serum creatinine concentration (beta = 0.53). The independent association between interstitial PI and serum creatinine (beta = 0.64) was also found in IgAN. Proximal tubular PI was correlated to interstitial fibrosis score (beta = 0.59) and proteinuria (beta = 0.54). In MCD, high PI values were noted in proximal tubular cells (1.42) but not in glomeruli and the interstitium. In conclusion, assessment of proliferation activity by immunohistology provides additional information beyond conventional pathological techniques to evaluate disease activity and prognosis in renal biopsies.

Adhesion molecules and rejection of renal allografts

Despite an increasing amount of immunohistochemical and molecular biology data relating to the pathogenesis of kidney transplant rejection, the pathological diagnosis of this condition still rests on routine light microscopy. The detection of changes in expression and distribution of adhesion molecules in renal allograft biopsies may open a new era of increased accuracy of rejection diagnosis. Of the various adhesion molecule reactivities, peritubular capillary VCAM-1 staining appears to be the most specific finding for chronic rejection. This same staining reaction is seen in acute rejection, but may have less specificity in that setting.

Intragraft IL-15 transcripts are increased in human renal allograft rejection

IL-15, a novel growth factor made by a variety of cells, stimulates T cell proliferation in a fashion similar to IL-2. IL-2 transcripts are not routinely found in rejecting human renal allografts at the time of clinically evident rejection. However, T cell proliferation continues as the rejection progresses. We postulated that IL-15 may be actively transcribed during clinical rejection and account, at least in part, for the ongoing T cell expansion. RNA was extracted from renal biopsies and reverse transcribed to cDNA which was used as template for competitive PCR. IL-2 mRNA was detected in just 3 of the 45 biopsy samples. IL-15 transcripts were detected in all renal biopsy specimens and was significantly increased in specimens obtained from rejecting as compared with nonrejecting renal allografts. IL-15 transcription correlates with rejection and may play an important role in T cell mediated rejection.

Expression of the intercellular adhesion molecule-3 (ICAM-3) in human renal tissue with relation to kidney transplants and various inflammatory diseases

Adhesion molecules are important for immune regulatory mechanisms concerning antigen presentation, lymphocyte activation, localisation and migration as well as effector-target cell interactions in inflammatory processes. The immunohistochemical expression of ICAM-3, a recently cloned new member of the immunoglobulin family which also binds leucocyte function antigen 1 (LFA-1), was examined in 80 needle core biopsies from 35 renal allografts, 7 patients with mesangioproliferative glomerulonephritis, 5 patients with extracapillary glomerulonephritis, 4 patients with interstitial nephritis and 5 patients with diabetic nephropathy and 20 normal kidneys. In all types of lesions ICAM-3 was constitutively expressed on the majority of infiltrating leucocytes without detectable upregulation or presentation on possible target structures during inflammation indicating its possible role to be mainly in initiation of the inflammatory response.