Cytolytic T lymphocytes from human renal allograft biopsies are tissue specific

The TreaT-Assay: A Novel Urine-Derived Donor Kidney Cell-Based Assay for Prediction of Kidney Transplantation Outcome

Donor-reactive immunity plays a major role in rejection after kidney transplantation, but analysis of donor-reactive T-cells is not applied routinely. However, it has been shown that this could help to identify patients at risk of acute rejection. A major obstacle is the limited quantity or quality of the required allogenic stimulator cells, including a limited availability of donor-splenocytes or an insufficient HLA-matching with HLA-bank cells. To overcome these limitations, we developed a novel assay, termed the TreaT (Transplant reactive T-cells)-assay. We cultivated renal tubular epithelial cells from the urine of kidney transplant patients and used them as stimulators for donor-reactive T-cells, which we analyzed by flow cytometry. We could demonstrate that using the TreaT-assay the quantification and characterization of alloreactive T-cells is superior to other stimulators. In a pilot study, the number of pre-transplant alloreactive T-cells negatively correlated with the post-transplant eGFR. Frequencies of pre-transplant CD161⁺ alloreactive CD4⁺ T-cells and granzyme B producing alloreactive CD8⁺ T-cells were substantially higher in patients with early acute rejection compared to patients without complications. In conclusion, we established a novel assay for the assessment of donor-reactive memory T-cells based on kidney cells with the potential to predict early acute rejection and post-transplant eGFR.

Autoimmune Reactivity in Graft Injury: Player or Bystander?

Organ transplantation is the only viable treatment for several end-stage organ failures. However chronic rejection prevents long-term graft survival. Traditionally this rejection was attributed to the development of alloimmunity in transplant patients. However recent evidence suggests that autoimmunity plays a larger role in chronic rejection of certain organ transplants, than alloimmunity. In this review we will focus on the history of autoimmunity in solid-organ transplantation and at look the Collagen Type V, K-α-tubulin, Vimentin, Cardiac myosin and Heat Shock Proteins as classical examples of auto-antigens in organ transplantation. We will also look at some of the recent reports looking at the mechanisms of autoimmunity and try to provide answers to some of the age-old questions in autoimmunity.

Role of the mucosal integrin alpha(E)(CD103)beta(7) in tissue-restricted cytotoxicity

The effectiveness of lung transplantation is marred by the relatively high incidence of rejection. The lung normally contains a large population of lymphocytes in contact with the airway epithelium, a proportion of which expresses the mucosal integrin, alpha(E)(CD103)beta(7). This integrin is not a homing receptor, but is thought to retain lymphocytes at the epithelial surface. Following transplantation, a population of 'tissue-restricted' cytotoxic T cells (CTL) have been identified which have the ability to lyse epithelial cells, but not major histocompatibility complex (MHC)-identical splenic cells. We tested the hypothesis that expression of the mucosal integrin confers the ability of CTL to target and destroy e-cadherin expressing targets. Immunohistochemical and flow cytometric analyses were used to demonstrate the relevance of this model to human lung. Allo-activated CTL were generated in mixed leucocyte reactions and CD103 expression up-regulated by the addition of transforming growth factor (TGF)-beta. The functional effect of CD103 expression was investigated in (51)Cr-release assays using e-cadherin-expressing transfectant targets. Human lung epithelial cells express e-cadherin and one-third of intraepithelial lymphocytes (IEL) expressed CD103. Allo-activated and bronchoalveolar lavage (BAL) lymphocytes express more CD103 than those in blood. Transfection of e-cadherin into murine fibroblasts conferred susceptibility to lysis by alpha(E)beta(7)-expressing CTL which could be blocked by specific monoclonal antibodies to CD103 and e-cadherin. CD103 functions to conjugate CTL effectors to e-cadherin-expressing targets and thereby facilitates cellular cytotoxicity. E-cadherin is expressed prominently by epithelial cells in the lung, enabling CTL to target them for destruction.

Lymphocyte propagation from biopsies of kidney allografts

Morphological evaluation of transplant biopsies, usually using the Banff classification, is the most important tool to diagnose rejection after kidney transplantation. However, morphological analysis only scores the amount and localisation of infiltrating cells, and studies show that up to 30% of grafts with a stable function display infiltration of lymphocytes consistent with acute cellular rejection. Methods to study the functional properties of the infiltrating lymphocytes are therefore needed. We applied a tissue culture system on biopsies from transplanted human kidneys, allowing infiltrating cells to propagate out from the tissue. Cells were then counted and subtyped by flow cytometry. The results were correlated to morphology. In total, 92 biopsies from 69 patients were analysed. For 14 patients, serial biopsies were available. In grafts with cellular or combined cellular and vascular rejection, the number of ex vivo propagated mononuclear cells was higher than from non-rejecting grafts. A similar pattern was seen for CD3(+) T cells as well as for T cells expressing CD25 or MHC class II antigens. However, the proportion of CD25(+) or MHC class II(+) T lymphocytes was similar in all groups (no rejection, vascular rejection, borderline changes, cellular rejection, combined cellular and vascular rejection). In all groups the number of CD4(+) cells was higher than the number of CD8(+) cells. The results confirm previous experimental studies showing that graft-infiltrating cells are possible to culture in vitro and that lymphocyte propagation correlates to acute cellular rejection. Tissue culturing is easy to perform and evaluate and can be used to determine and analyse the cellular immune response to allografts and may thus be used as a complement to morphological analyses.

Urinary cytotoxic molecular markers for a noninvasive diagnosis in acute renal transplant rejection

Perforin (P), Granzyme B (GB) and Fas-Ligand (FAS-L) are cytotoxic molecules involved in acute rejection (AR) after renal transplantation. A noninvasive diagnostic test to monitor AR and other complications could improve clinical management. We investigated the predictive and diagnostic interest of target mRNA measurements, with a quantitative PCR assay, in AR, as well as in other clinical complications recurrent in kidney transplantation. One hundred and sixty-two urine specimens from 37 allograft recipients were investigated. Clinical settings were AR, urinary tract infection (UTI), cytomegalovirus infection (CMVi) or disease (CMVd), chronic allograft nephropathy (CAN), delayed graft function (DGF) and stable graft course (controls). In the case of AR, mRNA levels of all three molecules were significantly higher than in recipients not showing any clinically evident signs of complication. Indeed, it was observed that expression levels of P, GB and Fas-L mRNA also increase in other clinical situations such as UTI, CMV and DGF. Finally, kinetic studies in three patients with AR revealed that increased P, GB and Fas-L mRNA levels could precede or were concomitant with increased serum creatinin levels. P, GB and Fas-L gene expression in urine specimens were upregulated in AR episodes but also in UTI, CMV infection and DGF. Therefore, this technique would appear to be of limited clinical value as a noninvasive method of diagnosing AR.

TGF-{beta}-dependent CD103 expression by CD8(+) T cells promotes selective destruction of the host intestinal epithelium during graft-versus-host disease

Destruction of the host intestinal epithelium by donor effector T cell populations is a hallmark of graft-versus-host disease (GVHD), but the underlying mechanisms remain obscure. We demonstrate that CD8⁺ T cells expressing CD103, an integrin conferring specificity for the epithelial ligand E-cadherin, play a critical role in this process. A TCR transgenic GVHD model was used to demonstrate that CD103 is selectively expressed by host-specific CD8⁺ T cell effector populations (CD8 effectors) that accumulate in the host intestinal epithelium during GVHD. Although host-specific CD8 effectors infiltrated a wide range of host compartments, only those infiltrating the intestinal epithelium expressed CD103. Host-specific CD8 effectors expressing a TGF-β dominant negative type II receptor were defective in CD103 expression on entry into the intestinal epithelium, which indicates local TGF-β activity as a critical regulating factor. Host-specific CD8 effectors deficient in CD103 expression successfully migrated into the host intestinal epithelium but were retained at this site much less efficiently than wild-type host-specific CD8 effectors. The relevance of these events to GVHD pathogenesis is supported by the finding that CD103-deficient CD8⁺ T cells were strikingly defective in transferring intestinal GVHD pathology and mortality. Collectively, these data document a pivotal role for TGF-β–dependent CD103 expression in dictating the gut tropism, and hence the destructive potential, of CD8⁺ T cells during GVHD pathogenesis.

Human leukocyte antigen-C in short- and long-term liver graft acceptance

In liver transplantation, rejection is still an important problem, and the role of human leukocyte antigens (HLA) has not been clearly established. At present, the possible involvement of HLA-C antigen in liver transplantation is still unexplored. The aim of this work was to analyze the influence of HLA-C polymorphism on the outcome of liver transplantation. For this purpose, genotyping of 100 orthotopic liver transplant recipient-donor pairs for HLA-C was performed with polymerase chain reaction-sequence-specific primers (PCR-SSPs). Liver recipients were stratified according to the occurrence of acute rejection. Patients without acute rejection were found to have a lower frequency of the HLA-Cw*06 allele compared with those with acute rejection or the control group. Moreover, when the role of HLA-C dimorphism was analyzed, natural killer (NK)1-alloantigens were found to be predominant in recipients without acute rejection. When the match of HLA-C single alleles and NK-alloantigens between donor and recipient was analyzed, it appeared that the frequency of acute rejection gradually decreased with decrease of the number of allele mismatches. Graft survival was increased when the number of mismatches in both HLA-C or NK-alloantigens was lower. In conclusion, the HLA-C locus may play a role in liver graft alloreactivity or allotolerance and, therefore, may be useful to avoid acute rejection and to achieve graft acceptance, resulting in a better final outcome in liver transplantation.

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.

Organ Transplant Specificity of Tolerance to Skin Grafts with Heart or Kidney Grafts Plus Nondepleting Anti-CD4 Monoclonal Antibody (RIB 5/2) and Intravenous Donor Alloantigen Administration

BACKGROUND

CD4+ T cells play an essential role in allograft rejection. Monoclonal anti-rat CD4 antibody, RIB 5/2, has been shown to modulate the CD4 glycoprotein without eliminating recipient T cells. A single dose of monoclonal anti-rat CD4 antibody RIB 5/2 plus donor splenocytes results in donor-specific unresponsiveness to heart and kidney allografts, but not skin allografts. This study examined whether tolerance to the more resistant skin graft could also be achieved with RIB 5/2.

METHODS

Buffalo (RT1(b)) recipients were given a single dose (20 mg/kg) of monoclonal antibody RIB 5/2 IP plus IV Lewis (RT1(l)) splenocytes (25 x 10(6)) 21 days before Lewis heart, kidney, or skin grafts. In addition, Lewis skin was grafted either simultaneously with or after long- term Lewis heart or kidney allograft acceptance (>50 days).

RESULTS

While IV alloantigen plus RIB 5/2 results in long-term acceptance of both heart and kidney, skin allografts are rejected when transplanted alone. Simultaneous transplantation with a Lewis kidney, but not with a Lewis heart, resulted in long-term Lewis skin graft acceptance. However, recipients tolerant to Lewis kidney or heart alone will not accept subsequent Lewis skin grafts, while recipients of simultaneous Lewis skin and kidney grafts subsequently accept a second Lewis, but not third-party Brown Norway (RT1(n)), skin graft.

CONCLUSION

RIB 5/2 plus Lewis donor splenocytes tolerize for donor-specific heart and kidney but not skin grafts. However, Lewis skin grafted simultaneously with a Lewis kidney, but not Lewis heart, is accepted and protects a subsequent donor-specific Lewis skin graft.

ANTIVIMENTIN ANTIBODIES ARE AN INDEPENDENT PREDICTOR OF TRANSPLANT-ASSOCIATED CORONARY ARTERY DISEASE AFTER CARDIAC TRANSPLANTATION1

BACKGROUND

Transplant-associated coronary artery disease (TxCAD) is the most serious long-term complication after cardiac transplantation. Anti-endothelial antibodies are associated with disease, and one of the major endothelial antigens recognized in the sera of patients has been shown to be the protein filament vimentin. In this study, we investigated whether antivimentin antibodies are associated with TxCAD and whether their presence can be used to identify patients at high risk of developing angiographically detectable TxCAD.

METHODS

Up to 5 years after transplantation, 880 sequential sera (7.07+/-1.8 samples/patient) were collected retrospectively from 109 patients; the majority were collected in the first 2 years. Sera were assessed for antivimentin antibodies using ELISA. TxCAD was assessed by annual angiography.

RESULTS

Mean titres of antivimentin antibodies, calculated up to 1, 2, and 5 years, were significantly higher in patients who developed TxCAD than those who remained disease free (P<0.0001, P<0.0038, and P<0.0001, respectively). A predictive test based on the first-year mean vimentin titre alone (> or = 120) produced a test with 63% sensitivity and 76% specificity. Inclusion of persistent rejection or high 1-year mean titre (> or = 270) as a risk factor produced a test with 66% sensitivity and 82% specificity. Multivariate analysis of time to occurrence of transplant vasculopathy showed that mean titre at 1 or 2 years was an independent predictor of time until disease in the presence of all other variables.

CONCLUSIONS

Antivimentin antibodies are an independent predictor of TxCAD and can be used to identify some of the patients who are at high risk of developing this complication.

Characterization of an HLA-A3 restricted human kidney specific T cell clone

BACKGROUND

The tissue specificity of a cytolytic T lymphocyte is determined by the MHC class I bound peptide it recognizes. We have developed an allorestricted human CTL clone, DBS 1.5, that recognizes an epitope found on HLA-A3+ kidney epithelial cells but not on HLA identical B-lymphoblastoid cells. The peptide recognized by this clone has been isolated from HPLC separated, acid eluted peptides from purified HLA class I molecules from HLA-A3+ kidney tissue. This peptide shares no sequence homology with any known protein.

METHODS

To confirm the tissue specificity of the HLA-A3 restricted clone and the peptide it recognizes we have transfected the gene for HLA-A3 into a number of tumor cell lines both human and murine not expressing this antigen. The resulting transfected lines, confirmed by immunofluorescent staining, were used as targets to determine if expression of HLA-A3 alone was sufficient to allow recognition and lysis by the HLA-A3 restricted T cell clone.

RESULTS

The HLA-A3 restricted T cell clone recognized HLA-A3 when expressed on human kidney epithelial cells and to a lesser extent on human lung epithelium and human epidermal cells. Of the tumor lines transfected with HLA-A3 only the human kidney tumor cell line was lysed at a level equal to the original kidney epithelial cell used to develop the clone.

CONCLUSION

These results confirm that this allorestricted human CTL clone is tissue specific recognizing a peptide found in human epithelial tissue that must be presented in the context of HLA-A3 for recognition.

De Novo Autoimmunity to Cardiac Myosin After Heart Transplantation and Its Contribution to the Rejection Process

Allograft rejection is initiated by an immune response to donor MHC proteins. We recently reported that this response can result in breakdown of immune tolerance to a recipient self Ag. However, the contribution of this autoimmune response to graft rejection has yet to be determined. Here, we found that after mouse allogeneic heart transplantation, de novo CD4+ T cell and B cell autoimmune response to cardiac myosin (CM), a major contractile protein of cardiac muscle, is elicited in recipients. Importantly, CM is the autoantigen that causes autoimmune myocarditis, a heart autoimmune disease whose histopathological features resemble those observed in rejected cardiac transplants. Furthermore, T cell responses directed to CM peptide myhcα 334–352, a known myocarditogenic determinant, were detected in heart-transplanted mice. No responses to CM were observed in mice that had received an allogeneic skin graft or a syngeneic heart transplant, demonstrating that this response is tissue specific and that allogeneic response is necessary to break tolerance to CM. Next, we showed that sensitization of recipient mice with CM markedly accelerates the rejection of allogeneic heart. Therefore, posttransplant autoimmune response to CM is relevant to the rejection process. We conclude that transplantation-induced autoimmune response to CM represents a new mechanism that may play a significant role in cardiac transplant rejection.

Apoptosis and expression of cytotoxic T lymphocyte effector molecules in renal allografts

Cytotoxic T lymphocyte (CTL) mediated apoptosis is thought to play a major role in the rejection of renal allografts following transplantation, however, the CTL effector mechanism that is primarily responsible for immunological rejection is unknown. The two major effector pathways of CTL killing which lead to apoptosis involve the Fas/Fas ligand (Fas L) lytic pathway, and the perforin/granzyme degranulation pathway. The expression of CTL effector molecules which influence these pathways include Fas, Fas L and TiA-1 (cytotoxic granule protein). This study has investigated apoptosis by in situ terminal deoxytransferase-catalysed DNA nick end labelling (TUNEL), and the expression of CTL effector molecules by immunohistochemistry, in renal allograft biopsies obtained from patients following kidney transplantation. Renal biopsies were classified into three histological groups; acute cellular rejection, chronic rejection, or no rejection. The extent of T-cell infiltration of renal tissues was assessed by immunohistochemical staining with an anti-CD3 monoclonal antibody. Numerous TUNEL positive cells were detected in all transplant biopsies examined; these consisted mainly of renal tubular cells and infiltrating cells, with some TUNEL positive cells also detected in the glomeruli. In the case of normal kidney tissue, renal cells also stained positive for TUNEL but there was no lymphocytic infiltration. There was significantly more T-cell infiltration observed in acute rejection biopsies compared to the no rejection biopsies. In the case of Fas L expression, there was little expression in all three biopsy groups, apart from one case of chronic rejection. Conversely, although there were no significant differences in TiA-1 expression between the three biopsy groups, TiA-1 expression was more prominent in acute rejection biopsies. Furthermore, Fas expression was significantly decreased in acute rejection biopsies when compared to those of chronic and no rejection in which Fas was predominantly localized in the renal tubular cells. These results indicate that the mechanism of CTL killing leading to the rejection of renal allografts may be different in acute and chronic rejection. Moreover, our data indicate the potential for cytotoxic granule-based CTL killing in acute renal allograft rejection but not in chronic rejection.

Tissue-specific characteristics of cytotoxic graft-infiltrating T cells during renal allograft rejection

BACKGROUND

The alloresponse after renal transplantation was studied using alloreactive T cells generated in vivo (from renal biopsies) and in vitro (from mixed kidney lymphocyte cultures).

METHODS

Tissue specificity of graft-infiltrating T cells (GIC) was investigated using donor-derived proximal tubular epithelial cells (PTEC) and splenocytes as targets in cytotoxicity assays.

RESULTS

The outgrowth of cytotoxic T cells was associated with histologically proven interstitial rejection. GIC were categorized into four groups: (1) GIC cytotoxic for both PTEC and splenocytes (n=30), (2) noncytotoxic GIC (n=8), (3) GIC recognizing only splenocytes (n=1), and (4) GIC specifically recognizing PTEC (n=7). Similar tissue-specific T cells could be generated in vitro using mixed kidney lymphocyte cultures. Cytotoxicity of GIC from biopsies with moderate to severe rejection was CD8 independent, whereas cytotoxicity toward splenocytes was CD8 dependent.

CONCLUSIONS

Our results show that polyclonal cytotoxic T-cell responses with tissue-specific characteristics are elicited during rejection episodes after renal transplantation.

Renal allograft infiltrating lymphocytes: frequency of tissue specific lymphocytes

Acute rejection, mediated by T lymphocytes recognizing donor MHC class I and II, is a major factor influencing renal transplant survival. To define the specificity of these effector cells we examined cytolytic activity of graft infiltrating T lymphocytes (GIL) from renal biopsies of individuals undergoing acute cellular rejection. The majority of these cells recognized MHC class I on both donor kidney epithelial cells (KCL) and B-lymphoblastoid cells (LCL) suggesting these T cells recognized peptides from various tissues. However, cold target inhibition experiments demonstrated a significant proportion of GIL T cells were tissue specific. We reported previously that kidney specific CTL can be isolated from biopsies of kidney allografts undergoing acute cellular rejection. Here we extend that observation showing we were able to isolate tissue specific CTL from two additional biopsies. Greater than 10% of the clones isolated (4 of 36 and 5 of 37) from these biopsies were CTL recognizing donor KCL but not LCL targets suggesting that peptides, recognized in the context of donor MHC, were tissue specific. Repeated isolation of significant numbers of tissue specific CTL suggests these T cells play a role in allograft rejection and may be important effector cells mediating rejection in HLA matched transplants.

Pancreas and kidney allograft-infiltrating cells in simultaneous pancreas-kidney transplantation

BACKGROUND

Rejection after pancreas-kidney transplantation may occur isolated or concurrently in both grafts. To get more insight into the cellular mechanisms underlying these rejection episodes, we compared the functional characteristics of pancreas and kidney graft-infiltrating T cells.

METHODS

Graft-infiltrating T cell (GIC) lines were cultured from simultaneously taken pancreas and kidney biopsies from eight patients. CD4 to CD8 ratios were determined by fluorescence-activated cell sorter and cytotoxicity toward donor proximal tubular epithelial cells (PTEC) and donor spleen cells (DSC) using a standard cytotoxicity assay. Cytokine production was determined by enzyme-linked immunosorbent assay.

RESULTS

CD4 to CD8 ratios were comparable between the pancreas and kidney lines for each patient, but differences were observed in cytotoxicity toward PTEC and DSC. For four of eight patients, the lysis of PTEC by pancreas GIC was less than the lysis induced by kidney GIC. This was also seen in three of five patients for lysis of DSC. The specificity of GIC lines toward mismatched donor antigens was studied for two patients and appeared to be comparable for pancreas and kidney. Most GIC lines produced interferon (IFN)-gamma (75.5+/-22.7 pg/ml), but no IL-10, indicating that the cell lines consisted primarily of Th1 and type 1 CD8+ cells. Mean production of IL-6 was 465.6+/-193.6 pg/ml. No major differences were observed between kidney and pancreas GIC for either cytokine.

CONCLUSIONS

We conclude that pancreas and kidney GIC lines have the same phenotype, cytokine production, and allospecificity. Differences were, however, seen for lysis of PTEC and DSC, suggesting that tissue-specific antigens might play a role.

Killer cell inhibitory receptor interactions with HLA class I molecules: implications for alloreactivity and transplantation

Human killer cell inhibitory receptors (KIR) are novel members of the immunoglobulin superfamily of cell surface glycoproteins, which are expressed by lymphocytes with natural killers (NK) and cytotoxic T-cell (CTL) phenotypes. These receptors have specificity for relatively conserved epitopes of HLA-A, -B, and -C class I antigens. Recent studies have identified KIR as being involved in the transmission of negative, inhibitory signaling events to the cytotoxic cell which prevent or diminish target cell lysis. KIR are thus likely to play an important role in the responses of alloreactive NK cells and CTL to allogeneic HLA antigens. In this article, we review the known structural and functional characteristics of KIR, suggest a possible mechanism for the transmission of intracellular negative signaling by these receptors, and discuss the relevance of KIR function and HLA specificity to the clinical transplantation of allogeneic tissues.

Human minor histocompatibility antigens

Disparities in minor histocompatibility antigens between HLA-matched organ and bone marrow donors and recipients create a potential risk for graft failure and graft-versus-host disease. These conditions necessitate lifelong pharmacological immunosuppression of organ and bone marrow transplant recipients. Recent technical advances have resulted in the identification of the chemical nature of the first human minor histocompatibility antigens. A new era of research has begun to provide insights into the genetics of minor antigens and their putative role in transplantation.