Renal allograft-infiltrating lymphocytes. A prospective analysis of in vitro growth characteristics and clinical relevance

Biomarkers for kidney transplant rejection

The immune management of organ transplant recipients is imperfect. Beyond general dosing guidelines for immunosuppressive agents and clinical diagnostic tests for rejection or infection, there are few objective tools to determine the aggregate status of a patient's alloimmune response or protective immune capacity. The lack of prognostic precision significantly contributes to patient morbidity and reduces long-term allograft survival after kidney transplantation. Noninvasive biomarkers that could serve as predictive tools or surrogate end points for rejection might help clinicians individualize immunosuppression and allow for early intervention, ideally prior to clinically evident organ dysfunction. Although the growing understanding of organ rejection has provided numerous candidate biomarkers, none has been confirmed in robust validation studies as sufficiently useful to guide clinical practice independent of traditional clinical methods. In this Review, the general characteristics of biomarkers and surrogate end points; current biomarkers under active clinical investigation; and the prominent barriers to the translation of biomarkers into clinical practice are discussed.

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.

Phenotyping of ex vivo propagated graft-infiltrating cells—A tool to monitor rejection in the early post-operative period

Objective and fast methods to diagnose rejection after organ transplantation are needed. In the present study, the ex vivo propagation technique was evaluated for its ability to detect rejection at two different time-points after experimental heart transplantation. Syngeneic and allogeneic heterotopic heart transplantations were performed using inbred rat strains. After 6 or 15 days, cardiac graft biopsies were put in culture and infiltrating cells isolated by the ex vivo propagation technique. The isolated cells were counted and phenotyped by flow cytometry. In parallel, graft sections were analysed with regard to morphology and the presence of infiltrating cells as determined by immunohistochemical stainings. On day 15 after transplantation, the number of cells possible to isolate through ex vivo propagation reflected the morphological changes of the graft, i.e. considerably more cells were obtained from allogeneic transplants undergoing rejection (1052 +/- 205) than from allogeneic grafts under cyclosporine protection (513 +/- 135; p < 0.05) or from syngeneic grafts (378 +/- 87; p < 0.01). Six days after transplantation the allogeneic grafts were strongly rejected with massive cellular infiltration, still there was no difference between allogeneic and syngeneic grafts as to the number of ex vivo propagated cells. However, the proportion of IL-2-receptor expressing T lymphocytes was increased (15.4 +/- 1.8% vs. 9.5 +/- 1.4%; p < 0.05) and the CD4/CD8 ratio reduced (1.0 +/- 0.1 vs. 2.8 +/- 0.2; p < 0.001) in the allogeneic group as compared with the syngeneic. We conclude that the ex vivo propagation technique can be used to distinguish rejection from non-rejection both early and later after transplantation, provided that not just cell counting but also phenotyping of the graft-infiltrating cells is performed.

Mixed lymphocyte cultures can predict TCR Vbeta repertoires of T cells infiltrating kidney transplants during acute rejection episodes

Alloreactive T cell populations can show skewing of T-cell antigen receptor (TCR) Vbeta gene usage. The aims of the experiments were to compare in vivo and in vitro T cell alloresponses against donor alloantigens for TCR Vbeta gene usage. T-cell cultures from renal biopsies taken during acute rejection and pretransplant mixed lymphocyte cultures (MLC) were established from five renal transplant patients. TCR Vbeta gene usage, assessed with Vbeta family specific antibodies, showed that up to five different Vbeta families were significantly expanded. In four of five cases, there was close concordance between Vbeta families expanded from the biopsy and in MLC. T-cell clones from one renal biopsy were specific for the mismatched donor alloantigen and showed similar TCR Vbeta gene usage to the original T-cell line. The results show very similar patterns of TCR Vbeta gene usage in alloreactive T cells generated ex vivo or in vitro.

Donor non-specific IFN-gamma production by primed alloreactive cells as a potential screening test to predict the alloimmune response

In order to devise an in vitro experimental system that predicts the in vivo generation of T lymphocytes capable of initiating the rejection process and thereby to individualize the immunosuppressive strategy in a rational way, we studied the in vitro strength of alloresponses to non-specific donors as a surrogate tool to identify patients with heightened alloimmunity. We measured interferon gamma (IFN-gamma) produced by primed alloactivated peripheral blood lymphocytes (p-allo-PBL) against third party stimulator PBLs in four groups by the enzyme linked immunospot (Elispot) assay: 16 with excellent renal transplant function (group 1); nine with chronic rejection (group 2); 11 allo-sensitized (PRA>60%) by graft loss on dialysis (group 3) and 36 normal controls (group 4). The Elispot assay was performed using 10(6) irradiated stimulator PBLs and 10(5) responder PBLs for 24 and 48 h. Each responder was challenged by 2-4 independent stimulators.

RESULTS

At 24 h, mean+/-S.D. and 95% confidence intervals (CI) of spots/10(5) responder cells were 12.8+/-8.7 (10-15.5); 57.8+/-116 (11.9-103.7); 77.5+/-91.3 (39.8-115.2); and 20.7+/-17.9 (17.4-24.1) in groups 1-4, respectively. P<0.01 between groups 1 or 4 vs. 2 or 3. An arbitrary spot level of >or=30 has positive and negative predictive values of 58% and 95%, respectively, sensitivity of 94% and specificity of 65% to identify patients with enhanced immunity.

CONCLUSION

Chronic allogeneic stimulation is associated with enhanced p-allo-PBL. IFN-gamma producing frequencies against third party stimulators. Significant variation in IFN-gamma spots produced by p-allo-PBL may be useful to choose less allogeneic donors. Diminished p-allo-PBL alloresponse to third party stimulators may predict transplant patients with decreased alloresponses who may benefit from lesser immunosuppressive drugs.

Protective effects of FTY720 on chronic allograft nephropathy by reducing late lymphocytic infiltration

BACKGROUND

Lymphocytic infiltration is obvious throughout early and late stages of chronic allograft nephropathy. Early infiltrating lymphocytes are involved in initial insults to kidney allografts, but the contribution of late infiltration to long-term allograft attrition is still controversial. Early application of FTY720 reduced the number of graft infiltrating lymphocytes, and inhibited acute rejection. The present study investigated the potential of FTY720 to reduce the number of infiltrating lymphocytes even at a late stage, and, thus, slow the pace of chronic allograft nephropathy.

METHODS

Fisher (F344) rat kidneys were orthotopically transplanted into Lewis recipients with an initial 10-day course of cyclosporine A (1.5 mg/kg/day). FTY720, at a dose of 0.5 mg/kg/day, or vehicle was administered to recipients either from weeks 12 to 24 or from 20 to 24 after transplantation. Animals were harvested 24 weeks after transplantation for histologic, immunohistologic, and molecular analysis.

RESULTS

FTY720, either initiated at 12 or 20 weeks after transplantation, reduced urinary protein excretion, and significantly ameliorated glomerulosclerosis, interstitial fibrosis, tubular atrophy, and intimal proliferation of graft arteries at 24 weeks after transplantation. Furthermore FTY720 markedly suppressed lymphocyte infiltration and decreased mRNA levels of interleukin-10 (IL-10), transforming growth factor-beta (TGF-beta), and platelet-derived growth factor-B (PDGF-B) but enhanced the number of apoptotic cells in grafts.

CONCLUSIONS

FTY720 ameliorated chronic allograft nephropathy even at advanced stages. Furthermore, our data suggest that this effect was achieved by a reduction of graft infiltrating lymphocytes.

Cytokine gene expression by alloactivated cells in SCID mice

OBJECTIVES

The severe combined immune deficient (SCID) mouse provides a neutral environment to study human immune responses. We therefore tested human gene expression of Interleukin (IL) 2, 4 and 10, interferon gamma (IFNgamma); transforming growth factor beta 1 (TGFbeta1); and CD40 ligand (CD40L) in splenic extracts of SCID mice after engraftment of PBLs from two persons (direct MLR) or one person plus allopeptides (indirect MLR) in the presence or absence of cyclosporin A (CsA) or FK506.

METHODS

Cytokine gene expression was detected by RT and quantitative (for IFN-gamma, TGFbeta1 and CD40L) PCR. All cells, allopeptides, CsA (25 mg/kg/day for 7 days) or FK 506 (0.5 mg/kg/day for 7 days) were administered intraperitoneally (IP).

RESULTS

In both direct and indirect MLR the numbers of SCID mice expressing the human cytokine genes varied between 33% for IL4 and 100% for IL10, IFN-gamma, TGFbeta1, and CD40L. There was significant interpersonal variation in levels of gene expression. Concomitant CsA or FK506 administration for 7 days did not abrogate early or late (1 week after discontinuation of CsA or FK506) cytokine gene expression in either the direct or indirect MLR, but paradoxically enhanced levels of IFN-gamma, TGFbeta1 and CD40L gene expression in some experiments.

CONCLUSIONS

The results explain late rejection after rapid calcineurin inhibitor withdrawal or reduction, and illustrate the potential use of SCID mice as a surrogate model to study graft outcome by determination levels of gene expression and sensitivity to immunosuppressive agents in the in vivo alloresponse.

In vitro T cell proliferation from kidney allograft biopsies with unremarkable pathology: new strategies for an old problem

Acute rejection of renal allografts is mediated by infiltrating alloreactive T cells. The goals of this study were to correlate T cell proliferation with rejection and to determine whether T cell proliferation in the absence of rejection would predict future rejection episodes. Toward this, kidney biopsies (n=100) were cultured in the presence of interleukin-2. Cultures were examined at 4, 24, and 48 hr for T cell proliferation. A strong correlation was observed between T cell proliferation at any time point and rejection. There was not a significant correlation between T cell proliferation in biopsies with no rejection and the occurrence of a rejection episode within 2 months. However, T cell proliferation after 4 hr was a better predictor of the occurrence of rejection within 2 months compared with observations after 24 and 48 hr. Therefore, a subgroup of patients with unremarkable biopsies but T cell proliferation may be at risk for rejection and warrant closer observation and possible tailoring of immunosuppression.

Do serum C-reactive protein measurements help to discriminate episodes of renal dysfunction in patients after renal transplantation?

INTRODUCTION

This study investigated whether serial daily measurements of serum C-reactive protein (sCRP) could help differentiate episodes of transplant dysfunction due to rejection, infection, cyclosporine A (CsA) nephrotoxicity, or acute tubular necrosis (ATN) in renal-allograft recipients.

MATERIALS AND METHODS

Morning serum was obtained daily from 134 patients during the first 30 days after renal transplantation. All episodes of graft dysfunction were recorded and differentiated with transplant biopsies. CRP concentrations were correlated with post-operative graft function and the various causes of graft dysfunction.

RESULTS

All patients showed an increase in sCRP in response to surgery, with a maximum on day 2 after transplantation. The sCRP concentration was significantly higher in patients with delayed graft function (mean 61.50 microg/ml) than in patients with primary graft function (mean 38.01 microg/ml) (p=0.001). Bacterial infections other than asymptomatic bacteriuria (mean sCRP 33.98 microg/ml), interstitial graft rejection (mean sCRP 16.43 microg/ml), and ATN (mean sCRP 30.50 microg/ml) were accompanied by significant increases in sCRP compared with uneventful courses. sCRP was unchanged in the presence of viral infections or CsA toxicity.

CONCLUSION

Serial sCRP measurements help to identify renal-transplant dysfunction of different origins. However, rejection, infection and ATN show similar patterns of sCRP increase. Thus, sCRP is unable to discriminate the causes of renal-graft dysfunction. Biopsy remains the gold standard for the differential diagnosis of renal-allograft dysfunction.

Characterization of CMVpp65-specific CD8+ T lymphocytes using MHC tetramers in kidney transplant patients and healthy participants

BACKGROUND

Cytomegalovirus (CMV) is a ubiquitous herpesvirus that infects 50-90% of individuals in different populations. After primary infection, the virus persists latently in myeloid cells under the control of specific T-cells. Reactivation of CMV infection may cause lethal organ dysfunction and is frequently seen in immunosuppressed individuals. CD8+ cytotoxic T-cells (CTL) have a primary role in suppressing CMV reactivation, and the dominating CTL response is directed against pp65.

METHODS

MHC tetramers, that is, complexes between HLA class I (or class II) molecules and antigenic peptides conjugated to fluorochromes allow the direct visualization of antigen-specific receptor-carrying T-cells using flow cytometry. We constructed a novel MHC tetramer for identification of CMVpp65-specific CD8+ T-cells using HLA-A2 molecules folded with the immunodominant NLVPMVATV peptide.

RESULTS

The A2/pp65 tetramer specifically stained CMV-directed T-cell lines, and sorted cells showed CMV-specific cytotoxicity. High proportions (0.1-9%) of the CD8+ T-cells were A2/pp65 tetramer+ in healthy HLA-A2+ CMV carriers and in immunosuppressed kidney transplant patients with latent infection. Patients with reactivated CMV infection exhibited up to 15% A2/pp65 tetramer+ cells, which seemed to correlate with CMV load over time. A2/pp65 tetramer+ cells expressed T-cell activation markers.

CONCLUSIONS

The construction of a novel A2/pp65 MHC tetramer enabled the design of a rapid and precise flow cytometric method allowing quantitative and qualitative analysis of CMV-specific T-cells. The number of A2/pp65 tetramer binding CTLs in blood may prove to be clinically relevant in assessing the immune response to CMV.

Ex vivo propagation and characterization of lymphocytes from rejecting rat-kidney allografts

Today, most clinically used methods for analysis of alloreactivity in organ transplantation are based on humoral immunity. In order to study the cellular alloresponse, a rat kidney transplantation model with culturing of graft infiltrating lymphocytes was developed. Kidney transplantations between inbred rat strains were performed with the animals initially immunosuppressed with cyclosporine. In order to initiate acute cellular rejection, immunosuppression was withdrawn after 10 days. Infiltrating lymphocytes were analysed using an in vitro culture system, allowing cells to propagate from the biopsies to culture medium. The propagated cells were counted and analysed for subtype activation markers and donor-specificity using flow cytometry and a proliferation assay. Syngeneically transplanted animals and animals given constant immunosuppression upon transplantation were used as controls. During rejection, significantly more T lymphocytes were propagating from the biopsies compared to controls. A higher percentage of the propagated T lymphocytes in the rejection group expressed activation markers [CD25 and major histocompatibility complex (MHC) class II antigen] compared to spleen- and peripheral blood T lymphocytes from the same individuals. Propagated mononuclear cells from biopsies in the rejection group were proliferating and showed donor-specific reactivity whereas mononuclear spleen cells from animals in the same group did not show this donor specificity. In conclusion, we have presented a rat kidney allotransplantation model with in vitro propagation of graft-infiltrating, activated and donor-specific T lymphocytes. This technique offers a possibility to study cellular reactivity in allotransplantation.

Clinically stable human renal allografts contain histological and RNA-based findings that correlate with deteriorating graft function

BACKGROUND

Chronic rejection (CR) remains idiopathic, difficult to prospectively identify, and once detected, unresponsive to increased immunosuppression. We hypothesized that clinically stable human renal allografts have ongoing evidence of injury and immune activity, and that this correlates with the worsening of allograft function characteristic of CR.

METHODS

The allografts of 40 stable renal allograft recipients were biopsied 2-3 years after transplantation. Biopsies were processed for histology and RNA extraction. RNA was evaluated by semi-quantitative RT-polymerase chain reaction for CD3y mRNA (a marker of T cell receptor turnover), and mRNA from cytokine genes previously shown to be transcribed during acute rejection: tumor necrosis factor-alpha, interferon-gamma, interleukin- (IL) 1beta, IL-2, IL-4, IL-6, and IL-8. Clinical parameters including urine protein and glomerular filtration rate were measured the day of biopsy. Findings were then compared with clinical outcome to establish associations between subclinical inflammation and graft dysfunction. Allograft function was measured again 2 years after biopsy and correlated with findings at the time of biopsy.

RESULTS

Cytokine transcripts and histological evidence of injury were detected in more than two-thirds of stable grafts. The degree of the lymphocytic infiltrate correlated with the degree of proteinuria (P=0.034) and histological fibrosis (P=0.005). Similarly, the degree of intragraft CD3y transcription correlated with increasing proteinuria (P=0.043). IL-6 and IL-8 transcripts were also correlated with evidence of graft injury. After 2 years, those biopsies originally found to have evidence of fibrosis, tubular atrophy, or CD3gamma transcription had worsening graft function as determined by creatinine and glomerular filtration rate.

CONCLUSIONS

These data demonstrate that significant injury and immune activity can be detected in patients who are stable on clinical grounds. Undetected subclinical graft injury may be a cause of chronic allograft rejection.

Differences in Type 1 and Type 2 intracytoplasmic cytokines, detected by flow cytometry, according to immunosuppression (cyclosporine A vs. tacrolimus) in stable renal allograft recipients

Recent multicenter, randomized clinical trials have shown that in renal transplant patients tacrolimus (FK506) was more efficient than cyclosporine A (CsA) at preventing acute rejection. In order to try and evaluate whether this difference was related to a different in vivo T-cell suppression we assessed, in a prospective study, the frequencies of interleukin (IL)-2-, IL-4-, IL-5-, IL-6-, IL-10-, interferon-gamma (IFN-gamma)- and double-positive IL-2/IFN-gamma-producing whole T cells, CD4 + and CD8 + T-cell subsets by means of cytokine flow cytometry. This was performed after in vitro stimulation of peripheral blood mononuclear cells (PBMCs) with phorbol myristate acetate (PMA) and ionomycin, in the presence of monensin, in 14 healthy volunteers (controls) and in 14 renal transplant patients. The immunosuppression of the latter was based either on CsA (n = 7) or on FK506 (n = 7). Cytokine-expressing T-cell frequencies were assessed immediately pretransplantation (DO), and subsequently 3 months (M3) and 6 months (M6) afterwards in fasting patients prior to the morning intake of the immunosuppressive drug. We found that at DO the frequencies of IL-2-(22 +/- 2% vs. 22.2 +/- 2%), IFN-gamma-(26 +/- 3% vs. 29 + 3.4%) and IL-4-(0.8 +/- 0.2% vs. 1.4 +/- 0.2%)-expressing T lymphocytes were not significantly different between the controls and the patients, respectively. Conversely, the frequency of IL-2/IFN-gamma double positive cells was higher in the latter (9.3 +/- 1.6%) than in the controls (5.6 +/- 0.8); p = 0.06. Finally, on D0 the frequencies of IL-5-, IL-6-, and IL-10-producing T lymphocytes were lower than 1%, in both groups, as well as after grafting, i.e. on M3 and M6. As compared to baseline (DO): (a) chronic immunosuppression significantly decreased the frequencies of IL-2-, IL-4- and IL-2/IFN-gamma-expressing T cells, whereas those of IFN-gamma, IL-5, IL-6, and IL-10 were not significantly affected; (b) the frequencies of cytokine-expressing T cells were not statistically different between M3 and M6; (c) the decrease in the frequencies of IL-2- and IL-2/IFN-gamma-expressing T cells affected CD4 + and CD8 + cells equally; (d) there was a marginal decrease in the frequency of IFN-gamma-expressing cells only in the CD4 + subset but not in the CD8 population; and (e) for CsA, but not for FK506, the frequency of the IL-2-expressing T cells was negatively correlated with the whole blood trough levels. When we compared the frequencies of cytokine-expressing cells in FK506- and CsA-treated patients, we found that the frequency of IL-2-expressing T cells was significantly lower with FK506 (10.9+/-1.61%) than with CsA (16.3 +/- 1.8%; p = 0.03), whereas the frequencies of the other cytokine-expressing cells were not statistically different between the two groups. In conclusion, our study clearly demonstrated that studied ex vivo, FK506 and CsA decrease the frequencies of cells expressing IL-2, IL-4 and IL-2/IFN-gamma in vivo but do not affect those expressing IFN-gamma. Meanwhile, the frequency of IL-2-producing T cells was more affected with FK506 than with CsA and was negatively correlated with the CsA trough level. Finally, our results regarding IL-2 might explain to some extent the higher efficiency of FK506 in vivo than CsA.

Regulation of the epithelial cell-specific integrin, CD103, by human CD8+ cytolytic T lymphocytes

BACKGROUND

The destruction of the graft epithelium by CD8+ cytolytic T lymphocytes (CTL) is an important aspect of organ allograft rejection. Our recent finding in a mouse model that the epithelial cell-specific integrin, CD103, defines a subset of CD8+ CTL potentially sheds new light onto such interactions. The goal of the present study was to assess the relevance of these data to the human system.

METHODS

CD103 expression by human T-cell populations generated in mixed lymphocyte cultures or isolated from transplant nephrectomy specimens was quantitated using multiparameter FACS analyses.

RESULTS

CD103 defined a major subset (26-76%) of CD8+ CTL generated in human mixed lymphocyte cultures; cell sorting experiments confirmed that the CD103+ and CD103- subsets both possess allospecific lytic activity. Anti-transforming growth factor (TGF)-beta blocked the appearance of the CD103+ CTL subset, and persistent expression of CD103 by CD8+ CTL was dependent on bioactive TGF-beta. Isolated CD103+ and CD103- CD8 subsets maintained their phenotypic integrity during in vitro expansion, although optimal CD103 expression on the former was TGF-beta dependent. Although CD103+ cells were rare among activated CD8 cells in peripheral lymphoid compartments (< 10%), analyses of transplant nephrectomy specimens revealed that a major subset (21-61%) of CD8 memory/effector cells that infiltrate rejecting renal allografts express high levels of CD103.

CONCLUSIONS

We conclude that CD103 defines a discrete and stable subset of human CD8+ CTL and that CD103 expression by such cells is initiated and maintained by bioactive TGF-beta. These data point to the existence of a human effector subset that is uniquely specialized for the destruction of the graft epithelium.

Regulatory function of human CD4+ cytolytic T lymphocytes

Allograft rejection is mediated by both CD4+ and CD8+ T cells. The lytic function of the classic CD8+ cytolytic T lymphocytes (CTL) occurs through recognition of allogeneic major histocompatibility complex (MHC) class I on the surface of the graft. CD4+ CTL recognize MHC class II through a direct recognition pathway or an indirect pathway where MHC peptides are presented in the context of self MHC class II. Lytic CD4+ cells may destroy graft tissue or, we hypothesize, the indirect CD4+ T cell may down regulate CD8+ CTL by recognition of donor MHC peptides presented by self MHC class II expressed on CD8+ T cells. To define the role of CD4+ CTL in allograft outcome we used a CD4+ CTL that is MHC class II restricted, recognizing human leucocyte antigen (HLA)-A1 and HLA-B8 peptides in the context of HLA-DR4. This line (MDSxA1/B8) will lyse DR4+ B lymphoblastoid cells (LCL) pulsed with HLA-A1/B8 peptides (amino acids 60-84 of the alpha1 domain of the MHC class I molecule). These T cells will also lyse peptide-pulsed antigen-specific T cell clones, both CD4+ and CD8+, that express HLA-DR4. These clones must process and present the MHC class I peptides for recognition and lysis to occur. These results suggest a possible mechanism to explain allograft tolerance. Lytic CD4+ T cells, that recognize donor HLA peptides through an indirect antigen presentation pathway, down-regulate donor-specific CTL through peptide-specific lysis resulting in graft tolerance.

Localization of C-X-C and C-C chemokines to renal tubular epithelial cells in human kidney transplants is not confined to acute cellular rejection

Chemokines are important mediators of leucocyte chemoattraction to inflammatory sites. Previous work has shown that the expression of some chemokines is upregulated during renal transplant rejection. The objectives of the present study were to determine whether chemokine expression is increased during renal transplant rejection. Immunohistochemistry was used to localize the C-X-C (alpha) chemokine interleukin-8 (IL-8) and the C-C (beta) chemokines monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1beta (MIP-1beta) in 30 needle biopsies of human kidney transplants taken for diagnosis of renal dysfunction. Urine samples from transplant patients taken immediately prior to biopsy were assayed for chemokine content using enzyme-linked immunosorbent assays (ELISAs). Results from groups of patients having different clinicopathological diagnoses were then compared. All three chemokines were detected in most renal transplant biopsies showing acute cellular rejection but, although infiltrating leucocytes were often positive, staining was predominantly localized to renal tubular epithelium. Staining for MCP-1 was generally weaker than for the other chemokines, and collecting tubules were usually stained more strongly than proximal convoluted tubules. Tubular epithelial staining was also found in biopsies from patients without signs of acute cellular rejection. There were significantly higher amounts of IL-8 in the urine of patients with acute cellular rejection, even when patients with urinary tract infections were excluded, but mean titres of urinary MIP-1beta did not differ between patient groups. This was also found when titres were normalized for urine volume and creatinine levels. Production of IL-8, MCP-1 and MIP-1beta is not confined to kidney transplants showing acute cellular rejection, and may be a relatively nonspecific response of tubular epithelial cells to renal damage.

Interleukin-12 p40 m-RNA expression in human kidney allograft biopsies

Interleukin-12 (IL-12) is a heterodimeric cytokine implicated in the early differentiation of naive T-lymphocytes into the Th1 subset. IL-12 is important for induction of the cellular immune response against viruses, intracellular parasites and neoplasms. Its role in alloresponsiveness has not been fully elucidated. Preliminary data in the literature point toward the prevalence of Th1 lymphocytes in processes of allograft rejection. In attempt to further investigate the expression of this cytokine during episodes of cellular rejection of renal allografts, we searched for IL-12 message in human kidney allograft biopsies using the reverse transcriptase-polymerase chain reaction technique. Twenty-three allograft core biopsies from 19 patients were obtained percutaneously for clinical indications in 18 cases, and as part of an investigational protocol in five cases. A portion of the tissue was used for RNA extraction using the guanidium-thiocyanide phenol-chloroform method. Histology was performed on the remaining core material. Ten mg of total RNA were used for reverse transcription. PCR of the c-DNAs was done for 40 cycles using primers for the p40 subunit of IL-12 and GAPDH which was used as a control. PCR products were photographed after electrophoresis, transferred to a nylon membrane and hybridized with a radiolabelled cloned human IL-12 p40 1 kb c-DNA fragment. Autoradiographies were developed after 20-min exposure. All samples were run in triplicate. IL-12 p40 m-RNA was expressed in all 17 biopsies showing acute cellular rejection as well as in all three biopsies showing focal interstitial fibrosis. No message was found in the presence of normal allograft histology. This is the first in vivo report of IL-12 p40 subunit m-RNA expression during renal allograft rejection in humans. The role of this Th1 cytokine in the alloresponse deserves further investigation.

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.

Predominant Th1 cell infiltration in acute rejection episodes of human kidney grafts

T-cells and their cytokines are thought to play a major role in the genesis of cellular infiltration and rejection in human kidney allografts. Production of Th1 (IFN-gamma) and Th2-type (IL-4 and IL-5) cytokines was assessed in a large series of T-cell clones, derived from core biopsies of kidney grafts in 10 patients with acute interstitial grade I/II rejection (AIR), 6 patients with a histology of "borderline rejection" (BLR) and 3 with cyclosporine A (CsA) toxicity, all receiving standard maintenance immunosuppression. Biopsies were pre-cultured in IL-2 in order to preferentially expand T-cells activated in vivo, and T-cell blasts were cloned with phytohemagglutinin (PHA) and IL-2 using a highly efficient (23 to 98%) cloning technique. A total of 483 T-cell clones obtained from AIR episodes were compared with 346 and 132 clones derived from patients with BLR episodes and CsA toxicity, respectively. In two series of 22 AIR and 77 BLR T-cell clones, alloreactivity against donor cells was shown by 25 and 14% of CD8+ and 21 and 4% of CD4+ clones, respectively. When stimulated by donor-derived EBV B-cells, all these alloreactive clones produced IFN-gamma, but not IL-4 or IL-5 (Th1 clones). Upon stimulation with PHA, the principal qualitative and quantitative differences between AIR- and BLR-derived T-cell clones were that cells derived from AIR patients: (i) showed significantly higher proportions (80 +/- 15 vs. 55 +/- 13%) of Th1 clones in their progeny; (ii) included smaller proportions (3 +/- 4 vs. 20 +/- 17%) of clones incapable of producing IFN-gamma, IL-4 or IL-5 ('null' clones); and (iii) produced significantly higher quantities of IFN-gamma (100 +/- 50 vs. 36 +/- 7 U/10(6) cells/ml), these quantities also being significantly correlated (r = 0.83) with the degree of interstitial graft infiltration (item 'i' in the Banff histological grading). The clones derived from CsA toxicity biopsies exhibited a pattern very similar to that found in BIR cases. These data lead us to conclude that the powerful inflammatory response elicited in acute rejection of a kidney graft recruits and activates both allospecific and non-specific Th1 effector cells, which are primed to high IFN-gamma production. Our results also suggest that IFN-gamma could contribute, at least in part, to the degree of graft infiltration and to the severity of the rejection episode.

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.

Selective increase in CD4-positive graft-infiltrating mononuclear cells among the infiltrates in class I disparate kidney grafts undergoing rejection

Long-term tolerance to kidney allografts across a two-haplotype class I disparity is uniformly induced in miniature swine with a short course of cyclosporine (CsA). In the absence of CsA, all recipients acutely reject kidney allografts within 2 weeks. Previous experiments have shown that graft-infiltrating mononuclear cells (GIC) migrate to the allograft in both CsA-treated and untreated animals. To evaluate the correlation between GIC phenotype and the clinical status, infiltrating cells were examined by flow cytometry, using selective gating to distinguish them from other renal cells. GIC from tolerant and rejector animals were mostly mature T cells, with 84% CD8+ cells, which consisted of 68% CD8+/CD4- and 16% CD8+/ CD4+ cells. This cellular phenotype was, however, markedly different from that of peripheral blood lymphocytes, suggesting a selective migration of cells into the graft. This selective process counterselected the CD3+/CD2- subset of GIC, which was never found in the graft. The distribution of GIC subsets was initially comparable in tolerated and rejected kidneys, but the CD4 single-positive subset then increased specifically in the allograft destined to rejection. The absence of CD4 single-positive cells in tolerated grafts was unlikely to be due to a direct effect of the CsA, because long-term tolerant animals, which received a second kidney without further immunosuppression, also showed no increase in CD4 single-positive cells. The fact that CD4 single-positive cells appeared only within the rejected kidneys, strongly suggests that this cell subset may be important in mediating immune rejection and supports the hypothesis that the development of tolerance in this model depends on a relative deficit of T-cell help.

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

Understanding of the events preceding acute cellular rejection of kidney transplants would be useful in the development of immunosuppressive strategies to prevent rejection. Information about these events in humans has been scarce, because of the lack of early, serial, biopsy samples. We took daily fine needle aspirates from kidney allografts for the first 10 days after transplant. Samples were analyzed by morphological cytology of graft-infiltrating cells, and reverse transcriptase-polymerase chain reaction for detection of interleukin (IL)-2, IL-4, IL-6, IL-10, and gamma-interferon gene expression. During the first 4 days, all of the grafts developed a low-grade monocyte-rich mononuclear cell infiltrate, accompanied by IL-10 gene expression. Thereafter, the infiltrates either remained stable or intensified. Of the 13 grafts with dense infiltrates, seven developed graft dysfunction. The remaining six did not, despite significant interstitial infiltrates. Both rejecting and nonrejecting dense infiltrates were associated with a biphasic pattern of IL-2 and gamma-interferon gene expression, preceding and accompanying lymphocytic graft infiltration. Grafts that did not develop dense infiltrates had no detectable IL-2 or gamma-interferon gene expression and did not suffer cellular rejection during the study period. The development of both rejecting and nonrejecting infiltrates was strongly associated with DR mismatches between donor and recipient. IL-2 and gamma-interferon gene expression are necessary, but not sufficient, for the development of acute cellular rejection in the first 10 days of kidney transplantation, and are more closely associated with the period leading up to rejection than with the period of graft dysfunction.

Molecular and cellular events implicated in local tolerance to kidney allografts in miniature swine

Long-term tolerance to class I-mismatched renal allografts can be induced in miniature swine by treatment with a short course of cyclosporine (CsA). Kidney recipients treated with CsA and untreated control kidney recipients both demonstrated infiltration of the transplanted kidney by mononuclear cells, which reached a maximum between postoperative days 8 and 11. Recipients that did not receive the tolerizing regimen rejected their grafts between postoperative days 8 and 12 in this model. The kinetics of cytokine gene expression, including interleukin (IL)-1alpha, IL-1beta, IL-2, IL-6, IL-10, tumor necrosis factor, and interferon-gamma (IFN-gamma), within the grafted kidney of rejector and acceptor animals, were determined using Northern blot hybridization. A strong correlation between rejection and up-regulation of the IFN-gamma gene was observed, whereas animals with long-term tolerance showed low levels of IFN-gamma, but high levels of IL-10 gene transcription. None of the other cytokine genes demonstrated a reproducible pattern of expression that correlated with acceptance/rejection of allografts. Analysis of transcription patterns of cytokine genes in mononuclear cells purified from renal grafts confirmed the initial observations made on biopsies. The phenotype of graft-infiltrating cells (GIC) showed a dominance of CD8+ cells, with an average of 66% single-positive cells and 19% CD4/CD8 double-positive cells, compared with 30% and 14%, respectively, for peripheral cells. Predominance of CD8+ GIC was dictated neither by the MHC antigen disparity nor the rejector/acceptor status. These results, therefore, suggest that GIC represent a regulated combination of mononuclear cells producing local immune mediators that, in part, control the fate of allografts in this large animal model.

Serum C-reactive protein. A useful and economical marker of immune activation in renal transplantation

This study investigated whether serial daily measurements of serum C-reactive protein (sCRP) in 187 renal allograft recipients could help discriminate episodes of renal dysfunction due to rejection or cyclosporine (CsA) nephrotoxicity and help adjust immunosuppression in the early posttransplant period. Excellent primary graft function was associated with an initial peak of sCRP on day 2 after transplant (median, 29 microg/ml; range, 4 to >200 microg/ml) with a return to <20 microg/ml in all patients by day 5 (median, 7 microg/ml; range, 2-19 microg/ml). Stable graft function (mean creatinine, 155 microg/ml) was accompanied by a median sCRP of 4 microg/ml (range, 1-19 microg/ml). In 30 episodes of rejection responsive to methylprednisolone, sCRP was initially significantly raised to a median of 49 microg/ml (P<0.001) but fell rapidly in response to treatment to a median of 11 microg/ml and continued to fall. In 19 episodes of rejection unresponsive to methylprednisolone, median initial sCRP levels were significantly higher (P<0.001) at 119 microg/ml and were still at a median of 77 microg/ml at the end of the treatment. Twenty-four patients in whom renal dysfunction was associated with CsA nephrotoxicity showed no increase in sCRP concentrations; median sCRP concentrations remained at <5 microg/ml throughout the episodes. A similar pattern was seen in patients with acute tubular necrosis. Serial sCRP measurements provide economical and reproducible evidence of immune activation, help discriminate renal dysfunction due to CsA nephrotoxicity or rejection, and allow appropriate modification of immunosuppressive therapy.

Immunologic monitoring in lung allograft recipients

To identify patients with increased risk of chronic lung allograft rejection, we assessed the utility of an in vitro biopsy-derived lymphocyte growth assay and serum anti-HLA antibody screening as a complement to currently available methods of monitoring lung allograft recipients. Lymphocyte growth assay was performed on bronchoscopic fragments of tissue cultured in medium with rIL-2. Seventy-nine biopsies from 31 lung transplant recipients were tested by lymphocyte growth assay, and results were correlated with histopathology findings. Positive lymphocyte growth was found in 12/26 (46%) episodes of acute rejection, 5/44 biopsies without rejection (11%), and 0/9 episodes of bronchitis. Positive lymphocyte growth was seen in 7/16 (44%) grade A1 rejections and in 5/10 (50%) grade A2 rejections, as opposed to only 5/44 (11%) grade A0 (no rejection) biopsies (P < 0.01 for both A1 and A2 with respect to A0). Actuarial probability of remaining free from obliterative bronchiolitis (OB)* tended to be higher in patients who did not exhibit lymphocyte growth in biopsies. Sequential samples of sera obtained at the time of the biopsy were screened for lymphocytotoxic anti-HLA antibodies. Twenty-two of 44 recipients (50%) developed anti-HLA antibodies during the first postoperative year, exhibiting greater than 10% reactivity to an HLA reference panel of lymphocytes in four or more consecutive serum samples. Actuarial survival of lung allograft recipients with anti-HLA antibodies (n = 22) was lower than in those without anti-HLA antibodies (n = 22; P = 0.03). Of the 22 antibody producers, 7/12 died as a consequence of OB. Of the 22 non-antibody-producers, 1/2 deaths occurred as a consequence of OB. Anti-HLA antibodies were present in 9/11 instances of OB (82% sensitivity) and in 13/33 patients without OB (61% specificity; P = 0.03). These data indicate that lung transplant recipients with positive lymphocyte growth and anti-HLA antibodies are at an increased risk of chronic allograft rejection.

Cytolytic T lymphocytes from human renal allograft biopsies are tissue specific

The cytolytic activity of T lymphocytes infiltrating renal allografts from recipients undergoing episodes of acute cellular rejection was studied. These T-cell populations, composed of both CD4+ and CD8+ cells, demonstrated significant cytolytic activity against both donor-derived KCLs and B-LCLs. In five of 21 biopsy-derived lines greater cytolytic activity was measured against donor KCLs compared to donor B-LCLs, suggesting the presence of kidney antigen-specific, MHC-restricted clones. Clones developed by stimulation with donor B-LCLs lysed both donor B-LCLs and KCLs while clones developed on donor KCLs as stimulator cells showed tissue specificity. Three of 26 clones recognized tissue-specific antigens in the context of donor MHC class I antigens lysing donor KCLs but not B-LCLs. These data demonstrate that a subpopulation of T cells recognizing kidney-specific antigens are present in biopsies of renal allograft recipients undergoing acute cellular rejection. This subpopulation of tissue-specific cytotoxic T lymphocytes may prove to contribute significantly to the pathology of allograft rejection.

Rapid, comprehensive analysis of human cytokine mRNA and its application to the study of acute renal allograft rejection

Cytokine mRNA analysis was performed on human renal allograft needle core biopsies by a PCR-based assay. The assay was specifically developed to be capable of simultaneous analysis of multiple interleukin transcripts (IL-1-IL-12), as well as those of other relevant cytokines, by one person in less than 1 day from cultured cells or directly from tissue samples. It was initially used on preparations containing known amounts of plasmid DNA encoding individual cytokine cDNA sequences, confirming that the sensitivity of this technique was both well defined and comparable for all target sequences tested. Analysis of human PBLs prior to stimulation, after polyclonal stimulation with PHA and after simultaneous treatment with PHA and MP or CyA, was also performed to show a proportional relationship between mRNA levels measured by PCR and protein release measured by ELISA (R2 = 0.86). This correlation was not adversely altered by pharmacologic immunosuppression by MP or CyA. Thus, this method of PCR primer design and usage was appropriate for the clinical study of cytokine mRNA levels during allograft rejection. Direct study of cytokine mRNA in allograft biopsy tissue showed that IL-2 was specifically and significantly (p = 0.006) elevated during ACR when compared to other causes of graft dysfunction. Transcripts from the IFN-gamma and IL-6 genes were also increased in ACR (p = 0.001 and 0.017, respectively), whereas increased IL-8 mRNA was correlated with irreversible loss of graft function (p = 0.02). TNF-alpha, IL-1 beta, and IL-10 gene transcripts were also detected during ACR, but were not quantitatively increased compared to other forms of graft injury (p > 0.2). We conclude that acute cellular rejection is associated with intragraft mRNA from the IL-2 gene. Other transcripts, including those from the IFN-gamma, IL-6, and IL-8 genes, are detected in increased amounts during this process. Messenger RNA from the TNF-alpha, IL-1 beta and IL-10 genes is also detected during ACR, but the presence of these transcripts is not exclusive to this process.

Expression of granzyme A and B proteins by cytotoxic lymphocytes involved in acute renal allograft rejection

Granzymes A and B are serine-proteinases stored in the granules of activated cytotoxic T-lymphocytes and natural killer (NK) cells. Expression of granzymes in tissues can be used as an activation marker for cytotoxic cells. Using mAbs specific for human granzyme A or B in immunohistochemical staining techniques we investigated expression of granzyme A and B by lymphocytes infiltrating acutely rejected renal allografts. Twelve core needle biopsies were taken from ten different patients during an episode of acute rejection. Eleven biopsies contained high numbers of granzyme A and B positive lymphocytes infiltrating tubular epithelium, and vascular and glomerular structures. In one patient infiltrating lymphocytes did not express granzyme A and only low amounts of granzyme B. No correlation was found between the number of granzyme positive cells and the severity of the rejection as classified by conventional histological criteria. In one tissue specimen from a patient with a renal allograft without signs of rejection, the number of granzyme positive cells was much lower compared to that of the transplant group. In spite of the presence of a marked inflammatory infiltrate, no granzyme positive cells were detected in renal biopsies from patients with various inflammatory, not transplant-related, renal diseases. Phenotypic analysis showed that granzymes A and B were expressed by CD56+ NK cells and CD3+ cells, representing cytotoxic T-lymphocytes. Thus, this study demonstrates that granzyme A and B protein-expressing lymphocytes infiltrate the kidney allografts during an acute cellular rejection but not in several other inflammatory renal diseases.(ABSTRACT TRUNCATED AT 250 WORDS)

T-cell receptor alpha and beta chain gene expression in cells infiltrating human cardiac allografts

Intragraft T-cell receptor (TCR) alpha and beta chain variable region gene expression was analyzed in human cardiac allograft biopsies by reverse transcription polymerase chain reaction. Rearranged TCR alpha and beta chain gene transcripts were detected in all biopsies examined (N = 23), indicating the presence of T cells bearing the alpha/beta TCR even in the absence of microscopically apparent leukocyte infiltration. In this analysis, a broad TCR alpha/beta repertoire in actively rejecting lesions was demonstrated, whereas fewer TCR alpha and beta chain gene families were detected in nonrejecting lesions. The number of expressed TCR V beta chain gene families typically was two- to sixfold higher than that of V alpha chain families in all biopsies tested. This asymmetric relation was present throughout the histologic grading spectrum of the biopsies. Based on these data, the TCR repertoire is heterogenous even in the early stages of mononuclear cell infiltration of the allograft. Also based on the data, the presence of T cells in grafts with minimal cellular infiltrates is not a specific marker of subsequent rejection episode, because T cells were identified in all allograft biopsies.

Variables affecting the T cell receptor V beta repertoire heterogeneity of T cells infiltrating human renal allografts

Donor-specific, alloreactive T cell lines may be grown from cells infiltrating human renal allografts. These T cell lines utilize restricted T cell receptor (TCR) beta-chain variable (V beta) gene repertoires, although long-term culture appears to be necessary for restriction to be observed. This study was undertaken to determine the effects of potential selective pressures on the TCR repertoires of allograft-infiltrating cells. TCR V beta repertoires of 30 allograft-derived T cell populations, cultured for defined, short time periods, were examined using polymerase chain reaction. When first derived, V beta repertoires of graft-infiltrating T cells were as heterogeneous as those of peripheral blood lymphocytes (PBL). There was no relationship between the length of time an allograft was in situ or the extent of HLA mismatch and repertoire heterogeneity. Repertoire restriction was positively correlated with the length of time cells were cultured in vitro. Long-term, alloreactive mixed lymphocyte reactions (MLR), established from normal, unsensitized PBL, also demonstrated V beta repertoire restriction during expansion in vitro. Restricted alloreactive populations emerged much more slowly from the MLR than from the allograft-derived cultures, however, implying that graft infiltrates contain previously activated populations of T cells. This observation, taken together with the fact that long-term, graft-derived cell lines maintain donor specificity, suggests that functional subsets must be allowed to emerge from heterogeneous infiltrates before TCR repertoire may be correlated with alloreactivity and/or graft rejection.

Characterization of T cells expressing the gamma/delta antigen receptor in human renal allografts

To investigate the role of gamma/delta+ T cells in allograft rejection, we have studied the TCR phenotype and function of lymphocytes infiltrating rejecting, rejected, and nonrejecting human renal allografts. Two-color immunohistologic staining showed that 19% of rejecting biopsies and 40% of rejected nephrectomies had significant infiltration (> 10% of the total T-cell population) with gamma/delta+ T cells. No biopsies from nonrejecting kidneys showed > 10% gamma/delta+ T cells. Flow-cytometry analysis of T-cell populations expanded from rejecting and rejected allografts demonstrated that 33% of biopsy- and 40% of nephrectomy-derived populations had significant percentages (> 10%) of gamma/delta+ T cells. Six cell lines with increased numbers of gamma/delta+ T cells were tested for cytolytic activity against the NK target cell line K562 and compared with cytotoxic activity of exclusively alpha/beta T-cell populations. Lysis was noted by all gamma/delta+, but no gamma/delta-, populations. To confirm that the cytotoxicity of these gamma/delta+ T-cell populations was not MHC directed, one nephrectomy-derived population with 69% gamma/delta+ T cells by cytometry and > 50% by immunohistology was studied extensively. High levels of killing were seen against the NK targets K562 and Daudi as well as other malignant, benign, and third-party renal cell lines, but relevant alloantigen-expressing targets were not killed. Sterile cell sorting was used to isolate the gamma/delta+ T cells. The gamma/delta+ cells displayed enhanced killing of K562 while the gamma/delta- cells showed no cytolytic activity. Cytotoxicity mediated by gamma/delta+ T cells was also demonstrated against donor-derived, untransformed renal cells.(ABSTRACT TRUNCATED AT 250 WORDS)

Specificity of T cells invading the skin during acute graft-vs.-host disease after semiallogeneic bone marrow transplantation

The mechanisms responsible for skin lesions during acute graft-vs.-host disease (aGVHD) after allogeneic bone marrow transplantation (BMT) are poorly understood. The exact role of various effector cell populations and "major" (particularly HLA-DP) or "minor" antigens as target molecules is not known. To investigate the nature of cells responsible for tissue injury, we cultured T cells from skin biopsy first with interleukin 2 (IL-2) alone and then in polyclonal activation conditions to avoid in vitro antigenic sensitization before specificity testing. We applied this method to two biopsies performed during aGVHD after semiallogeneic BMT and obtained cytotoxic T cells against four graft mismatches: CD8+ T cells against HLA-A2.2 and HLA-B27 and CD4+ T cells against HLA-DP101 and HLA-DP401. This demonstrates that T cells with documented specificity can be obtained from an aGVHD lesion without antigenic selection. Moreover, these data directly implicate DP as a potential target antigen for aGVHD.