Human allograft-derived T-cell lines: donor class I- and class II-directed cytotoxicity and repertoire stability in sequential biopsies

CD4+ cells play a major role in xenogeneic human anti-pig cytotoxicity through the Fas/Fas ligand lytic pathway

BACKGROUND

In this study, the role of cell-mediated cytotoxicity by human leukocytes against pig endothelial cells was examined in vitro. The aim was to determine which cell subsets were responsible for this phenomenon and which pathways were involved in cell lysis.

METHODS

Primed human peripheral blood mononuclear cells (PBMC) or purified CD4+ or CD8+ T cells were used in a cell-mediated cytotoxicity assay in which cytotoxicity of an SV40 transformed porcine endothelial cell (EC) line (SVAP) was determined by Annexin V binding.

RESULTS

Human PBMC demonstrated specific lysis of porcine EC that was proportional to the effector: target ratio. CD4+ T cells accounted for >60% of this lysis, whereas CD8+ T cells accounted for <20%. CD4+ T cell-mediated lysis depended on direct recognition of porcine major histocompatibility complex class II molecules as inhibition of swine leukocyte antigen class II on porcine EC-inhibited CD4+ T cell cytotoxicity. This lysis was mediated through the Fas/FasL pathway as addition of anti-Fas and/or anti-FasL antibody profoundly inhibited antiporcine lysis. In addition, FasL gene expression was detected in primed PBMC and CD4+ T cells by RT-PCR, whereas granzyme B gene expression was not. Primed CD4+ T cells demonstrated high level FasL protein by Western blotting and two-color FACS analysis, whereas NK cells and CD8+ T cells did not. Finally, recombinant human FasL induced apoptosis in Fas expressing porcine EC cells, demonstrating that human FasL interacted with and activated Fas on porcine EC cells.

CONCLUSIONS

In conclusion, human to pig cell-mediated cytotoxicity was mediated predominantly by CD4+ T cells through the Fas/FasL pathway of apoptosis. These results suggest that direct cytotoxicity by xenoreactive CD4+ T cells may be one of several effector mechanisms involved in cellular xenograft rejection.

Apoptosis of mononuclear cell infiltrates in cardiac allograft biopsy specimens questions studies of biopsy-cultured cells

During acute rejection, CD4 and CD8 T cells infiltrate the myocardium and cause myocyte death and dropout. CD4 and CD8 cells use a number of cytotoxic mechanisms, including fas-fas ligand interactions, which lead to apoptotic death. Since fas is expressed on myocytes, we investigated endomyocardial biopsy specimens from cardiac transplant patients to determine whether apoptosis is one of the mechanisms of cell death in acute rejection. Serial sections of individual endomyocardial biopsy specimens from patients histologically diagnosed as having grade 3A rejection (n=22 biopsy specimens), biopsy specimens showing a typical "Quilty effect" (n=10), and specimens with concurrent grade 3A rejection and the Quilty effect (n=6) were evaluated using the C-terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) technique for frequency of apoptosis in myocytes and mononuclear cell infiltrates. None of the examined sections showed detectable evidence of apoptotic myocytes, even within regions clearly showing myocyte damage. Of interest was our consistent finding that 85-98% of mononuclear cell infiltrates within biopsy specimens scored as having grade 3A rejection had undergone apoptosis. In marked contrast, 9 of the 10 specimens with Quilty lesions showed <5% apoptotic mononuclear cells in the endomyocardial infiltrates. Of further interest was our finding of 85-98% apoptotic mononuclear cell infiltrates within Quilty lesions associated with biopsy specimens scored as having grade 3A rejection. The frequency of apoptotic cells determined by the TUNEL technique was confirmed by histological examination of the morphology of the cells and with a technique that involves detection of c-jun. These results prompt a note of caution in the interpretation of data on the phenotype, cytokine profile, Vbeta T cell receptor repertoire, and donor specificity of mononuclear cells cultured and propagated from such cardiac biopsy specimens. The possible reasons for apoptosis of graft-infiltrating mononuclear cells are discussed.

T cell receptor (TCR) repertoire in alloimmune responses

A large number of alloantigenic determinants could be generated by both the direct and indirect alloantigen presentation pathways. Hence, a heterogeneous population of T cells expressing a wide variety of receptors would be expected to respond to this diverse array of alloantigenic determinants. However, T cells expressing highly restricted T cell receptor (TCR) variable genes have been reported in a variety of alloimmune responses. A similar phenomenon has been observed in a wide variety of other immune responses, from those induced by superantigens, to very specific responses induced by a single peptide presented by a single MHC molecule. Given this scenario, the limited number of T cell clones which dominate an allograft rejection response, or for that matter an autoimmune response or a tumor specific response, could be therapeutically targeted by virtue of the selected TCR expression.

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)

Family study on HLA-DPB1 polymorphism: Linkage analysis with HLA-DR/DQ and two “new” alleles

An extensive family study on HLA-DPB1 was performed in 105 families living in northeastern Japan. In a linkage study between HLA-DPB1 and other HLA loci, five apparent recombinations between DPB1 and DR/DQ loci were observed. The recombination frequency (theta) with maximum probability was estimated to be 0.017 by the lod score method. DPB1 allele and haplotype frequencies in unrelated parents were determined by direct counting. The most common allele was DPB1*0501 with the frequency of 41.2% and the second was DPB1*0201 with 24.0%. Nine DPB1-DR and six DPB1-DQ haplotypes were in significant linkage disequilibrium. Seven kinds of extended haplotypes were observed to be over 1%, in which the most common haplotype A24-B52-DR15-DQ6-DPB1*0901 occurred at 6.0%. Moreover, we found two "new" DPB1 alleles in this study. The first one possesses a single base substitution from DPB1*0501 resulting in an amino acid change. The other is most likely to be formed by an intraexonic recombination between DPB1*0301 and DPB1*0501.

Positive correlation between oligonucleotide typing and T-cell recognition of HLA-DP molecules

The identification of 19 different HLA-DPB1 sequences implicates the existence of more DP specificities than can be typed for with cellular methods. How many of the DP beta sequences can be specifically recognized by T cells, and which of the polymorphic regions can contribute to the specificity of allorecognition, is not known. In order to investigate the distribution and the immunological relevance of recently described DPB1 alleles, we have typed a panel of 98 randomly selected Dutch Caucasoid donors for the HLA-DPB1 locus by oligonucleotide typing. Comparison of the typing results with primed lymphocyte typing (PLT) defined DP specificities shows an extremely good correlation. Moreover, additional alleles could be defined by oligonucleotide typing reducing the number of DP blanks in the panel. By selecting the appropriate responder stimulator combinations we were able to show that distinctive PLT reagents against oligonucleotide defined specificities DPB1*0401, DPB1*0402, DPB1*0901, and DPB1*1301 can be generated. To investigate in more detail which part of the DP molecule is responsible for the specificity of T-cell recognition, T-cell clones were generated against HLA-DPw3. The clones were tested for the recognition of stimulators carrying DPB1 alleles which had been defined by oligonucleotide typing and sequence analyses and which differed in a variable degree from DPB1*0301. The recognition patterns demonstrated that differences of one amino acid in polymorphic regions situated either in the beta sheets or alpha helix of the hypothetical model of the HLA class II molecule can eliminate T-cell recognition. Furthermore, sequence analyses revealed a new DPB1 allele designated DPB1*Oos.

Clonal analysis of graft-infiltrating lymphocytes from renal and cardiac biopsies. Dominant rearrangements of TcR beta genes and persistence of dominant rearrangements in serial biopsies

Graft-infiltrating lymphocytes from both human renal and cardiac allografts were propagated in interleukin 2 in order to evaluate rearrangements in the T-cell receptor (TcR) beta-chain genes. Individual biopsies from renal allografts during episodes of cellular rejection were examined as well as multiple biopsies of heart transplant patients from whom endomyocardial samples were taken prior to, during, and after episodes of rejection. TcR beta-chain rearrangements were evaluated in Southern blots using DNA extracted from interleukin 2-propagated cells and digested with restriction endonucleases permitting assessment of rearrangements to both C beta 1 and C beta 2. Rearrangements shared among greater than 5% of the "bulk" culture appear as nongermline bands when hybridized with a C beta probe. Single-cell progeny were generated from limiting dilution, and the rearrangements among the cloned progeny compared to the "bulk" of the cultured progeny of graft-infiltrating lymphocytes. The results indicate that "dominant" rearrangements are a common feature of renal allograft-infiltrating lymphocytes (14 of 15 cases examined). Since the number of cells which can be recovered from a given cardiac biopsy may be limiting, evaluation of clonal dominance from these cultures is more difficult to evaluate. However, sharing of "dominant" rearrangements among multiple biopsies from the same cardiac allograft patient indicates an in vivo selection for T cells with the same receptor rearrangement. Analysis of individual clones showed 3/33 clones from a renal allograft sharing the "dominant" rearrangement noted in the bulk culture, but none of these "dominant" clones showed antidonor specificity.(ABSTRACT TRUNCATED AT 250 WORDS)

T-cell receptor gene usage and expression in renal allograft-derived T-cell lines

Southern blot analyses indicate that the T-cell receptors of alloreactive T-cell lines derived from needle biopsies of human kidney allografts are selected based on beta-chain usage. In order to examine this selection at the level of T-cell-receptor expression, we have generated monoclonal antibodies directed toward the T-cell-receptors of three allograft-derived T-cell lines, MH3, WP3, and EH3. Monoclonal antibodies have been isolated which appear to react specifically with each of these three T-cell lines. One anti-MH3 antibody precipitates a molecule from the surface of MH3 cells that comigrates with the alpha/beta TcR on a polyacrylamide gel. Ten WP3-reactive monoclonal antibodies were identified which cause a modulation of CD3 from the surface of WP3 T cells, although none as yet precipitates a molecule from lysates of surface 125I-labeled WP3 cells. Since Northern blot analysis of EH3 RNA has revealed that a member of the V beta 6 gene family is expressed by this T-cell line, we are attempting to identify a monoclonal antibody reactive with this V beta 6 gene product.

Specific, major histocompatibility complex-unrestricted recognition of tumor-associated mucins by human cytotoxic T cells

We have previously reported the establishment of cytotoxic T-cell lines from pancreatic cancer patients, by continuously stimulating tumor-draining lymph node cells with allogeneic pancreatic tumor cell lines. After the preliminary characterization of their phenotype and tumor specificity, detailed studies performed with one of the cell lines, W.D., show that it recognizes a specific antigen, a large and heavily glycosylated mucin molecule, expressed on pancreatic and breast tumors and tumor cell lines. Although this recognition appears major histocompatibility complex (MHC)-unrestricted, the antigen receptor used by the cytotoxic T cell is the alpha/beta heterodimer, typically found on MHC-restricted T cells. The target antigen is atypical, however, in its ability to directly bind and activate the T cells in the absence of self MHC, presumably by abundant and regularly repeated antigenic epitopes. These findings are important because they demonstrate a specific T-cell response against a human tumor-associated antigen. In addition to pancreatic and breast tumors, various mucin molecules are known to be produced by other tumors of epithelial cell origin and could be expected to stimulate similar T-cell-mediated immune responses.