Circulating donor-specific cytotoxic T lymphocytes with high avidity for donor human leukocyte antigens in pediatric and adult cardiac allograft valved conduit recipients.

OBJECTIVE: Specific immunological responses may be involved in the process of cryopreserved allograft valved conduit (AVC) degeneration, which is more frequently seen in young recipients. Rejection of heart and corneal allografts is preceded by an increase in the fraction of cytotoxic T lymphocytes (CTL) with high avidity for donor human leukocyte antigens (HLA) circulating in both peripheral blood and the affected graft. These donor-specific high-avidity CTLs are regarded as the destructive cells capable of causing graft damage. To monitor the precursors of these cells (CTLp) in young and adult AVC recipients, in vitro quantitative tests were performed on sequentially taken blood samples to quantitate CTLp frequencies and their avidity for donor antigens. METHOD: Six children and nine adults who received a cryopreserved AVC in the period between 1994 and 1997 were included in the study. From these patients, two to six blood samples were obtained up to 3 years after valve implantation. The number of circulating CTLp present within the peripheral blood mononuclear cell (PBMC) population was determined by limiting dilution analysis (LDA). The fraction of CTLp with high avidity for donor HLA class I was determined by addition of CD8 monoclonal antibodies (mAb) during the cytotoxic phase of the assay. Third-party stimulator cells were used to verify the donor-specificity of the response. RESULTS: The number of donor-specific CTLp increased significantly in the period 6-12 months after AVC implantation, while third-party-specific CTLp frequencies were not affected. Additionally, we found a significant increase of the high-avidity fraction of CTLp directed against donor antigens as early as during the first 6 months after AVC implantation. The fraction of high-avidity CTLp remained significantly higher post- compared with pre-implantation, even after 12 months. We observed no significant difference in the kinetics of CTLp frequencies between pediatric and adult AVC recipients. CONCLUSION: Implantation of cryopreserved human AVC induces an increase in the total number of circulating CTLp directed against donor HLA class I in both adults and children. The shift towards more destructive high-avidity CTLp in the peripheral blood indicates their potential damaging effect towards the heart valve allograft.     

Induction of human cytotoxic T lymphocytes specific for prostate-specific antigen

Prostate-specific antigen (PSA), a tissue-specific protein expressed by most adenocarcinomas of the prostate, might be a useful target for T-cell-mediated immunotherapy of prostate cancers. The current study examined whether it is possible to elicit human cytotoxic T lymphocytes (CTL) with specificity for PSA. A synthetic nonamer peptide, corresponding to residues 146–154 of PSA and containing a canonical HLA-A2-binding motif, was shown to stabilize the expression of HLA-A2 on the T2 antigen-processing mutant cell line. Repeated in vitro stimulation of peripheral blood lymphocytes from a normal HLA-A2⁺ donor induced CTL with specificity for the PSA 146–154 peptide. The peptide-induced CTL expressed the CD4⁻ CD8⁺ cell surface phenotype and were restricted by HLA-A2. A large portion of patients with prostate cancer express the HLA-A2 phenotype, implying that many prostate cancers might be targeted by HLA-A2-restricted CTL with specificity for the PSA 146–154 epitope. Prostate 30:73–78, 1997. © 1997 Wiley-Liss, Inc.     

Increase of donor-specific cytotoxic T lymphocyte precursors after transfusion

Cytotoxic T lymphocyte precursor (CTLp) frequencies were determined in the blood of 10 patients before and after transfusion. The male patients were selected from those on the waiting list for a heart or kidney transplantation, who had received no previous blood transfusions and had no panel-reactive antibodies. Both the limiting dilution curves obtained before as well as after transfusion were linear and applied to zero-order kinetics, indicating that only cytotoxic T cells were limiting in the assay. In 9 out of 10 patients CTLp frequencies against the blood donor antigens significantly increased (up to 107 times) compared to the CTLp frequencies measured before transplantation. The CTLp frequencies against controls, sharing no HLA antigens with the blood transfusion donor, were only slightly increased (up to 5 times) in 7 patients and decreased in 3.     

Analysis of cytotoxic T lymphocyte response in rejecting allografted canine kidneys

The involvement of cytotoxic T lymphocytes (CTL) in the rejection process of allografted canine kidneys was studied. The frequency of donor-specific (precursor) CTL was determined with a sensitive limiting dilution assay. Longitudinal sampling of peripheral blood and kidney aspiration biopsies were used to obtain information on the CTL response toward the graft. An accurate analysis of CTL kinetics in both kidney and peripheral blood of allografted dogs appeared to be technically possible. During the first days after transplantation precursor CTL (CTLp) frequencies decreased in both blood and kidney. A minimum CTLp frequency of 5-15% of the pretransplant value was reached in the peripheral blood at day 4 after transplantation. The cause of this decrease, which was observed in all 5 allografted dogs is discussed. CTLp frequencies increased after day 4 and showed an exponential rise in the kidney before serum creatinine increased due to loss of kidney function caused by rejection. The data obtained with the quantitative study of CTL show that rejection of a canine kidney allograft is accompanied by a rise in CTL numbers in the kidney. The methodology developed permits extensive functional analysis of cellular processes in allografted organs.     

Adoptive immunotherapy using specific cytotoxic T lymphocytes against human lung-cancer-engrafted severe combined immunodeficiency mice.

OBJECTIVE: We studied the ability of human lung-cancer-specific cytotoxic T lymphocytes to suppress the growth of human lung adenocarcinoma (PC-9) engrafted in severe combined immunodeficiency mice. METHODS: PC-9-specific cytotoxic T lymphocytes were generated by multiple stimulation with irradiated PC-9 cells of regional lymph node lymphocytes from lung cancer patients expressing the same human leukocyte antigen-A locus haplotype as PC-9 following expansion due to the administration of immobilized anti cluster of differentiation 3 mAb and interleukin-2. Cytotoxic T lymphocytes showed specific cytotoxicity against PC-9 cells in vitro. Severe combined immunodeficiency mice with a subcutaneous graft of PC-9 were treated with a PC-9-specific cytotoxic T lymphocyte by i.v. injection and/or with interleukin-2 by s.c. injection. RESULTS: Cytotoxic T lymphocyte treatment suppressed PC-9 graft growth significantly an effect, significantly enhanced when combined with interleukin-2 injection. To evaluate the in vivo specificity of anti-PC-9 cytotoxic T lymphocytes, each mouse was subcutaneously inoculated in the right flank with PC-9, and in the left flank with A549 or Sq-1. Cytotoxic T lymphocytes plus interleukin-2 treatment was found to suppress PC-9 growth selectively, but not A549 or Sq-1 growth. CONCLUSIONS: These results provide sufficient rationale for conducting further clinical trials on immunotherapy using cytotoxic T lymphocyte for lung cancer patients.     

Treatment of human melanoma hepatic metastases in nude mice with human cytotoxic T lymphocytes

We investigated the effects of human melanoma-specific cytotoxic T lymphocytes in treating experimental human melanoma hepatic metastases in a nude mouse model of adoptive immunotherapy. Hepatic metastases were generated by intrasplenic injection of 1.5 x 10(6) human melanoma cells. Three days after injection, animals received salt solution and interleukin 2 or interleukin 2 and cytotoxic T lymphocytes. Twenty-four of 25 control animals had developed multiple tumor nodules in the liver; 11 of 13 animals receiving only interleukin 2 also had significant tumor burdens. In striking contrast, 17 of 18 animals receiving cytotoxic T lymphocytes and interleukin 2 had no gross or histologic evidence of tumors. The remaining animal had a 2-mm nodule. Human tumor-specific cytotoxic T lymphocytes are effective in vivo in a model of adoptive immunotherapy and may prove useful in adoptive immunotherapy of humans with metastatic melanoma.     

Clonotype analysis of cytomegalovirus-specific cytotoxic T lymphocytes

Cytotoxic T lymphocytes (CTL) control the replication of human cytomegalovirus (CMV). Previous studies assessed the clonotypic composition of CTL specific for individual immunodominant peptides within a certain HLA context. Such an approach has inherent limitations and may not assess the true clonal CTL response in vivo. Here, the clonotypic composition of CMV-specific CTL was determined in HLA-A2, CMV-seropositive kidney transplant recipients and healthy blood donors after stimulation of peripheral blood mononuclear cells with either a pp65 whole-peptide pool or a single immunodominant peptide. Even after stimulation with the whole peptide pool, CMV-specific CTL remained monoclonal or oligoclonal. Regarding intraindividual variation, the CDR3 motifs of the dominant clones were identical to those observed in CTL generated by the single immunodominant peptide. Sequencing of the CDR3 regions demonstrated significant interindividual variation; however, structural homology was observed for immunodominant clonotypes in three individuals. In conclusion, the highly focused T cell receptor repertoire found after stimulation with either a single immunodominant peptide or a peptide pool demonstrates a pivotal role for immunodominant epitopes in the generation of a clonal repertoire. These results provide new insights into the regulation of CMV clonal dominance and may contribute to the design and monitoring of adoptive immunotherapy.     

Mesenchymal stem cells inhibit the formation of cytotoxic T lymphocytes, but not activated cytotoxic T lymphocytes or natural killer cells

BACKGROUND: Mesenchymal stem cells (MSCs) can reduce the incidence of graft-versus-host disease because of their ability to inhibit T-lymphocyte proliferation. There are no publications on the effect that MSCs have on cytotoxic T lymphocytes (CTLs) and natural killer (NK) cells, effector cells vital for the graft-versus-leukemia effect. METHODS: Cytotoxic T cells were primed in mixed lymphocyte culture (MLC) against irradiated stimulator lymphocytes, and irradiated third-party MSCs were added at different time points. The CTLs were collected, and their cytotoxic potential was analyzed in a chromium-release assay against the same stimulator cells as in the MLC. Purified NK cells were mixed with irradiated MSCs, and the lysis was measured in chromium-release assay against K562 target cells. RESULTS: We found that MSCs inhibited CTL-mediated lysis by 70% if added at the beginning of the 6-day MLC. The lysis was not affected on day 3 or in the cytotoxic phase. Furthermore, MSCs inhibited the formation of cytotoxic lymphocytes when the cells were separated in a transwell system, which indicates that the effect is mediated by a soluble factor. NK cell-mediated lysis of K562 cells was not inhibited by MSCs. MSCs did not induce proliferation of allogeneic lymphocytes, and they were not lysed by allogeneic CTLs or NK cells. CONCLUSION: Our findings indicate that MSCs escape recognition by CTLs and alloreactive NK cells, and inhibit the formation of cytotoxic T cells by secreting a soluble factor, but that they do not interfere with CTLs and NK cell lysis.     

Reactivity of in-vitro-expanded alloimmune cytotoxic T lymphocytes and Qa-1-specific cytotoxic T lymphocytes against AKR leukemia in vivo

The ability of alloimmune spleen cells expanded in mixed leukocyte culture (MLC) and cloned cytotoxic T lymphocytes (CTL) to kill H-2-compatible leukemia in vivo was evaluated. In comparison with fresh alloimmune spleen cells, MLC-expanded cells had a significantly higher frequency of CTL reactive against leukemia targets in vitro. However, the reactivity of MLC-expanded cells against first-passage spontaneous AKR (H-2k) leukemia in vivo was significantly less than when an equivalent number of fresh alloimmune spleen cells was injected. Comparable antileukemia reactivity was observed in vivo only when the inoculum of MLC-expanded cells was 2-3-fold higher than that of fresh spleen cells. This relative ineffectiveness was attributed to the altered migration pattern of cultured cells in vivo. IL-2-dependent cloned CTL, specific for a normal lymphocyte antigen (Qa-1b) also present on leukemia cells, were derived from MLC-expanded cultures and tested in vivo. For cloned CTL, as with MLC-expanded cells, eradication of AKR leukemia in vivo was associated with the tissue distribution pattern of the injected effector cells. That is, an effective antileukemia reaction was achieved only in tissues in which effector and target proximity was maintained. Qa-1b-specific cloned CTL did not interfere with engraftment of autologous or allogeneic bone marrow in lethally irradiated host mice, nor did they cause any clinically evident graft-versus-host disease. These findings suggest that cloned CTL specific for a normal cell surface antigen with limited host tissue distribution, but present on tumor cells, could be used for adoptive immunotherapy, provided CTL and tumor cell proximity can be attained.     

A sensitive micromethod for generating and assaying allogeneically induced cytotoxic human lymphocytes.

A sensitive micromethod for generating and assaying allogeneically induced cytotoxic human lymphocytes in vitro is described. Responding lymphocytes are cultured with mitomycin-C treated allogeneic stimulating cells in wells of replicate microtrays for both one-way mixed leukocyte culture (MLC) and cell-mediated lympholysis (CML) assays. On day 5, MLC response is determined by measuring 3H-thymidine (3H-TdR) incorporation directly in wells of the MLC tray. On day 6 or 7 CML response is determined by measuring 51Cr released from labeled target cells added to replicate culture cells in the CML tray. It is thus possible to measure both MLC and CML responses of the 2.5 X 10(4) -U X 10(5) responding lymphocytes originally placed in replicate wells. 51Cr-labeled target cells can be added to wells containing dilutions of the stimulated cells and a log-linear relationship between the per cent specific 51Cr release and number of effector cells is observed. Significant levels of specific cytoxicity are detected at ratios as low as one effector cell per target cell; little cross-killing on third-party cells and no autokilling is observed. Lymphocytes purified from whole blood that is stored overnight at room temperature and purified lymphocytes stored overnight in the cold generate MLC and CML responses comparable to those of lymphocytes purified from fresh blood. Only 2 or 3 ml of whole blood are required to perform both MLC and CML assays, thus enabling the study of both proliferative and cytotoxic lymphocyte responses in young children and other individuals from whom only a few milliliters of blood can be obtained.     

Preparation of antisera with specificity for human T lymphocytes.

Antisera were raised in rabbits and sheep against human or monkey thymocyte or lymphocyte antigens. The unabsorbed antisera reacted equally strongly with T and B lymphoblasts. After partial absorption with B lymphoblasts antisera were specific for T lymphoblasts when tested by cytotoxicity, but still reacted with B lymphoblasts in indirect immunofluorescence. Extensive absorption with reusable columsn made from B cell antigens produced sera which reted selectively with T lymphoblasts and T leukaemic cells and were able to differentiate T and B cells in human peripheral blood.     

Successful treatment of a malignant rat glioma with cytotoxic T lymphocytes.

Brain tumors are highly resistant to therapy. Their diffuse infiltrative nature and the relative inaccessibility of brain tissue to blood and lymph are barriers to surgical and cytotoxic treatments alike. The purpose of this study was to produce immune cells specifically reactive with an anaplastic rat glioma (RT2) and determine whether those cells could affect tumor progression in the brain. RT2-specific cytotoxic cells were prepared by priming rats in vivo with RT2 tumor cells and Corynebacterium parvum and stimulating the primed lymphocytes in vitro with irradiated RT2 tumor cells and interleukin-2 (IL-2). Cultured cells exhibited a high level of cytotoxicity against RT2, but not C6 (an allogeneic glioma), 3M2N (a syngeneic mammary tumor), or CSE (a syngeneic fibrosarcoma) tumor cells. To generate a model for therapy, rats were injected intracerebrally with RT2, generating progressing brain tumors, which killed untreated rats in approximately 2 weeks. To test the therapeutic potential of the effector cells, tumor-bearing rats were treated by intravenous injection of lymphocytes on Day 5 of tumor growth. Treated rats also received a 5-day course of systemic IL-2 beginning on Day 5. Treatment with IL-2 alone, RT2-primed spleen cells, or RT2-primed spleen cells stimulated in vitro with C6 did not affect rat survival. However, tumor-bearing rats treated with RT2-stimulated lymphocytes exhibited increased survival or were cured. Systemic IL-2 was an essential adjunct, because survival was not affected by treatment with effector cells alone. Therapy initiated on Day 8 of tumor progression lacked effect on survival.(ABSTRACT TRUNCATED AT 250 WORDS)     

Donor-specific cytotoxic T lymphocyte hyporesponsiveness following renal transplantation in patients pretreated with donor-specific transfusions

Our purpose was to investigate the mechanism of the continuing beneficial effect of donor-specific transfusions in the cyclosporine era. We describe the development of donor-specific cytotoxic T lymphocyte hyporesponsiveness in peripheral blood lymphocytes obtained up to 2 years posttransplant in patients preconditioned with 3 DST plus azathioprine. In a group of 12 such patients, hyporesponsiveness developed gradually, becoming detectable in some patients as early as 1 month posttransplant and becoming statistically significant for the entire group at 9-12 months posttransplant. A complete specificity for donor alloantigens was seen in the hyporesponsiveness of some patients; in others, partial suppression of the response to a third party HLA-mismatched control was also seen. Although slight suppression of the mixed lymphocyte culture response was seen in some patients, overall there were no statistically significant differences in MLC responses to control or donor stimulators at any time point posttransplant as compared with pretransplant, pre-DST. The mechanism of donor-specific CTL hyporesponsiveness 2 years posttransplant was explored in one patient (HLA A1, 2, B 57, 60; DR 3, 6) who had received a 2-HLA haplotype-mismatched kidney transplant from her husband (HLA A2,--; B5, 8; DR4,--) following DST plus AZA pretreatment. Bulk culture CTL analysis showed specific nonresponsiveness to donor stimulators; however in the presence of exogenous recombinant IL-2, the antidonor response was restored to the level of pretransplant PBL. Limiting dilution analysis using recombinant IL-2 revealed equivalent precursor frequency of antidonor CTL in pre- and posttransplant PBL. These data suggest that the hyporesponsive PBL contained donor-specific CTL precursors but were deficient in helper function necessary for CTL maturation.     

Calcineurin inhibitor withdrawal in stable kidney transplant patients decreases the donor-specific cytotoxic T lymphocyte precursor frequency

BACKGROUND: In a prospective study, calcineurin inhibitors (CNI) were withdrawn in patients two years after kidney transplantation. We questioned whether stopping CNI had an effect on the donor-specific reactivity, as CNI might hinder immune responses leading to graft acceptance. METHODS: We measured the donor-specific cytotoxic T lymphocyte (CTL) precursor frequency (CTLpf) in 54 patients before and after withdrawal of CNI. In addition, the T-cell reactivity of PBMC to donor and third-party antigens was tested in MLR, and in IFNgamma-Elispot. Reactivity to tetanus toxoid (TET) was studied as well. RESULTS: Donor-specific CTLpf significantly decreased after CNI withdrawal (P=0.0001). In contrast, no difference was observed in third-party reactive CTLpf, donor and third-party reactive MLR and IFNgamma-Elispot. Proliferative responses and the number of IFNgamma-producing cells to TET also decreased after CNI withdrawal. The decrease in CTLpf correlated with the time between the two blood samples (before and after stopping CNI, P=0.05). This decrease was caused by stopping CNI, because there was no correlation between CTLpf and the duration of the CNI treatment after transplantation. Moreover, the percentage of regulatory T cells in the peripheral blood increased after CNI withdrawal. CONCLUSIONS: We report here that after withdrawal of CNI the donor-specific CTLpf decreases. We hypothesize that CNI suppress regulatory mechanisms that have the potential to down-regulate donor-specific CTL responses and reactivity to TET.     

Kinetics of cytotoxic T lymphocytes in stage IV-S neuroblastoma

The kinetics of cytotoxic T lymphocytes (CTL) in a patient with stage IV-S neuroblastoma were examined for 2 months. CTL were detectable during the preoperative and postoperative periods in this stage IV-S neuroblastoma patient, in spite of the tumor-bearing condition. Furthermore, the patient's mother showed the same level of CTL. This experiment suggests that patients with stage IV-S neuroblastoma have a constantly high level of CTL, and that this immunologic response is predominantly hereditary.