Autologous Mixed Lymphocyte-tumor Cultures Research Articles

Interleukin-2 gene-transduced human leukemic cells induce major histocompatibility complex-restricted and -unrestricted anti-leukemic effectors in mixed lymphocyte-tumor cultures.

To explore the feasibility of designing vaccination protocols in acute leukemia patients with cytokine gene-transduced leukemic cells, we studied in vitro the growth potential of human leukemic cells transduced with the interleukin-2 (IL-2), IL-7, or IL-7 plus IL-2 genes, as well as the capacity of generating both autologous and allogeneic cytotoxic lymphocytes directed against the parental cells. A lymphoblastic T-cell line, ST4, obtained from a patient in long-lasting complete remission, was retrovirally engineered with the IL-2, IL-7, and IL-7 plus IL-2 genes; in addition, clones releasing different amounts of the cytokines were obtained by limiting dilution. Mixed lymphocyte-tumor cultures (MLTCs) were set up with parental or transduced leukemic cells as stimulators and with autologous or allogeneic lymphocytes as responders. When nonirradiated ST4 parental cells or clones producing <50 international units (IU)/mL/10(6) cells/72 hours of IL-2 were used as stimulators, leukemic overgrowth was observed in MLTCs within 16 days of culture. When clones producing >80 IU/mL/10(6) cells/72 hours of IL-2 were used as stimulators, the proliferation of leukemic cells was blocked and the transduced leukemic cells were completely cleared from the cultures by day 16; repeated restimulations with IL-2-producing leukemic cells were required to sustain long-term lymphocyte survival. On the contrary, when IL-7- or IL-7-IL-2-producing cells were used as stimulators, only a delay in leukemic cell overgrowth was observed, and lymphocytes were completely cleared from the cultures after day 60. IL-7 production by the different clones ranged between 11 and 36 ng/mL/10(6) cells/72 hours, whereas the highest IL-2-producing IL-7-IL-2 clone released 50 IU/mL/10(6) cells/72 hours of IL-2. When the stimulator efficacy of the highest IL-2-producing clone (ST4/IL-2#A7) was compared with that of exogenous IL-2 plus parental cells, a 7-fold higher amount of exogenous IL-2 was required to achieve the same results obtained with IL-2-producing leukemic cells. Autologous and allogeneic long-term MLTCs (up to 35 days) with ST4/IL-2#A7 as the stimulator were capable of generating cytotoxic effectors equally endowed with both major histocompatibility complex (MHC) class I-unrestricted and -restricted activity against parental ST4 cells. By day 18 of both autologous and allogeneic cultures, a substantial proportion of CD56+ cells was consistently recorded; this was coupled to a predominantly MHC-unrestricted cytotoxic activity directed against parental ST4 cells. CD56+ cells decreased considerably at the end of the different MLTCs, together with the unrestricted cytotoxic activity. At this time, >50% of the cells were CD8+, and 55% of the activity could be blocked by an anti-MHC class I monoclonal antibody. The results of this study demonstrate that IL-2 gene-transduced human acute leukemia cells cocultured with both autologous and allogeneic lymphocytes are capable of inducing a strong MHC-unrestricted anti-leukemic activity and subsequently "educating" MHC class I-restricted anti-leukemic effectors. The evidence that the immunogenic potential of human leukemic blasts can be boosted after transfer of the IL-2 gene suggests that the possibility of using leukemic cells engineered to release IL-2 as a therapeutic vaccine needs to be explored further.

Specific Autologous Anti-Melanoma T Cell Response in vitro Using Monocyte-Derived Dendritic Cells

Dendritic cells (DC) are antigen-presenting cells initiating primary and secondary immune responses. Since malignant tumors are able to escape immunologic control, DC might be prime candidates to activate the immune system against tumor cells. In an autologous system, a dynamic interaction among monocyte-derived DC (MoDC), T lymphocytes, and tumor cells obtained from melanoma patients could be noted. MoDC were generated from blood monocytes in the presence of GM-CSF, IL-4, and IFN-gamma. T cells were isolated either from peripheral blood or from lymph nodes. Melanoma cells were harvested from surgically removed tumor metastases. They were then gamma-irradiated and co-cultured with autologous MoDC and T lymphocytes. After 5 days, the lymphocytes showed a high proliferative activity and the majority of them were CD8-positive. In five cases tested, they revealed a high cytotoxic activity resulting in apoptosis of tumor cells. These findings suggest that MoDC are capable of initiating an effective specific anti-tumor response in a strictly autologous mixed lymphocyte tumor culture (MLTC), even though tumor-specific antigens had not been individually defined. Therefore (I) whole melanoma cells can serve as a source of antigen, (II) monocyte-derived dendritic cells may process and present melanoma-specific antigens resulting in a strong lymphocyte proliferation, (III) the majority of responding T lymphocytes are CD8-positive, and (IV) an acquired cytotoxic response eventually leads to apoptosis of the melanoma cells. The reaction demonstrated here permits to in vitro and quantitatively monitoring the effect of T cell directed immunotherapies such as the adoptive immunotherapy of tumors.

Prediction of Postoperative Clinical Course by Autologous Tumor-Killing Activity in Lung Cancer Patients

Fifty patients with primary localized lung cancer were tested at the time of surgery for the ability of their lymphocytes to kill autologous, freshly isolated tumor cells, and the assay was evaluated for prognostic significance. Peripheral blood lymphocytes of 27 patients (54%) demonstrated significant autologous tumor-killing activity in 6-hour 51Cr-release assays. Twenty-three of the 27 patients with autologous tumor-killing activity remained tumor free and survived more than 5 years after curative surgery, while all 23 who were negative for autologous tumor-killing activity relapsed by 18 months after surgery and died within 42 months after surgery. The differences in survival curves for the two groups were highly significant (P less than .00003). Autologous tumor-killing activity was not correlated with natural killer (NK) cell activity against K562 human myeloid leukemia cells or proliferation of lymphocytes stimulated with autologous, freshly isolated tumor cells in mixed culture. There were no differences in total survival between patients with positive results and those with negative results in tests of NK cell activity and autologous mixed lymphocyte-tumor culture reaction. These results indicate that autologous tumor-killing activity is a meaningful prognostic indicator and provide evidence for immunological control of tumor growth and metastasis. According to our preliminary data, it is unlikely that lung cancer patients who remain tumor free after 60 months of follow-up will develop recurrence or die from the disease. We are conducting a study to determine whether induction of autologous tumor-killing activity before surgery, by treatment with biological response modifiers,can improve the clinical outcome in patients who do not naturally have this potential.

Tumor‐specific T‐cell clones recognize different protein determinants of autologous human malignant melanoma cells

This study attempts to characterize human melanoma-associated tumor antigens that are recognized by autologous T-lymphocyte clones. Peripheral blood lymphocytes of a melanoma patient (AV) were activated in an autologous-mixed-lymphocyte tumor culture (AMLTC) and responding cells were cloned using irradiated autologous melanoma cells (AV-Mel) as antigen source, EBV-transformed B-lymphoblasts as feeder cells and recombinant Interleukin 2. T-cell clones were isolated which proliferated in response to autologous tumor cells, but not to autologous B-lymphoblasts (AV-B), and which were cytolytic for AV-Mel cells. In an attempt to identify the antigens recognized, an in vitro test system was used, in which 3H-Thymidine (3H-TdR) incorporation by T lymphocytes was measured in the presence of protein from AV-Mel cells presented by irradiated autologous accessory cells. Antigen-bearing particles of AV-Mel or AV-B cells were prepared by spotting cell lysates onto nitrocellulose (NC) followed by dissolution with DMSO and precipitation with an aqueous buffer. T cells sensitized against autologous melanoma cells were specifically stimulated by NC-bound AV-Mel protein. Stimulation required the presence of AV-B accessory cells, indicating that B-lymphoblasts are able to present tumor antigens. This approach facilitates screening of polypeptide fractions of AV-Mel cells separated by polyacrylamide gel electrophoresis followed by Western blotting for their capacity to stimulate antigen-dependent T-cells. CD4+ and CD8+ tumor-specific clones appear to recognize different antigens on the tumor cell: proliferation of an antigen-dependent CD8+ clone was stimulated by 240- and 24-kDa protein fractions, while proliferation of 2 antigen-dependent CD4+ clones was observed either with an 84- or with 140- and 55-kDa fractions. Molecular definition of the different antigens of tumor cells recognized by autologous T cells may be a prerequisite in attempts to manipulate T-cell-mediated anti-tumor responses in a controlled way.

DR antigen expression on ovarian carcinoma cells does not correlate with their capacity to elicit an autologous proliferative response.

Expression of HLA-DR antigens by purified preparations of human ovarian carcinoma cells freshly isolated from surgical specimens was examined in parallel with the capacity of tumor cells to elicit a blastogenic response from autologous lymphocytes in mixed lymphocyte-tumor culture (MLTC) assay. Of 21 tumor preparations, 11 (52%) reacted with monoclonal antibodies 279 and/or 949 specific for a monomorphic determinant of HLA-DR antigens, with heterogeneous positivity, ranging between 30% and 95%. In this series of patients positive MLTC occurred in 8/21 individual experiments. The HLA-DR expression was proportionally similar in tumors giving positive MLTC (4/8 = 50%) and negative MLTC (7/13 = 53%). The lack of correlation between DR expression on tumor cells and stimulatory activity in autologous MLTC and the fact that DR-negative tumors could induce lymphocyte stimulation, support the hypothesis that blastogenesis occurs upon recognition of tumor-associated antigens, different from DR molecules, possibly tumor-specific antigens.

Autologous mixed lymphocyte-tumor reaction and autologous mixed lymphocyte reaction. II. Generation of specific and non-specific killer T cells capable of lysing autologous tumor.

The specific and non-specific nature of autotumor cytotoxicity induced in autologous mixed lymphocyte-tumor culture (AMLTC) and autologous mixed lymphocyte culture (AMLC) was studied in patients with carcinomatous pleural effusions. Small- and medium-sized blood lymphocytes that were isolated by centrifugation on discontinuous Percoll gradients did not lyse autologous, freshly isolated effusion tumor cells. In vitro activation of the small lymphocytes, but not of the medium lymphocytes, with autologous tumor cells generated cytotoxic potential restricted to autologous tumor. When stimulated with autologous non-malignant non-T cells, the medium lymphocytes, but not small lymphocytes, were triggered to cytotoxicity that acted not only on autologous tumor cells but also on allogeneic tumor cells, T blasts, and tumor cell lines. Experiments using monoclonal antibodies (MAb) and complement (C') showed that both types of killer cells were CD2+ CD3+ CD16- T cells. Autotumor cytotoxicity developed in AMLTC was mediated by the CD4- CD8+ T cell subset in 6 of 9 cases and the CD4+ CD8- subset in the other 3 cases. In contrast, cytotoxicity induced in AMLC was exerted exclusively by the CD8+ subset. The enrichment of blasts from cultured T cells on discontinuous density gradients enhanced autotumor killing activity, with no reactivity recorded for blast-depleted, resting T cells. Addition of mitomycin-C-treated large granular lymphocytes (LGL) to AMLTC abolished the induction of autotumor killer cells, whereas non-specific killer cells were generated in AMLC irrespective of the presence of LGL. These results indicate that stimulation of autoreactive T cells in AMLTC and in AMLC could induce 2 distinct types of autotumor killer cells.

Autologous mixed lymphocyte-tumor reaction and autologous mixed lymphocyte reaction. I. Proliferation of two distinct T-cell subsets.

In patients with carcinomatous pleural effusions blood T lymphocytes proliferated in vitro in response to autologous, freshly isolated effusion tumor cells in the autologous mixed lymphocyte-tumor culture (AMLTC) and to autologous blood non-T cells in the autologous mixed lymphocyte culture (AMLC). Treatment of the stimulator cells with the anti-HLA-DR monoclonal antibody (MAb) abrogated the stimulatory capacity in AMLC, but not in AMLTC. A subset of T cells that formed rosettes with autologous erythrocytes showed proliferative response to autologous non-malignant cells, whereas this subset did not respond to autologous tumor cells. Non-adherent lymphocytes were fractionated by centrifugation on discontinuous Percoll density gradients. Medium-sized T lymphocytes were excellent responders in AMLC, but were weak responders in AMLTC. Small T lymphocytes proliferated preferentially in AMLTC, but responded poorly in AMLC. Large granular lymphocytes (LGL) did not proliferate in mixed cultures of either type. Instead, LGL suppressed the T-cell proliferation in AMLTC. The same suppressor LGL, however, had no inhibitory effect on AMLC. Elimination of the CD4 subset reduced or abolished proliferative response in AMLC in all cases, whereas it was ineffective in diminishing the reaction in 6 of 8 AMLTC. In contrast, removal of the CD8 subset decreased or eliminated T-cell proliferation in 4 of 8 AMLTC, but in none of the AMLC. These results indicate that the autoreactive T lymphocytes detectable in response to tumor cells and non-malignant non-T cells differ in several characteristics. Thus, the reaction in the AMLTC is not due to contaminating non-malignant cells in the stimulator population and may be a tumor-induced proliferative response.

Suppression of T-cell Response in Autologous Mixed Lymphocyte-Tumor Culture by Large Granular Lymphocytes&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

The role of large granular lymphocytes (LGL) in the autologous mixed lymphocyte-tumor culture (MLTC) was studied in cancer patients with malignant pleural effusions. When blood lymphocytes were cocultured in vitro with autologous tumor cells freshly isolated from carcinomatous pleural effusions, [3H]thymidine incorporation was weakly stimulated on day 6 in 6 of 30 samples. Removal of LGL from the responder population by treatment with the Leu-7 or Leu-11b monoclonal antibody plus complement (C') induced or augmented the proliferative response. LGL and small T-lymphocytes were isolated by discontinuous Percoll gradient centrifugation and tested separately for the proliferative response to autologous tumor. T-cells proliferated in 24 of 30 cases, while LGL showed no proliferation. Addition of LGL to autologous mixed T-cell-tumor cultures suppressed the proliferation of T-cells. LGL, however, did not inhibit T-cell proliferation induced by alloantigens and lectins. The suppressive activity of Percoll-purified LGL was not reduced by OKT3 plus C' treatment, but it was totally abrogated by Leu-11b plus C'. Supernatants produced by 24-hour culture of LGL with autologous tumor contained soluble factors that suppressed the autologous MLTC without killing the autologous tumor or T-blasts. The LGL-mediated suppression was not abolished by anti-interferon-alpha or anti-interferon-gamma antibody. Activation of T-cells in the autologous MLTC induced lytic potential restricted to autologous tumor. In the presence of LGL, T-cells failed to develop autotumor killing activity. Once autotumor killer T-cells were generated in autologous MLTC, their cytotoxicity was no longer inhibited by LGL. These results indicate that LGL from patients with carcinomatous pleural effusions suppress the capacity of autotumor-recognizing T-lymphocytes to proliferate and develop autotumor cytotoxicity in the autologous MLTC. This could explain why fresh T-cells have no cytolytic activity to autologous tumor.

Lysis of Fresh Human Tumor Cells by Autologous Large Granular Lymphocytes and T-Lymphocytes: Two Distinct Killing Activities Induced by Coculture With Autologous Tumor&lt;xref ref-type="fn" rid="FN2"&gt;2&lt;/xref&gt;

The specific and natural killer (NK)-restricted nature of autologous tumor killing by blood lymphocytes was studied in patients with carcinomatous pleural effusions. Large granular lymphocytes (LGL) and small T-lymphocytes were isolated by centrifugation on discontinuous Percoll density gradients. Tumor cells freshly isolated from pleural effusions of cancer patients were classified according to their susceptibility to purified LGL from normal donors in a 4-hour 51Cr release assay. Of 15 NK-sensitive tumors, 14 were lysed by fresh autologous LGL, whereas only 2 were killed by T-cells. Neither LGL nor T-cells were cytotoxic to NK-resistant autologous tumor. LGL and T-cells were then cultured in vitro with autologous tumor cells for 6 days. In 13 of 15 autologous mixed lymphocyte-tumor cultures (MLTC) NK-sensitive tumor-cultured LGL maintained their autotumor killing activity, whereas LGL cultured alone lost the activity. Depletion of high-affinity sheep erythrocyte-rosetting cells from Percoll-purified LGL resulted in an enrichment of effector cells. LGL from autologous MLTC were able to kill NK-susceptible allogeneic effusion tumor and K562 as were fresh LGL. No lysis of NK-resistant autologous tumor was observed with cultured LGL. In contrast, activation of T-cells in autologous MLTC resulted in the generation of autotumor killer cells in 10 of 15 NK-sensitive and 3 of 6 NK-resistant tumor samples. However, cultured T-cells were incapable of killing allogeneic tumor and K562. In autologous MLTC T-cells proliferated in response to autologous tumor, whereas no proliferation was observed in the culture of LGL. The enrichment of blasts from cultured T-cells on discontinuous Percoll gradients induced an augmentation of autotumor cytotoxicity, with no reactivity in blast-depleted, small, resting T-lymphocytes. These results indicated that 2 distinct types of autotumor-recognizing lymphocytes, LGL and T-cells, are present in the peripheral blood of cancer patients.