The human mixed lymphocyte-tumor cell interaction test. I. Positive autologous lymphocyte proliferative responses can be stimulated by tumor cells as well as by cells from normal tissues

Lymphocyte in vitro response to human giant cell tumors

Peripheral blood lymphocytes and tumor cells were obtained from 31 patients with giant cell tumors of bone and cocultured in vitro in a mixed lymphocyte tumor cell assay. The lymphocyte proliferative response was measured by incorporation of 3H thymidine. Also, the patients' lymphocytes were tested for proliferative reactivity to phytohemagglutinin and allogenic lymphocytes to evaluate nontumor immunologic competence. Mixed lymphocyte tumor cell assays showed higher lymphocyte stimulation in patients with Stage I as compared with Stages II and III giant cell tumors. The proliferative response was blocked partially when the patients' sera was used to supplement the cultures. Lymphocytes from patients with a recurring tumor showed lower responses, but the differences with primary tumors were not significant. This evidence suggests that there is an immune response to giant cell tumor antigens and that this response might be related to the aggressiveness of the tumor.

Augmentation of the generation of lymphokine-activated killer cells after a single dose of mitomycin C in cancer patients

The effect of mitomycin C administration on the generation of cytotoxic cells, induced by in vitro activation of peripheral blood mononuclear cells (PBM) with interleukin-2, was studied in patients with various carcinomas. The ability of PBM to generate lymphokine-activated killer (LAK) cell activity against Raji cell targets was significantly augmented 5 and 7 days after a single intravenous dose of 12 mg/m2 mitomycin C, when compared to that of PBM obtained before mitomycin C injection. Further, LAK cell activity against autologous tumor cells was also significantly increased after the drug administration. The distribution of lymphocyte subsets exhibited a significant increase in the percentage of CD3+ cells after injection, with the elevation of the CD4/CD8 ratio. Furthermore, the proportion of the CD4+ Leu8+ subpopulation, which identifies inducers of suppression, was significantly reduced. Thus, the decrease in the proportion of suppressor-inducer subsets of PBM might be at least partially, responsible for the augmented generation of LAK cells after mitomycin C administration.

Inhibition of lymphokine-activated killer cell generation by cultured tumor cell lines in vitro

The co-culture of human peripheral blood mononuclear cells (PBMC) with high concentrations of interleukin 2 normally generates lymphokine-activated killer (LAK) cells capable of indiscriminate lysis of tumor targets. However, the addition of certain cell-line-derived tumor cells to the LAK generation cultures within the first 48 h of culture initiation resulted in the suppression of the LAK cytotoxicity measured after 3-4 days of culture. Suppression could be achieved with tumor cell:PBMC ratios as low as 1:50 when tumor cells were derived from melanoma and colorectal cancer (G361, COLO320, HT-29), but suppression was not observed with cells from the breast cancer cell line SKBr3. No suppression of LAK generation was observed with normal epithelial cells from colon or breast, with autologous or allogeneic lymphoblasts, or with allogeneic vascular endothelial cells. Suppression was independent of the removal of adherent cells from PBMC, could not be prevented by indomethacin and was not attributable to interleukin 2 absorption/adsorption by tumor cells. The suppressive activity of some tumor cells could be augmented by preculture in recombinant gamma interferon. Serum-free supernatants from G361, COLO320 and HT-29 (but not SKBr3 or endothelial cells) were also highly suppressive towards the generation of LAK cells. The elaboration by tumor cells of factors capable of inhibiting LAK generation may partially explain the failure of LAK/interleukin 2 therapy in some experimental and clinical protocols.

Cancer patients' lymphocytes contain CD3+ CD4+ cells that proliferate in response to autologous tumor cells in the presence of exogenous low-dose interleukin-2 and autologous accessory cells

To see whether cancer patients possess CD3+ CD4+ lymphocytes able to proliferate in response to autologous tumor cells (Auto-Tu), this lymphocyte subset was isolated either by positive or negative selection, both methods resulting in highly enriched CD4+ populations. Unseparated and isolated CD3+ CD4+ lymphocytes were then assayed for proliferating activity in the presence or absence of various amounts of Auto-Tu, with or without recombinant interleukin-2 (IL-2) (1.5-15 U/ml) and DR+ adherent cells or E- lymphocytes as autologous accessory cells (Auto-AC). Isolated CD3+ CD4+ lymphocytes were stimulated by Auto-Tu alone in only 1 out of 12 cases. CD3+ CD4+ cells failed to proliferate significantly in response to low doses of IL-2 alone but the addition of Auto-Tu caused stimulation in 8 out of 12 cases (67%). The further addition of Auto-AC to Auto-Tu + IL-2 resulted in enhanced response of isolated CD3+ CD4+ lymphocytes in 6 out of 8 cases tested. When reactivities to Auto-Tu in the presence of IL-2 and IL-2 + Auto-AC were considered together, positive responses of CD3+ CD4+ lymphocytes were seen in 11 out of 12 cases (92%). On the other hand, unseparated lymphocytes were stimulated by Auto-Tu alone in none out of 12 cases. Unseparated lymphocytes, however, responded to IL-2 in 11 out of 12 cases; such a response was increased by the addition of Auto-Tu in only 2 cases. Moreover, the IL-2 proliferation of unseparated lymphocytes was suppressed in 4 and in 3 out of 12 cases tested when Auto-Tu or Auto-Tu + Auto-AC were added respectively. These data indicate that lymphocytes of cancer patients contain CD3+ CD4+ cells that are usually unable to proliferate in response to Auto-Tu only. This proliferation, however, occurs when low doses of exogenous IL-2 are present and can be further amplified by the addition of Auto-AC. No response of CD4+ cells is observed in the presence of DR+ Auto-AC + IL-2 except in 2 out of 7 cases tested (28%), suggesting an Auto-Tu-restricted reactivity of CD3+ CD4+ lymphocytes in the majority of cases.

Tumour-associated proliferative responses in vitro of regional lymph nodes draining solid cancers in man

The proliferative responses in vitro of tumour-draining lymph node lymphocytes were evaluated against autologous colon and lung carcinoma cells. The reactivity of lymphocytes appeared to be directed against tumour-associated rather than tumour-specific antigens. The lymphocyte reactivity detected was not due to an autologous mixed lymphocyte reaction. Recombinant interleukin-2 augmented the responses detected but not their tumour specificity. Phenotypic characterisation indicated the presence of T suppressor/cytotoxic (TS/C) cells as well as natural killer (NK) cells. Only the later, however, were active in functional cytotoxicity assays. The inability to generate both tumour-specific proliferation of tumour-draining lymph node lymphocytes and tumour-specific cytotoxic killer cells may be due to the presence of suppressor cells in the regional lymph nodes; preliminary data suggest the presence of such 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.

Activation of lymphocyte anti-tumour responses in man: effector heterogeneity and the search for immunomodulators

Data continues to accumulate on the immunological reaction against solid human cancers. The evidence at the present time supports the view that rather than being immunologically invisible, tumour cell antigens are recognised by at least three lymphocyte subsets. Helper T cells can be induced to proliferate upon exposure to cells of the autologous tumour and to secrete detectable levels of interleukin 2 (IL-2). Cultured T cell lines and clones can be shown to respond in primed lymphocyte tests not only to autologous tumour cells but also to allogeneic tumour cells of the same histology and anatomic location. Cytotoxic T cells manifest specific reactivity against cells of the autologous tumour which is distinguishable from natural killing (NK) on the basis of specificity and organ distribution. Natural killer cells can lyse freshly isolated autologous tumour cells after purification on Percoll gradients or when activated by IL-2. There is thus a demonstrable heterogeneity of response to human cancer in unseparated lymphocyte populations and at the clonal level. In limiting dilution assays lymphocytes at the tumour site respond more frequently to autologous tumour relative to NK targets. For at least some tumours there is evidence that the expression of auto-tumour reactivity but not NK correlates with the clinical course of the disease and is a favourable prognostic indicator. The finding of these auto-tumour reactivities has important implications for the search for immunomodulating drugs for cancer treatment. However, it must be recognised that the response is heterogeneous and that the immune system comprises multiple interactive elements that exhibit both positive and negative control. Any treatment modality must take this into account and seek to focus on specific activation of the tumour lytic populations or the inhibition of negative regulatory elements as opposed to seeking a more general augmentation of immune reactivity which may, by stimulating suppressor cells, have a counterproductive effect.

Lymphokine-activated killer (LAK) cells. Analysis of factors relevant to the immunotherapy of human cancer

Lymphokine-activated killer (LAK) cells can be generated by incubating fresh peripheral blood lymphocytes (PBL) in Interleukin-2 (IL-2). LAK cells kill fresh autologous and allogeneic human tumor cells in vitro. This study analyzes aspects of LAK cells that make them a promising candidate for the adoptive immunotherapy of human cancer. LAK cells can be generated from PBL of normal individuals and tumor-bearing patients. Pure, recombinant IL-2 generates LAK cells capable of killing a wide variety of tumors including sarcomas and cancers of the colon, pancreas, adrenal gland, and esophagus. Thirty-six of 41 (88%) fresh, noncultured, human tumor cell suspensions prepared from surgical specimens were lysed by LAK cells in a standard 4-hour chromium-release assay. Normal PBL were not killed. LAK cells can be expanded in vitro for periods longer than 2 months, potentially more than 10(20)-fold, while maintaining lytic ability. These results and the demonstrated efficacy of LAK cells in the therapy of murine tumors make LAK cells a candidate for clinical use in the adoptive immunotherapy of human cancer.