Activation of human T cells obtained pre- and post-interleukin-2 (IL-2) therapy by anti-CD3 monoclonal antibody plus IL-2: implications for combined in vivo treatment

Injury to autologous normal tissues and tumors mediated by lymphokine-activated killer (LAK) cells generated in vitro from peripheral blood mononuclear cells of glioblastoma patients

Activation of peripheral blood mononuclear cells (PBMC) with IL-2 generates lymphokine-activated killer (LAK) cells that show a broad target cell range. In adoptive immunotherapy using in vitro-generated LAK cells, the intensity and specificity of their cytotoxic activity affect the prognosis of cancer patients. The present study was designed to examine the tumor-specific spectrum of T lymphocytes generated from the PBMC of patients with recurrent glioblastoma by in vitro propagation with IL-2 plus either soluble or solid-phase anti-CD3 monoclonal antibody (MAb) in short-term or long-term cultures. Both short-term and long-term culturing with solid-phase anti-CD3 MAb plus IL-2 yielded broad-reactivity CD8+ alphabetaT and gammadeltaT lymphocytes, both of which were non-MHC restricted, as shown by the fact that they were able to lyse autologous glioblastoma cells, MHC class I+II- allogeneic glioblastoma cells, and MHC class I-II-NK-sensitive K562 target cells. More importantly, these cells from patients failed to lyse fresh autologous PBMC. These results demonstrate that cells generated using this approach are non-MHC-restricted LAK cells and exhibit marked tumor specificity. In contrast, incubation with soluble anti-CD3 MAb generated T lymphocytes that after long-term culture, were either CD4+ or CD8+. These caused significant lysis of both allogeneic and autologous glioblastoma target cells, the extent of lysis being greater than that using cells produced by culturing with the solid-phase MAb. However, both the CD4+ and CD8+ cells also caused greater lysis of autologous normal PBMC, indicating that cells generated using this approach may cause significant adverse reactions in cancer patients if used for immunotherapy.

High concentrations of interleukin-2 selectively suppress T-cell dependent humoral immune responses

The recent therapeutic application of immunoregulatory cytokines, most notably the T-cell growth factor, interleukin-2 (IL-2), marks the advent of a new class of pharmacologic agents. In the present studies the effects of exogenous IL-2 on in vitro humoral immune responses in spleen cells isolated from female B6C3F1 mice were investigated. In vitro direct addition of low concentrations of rmIL-2 (25 U/ml) to naive spleen cells induced a moderate enhancement of the T-cell dependent antibody forming cell (AFC) response to sRBC. Similarly, low concentrations of rmIL-2 (10-50 U/ml) enhanced T-cell independent AFC responses to DNP-Ficoll and LPS. Interestingly, high concentrations of rmIL-2 (100 or 250 U/ml) selectively suppressed the T-cell dependent AFC response but not T-cell independent AFC responses to either DNP-Ficoll or LPS. Neither immunoenhancing (25 U/ml) nor immunosuppressive (200 U/ml) concentrations of rmIL-2 altered the kinetics of the sRBC response. Temporal addition studies indicated that high concentrations of rmIL-2 (200 U/ml) were only inhibitory when added to the cultures during the first 24 h following antigen sensitization. Conversely, a significant enhancement of the response was observed when 200 U/ml rmIL-2 was added 48 h following antigen sensitization. These results are in agreement with previous reports that the presence of high concentrations of IL-2 render T-cells unresponsive to subsequent antigen stimulation but that the high concentrations of IL-2 enhance immune responses when added at 48 h following antigen sensitization.

Immune response developing in tumorous organism as a result of immunotherapy. Chance of recovery?

S-allylgutimine has immunostimulant and tumor cell inhibitory activities. This complex action may be a result of the stimulation of IL-2 production. The effectiveness of immunotherapy depends on the uncoupling of IL-2 downregulation. This principle can be widely used with those immunological diseases where IL-2 level is decreased through downregulation. The Kokonov reaction, which was used originally to indicate tumors, is presumably a marker of immunoreactivity. According to one hypothesis no specific antigen can be found on the surface of neoplastic cells but another type, 'weak antigen' appears, which originates from the alteration of a cell surface glycoprotein beta 1-6 saccharide chain branching that is directly related to the increased immune reactivity. The inhibition of downregulation enhances the elimination of neoplastic cells whose membrane surface glycoproteins are altered.

Application of the direct beta counter Matrix 96 for cytotoxic assays: simultaneous processing and reading of 96 wells using a 51Cr-retention assay

To assess the cytotoxic activity of immune cells, we have developed a 51Cr-retention assay in which the radioactivity retained by 51Cr-labeled target cells, following coincubation with cytotoxic cells, is monitored using the automated Matrix 96 beta counter. The Matrix 96 is designed for simultaneously counting 96 samples isolated from a 96-well microplate. It uses 96 uniform and independent detectors operating on the principle of avalanche gas ionization in the Geiger-Muller mode. Samples must be dry because the detectors are of the open-window type. Therefore, samples from the 96 wells of the microplate are simultaneously harvested onto a filter using the MicroMate 196, a 96-well cell harvester, dried and quantified in the Matrix 96. Usually the 51Cr isotope is measured by the detection of gamma radiation in gamma counters. The Matrix 96, however, monitors Auger electrons, which are also emitted by 51Cr. We have shown that the retention assay can be used to monitor the cytotoxic activity of activated lymphocytes including lymphokine-activated killer cells and tumor-infiltrating lymphocytes against various tumor cell lines. This assay is most suitable for experiments in which low E/T ratios are sufficient to detect highly cytotoxic cells, such as clone screening in cloning assays or in limiting-dilution analysis assays. These assays involve processing and reading large numbers of microplates. In this case, the retention assay monitored in the Matrix 96 will improve the work flow and decrease the amount of radioactive waste.

HLA-Dr-expressing CD8bright cells are only temporarily present in the circulation during subcutaneous recombinant interleukin-2 therapy in renal cell carcinoma patients

The effect of subcutaneous recombinant interleukin-2 (rIL-2) therapy on the "activation status" of peripheral blood lymphocytes (PBL) of 17 renal cell carcinoma patients was investigated in a longitudinal study. The expression of the activation markers HLA-Dr and CD25 on cytotoxic T cells, helper T cells, and natural killer (NK) cells, was analysed using two-colour flow cytometry of whole-blood samples. In addition, the ability of isolated PBL to proliferate in vitro in response to various stimuli was investigated. The absolute amounts of NK cells and HLA-DR-expressing NK cells increased continuously during the whole course of therapy. The absolute amounts of T cells and HLA-Dr-expressing T cells, however, showed an early increase only during the first 1 or 2 weeks of therapy, after which the absolute amounts of HLA-Dr-expressing T cells decreased. In particular, the absolute amount of HLA-Dr-expressing CD8bright+ T cells was significantly lowered in the second half of therapy. PBL collected on day 7 of therapy (post-cycle-1 PBL) showed, as compared to those collected prior to therapy (pretherapy PBL), a decreased proliferative response in vitro after stimulation with phytohaemagglutinin, concanavalin A, soluble CD3 mAb (WT32) or rIL-2. This decreased in vitro response of post-cycle-1 PBL was also reflected in a decrease in the percentage of CD8bright+ T cells expressing HLA-Dr in cultures with rIL-2 or CD3 mAb, in contrast to cultures of pretherapy PBL, which showed an increase of this percentage. We conclude that T cells are the predominantly stimulated subpopulation during the first 2 weeks of subcutaneous rIL-2 therapy. The significant decrease in the absolute amounts of HLA-Dr-expressing T cells in the peripheral blood during the second half of therapy may partly be explained by a decreased responsiveness to rIL-2, but a selective redistribution of HLA-Dr-expressing cells may also be involved.

Adoptive immunotherapy of cancer: biological response modifiers and cytotoxic cell therapy

Immunotherapy has been developed for the treatment of metastatic cancers refractory to conventional therapies. Immunotherapy utilizes immune cells and/or biological response modifiers (BRMs) to induce an anti-tumor response mediated by the patient's immune system. BRMs, including lymphokines and cytokines, are used as single agents or in combination for cancer therapy. Some BRMs, particularly interleukin 2 (IL-2), can activate and expand in vitro lymphocytes with anti-tumor reactivity which will be adoptively transferred to the patient. To enhance the therapeutic effect of immunotherapy, gene therapy is currently under investigation and involves the insertion of cytokine genes in immune cells or in tumor cells. The development and future of cancer immunotherapy will be discussed in this review.

Antibody-targeted interleukin 2 stimulates T-cell killing of autologous tumor cells

A genetically engineered fusion protein consisting of a chimeric anti-ganglioside GD2 antibody (ch14.18) and interleukin 2 (IL2) was tested for its ability to enhance the killing of autologous GD2-expressing melanoma target cells by a tumor-infiltrating lymphocyte line (660 TIL). The fusion of IL2 to the carboxyl terminus of the immunoglobulin heavy chain did not reduce IL2 activity as measured in a standard proliferation assay using either mouse or human T-cell lines. Antigen-binding activity was greater than that of the native chimeric antibody. The ability of resting 660 TIL cells to kill their autologous GD2-positive target cells was enhanced if the target cells were first coated with the fusion protein. This stimulation of killing was greater than that of uncoated cells in the presence of equivalent or higher concentrations of free IL2. Such antibody-cytokine fusion proteins may prove useful in targeting the biological effect of IL2 and other cytokines to tumor cells and in this way stimulate their immune destruction.