Interleukin 1 beta synergises with interleukin 2 in the outgrowth of autologous tumour-reactive CD8+ effectors

Extracorporeal Photopheresis: A Case of Immunotherapy Ahead of Its Time

Extracorporeal photopheresis (ECP) is a cell-based immunotherapy that involves the reinfusion of autologous leukocytes after exposure to psoralen and UVA. The treatment has been used for over 30 years, at first on patients with cutaneous T-cell lymphoma (CTCL) and later for the management of patients with graft-versus-host disease (GvHD), sclerosing disorders, atopic dermatitis, and other diseases that may share the common driving factor of a pathogenic T-cell clone or clones in blood circulation. Patients with clinical improvement mount an antigen-specific immune response that may have tolerance traits in the case of GvHD or anticlonal cytotoxic characteristics in the case of CTCL. The exact mechanisms that dictate one response or the other are not fully understood, but the evidence accumulated so far indicates that multiple events occur simultaneously and consequentially contribute to the end result. These include contact of cells with the outside (plastics and tubing of the ECP apparatus), exposure to psoralen and UVA that activates platelets, monocytes, and other myeloid cells, the release of damage-associated molecular patterns, differentiation of monocytes into dendritic cells, and generation and successive presentation of numerous antigens after the phagocytosis of apoptotic cells. Once reintroduced, the ECP product increases the frequency and activity of regulatory T cells (Tregs), shifts the systemic cytokine balance, and promotes extravasation of immune cells that together shape the effects of this treatment. In this review, we summarize the seminal work and most recent literature of the therapeutic mechanisms and reflect on future avenues of improvements and applications of ECP.

Extracorporeal photopheresis promotes IL-1β production

Extracorporeal photopheresis (ECP) is a widely used clinical cell-based therapy exhibiting efficacy in heterogenous immune-mediated diseases such as cutaneous T cell lymphoma, graft-versus-host disease, and organ allograft rejection. Despite its documented efficacy in cancer immunotherapy, little is known regarding the induction of immunostimulatory mediators by ECP. In this article, we show that ECP promotes marked release of the prototypic immunostimulatory cytokine IL-1β. ECP primes IL-1β production and activates IL-1β maturation and release in the context of caspase-1 activation in monocytes and myeloid dendritic cells. Of interest, IL-1β maturation by ECP was fully intact in murine cells deficient in caspase-1, suggesting the predominance of an inflammasome-independent pathway for ECP-dependent IL-1β maturation. Clinically, patient analysis revealed significantly increased IL-1β production in stimulated leukapheresis concentrates and peripheral blood samples after ECP. Collectively, these results provide evidence for promotion of IL-1β production by ECP and offer new insight into the immunostimulatory capacity of ECP.

Inflammasome activation of IL-1 family mediators in response to cutaneous photodamage

Although keratinocytes are relatively resistant to ultraviolet radiation (UVR) induced damage, repeated UVR exposure result in accumulated DNA mutations that can lead to epidermal malignancies. Keratinocytes play a central role in elaborating innate responses that lead to inflammation and influence the generation of adaptive immune responses in skin. Apart from the minor cellular constituents of the epidermis, specifically Langerhans cells and melanocytes, keratinocytes are the major source of cytokines. UVR exposure stimulates keratinocytes to secrete abundant pro-inflammatory IL-1-family proteins, IL-1α, IL-1β, IL-18, and IL-33. Normal skin contains only low levels of inactive precursor forms of IL-1β and IL-18, which require caspase 1-mediated proteolysis for their maturation and secretion. However, caspase-1 activation is not constitutive, but dependents on the UV-induced formation of an active inflammasome complex. IL-1 family cytokines can induce a secondary cascade of mediators and cytokines from keratinocytes and other cells resulting in wide range of innate processes including infiltration of inflammatory leukocytes, induction of immunosuppression, DNA repair or apoptosis. Thus, the ability of keratinocytes to produce a wide repertoire of proinflammatory cytokines can influence the immune response locally as well as systematically, and alter the host response to photodamaged cells. We will highlight differential roles played by each IL-1 family molecule generated by UV-damaged keratinocytes, and reveal their complementary influences in modulating acute inflammatory and immunological events that follow cutaneous UV exposure.

Malignant and tuberculous pleural effusions: immunophenotypic cellular characterization

INTRODUCTION AND OBJECTIVES

Tuberculosis and cancer are the main causes of pleural effusion. Pleural involvement is associated with migration of immune cells to the pleural cavity. We sought to characterize the immunophenotype of leukocytes in the pleural effusion and peripheral blood of patients with tuberculosis or malignancy.

METHODS

Thirty patients with tuberculosis (14) or malignancy (16) were studied. A control group included 20 healthy blood donors.

RESULTS

Malignant phycoerythrin pleural effusions showed higher percentages of CD3, CD4, CD3CD45RO, and CD20CD25 lymphocytes and lower percentages of CD3CD25 and CD20HLA-DR when compared to PB lymphocytes. Compared to PB, tuberculous effusions had a higher percentage of lymphocytes that co-expressed CD3, CD4, CD3CD45RO, CD3TCRalphabeta, CD3CD28, and CD20 and a lower percentage of CD14, CD8 and CD3TCRgammadelta-positive lymphocytes. Malignant effusions presented higher expression of CD14 whereas tuberculous effusions had higher expression of CD3 and CD3CD95L. Peripheral blood cells from tuberculosis patients showed higher expression of CD14, CD20CD25 and CD3CD95L. Compared with the control cells, tuberculosis and cancer peripheral blood cells presented a lower percentage of CD3CD4 and CD3CD28-positive cells as well as a higher percentage of CD3CD8, CD3CD25 and CD3CD80-positive cells.

CONCLUSIONS

Tuberculous and malignant peripheral blood is enriched with lymphocytes with a helper/inducer T cell phenotype, which are mainly of memory cells. CD14-positive cells were more frequently found in malignant effusions, while CD3-positive cells expressing Fas ligand were more frequently found in tuberculous effusions.

Ii-Key/HER-2/neu(776-790) hybrid peptides induce more effective immunological responses over the native peptide in lymphocyte cultures from patients with HER-2/neu+ tumors

We have demonstrated that coupling an immunoregulatory segment of the MHC class II-associated invariant chain (Ii), the Ii-Key peptide, to a promiscuous MHC class II epitope significantly enhances its presentation to CD4+ T cells. Here, a series of homologous Ii-Key/HER-2/neu(776-790) hybrid peptides, varying systematically in the length of the epitope(s)-containing segment, are significantly more potent than the native peptide in assays using T cells from patients with various types of tumors overexpressing HER-2/neu. In particular, priming normal donor and patient PBMCs with Ii-Key hybrid peptides enhances recognition of the native peptide either pulsed onto autologous dendritic cells (DCs) or naturally presented by IFN-gamma-treated autologous tumor cells. Moreover, patient-derived CD4+ T cells primed with the hybrid peptides provide a significantly stronger helper effect to autologous CD8+ T cells specific for the HER-2/neu(435-443) CTL epitope, as illustrated by either IFN-gamma ELISPOT assays or specific autologous tumor cell lysis. Hybrid peptide-specific CD4+ T cells strongly enhanced the antitumor efficacy of HER-2/neu(435-443) peptide-specific CTL in the therapy of xenografted SCID mice inoculated with HER-2/neu overexpressing human tumor cell lines. Our data indicate that the promiscuously presented vaccine peptide HER-2/neu(776-790) is amenable to Ii-Key-enhancing effects and supports the therapeutic potential of vaccinating patients with HER-2/neu+ tumors with such Ii-Key/HER-2/neu(776-790) hybrid peptides.

Pooled peptides from HER-2/neu-overexpressing primary ovarian tumours induce CTL with potent antitumour responses in vitro and in vivo

Unfractionated peptides (MW: up to 10 kDa), derived from HLA-A2.1 positive (+) HER-2/neu-overexpressing primary tumour cell acid cell extracts (ACE), were successfully used to generate in vitro cytotoxic T lymphocytes (CTL). Primary tumour cells were collected from peritoneal malignant effusions of patients with ovarian cancer. Acid cell extracts-induced CTL specifically lysed in an HLA-A2-restricted manner HER-2/neu+ autologous primary tumour cells as well as HER-2/neu+ tumour cell lines. In addition, adoptive transfer of such CTL significantly prolonged the survival of SCID mice xenografted with HLA-A2.1+, HER-2/neu+ human breast and ovarian tumour cell lines. Acid cell extracts collected from HLA-A2.1+ HER-2/neu negative (-) primary ovarian tumours induced HLA-A2.1-restricted CTL with weak in vitro and in vivo antitumour capacity, suggesting that HER-2/neu peptides within ACE from HER-2/neu-overexpressing primary ovarian tumour cells are immunodominant. The results presented herein serve as a rationale for the initiation of vaccination studies in patients with HER-2/neu-overexpressing ovarian tumours utilising autologous tumour-derived ACE.

p53 and FHIT mutations and microsatellite alterations in malignancy-associated pleural effusion

Cancer is a genetic disease and thus is influenced by oncogenes and tumor suppressor genes. To determine whether the genetic analysis of pleural fluid can be used to diagnose malignant effusion, we investigated p53 and FHIT mutations and microsatellite alterations (MA) in the pleural fluid of 40 patients with pleural effusion associated with malignancy (ME) and in the pleural fluid of 17 patients with tuberculous pleurisy (TB) as a control group. p53 mutations were detected in five ME patients (13%) and in no TB patient, and FHIT mutations were detected in seven ME patients (18%) and two TB patients (12%). For four microsatellite markers, D3S1234, D3S1285, D9S171, and TP53, in ME patients, loss of heterozygosity (LOH) was seen in 10 (25%), 5 (13%), 10 (25%), and 6 patients (15%), respectively, and microsatellite instability (MI) in 6 (15%), 0 (0%), 1 (3%), and 3 patients (8%), respectively. Using the same markers, in TB patients, LOH was seen in three (18%), one (6%), three (18%), and one (6%), respectively, and MI in one (6%), zero (0%), zero (0%), and zero (0%), respectively. Twenty-five ME cases (63%) exhibited MA (LOH or MI) in at least one marker. Moreover, in four (80%) of five ME cases with negative cytology and no carcinoembryonic antigen increase in pleural fluid, MAs were identified. In ME, positive cytology was found in 42.5%, and positive MA, using four markers, in 63%. Although still limited in terms of sensitivity and specificity, this study shows that molecular diagnostic strategies could enhance the diagnostic yield in cases of malignant effusion.

In vitro and in vivo antitumor activity of a mouse CTL hybridoma expressing chimeric receptors bearing the single chain Fv from HER-2/neu- specific antibody and the gamma-chain from Fc(epsilon) RI

To broaden the applicability of adoptive cellular immunotherapy against HER-2/neu overexpressing human cancers, we constructed a chimeric scFv/gamma gene composed of the variable regions of a HER-2/neu specific monoclonal antibody (mAb) joined to the signaling gamma-chain of the Fc(epsilon)RI receptor. The scFv(anti-HER-2/neu)/gamma chimeric gene was successfully expressed as functional surface receptor in the MD.45 cytolytic T-cell (CTL) hybridoma (MD.45-HER/gamma). Expression of the chimeric protein triggered IL-2 and IFN-gamma secretion in vitro upon encountering cell surface HER-2/neu and mediated non-major-histocompatibility-complex (MHC)-restricted HER-2/neu-specific target cell lysis. We also examined the in vivo activity of the MD.45-HER/gamma transduced cells. Severe combined immunodeficiency disease (SCID) mice that were given HER-2/neu positive (+) human tumor cell lines had significantly increased survival compared to mice treated with saline only, or with MD.45 cells transduced with a control anti-trinitrophenyl (anti-TNP) chimeric receptor gene (MD.45-TNP/gamma). These results demonstrate the feasibility of redirecting MD.45 CTL to react in vitro and in vivo with a variety of HER-2/neu(+) tumor cells by our gene transduction protocol. Moreover, they open the possibility of using the same chimeric gene for transducing primary lymphocytes and thus allowing adoptive immunotherapy against HER-2/neu(+) cancers.

A large quantity of CD3-/CD19-/CD16- lymphocytes in malignant pleural effusion from a patient with recurrent cholangio cell carcinoma

Tumor infiltrating lymphocytes (TILs) are candidates for adoptive cellular immunotherapy. Here we report on a patient whose TILs presented unusual lymphocyte antigens. Pleural effusions were collected from a 47-year-old man with recurrent cholangio cell carcinoma and malignant effusion. Effusion-associated lymphocytes (EALs) were separated by Ficoll-Hypaque gradient, and the EAL phenotype was determined by flow cytometry. The percentage of positive cells was determined for each lymphocyte-related differentiation antigen. The percentages of CD3+, CD19+, and CD16+ lymphocyte subpopulations among EALs were 20%, 7%, and 3%, respectively. Nearly 70% of EALs were CD3-/CD19-/CD56-/CD16- cells. The phenotypes of peripheral blood lymphocytes (PBLs) collected simultaneously from the patient's peripheral blood were CD3+ (52%), CD19+ (20%), and CD16+ (20%). When EALs were cultured in medium without pleural effusion, T cell-related antigens, but not B cell- or natural killer (NK) cell-related antigens, were newly expressed on EALs, and this expression reached a plateau after 48 h in culture. The proportions of CD3+, CD19+, and CD16+ cells were 69%, 7%, and 3%, respectively. However, when EALs were cultured in medium with pleural effusion, increased expression of T cell-related antigens was not observed; the proportions of CD3+, CD19+, and CD16+ cells were 16%, 6%, and 1%, respectively. Neither total cell numbers nor cellular viability of EALs changed significantly after in-vitro culture, suggesting that significant proliferation or death of EALs did not occur during the culture period. Co-culture of the patient's PBLs with autologous pleural effusion for 96 h did not alter the expression of lymphocyte-related antigens on the PBLs. These results indicate that expression of T cell-related antigens, but not B cell- or NK cell-related antigens, on EALs was blocked temporarily by the malignant pleural effusion. This is the first report concerning the existence of a large quantity of unclassified lymphocytes in which the T cell-related antigens were reversibly masked in the malignant pleural effusion.

Co-operation of IL-1 and IL-2 on T-cell activation in mononuclear cell cultures

In search of an optimized anti-cancer immunotherapy, the combination of IL-2 and IL-1 has been tried. In an in-vitro LAK model, this cytokine cocktail seemed to be quite promising. In our in-vitro model of IL-2 induced T-cell activation we have therefore investigated the co-operation of these two potent immunostimulators. Mononuclear cells were stimulated with CD3 activating antibody in the presence of different cytokines and blocking or neutralizing antibodies. Cytokine concentrations were detected in the supernatants with ELISA. Intracellular IFN-gamma and IL-4 in the different T-cell subsets was measured by flow cytometry. IL-1 and IL-1 receptor antagonist (IL-1Ra) were up-regulated by IL-2, this was achieved independently of IL-12 or CD40/CD40L interaction. As a negative feedback mechanism, IL-1beta induced its natural antagonist, IL-1Ra. Both endogenous and exogenous IL-10 suppressed IL-1beta and induced IL-1Ra, thus markedly decreased the amount of functional IL-1. The combination of IL-2 and IL-1beta lead to a mildly increased Interferon-gamma (IFN-gamma) secretion (+20%, p < 0.05), however, this appeared to be the result of an increased IFN-gamma production per secreting cell, rather than of an increased recruitment of non-secreting cells. Similarly, IL-6 was also induced in an additive fashion (+30%, p < 0.05). For both cytokines, this effect could be significantly augmented by neutralizing IL-1Ra. Concentrations of IL-2 induced IL-10 and soluble Fas ligand (sFasL) were not affected by IL-1beta. We were thus able to demonstrate that IL-1 relays its activity through different pathways than IL-2. Furthermore, we could show that the potentially synergistic action of IL-2 and IL-1 was hindered by the simultaneous induction of signficant amounts of IL-1Ra. From the latter findings we conclude that the combination of IL-2 and IL-1 for cytokine-induced anti-tumor activity may not, but a combination of IL-2 and anti-IL-1Ra might prove beneficial.

Tumor-specific CD4+ T lymphocytes from cancer patients are required for optimal induction of cytotoxic T cells against the autologous tumor

This study focuses on the specific CD4+ T cell requirement for optimal induction of cytotoxicity against MHC class II negative autologous tumors (AuTu) collected from patients with various types of cancer at advanced stages. CD4+ T cells were induced in cultures of cancer patients' malignant effusion-associated mononuclear cells with irradiated AuTu (mixed lymphocyte tumor cultures (MLTC)) in the presence of recombinant IL-2 and recombinant IL-7. Tumor-specific CD4+ T cells did not directly recognize the AuTu cells, but there was an MHC class II-restricted cross-priming by autologous dendritic cells (DCs), used as APC. CD8+ CTL, also induced during the MLTC, lysed specifically AuTu cells or DCs pulsed with AuTu peptide extracts (acid wash extracts (AWE)) in an MHC class I-restricted manner. Removal of CD4+ T cells or DCs from the MLTC drastically reduced the CD8+ CTL-mediated cytotoxic response against the AuTu. AWE-pulsed DCs preincubated with autologous CD4+ T cells were able, in the absence of CD4+ T cells, to stimulate CD8+ T cells to lyse autologous tumor targets. Such activated CD8+ T cells produced IL-2, IFN-gamma, TNF-alpha, and GM-CSF. The process of the activation of AWE-pulsed DCs by CD4+ T cells could be inhibited with anti-CD40 ligand mAb. Moreover, the role of CD4+ T cells in activating AWE-pulsed DCs was undertaken by anti-CD40 mAb. Our data demonstrate for the first time in patients with metastatic cancer the essential role of CD4+ Th cell-activated DCs for optimal CD8+ T cell-mediated killing of autologous tumors and provide the basis for the design of novel protocols in cellular adoptive immunotherapy of cancer, utilizing synthetic peptides capable of inducing T cell help in vivo.

Mistletoe lectin I-induced effects on human cytotoxic lymphocytes. I. Synergism with IL-2 in the induction of enhanced LAK cytotoxicity

This report demonstrates that in vitro activation of human cells with the beta-galactoside-specific lectin from mistletoe (ML-I) or interleukin-2 (IL-2) results in different patterns of activation and function of cytotoxic cells. It is now well established that natural killer (NK) and lymphokine-activated killer (LAK) cytotoxicity is mainly mediated by resting (NK) and IL-2-activated (LAK) CD56-positive (+) cells respectively. Culture of peripheral blood lymphocytes (PBL) for 3 days with ML-I led to expansion and activation of T cells which demonstrated NK- and LAK-like cytotoxicity. T lymphocyte subset analysis revealed that in total PBL, ML-I preferentially stimulated and expanded CD8+ T cells which mediated the cytotoxic effect. Incubation of highly purified CD8+ T cells alone with ML-I did not lead to induction of cytotoxicity, which required the presence of both CD4+ and CD14+ (monocytes) cells, suggesting that ML-I does not exert a direct effect on CD8+ T cells. Activation of PBL with both ML-I and IL-2 resulted in simultaneous induction of T and CD56+ cell-mediated NK and LAK cytotoxicity. These data suggest that treatment with ML-I and IL-2 might provide an approach to induce maximum cytotoxicity against tumors and to recruit both T and NK cells for tumor therapy.

Granulocyte-macrophage colony-stimulating factor improves immunological parameters in patients with refractory solid tumours receiving second-line chemotherapy: correlation with clinical responses

In this report, we studied the immunorestorative properties of subcutaneously administered granulocyte-macrophage colony-stimulating factor (GM-CSF) in patients with refractory solid tumours receiving second-line chemotherapy. Such patients exhibit abnormal immune responses in vivo and in vitro and, therefore, it was of interest to examine the effect of GM-CSF-induced immunomodulation on clinical response. We examined patients with primary malignant carcinomas (head and neck, n = 10; urogenital tract, n = 17; penis n = 6; colorectal, n = 8) who were treated with carboplatin (JM8), 300 ng/m2 on days 1 and 22, leucovorin (LV), 200 mg/m2 plus 5-fluoracil (5-FU), 500 mg/m2 on days 8, 15 and 29 and four cycles of daily injections with placebo or GM-CSF, 300 micrograms/day on days 3-6, 10-13, 17-20 and 24-27. Peripheral blood was collected from the patients one day after the end of each of the four-cycle injections with placebo or GM-CSF, namely on days 7, 14, 21 and 28. Peripheral blood mononuclear cells (PBMC) were tested in the autologous mixed lymphocyte reaction (AMLR) and for natural killer (NK) or lymphokine-activated killer (LAK) cell activity. Cytokine levels in serum were measured by immunoenzymatic (ELISA) assay. A total of 21 patients received a four-cycle regimen with GM-CSF (Group 1) and 20 were similarly treated with placebo (Group 2). All received standard chemotherapy as outlined above. Before GM-CSF treatment, all patients exhibited increased serum levels of interleukin-1 (IL-1 beta), tumour necrosis factor-alpha (TNF-alpha), IL-6 and prostaglandin E2 (PGE2) and decreased serum levels of IL-2. Cellular immune responses (AMLR, NK- and LAK-cytotoxicity) were also low in all patients. Five patients from Group 1 had a PR (partial response), 2 patients had CR (complete response), and 14 patients had stable disease. Seven patients from Group 2 showed progressive disease, 3 had a PR and 10 had stable disease. All immune parameters were significantly improved during treatment in Group 1 but remained unchanged or even deteriorated in Group 2. Administration of GM-CSF during treatment of cancer patients with conventional chemotherapeutic drugs results in a marked potentiation of deficient cellular immune responses in vitro and a change towards normalisation of cytokine serum levels. The results reported herein support the use of GM-CSF as immunopotentiator during chemotherapy, but more patients must be studied before definite conclusions can be drawn.

Elevation of interleukin-10 levels in malignant pleural effusion

STUDY OBJECTIVE

Human immunity has been found to have two major components, cellular and humoral immunity. T-helper type 1 (Th1) pathway favors cellular immunity and Th2 pathway favors humoral immunity. Early determination toward Th1 and Th2 cells in the immune response is dependent on the balance between interleukin-12 (IL-12), which favors Th1 responses, and IL-4, which favors Th2 responses. IL-2 and interferon-gamma (IFN-gamma) are produced in the Th1 pathway, and IL-4 and IL-10 are produced in the Th2 pathway. Lack of cellular immunity, IL-2, and IFN-gamma had been reported in malignant pleural effusions. However, to our knowledge, there are no previous reports on other cytokine components involving Th1 or Th2 pathway. The present study was designed to answer these questions.

DESIGN

Cytokine levels in peripheral blood and pleural fluid of 21 patients with malignant pleural effusion, including IL-4, IL-10, and IL-12, were analyzed with enzyme-linked immunosorbent assays. Lymphocyte subpopulations of peripheral blood and pleural effusion were also studied by using flow cytometry.

MEASUREMENTS AND RESULTS

The results showed a significant increase in IL-10 level as compared with blood samples. IL-4 and IL-12 were below minimal detectable concentrations both in the blood and the effusion. The ratio of pleural helper T cells was significantly higher than in the blood (p = 0.0002). The ratio of pleural natural killer (NK) cells was significantly lower than in the blood (p = 0.0001). The ratio of pleural suppressor T cells was lower than blood with borderline significance (p = 0.0522). No significant change in B-lymphocyte ratio between blood and pleural effusion was found (p = 0.2471). There was no correlation between difference in IL-10 level and lymphocyte subpopulation of pleural effusion and blood samples.

CONCLUSIONS

Helper T-cell subpopulations were increased while NK and suppressor T-cell subpopulations were decreased in malignant pleural effusions. The decrease in NK cell subpopulations with elevated IL-10 and minimal IL-12 concentration in neoplastic pleural effusion would suggest the usage of IL-12 or antibody of IL-10 to improve local cellular immunity. Further study is needed.

Enhanced human lymphokine-activated killer cell function after brief exposure to granulocyte-macrophage-colony stimulating factor

BACKGROUND

Lymphokine-activated killer (LAK) cell function can be generated in peripheral blood mononuclear cells (PBMC) after brief exposure of high dose interleukin-2 (IL-2) over the course of 1 or 2 days' culture in plain culture medium (IL-2-pulsed PBMC). The aim of the present study was to investigate the ability of granulocyte-macrophage-colony stimulating factor (GM-CSF) to augment LAK induction in low dose IL-2-pulsed PBMC derived from patients with cancer undergoing immunotherapy with IL-2.

METHODS

Peripheral blood mononuclear cells were collected from patients with cancer receiving a 5-day cycle of local (intraperitoneal or intrapleural) infusions with IL-2. The cells were incubated with IL-2 in the presence or absence of GM-CSF for 1 hour and then tested as effectors against allogeneic tumor cells and LAK-sensitive cell lines.

RESULTS

Granulocyte-macrophage-colony stimulating factor at doses between 10 and 100 ng/ml was synergized with low dose IL-2 (100 IU/ml) in the generation of LAK activity in PBMC. Lymphokine-activated killer cell-mediated cytotoxicity derived from PBMC cultures incubated with IL-2 and GM-CSF was significantly higher (up to three-fold) compared with that generated with IL-2 alone. The GM-CSF-induced enhanced LAK activity was maintained when tested at day 5. GM-CSF increased the percentages of IL-2 receptor (R) positive (+) and CD8+ cells in the IL-2-pulsed PBMC. In contrast to CD56+ cells, highly purified CD8+ cells isolated from PBMC pulsed with IL-2 and GM-CSF responded with increased LAK activity, thus representing the cell-type that mediates the augmenting effect of GM-CSF. Major histocompatibility complex (MHC) molecules or the CD3 surface antigens were not involved in the GM-CSF-mediated enhancement of LAK induction because anti-MHC class I and class II monoclonal antibodies (MoAb) or MoAb against the CD3 molecules remained without any effect in this system. The GM-CSF-mediated LAK-enhancement was IL-2-dependent because MoAb against IL-2 receptor completely inhibited the generation of LAK activity.

CONCLUSIONS

The use of GM-CSF for the enhancement of IL-2-induced LAK activity in 1 hour cultures may improve clinical results in cancer immunotherapy. In addition, implementation of this procedure could eliminate the high cost of cell culture which usually accompanies IL-2/LAK cell therapy as well as eliminate the known toxic side effects associated with this kind of therapy.

An improved fluorescence assay for the determination of lymphocyte-mediated cytotoxicity using flow cytometry

The use of the chromium-release assay to determine cytotoxicity of effector against target cells has various limitations mostly due to the inherent properties of the radioactive substance. We have developed an improved flow cytometric method that is able to measure cytotoxicity, based on two fluorescent dyes. Calcein-AM, a non-fluorescent substance which is intracellularly converted to the green fluorescent calcein by esterase activity in viable cells, is initially used to stain target cells. After incubating targets with effectors for 2 h, ethidium homodimer-1, a red DNA stain non-permeable to viable cells, is added. Dead target cells are distinguished by their double (green-red) staining. Data analysis is performed by gating the regions of living target, dead target and living effector cells, based on appropriate controls. Non-specific events are subtracted from the dead target region and the ratio of specific dead target events to total target events is expressed as percent cytotoxicity. The method is used to quantify natural killer (NK) and lymphokine-activated killer (LAK) activities against the human K562 and Daudi cell lines and the murine YAC-1 and L1210 cell lines respectively, as well as cell-mediated lympholysis (CML) exerted by tumor-infiltrating lymphocytes (TIL) against autologous and allogeneic human breast cancer tumor cells. The method is fast, reliable and correlates well with the standard 51Cr-release assay.