Involvement of cyclic adenosine monophosphate in the interleukin 4 inhibitory effect on interleukin 2-induced lymphokine-activated killer generation

The role of cytokine in regulation of the natural killer cell activity

Natural killer (NK) cells are characterized by a CD3-CD16+ CD56+ immunophenotype and have a central role in the innate immune system. They are defined by their capacity to kill certain tumor-target cells or virus infected cells without prior sensitization or MHC-restriction. The activity of the NK cells is determined by the balance between activation and inhibitory receptor molecules expressed on the surface of NK cells. However, several cytokines and chemokines can significantly modulate their activity, inducing increase of NK cell activity. Immunomodulation mediated by NK cells is very important mechanism in tumor immunity, as well as in other immunodepressions of the immune system. In this study, we summarize the role of several cytokines, including IFN, IL-1, IL-2, IL-4, IL-7, IL-12 and IL-17, on NK cell function. The NK cells, after activation, depending on cytokine environment, can differentiate into NK1 cells that produce Th1 cytokine type (IFN-?, IL-2, IL-12) or NK2 cells that produce Th2 type cytokines, enhance exocytosis and release of previously formed molecules from NK cells (granzyme, perforin). We also describe that the release of cytokines and mediators show local or distance effects, or induce apoptosis (mostly by secreted TNF-?) after binding appropriated killer cell receptors from TNF receptor superfamily.

The Induction of Nitric Oxide by Interleukin-12 and Tumor Necrosis Factor- in Human Natural Killer Cells: Relationship With the Regulation of Lytic Activity

We have investigated the interleukin-12 (IL-12) and tumor necrosis factor- (TNF)-induced regulation of human natural killer (NK) cell function and their relationship with nitric oxide (NO) generation. We demonstrate that both cytokines were efficient to trigger the transcription of the inducible nitric oxide synthase (iNOS) mRNA, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and intracytoplasmic fluorescence showed that iNOS protein was also induced by both cytokines. However, our data indicate that NO does not play a significant role in the effector phase of the cytotoxic activity mediated by NK-stimulated cells, inasmuch as the lytic activity was not affected in the presence of specific NO synthase inhibitors. When aminoguanidine (AMG), an inhibitor of iNOS, was added during the afferent phase of NK stimulation with IL-12 and TNF, a subsequent increase in the lytic potential of the effector cells towards the NK-sensitive target cells (K562) and lymphokine-activated killer (LAK) target cells (Daudi) was observed. Conversely, the addition of chemical NO donors during the afferent step resulted in a dose-dependent inhibition of the NK and LAK cytotoxicity. Our data suggest that the enhancement of NK-cell cytotoxic activity resulting from iNOS inhibition may be correlated, at least in part, to an increase in interferon-γ production and granzyme B expression.

© 1998 by The American Society of Hematology.

The Induction of Nitric Oxide by Interleukin-12 and Tumor Necrosis Factor- in Human Natural Killer Cells: Relationship With the Regulation of Lytic Activity

We have investigated the interleukin-12 (IL-12) and tumor necrosis factor- (TNF)-induced regulation of human natural killer (NK) cell function and their relationship with nitric oxide (NO) generation. We demonstrate that both cytokines were efficient to trigger the transcription of the inducible nitric oxide synthase (iNOS) mRNA, as detected by reverse transcriptase-polymerase chain reaction (RT-PCR). Western blot analysis and intracytoplasmic fluorescence showed that iNOS protein was also induced by both cytokines. However, our data indicate that NO does not play a significant role in the effector phase of the cytotoxic activity mediated by NK-stimulated cells, inasmuch as the lytic activity was not affected in the presence of specific NO synthase inhibitors. When aminoguanidine (AMG), an inhibitor of iNOS, was added during the afferent phase of NK stimulation with IL-12 and TNF, a subsequent increase in the lytic potential of the effector cells towards the NK-sensitive target cells (K562) and lymphokine-activated killer (LAK) target cells (Daudi) was observed. Conversely, the addition of chemical NO donors during the afferent step resulted in a dose-dependent inhibition of the NK and LAK cytotoxicity. Our data suggest that the enhancement of NK-cell cytotoxic activity resulting from iNOS inhibition may be correlated, at least in part, to an increase in interferon-γ production and granzyme B expression.

© 1998 by The American Society of Hematology.

Differential regulation of interleukin-12- and interleukin-15-induced natural killer cell activation by interleukin-4

The regulation of human natural killer (NK) cell activation is under the control of a network of regulatory signals provided by cytokines. In the present study, we investigated the functional interaction between interleukin (IL)-4 and two monocyte/macrophage-derived cytokines, IL-12 and IL-15, during the process of NK stimulation. Using freshly isolated human NK cells, we have demonstrated that IL-4 negatively regulates lymphokine-activated killer (LAK) activity induced by IL-15 against the NK-resistant Daudi target cells. In contrast, IL-4 had no effect on IL-12-stimulated LAK generation. The differential effect of IL-4 on NK cell activation by IL-12 and IL-15 correlates with its ability to increase or to down-regulate the level of tumor necrosis factor-alpha and interferon-gamma release by NK cells, respectively. In contrast, endogenous transforming growth factor-beta 1 does not appear to be involved in the IL-4 regulatory pathway. Furthermore, while IL-4 was found to decrease the basal expression of the IL-2 receptor beta subunit utilized by IL-15, it had no effect on the expression of the beta 1 chain of the IL-12 receptor compared to untreated cells. Northern blot analysis indicated that the IL-4 regulatory effect on NK lytic function was associated with its capacity to down-regulate granzyme B and perforin gene transcription in response to IL-15 and its failure to affect the expression of both gene's in response to IL-12. Together, these data suggest the existence of a distinct cross-talk between IL-4 and IL-15 or IL-12 signaling pathways during the regulation of human non-major histocompatibility complex-restricted cytotoxicity.

Human recombinant IL-4 decreases the emergence of non-specific cytolytic cells and favours the appearance of memory cells (CD4+CD45RO+) in the IL-2-driven development of cytotoxic T lymphocytes against autologous ovarian tumour cells

As IL-4 and IL-6 have also been reported to promote the development of T lymphocytes such as IL-2, we investigated their role in the development of specific cytotoxic T lymphocytes (CTL) against autologous ovarian tumours in mixed lymphocyte tumour cultures (MLTC). Peripheral blood lymphocytes (PBL) from five ovarian carcinoma (OC) patients were incubated with autologous OC cells at a PBL:OC cell ratio of 20:1 in IL-2 alone (50 U/ml for the first week and 200 U/ml thereafter) or with IL-4 (100 U/ml) and/or IL-6 (5 U/ml). Neither IL-4 nor IL-6 improved lymphocyte proliferation consistently. In contrast, IL-4 reduced significantly the development of LAK activity as assayed against Daudi cell line, and decreased modestly the emergence of natural killer (NK) activity as assayed against K562. This property was not shared by IL-6. The prevention of the development of non-specific cytolytic activity (LAK and NK activities) was much stronger when the MLTC was started with IL-4 in the absence of IL-2 during the first week in culture. A concomitant drop in NKH-1 expression (CD56) was observed. By inhibiting the emergence of non-specific cytotoxicity, IL-4 provided better evidence of the specific cytolytic activity directed at ovarian cells. In parallel, a significant increase in the generation of memory cells (CD4+CD45RO+) was observed with IL-4. In conclusion, in this model, IL-4 added before IL-2 decreases significantly the emergence of non-specific cytotoxic cells, and promotes the generation of memory cells. These properties may be of interest in the design of strategies aimed at obtaining tumour-specific cells for investigational and immunotherapeutic purposes.

Serum concentrations of cytokines in patients with Hodgkin's disease

Serum concentrations of interleukin (IL)-1 alpha, IL-2, IL-4, IL-6 and tumour necrosis factor (TNF) were measured in 24 untreated patients with Hodgkin's disease and in 24 healthy volunteers matched for age and sex. Serum levels of IL-1 alpha were significantly higher in patients with Hodgkin's disease. The number of patients with detectable serum IL-2 or IL-6 levels was significantly higher in patients with Hodgkin's disease as compared to the control group. No difference was observed for TNF. IL-4 was undetectable in all patients. Serum cytokine levels were not significantly different in patients with and without systemic "B" symptoms (weight loss or fever and night sweats) in the different histological subtypes and clinical stages. Serum concentrations of IL-1 alpha, IL-2, IL-6 and TNF were not correlated to the erythrocyte sedimentation rate, fibrinogenaemia or thrombocyte number. These results indicate that subsets of patients with Hodgkin's disease have detectable serum IL-1 alpha, IL-2 and IL-6 levels, but that other mediators are likely to be involved in the associated clinical and biological inflammatory syndrome.

Interleukin 4 prevents the induction of tissue factor mRNA in human monocytes in response to LPS or PMA stimulation

Increased expression of tissue factor (TF) procoagulant activity by blood monocytes and tissue macrophages is implicated in a number of thrombotic disorders, as well as in fibrin deposition associated with inflammatory lesions and immunological diseases. We found that interleukin 4 (IL-4), a T lymphocyte-derived cytokine known to regulate a number of monocyte functions, inhibited the production of TF by monocytes in response to endotoxin and phorbol myristate acetate (PMA) in vitro. IL-4 had a concentration-dependent inhibitory effect on functional TF procoagulant activity (PCA) and reduced the binding of an anti-TF antibody, as assessed by flow cytometry analysis. Moreover, IL-4 reduced LPS- and PMA-induced TF mRNA levels. TF mRNA stability was not modified by IL-4 after the arrest of transcription by actinomycin D. We thus conclude that mRNA suppression is mediated by an effect occurring at the transcriptional level. Our results also show that the suppressive effect of IL-4 is independent of an increase in the intracellular concentration of cyclic AMP, another established inhibitor of TF production. Locally produced IL-4 might thus contribute to limiting the consequences of monocyte activation.

Modulation of TNF-mediated cell lysis in vitro: further analysis of intracellular signaling

We have investigated the post-receptor events governing the Tumor Necrosis Factor (TNF)-mediated cytotoxicity in vitro. As calcium has been reported to be an essential mediator in the cell killing processes, we asked whether an early increase in intracellular calcium could be involved during TNF-induced cell death. Using the ACAS methodology (adherent cell analysis and sorting), we could not detect any significant increase in intracellular calcium following TNF treatment (40 s) within the TNF-sensitive human breast carcinoma MCF7 cell line. In addition, A23187 (0.1-0.4 microM) did neither enhance TNF-mediated MCF7 cell lysis, further confirming that TNF-mediated cell lysis can occur in the absence of an early calcium increase. Given the potentiating effect of cAMP-inducing agents, such as forskolin, on TNF-mediated cytotoxicity, we have investigated the relationship between cAMP accumulation and the TNF signaling pathway during cell death. Our results indicate that the potentiating effect of forskolin (50 microM) on TNF-mediated MCF7 cell lysis did not involve a modulation in the TNF-induced activation of the nuclear factor NF-kB but was associated with an increase in the DNA fragmenting capacity of TNF as assessed by agarose gel electrophoresis of target cell DNA.

Interleukin-2. A review of its pharmacological properties and therapeutic use in patients with cancer

Recombinant interleukin-2 (IL-2) products (e.g. aldesleukin, teceleukin) are nonglycosylated, modified forms of the endogenous compound. IL-2 acts as a pleiotropic mediator within the immune system, having a variety of effects via specific cell surface receptors. The interaction of IL-2 with the IL-2 receptor induces proliferation and differentiation of a number of T lymphocyte subsets, and stimulates a cytokine cascade that includes various interleukins, interferons and tumour necrosis factors. Antitumour effects of IL-2 appear to be mediated by its effects on natural killer, lymphokine-activated killer (LAK) and other cytotoxic cells. In vivo and in vitro effects of IL-2 seem to be dependent to a large extent on the environment; many studies have reported conflicting results, perhaps due to diverse populations of effector cells, the availability of other cytokines that have synergistic or inhibitory influences, and the dosage regimens used. The recombinant products appear to be biologically indistinguishable from native IL-2 in vitro and in vivo; the former induce minor antibody formation but this does not appear to alter functional properties. In patients with metastatic renal cell carcinoma, IL-2 therapy achieves average objective response rates of 20% (range 0 to 40%), with a complete response rate of about 5% (range 0 to 19%). Response duration varies considerably but can be durable (lasting for > 12 months), with some patients remaining in complete response for > 60 months. It is unclear at present whether higher dosage regimens improve clinical response, or whether combination therapy with other agents and/or adoptive therapy is beneficial. Survival duration may depend on the risk factors present, with poorer performance status and more than one site of metastases associated with shorter survival times. Patients with metastatic malignant melanoma receiving IL-2 as monotherapy show an average objective response rate of 13% (range 3 to 24%); however, objective response rate averages 30% (range 4 to 59%) when IL-2 is used in combination with other agents. Overall median survival appears to be about 10 months. Preliminary data indicate that IL-2 produces a lower response rate in patients with refractory colorectal carcinoma, ovarian cancer, bladder cancer, acute myeloid leukemia or non-Hodgkin's lymphoma. Adverse effects accompanying high dose, intravenous IL-2 therapy can be severe, with cardiovascular, pulmonary, haematological, hepatic, neurological, endocrine, renal and/or dermatological complications frequently requiring doses to be withheld.(ABSTRACT TRUNCATED AT 400 WORDS)

Interleukin-4 differentially regulates interleukin-2-mediated and CD2-mediated induction of human lymphokine-activated killer effectors

Natural killer (NK) cells can be differentiated into lymphokine-activated killer (LAK) effectors following stimulation with interleukin (IL)-2. This induction can be negatively regulated by IL-4. In this study, we demonstrate that the stimulation of NK cells through the CD2 pathway with (9-1 + 9.6) monoclonal antibodies can also induce these cells to secrete tumor necrosis factor-alpha (TNF-alpha) and to differentiate into LAK effectors. More importantly, our data indicate that, in contrast to the IL-2-induced LAK generation, the anti-CD2-triggered LAK activity was not regulated by IL-4. IL-4 was found to enhance the LAK activity as well as NK cell proliferation following activation with anti-CD2 by a mechanism involving, at least in part, an increased TNF-alpha production. Using immobilized monoclonal antibodies against the Fc receptor (Fc gamma RIII or CD16) for NK stimulation, we also observed that the anti-CD16-induced LAK activity was not inhibited by IL-4. These data further point to a pivotal role of TNF-alpha as a regulatory cytokine in anti-CD2-induced LAK generation, and suggest that IL-4 could serve as a discriminatory factor between two distinct pathways involved in the activation of non-MHC-restricted cytotoxicity.

Interleukin-4 suppression of monocyte tumour necrosis factor-alpha production. Dependence on protein synthesis but not on cyclic AMP production

The molecular mechanisms by which human interleukin-4 (IL-4) down-regulates tumour necrosis factor-alpha (TNF-alpha) production by monocytes remain unknown. Other studies of IL-4 action in B lymphocytes and large granular lymphocytes (LGL) suggested that IL-4 may suppress mediator production by augmenting intracellular cyclic AMP (cAMP) levels. However, this study did not find evidence for involvement of a cAMP-dependent signalling pathway for expression of IL-4 activity in monocytes. IL-4 reduced TNF-alpha production by monocytes when IL-4 and lipopolysaccharide (LPS) were added concomitantly, or upon subsequent activation by LPS 16 hr after first exposure to IL-4. The continued presence of IL-4 at the time of LPS stimulation was not necessary; however, the suppressive effects of IL-4 were dependent on protein synthesis. This sustained activity of IL-4 for down-regulation of the production of inflammatory signals may be important for control in vivo of excessively activated monocytes/macrophages, and in therapy.

Tumor necrosis factor-mediated cell lysis in vitro: relationship to cAMP accumulation and guanine nucleotide-binding proteins

We have investigated the modulation of tumor necrosis factor (TNF)-mediated tumor cell lysis by cAMP. Among a panel of human breast tumor cell lines, MCF7 and MDA MB 231 were shown to be, respectively, sensitive and resistant to TNF-mediated cell lysis in vitro. 125I-labeled TNF-binding experiments demonstrated that both cell lines bind TNF, indicating that the differential sensitivity to TNF was not related to TNF receptor expression. To study the relationship between TNF-mediated cell lysis and cAMP accumulation, cAMP measurement was performed following TNF treatment. Our data show that TNF alone did not induce an enhancement of intracellular cAMP accumulation either in the TNF-sensitive or in the TNF-resistant cell line. Experiments in which cells were exposed to forskolin revealed that this cAMP elevating drug was efficient in enhancing the sensitivity to TNF of MCF7 cell line. This potentiating effect of forskolin was maximal for suboptimal concentrations of TNF (10 ng/ml), reaching up to 100% when forskolin was added at 100 microM. However, co-stimulating with forskolin of either MDA MB 231 or a TNF-resistant MCF7 clone (MCF7-R-A1) did not induce any reversal of resistance to TNF. We further assessed the interaction of TNF with transmembrane signalling and the possible involvement of guanine nucleotide-binding proteins (G-proteins). Bacterial toxin-catalyzed ADP ribosylation of MCF7 and MDA MB 231 membranes was, therefore, performed. Using cholera toxin, we demonstrate that TNF treatment did not quantitatively alter the activity of stimulatory G-proteins either in MCF7 or MDA MB 231 cell line. In contrast, pertussis toxin-catalyzed ADP ribosylation experiments suggest a functional coupling of TNF receptors to a 40-kDa pertussis toxin-sensitive G-protein in the TNF-sensitive MCF78 cell line but not in the TNF-resistant MDA MB 231 cell line. Taken together, these data indicate that cAMP might play a role in TNF-mediated cell lysis and are in support of the involvement of a pertussis toxin-sensitive G-protein in TNF-mediated MCF7 cells lysis.

Cyclic adenosine monophosphate-stimulating agents induce ecto-5'-nucleotidase activity and inhibit DNA synthesis in rat cultured mesangial cells

The ecto-5'-nucleotidase activity of rat glomerular mesangial cells increases after exposure to prostaglandin E2 (PGE2) via cAMP stimulation (Savic et al., 1990, Immunology 70, 321). Therefore we examined whether other cAMP-stimulating agents had a similar effect. Forskolin (1 microM), PGE2 (10 microM), and isoproterenol (10 microM), three products stimulating rat mesangial cell adenylate cyclase activity, enhanced cAMP accumulation within 5 min and 5'-nucleotidase activity after a lag time of at least 24 h, 3-Isobutyl-1-methylxanthine (IBMX) and Ro 20-1724, two drugs inhibiting cAMP degradation, also stimulated cAMP accumulation and 5'-nucleotidase activity. The effects of these agents on 5'-nucleotidase activity were additive with those of the three products stimulating adenylate cyclase activity, except for Ro 20-1724 and forskolin which acted synergistically. Cycloheximide, a blocker of protein synthesis, suppressed the cAMP-dependent increase of 5'-nucleotidase activity. Because ecto-5'-nucleotidase activity is a marker of cell differentiation, the effect of the same cAMP-stimulating agents on cell proliferation was also studied. Forskolin, PGE2, and isoproterenol inhibited [3H]thymidine incorporation into rat mesangial cells in a dose-dependent manner. The same effect was obtained with IBMX (100 microM) and Ro 20-1724 (50 microM). Stimulation of 5'-nucleotidase activity and inhibition of [3H]thymidine incorporation occurred over the same range of concentrations for the various agonists tested. Taken together, these results indicate that expression of ecto-5'-nucleotidase in rat mesangial cells is induced by cAMP whatever the reason for its accumulation. The simultaneous inhibition of DNA synthesis may occur independently or be associated with the stimulation of 5'-nucleotidase expression.

Lymphokine-activated killer cells, natural killer cells and cytokines

In the past year, natural killer cells have been the subject of much active investigation. The analysis of the effect of cytokines on the generation, proliferation and function of natural killer cells, and the definition of the lymphokines that they produce, have been particularly important areas of research in view of their possible application in adaptive immunotherapy, combined with biological response modifiers.

Involvement of granzyme B and perforin gene expression in the lytic potential of human natural killer cells

Natural killer (NK) cells (CD3-) or large granular lymphocytes (LGL) spontaneously kill K562 targets but are unable to kill Daudi cells in the absence of IL-2 stimulation. IL-4 is reported to prevent or inhibit the IL-2-driven lymphokine-activated killer (LAK) generation in NK cells. Therefore, we wished to determine whether the antagonistic effect of IL-4 on IL-2-induced LAK activity might regulate the expression of genes encoding proteins involved in lysis, such as perforin, the pore-forming protein, or which are associated with lysis, such as granzymes A and B. By using in situ hybridization, we showed that, in addition to inducing LAK activity, IL-2 stimulation increased the amount of perforin and granzyme B mRNA at the single-cell level in 40 to 100% of the total CD3- LGL cell population. In addition, our results indicated that the stimulatory effect of IL-2 can be downregulated by IL-4 for both LAK activity and granzyme B and perforin gene expression. Here again, a decrease in the amount of specific mRNA per cell was noted. These findings suggest that modulation of the lytic machinery via lymphokines might be associated with regulation of the lytic potential of NK cells.