Interferon-gamma (IFN-gamma) and interleukin-2 in the generation of lymphokine-activated killer cell cytotoxicity--IFN-gamma-induced suppressive activity

Effect of interleukin (IL)-12 and IL-15 on activated natural killer (ANK) and antibody-dependent cellular cytotoxicity (ADCC) in HIV infection

The ability of IL-12 and IL-15 to enhance natural killer (NK) activity and antibody-dependent cellular cytotoxicity (ADCC) of mononuclear cells (MNCs) from HIV+ children and their mothers was investigated. MNCs from HIV+ patients were deficient in NK and ADCC activity compared to control MNCs against several target cells. Overnight incubation with IL-15 or IL-12 augmented NK activity of MNCs from both patients and controls, and the combination of IL-12 and IL-15 resulted in the greatest enhancement. ADCC in HIV+ patients against gp120-coated CEM.NKR cells or chicken erythrocytes could also be enhanced by IL-2 or IL-15 in overnight cultures. Culturing MNCs with either IL-2 or IL-15 for 1 week increased the NK activity in patients to levels of controls treated with these cytokines. However, the response to the combination of IL-12 and IL-15 was less than that to IL-15 alone in 1-week cultures. Culturing MNCs with IL-2 and IL-15 for 1 week also increased the percentage of CD16+/CD56+ cells in both patients and controls. Thus, IL-15 can restore the deficient NK activity in patients and may be a candidate for immunomodulative therapy in HIV+ patients.

Immunomodulation in patients receiving intravenous Bryostatin 1 in a phase I clinical study: comparison with effects of Bryostatin 1 on lymphocyte function in vitro

Bryostatin 1 is a protein kinase C activator that inhibits growth of tumour cells and activates lymphocytes in vitro, properties that have encouraged its use in phase 1 clinical studies as an anticancer agent. We investigated interleukin-2(IL-2)-induced proliferation and lymphokine-activated killer (LAK) cell activity in peripheral blood mononuclear cells (PBMC) from cancer patients receiving Bryostatin intravenously. After Bryostatin administration both LAK generation and proliferation were enhanced when patients' PBMC were stimulated with IL-2 in vitro. However, when normal donors' PBMC were cultured in vitro in the presence Bryostatin and IL-2, LAK induction was inhibited while IL-2-driven proliferation was increased. These effects were also seen following only 2 h exposure to Bryostatin and could be elicited by conditioned medium from Bryostatin-pretreated cells. Neither IL-4 nor interferon gamma was detected in the conditioned medium. Bryostatin in vitro was found to increase expression of IL-2 receptors on CD4+, CD8+ and CD56+ cells and augment the proportion of CD8+ cells in conjunction with IL-2. We conclude that Bryostatin in combination with IL-2 in vitro enhances proliferation and IL-2 receptor expression on lymphocytes, favouring CD8+ cells while suppressing the generation of LAK activity. Intravenous administration of Bryostatin increases the potential of IL-2 to induce proliferation and LAK activity in lymphocytes which, taken together with its putative direct antitumour effect, makes Bryostatin an interesting candidate for clinical trials in combination with IL-2.

Immunoregulatory effects of cytokines on natural killer cells

Natural killer (NK) cells are able to kill tumour cells or virus-infected cells spontaneously and independent of classical MHC-restriction. The activities of these cells can be regulated by different cytokines. Interleukin-2 has been shown to be a potent stimulatory factor for NK cells, inducing proliferation, cytokine production and increased cytotoxic activity. During recent years, the influence of various cytokines on NK cells have been studied, like interferons, IL-1, IL-6, IL-4 and TGF-beta. Recently, new cytokines like IL-7 and IL-12 have been shown to possess direct and potent stimulatory effects on NK cells. Furthermore, endogenous production of TNF seems to play an important role in mediating effects induced by several stimulatory cytokines. Here, an overview of the different regulatory effects of these cytokines on NK cells are presented.

Increased expression of perforin and granzyme B genes in patients with metastatic melanoma treated with recombinant interleukin-2

The frequency of peripheral blood cells expressing the perforin gene or the granzyme B gene was evaluated by in situ hybridization in nine patients suffering from metastatic melanoma and treated with recombinant interleukin-2 (rIL-2). A spontaneous expression of both genes was detected in five to seven patients. rIL-2 administration increased the frequency of positive cells in all patients (P < 0.03 for each gene), the highest frequency being reached in the patients who already expressed these genes prior to rIL-2 treatment (P < 0.02). Expressions of the granzyme B gene and of the perforin gene were strongly correlated before IL-2 treatment and they were similarly affected by rIL-2 administration. In contrast, their modification under treatment did not correlate with that of CD56+ cell counts, of natural killer activity and of sCD8 release. This indicates that perforin and granzyme B gene expressions are markers of cytotoxic cell activation independent of those previously described, and that they should be further evaluated in patients with malignancies to delineate their potential value in predicting clinical outcome.

Decrease in lymphokine-activated killer sensitivity of a human renal-cell carcinoma cell line after cytokine treatment

Recent studies have shown that cytokine treatment of tumor cells alters the sensitivity of these cells to lymphokine-activated killer (LAK) cells, depending on the cell line. In this study, we analyzed the decrease in LAK sensitivity of a human renal-cell carcinoma cell line (SMKT-R-3). The LAK sensitivity of SMKT-R-3 was decreased by treatment with a combination of interferon gamma (IFN gamma) and tumor necrosis factor (TNF). However, the cytokine treatment increased the expression of intercellular adhesion molecule-1 (ICAM-1) on the renal-cell carcinoma cell surface. The conjugate-formation assay also confirmed a slight increase in the binding rate of LAK cells to the renal-cell carcinoma cells. When actinomycin D (a protein synthesis inhibitor) was added to the culture medium prior to treatment with IFN gamma and TNF, the LAK sensitivity of SMKT-R-3 recovered to the level demonstrated by the cells that had not received any cytokine treatment. These results suggest that the effect of cytokines in reducing LAK sensitivity of SMKT-R-3 is mediated by protein synthesis occurring when LAK cells are bound to SMKT-R-3 cells.

Activation of human monocyte/macrophage cytotoxicity by IL-2/IFN gamma is linked to increased expression of an antitumor receptor with specificity for acetylated mannose

Spontaneous cytotoxicity of human monocytes (purity: 92-95%) against K562 tumor cells was only observed in 31% healthy donors but, in the presence of rhamnogalacturonan (500 ng/ml), enhanced cytotoxicity was recorded for 79% (n = 14) of the donors. Monocytes activated by culturing with interleukin-2 and/or IFN gamma showed increased antitumor cytotoxicity against K562 tumor cells in 86% (n = 21) of the donors exhibiting additional increases in specific cytotoxicity when the cytotoxicity assays were carried out in the presence of rhamnogalacturonan. Increases of monocyte cytotoxicity achieved by activation with cytokines coincided with increased formation of monocyte/tumor cell conjugates. Similarly, increased monocyte cytotoxicity mediated by rhamnogalacturonan also correlated with increased monocyte/tumor cell conjugate formation most likely due to effector cell/target cell bridging as was originally described for rhamnogalacturonan interacting with CD56+ natural killer or lymphokine-activated killer cells and tumor cells. The chemospecificity of the monocyte-based receptors responsible for cytotoxicity and for monocyte/tumor cell conjugate formation, as well as for their rhamnogalacturonan-mediated enhancements, appears to be identical since all these effects could be inhibited in a dose-dependent manner by partially deacetylated (60%) mannose pentaacetate.

Induction of bacillus-Calmette-Guérin-activated killer cells from human peripheral blood mononuclear cells against human bladder carcinoma cell lines in vitro

Cytotoxicity against two human bladder carcinoma cell lines (BT-A and BT-B) was investigated using human peripheral blood mononuclear cells (PBMC) stimulated with viable bacillus Calmette-Guérin (BCG) or sonicated BCG (s-BCG). We applied a cytotoxicity assay based on radioactive labelling of tumour cells by incorporation of L[3H]methionine. The results were compared with the cytotoxicity exerted by lymphokine-activated killer (LAK) cells generated by interleukin-2 (IL-2) and interferon gamma (IFN gamma). BCG-stimulated PBMC showed a cytotoxic potential against BT-A and BT-B comparable to that of IFN gamma-generated LAK cells, but this did not reach the level of IL-2-generated LAK cells. We termed these cytotoxic effectors BCG-activated killer (BAK) cells. In contrast to their cytotoxicity against bladder tumour cells, BAK cells did not differ from unstimulated PBMC in the killing of K562 cells. Only viable but not sonicated BCG was able to induce cytotoxicity against BT-A and BT-B. We could demonstrate the presence of the cytokines IFN gamma, IL-2, tumour necrosis factor alpha (TNF alpha) and TNF beta in the supernatants harvested during the generation of BAK cells. Monoclonal antibodies neutralizing IFN gamma were able to inhibit BCG-mediated cytotoxicity, giving evidence of the involvement of IFN gamma in the induction of BAK cells. Furthermore, we performed experiments to investigate the cytotoxic potential of distinct cell populations. The cells effective in BCG-activated killing of bladder tumour cells could be localized within the CD8+/CD56+ lymphocyte subset. CD4+ cells and macrophages did not exhibit cytolytic activity. Our findings imply that the activation by BCG of CD8+/CD56+ killer cells might be an important antitumoral mechanism during BCG therapy against superficial urothelial bladder cancer.

Cytotoxicity of interleukin 2-induced lymphokine-activated killer (LAK) cells against human leukemia and augmentation of killing by interferons and tumor necrosis factor

Adoptive immunotherapy with interleukin 2-induced lymphokine-activated killer (LAK) cells or tumor-infiltrating lymphocytes (TIL) and the induction of anti-tumor responses by IL-2 alone having proven to be promising approaches in cancer therapy. The present study investigated the cytotoxicity of LAK cells towards human leukemia cells. LAK cells were generated by culturing peripheral blood mononuclear cells from normal donors for six days in the presence of recombinant interleukin 2 (IL-2). Cytotoxicity was evaluated using a standard 4-h chromium-release assay. A significant lysis of fresh uncultured leukemia cells by IL-2-activated killer cells could be detected in 77 of 150 leukemias examined. The mean Cr-release was 35.7 +/- 12.9% in the LAK cell-sensitive vs 9.9 +/- 5.9% in the resistant leukemias. With a view to the therapeutic utilization of the LAK-cell system, we attempted to improve the efficiency of its cytotoxic mechanisms. Combined application of IL-2 and interferon-alpha, interferon-gamma, or tumor necrosis factor-alpha in cultures for generation of activated killer cells significantly improved the effectiveness of cytotoxic mechanisms. Our results suggest that the performance of adoptive immunotherapy with ex vivo-activated LAK cells and the in vivo induction of cytotoxic immune responses by IL-2 alone or combined with different lymphokines or cytokines may be of value in treating human leukemia, especially when the tumor burden is low, e.g. during maintenance therapy or after bone marrow transplantation to eliminate minimal residual disease or in early relapse.

Human nonspecific suppressive lymphokines

Since the term "lymphokine" first appeared in print over 20 years ago, a tremendous number of these soluble mediators of the immune system have been described. Within the past few years, many human nonspecific suppressive lymphokines have been identified. This review discusses the historical basis of immunologic suppression and suppressor factors. Later reports describing suppressive human lymphokines are then grouped into four categories: primarily stimulatory lymphokines that also mediate certain suppressive activities, suppressive lymphokines produced during altered states of immunity, suppressive lymphokines produced by exogenously stimulated lymphocytes, and suppressive lymphokines produced by unstimulated lymphocytes. Recent work I have been involved in focusing on the human suppressive lymphokine soluble suppressor factor (SSF) is also discussed.

Suppression of lymphokine-activated killer (LAK) cell induction mediated by interleukin-4 and transforming growth factor-beta 1: effect of addition of exogenous tumour necrosis factor-alpha and interferon-gamma, and measurement of their endogenous production

Recombinant human interleukin-4 (rhIL-4) and transforming growth factor-beta 1 (TGF-beta 1) suppressed the induction of lymphokine-activated killer (LAK) activity induced by recombinant human interleukin-2 (rhIL-2) in peripheral blood lymphocytes. DNA synthesis and the expression of the p55 alpha chain of the IL-2 receptor (Tac antigen) were also inhibited. The inhibitory effect was greatest when these factors were added during the first 48 h of a 4-day culture, with reduced cytolytic activity against both natural killer (NK) resistant and NK-sensitive tumour cell line targets. The suppressive action of both cytokines was accompanied by a reduction in tumour necrosis factor-alpha (TNF-alpha) and interferon-gamma (IFN-gamma) levels in lymphocyte culture supernatants. Recombinant human IFN-gamma (rhIFN-gamma), but not recombinant human TNF-alpha (rhTNF-alpha) was able to overcome the inhibitory effect of recombinant human interleukin-4 (rhIL-4) on LAK induction and DNA synthesis but not Tac antigen expression. However, cytotoxicity induced by rhIFN-gamma alone was also suppressed by rhIL-4 and TGF-beta 1, inferring that rhIFN-gamma-mediated abrogation of rhIL4 suppression was not simply a direct IL-2-independent effect on cytotoxicity. In addition, rhIL-4 did not increase TGF-beta production from rhIL-2-activated peripheral blood mononuclear cells, suggesting that rhIL-4 did not mediate reduction of rhIL-2 responses through the induction of TGF-beta release.

Phase I trial with recombinant interleukin-2 (rIL-2): immune activation by rIL-2 alone or following pretreatment with recombinant interferon-gamma

Alterations of immunological parameters were analysed in patients with advanced malignancies during a phase I trial with rIL-2. Five-day infusions of rIL-2 at doses from 1 x 10(6) to 24 x 10(6) biological response modifiers program (BRMP) U/m2 per day were given to 29 patients, with a minimum of three patients per dose. The dose of 24 x 10(6) U/m2 per day was the maximal tolerated dose (MTD). Immunological parameters were analyzed at days 0, 8 and 11 of the rIL-2 courses. Following a leucopenia during rIL-2 infusion, a lymphocytosis was found in all patients except one. The lymphocytosis peaked at day 8 and was detected at doses of rIL-2 as low as 1 x 10(6) U/m2 per day, reaching a plateau at a dose of 16 x 10(6) U/m2 per day. Although all lymphocyte subsets were increased in patients receiving rIL-2, some patients had predominant T cells (CD3+, NKH1(CD56)-), others had predominant natural killer (NK) cells (CD3-, NKH1 (CD56)+), and yet others showed a mixed profile. A strong induction of cells cytotoxic for K562 targets was found in all patients at days 8 and 11. Eighteen patients received, 1 month later, a second treatment in which infusion of rIL-2 was preceded by a course of 5 days infusion of 2 x 10(6) U/m2 per day recombinant interferon-gamma (rIFN-gamma). The infusion of rIFN-gamma prior to rIL-2 had no effect on the rIL-2-induced alterations of immunological parameters. Taken together, our results suggest that immune stimulation by rIL-2 occurs even at low doses and is maximal at a dose below the MTD; and that pretreatment with low-dose rIFN-gamma does not modify the immune stimulation by rIL-2.

Recombinant interleukin 2-activated natural killer cells regulate IgG2a production

In this report we have analyzed the effect of recombinant interleukin 2 (rIL 2) and rIL 2-activated natural killer (NK) cells on the production of immunoglobulin isotypes by lipopolysaccharide (LPS)-stimulated spleen cells from nude mice. We found that rIL 2 induced a dose-dependent increase of IgG2a secretion and a concomitant inhibition of the secretion of other Ig isotypes. The analysis of the phenotype of LPS- and LPS+ rIL 2-stimulated nude spleen cells showed the appearance of a Thy-1+ asialo GM-1+slgM-CD3-CD4-CD8- cell population in the presence of rIL 2. A population with a similar phenotype was generated upon stimulation of spleen cells from nude mice with rIL 2 alone. These cells lysed YAC-1 cells, did not contain the alpha or gamma transcripts encoding the corresponding T cell receptor chains and are therefore NK cells activated by rIL 2. In co-culture experiments, these cells selectively increased the secretion of IgG2a by LPS-stimulated splenocytes from nude mice. The IgG2a induction triggered by rIL 2-activated NK cells, as well as that triggered by rIL 2, were blocked by an anti-interferon gamma monoclonal antibody. Thus, rIL 2 activated-NK cells enhance the production of IgG2a by secreting interferon-gamma.

A Viscum album oligosaccharide activating human natural cytotoxicity is an interferon gamma inducer

Commercial Viscum album extract Helixor-M contains a dialysable oligosaccharide (HM-BP) that activates natural killer (NK) cytotoxicity against K562 tumour cells when preincubated with human peripheral blood mononuclear cells (PBMC) for 72 h. The activated effector cells were exclusively found in the monocyte/macrophage subpopulation. However, when peripheral non-adherent cells (PNAC) were preincubated with HM-BP for 72 h the NK cytotoxicity of CD56+CD3- NK cells was activated. This discrepancy was found to be due to the release of prostaglandin E2 from activated monocytes/macrophages, which blocked activation of the cytotoxicity of NK cells. Analysis of the supernatant culture medium after 72 h preincubation demonstrated that HM-BP induced release of interferon gamma (IFN gamma) from T cells (preferentially from CD3+CD4+ cells) and of tumour necrosis factor alpha (TNF alpha) from monocytes/macrophages. Release of IFN gamma was the crucial step for activation of NK cytotoxicity since enhancement of NK cytotoxicity during pretreatment of PBMC or PNAC with HM-BP was completely blocked in the presence of anti-IFN gamma antibodies. Anti-interleukin-2, anti-TNF alpha or anti-IFN alpha antibodies had no effect on the HM-BP-induced enhancement of NK cytotoxicity. The activation of the NK cytotoxicity of nonadherent cells by interleukin-2 treatment was found to be synergistic to the enhancement of NK cytotoxicity by treatment with HM-BP.