Cytotoxicity to tumor cells of monocytes from normal individuals and cancer patients

The use of supramolecular structures as protein ligands

Congo red dye as well as other eagerly self-assembling organic molecules which form rod-like or ribbon-like supramolecular structures in water solutions, appears to represent a new class of protein ligands with possible wide-ranging medical applications. Such molecules associate with proteins as integral clusters and preferentially penetrate into areas of low molecular stability. Abnormal, partly unfolded proteins are the main binding target for such ligands, while well packed molecules are generally inaccessible. Of particular interest is the observation that local susceptibility for binding supramolecular ligands may be promoted in some proteins as a consequence of function-derived structural changes, and that such complexation may alter the activity profile of target proteins. Examples are presented in this paper.

Clinical model: interferons activate human monocytes to an eradicative tumor cell level in vitro

Eradicative levels of antitumor activity by cytokines and leukocytes have not yet been reached experimentally and are needed clinically. Only a limited number of human cancers respond to therapy with interferon (IFN), other cytokines, or mononuclear leukocytes despite significant antitumor activity in vitro. We studied the IFN and monocytic cell conditions that would lead to an eradicative effect using human cells in vitro. Targets of the IFN-activated monocytic cells were either four human tumor cell lines (human osteosarcoma [HOS], LOX melanoma, A549 lung tumor, and SNB-19 glioblastoma) or two diploid cell lines (WI38 and MRC5). An average of 30-90 colony-forming tumor target cells were cultured overnight in 96-well tissue culture plates prior to treatment with serially diluted IFN with or without activated elutriation-purified monocytes or lymphocytes. The target cell colonies were treated for 3 days. The colonies were then stained with crystal violet to determine the levels of antitumor activity. IFN-activated human monocytes reached an eradicative level (95%-100%) against three of four tumor cell lines. The eradicative level (1) was induced best in human monocytes activated by combined type I and II IFNs, (2) was effective against tumor cells that were growing for 24 h, (3) was specific for human tumors, as diploid human cells were not inhibited, and (4) required contact between the macrophage and the tumor cells. Also, for the first time, the minimal effective concentration (MEC) of IFNs to activate monocytes can approach those needed for antiviral activity. To our knowledge, this is the first report of near total eradication of many tumor cells, but not diploid cells, by IFN-activated monocytes. Because of its potency and specificity, the IFN-activated monocyte arm of the innate immune system may be a candidate for therapy of established tumors.

Antitumor response of CD14+/CD16+ monocyte subpopulation

OBJECTIVE

Two main subpopulations of human blood monocytes are distinguished on the basis of CD14 and CD16 expression: the major population with enhanced expression of CD14 (CD14++ monocytes) and the minor one with a weak expression of CD14 coexpressing CD16 (CD14+/CD16+ monocytes). As monocytes and macrophages are involved in antitumor response of the host, we assessed the ability of CD14+/CD16+ monocytes to produce cytokines (intracellular expression, release) and reactive oxygen and nitrogen (ROI, RNI) intermediates following stimulation in vitro with tumor cells.

MATERIALS AND METHODS

Monocytes were isolated by elutriation and their subpopulations by FACS sorting. Monocytes and their subpopulations were cocultured with tumor cells. Cytokine (TNF-alpha, IL-12, and IL-10) production was assessed by determination of intracellular protein expression by flow cytometry, and release by ELISA. ROI induction was detected by chemiluminescence and O2- production by flow cytometry, whereas RNI by intracellular expression of inducible NO synthase (iNOS) and nitric oxide (NO) release assessed colorimetrically.

RESULTS

CD14+/CD16+ monocytes stimulated with tumor cells showed significantly enhanced production of TNF-alpha, IL-12p40, IL-12p70 (intracellular expression, release), whereas little IL-10 release was observed. CD14+/CD16+ subpopulation did not produce ROI, but showed an increased iNOS expression and NO release. CD14+/CD16+ monocytes also exhibited enhanced cytotoxic and cytostatic activities against tumor cells.

CONCLUSIONS

CD14+/CD16+ cells constitute the main subpopulation of blood monocytes involved in antitumor response as judged by enhanced production of proinflammatory cytokines, RNI, and increased cytotoxic/cytostatic activity.

Natural cytotoxicity and antibody-dependent cellular cytotoxicity (ADCC) is not impaired in patients suffering from chronic hepatitis C

BACKGROUND/AIMS

Recent observations suggest that natural killer (NK) cell activity might be impaired in chronic hepatitis C. However, to date antibody-dependent cellular cytotoxicity (ADCC) has not been studied in chronic hepatitis C in detail.

METHODS

Therefore, we investigated spontaneous and cytokine-induced (interleukin-2 and interferon-gamma) natural cytotoxicity and ADCC in 29 patients suffering from chronic hepatitis C and 19 healthy controls. Cytotoxicity was determined with a flow-cytometric assay, which can also assess monocyte cytotoxicity. As target cells we used the colorectal tumor cell line HT29 and the lymphoma cell line Raji.

RESULTS

We found no significant differences with respect to spontaneous cytotoxicity (HCV versus healthy controls (32 vs. 46%) and 17-1A specific ADCC (59 vs. 48%), even if isolated monocytes or NK cells were studied. Preincubation and stimulation of effector cells with cytokines increased both natural cytotoxicity and ADCC by 20-30%. However, natural cytotoxicity and ADCC after stimulation did not differ between the two groups.

CONCLUSIONS

Our data obtained with a long-term cytotoxicity assay do not reveal impaired cytolytic capacity of the innate immune system in chronic hepatitis C, even when isolated monocytes and NK cells were studied as effector cells.

In vitro and in vivo biocompatibility of chitosan-xanthan polyionic complex

A novel hydrogel, CHITOXAN(TM) (CH-X), has potential as a vehicle for controlled drug delivery. The hydrogel is obtained by complexation of two polysaccharides, chitosan and xanthan. In the present work we investigated the biocompatibility of the complex using in vitro and in vivo models. The cytotoxic effects of CH-X microspheres as well as their degradation products at different concentrations were assessed on fibroblasts (fibroblast cell line L-929) using 3-(4,5-dimethylthiazole-2yl)-2,5-triphenyl tetrazolium) (MTT). The test is based on mitochondrial dehydrogenase cell activity as an indicator of cell viability. Interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) cytokines as well as nitric oxide (NO) production by macrophages (macrophage cell line J-774) were examined as indicators of cell activation. In vivo biocompatibility assessment was performed for 1 to 12 weeks. This study was performed using tablets obtained after compression of CH-X particles implanted at the subcutaneous level in male Wistar rats. CH-X biocompatibility and degradation were investigated using histological studies. Light and transmission electron microscopy (TEM) analyses were used to determine the foreign-body reaction and phagocytosis of the implants by macrophages. Fibroblast exposition to CH-X particles and degradation products did not show cytotoxic effects as measured by MTT test. TNF-alpha production was dependent on CH-X particles concentration, whereas IL-1beta production was found to be dose independent. CH-X extract products stimulated TNF-alpha secretion when used at the highest concentration (10 mg/mL), notably after 28 days' degradation time. No effect was observed on IL-1beta production when CH-X extracts were used in comparison to the control. The effects of CH-X particles on NO secretion were similar as on TNF-alpha. Histological studies showed that CH-X tablets broke down into particles which progressively degraded into smaller fragments. A significant fraction of the fragments was ingested by the macrophages after 12 weeks of implantation. Light microscopy studies showed a weak foreign-body reaction as a function of time and the fibrous layer thickness decreased with time of implantation.

DNA vaccination with full-length or truncated neu induces protective immunity against the development of spontaneous mammary tumors in HER-2/neu transgenic mice

Genetic immunization against tumor antigens is an effective way to induce an immune response able to oppose cancer progression. Overexpression of HER-2/neu can lead to neoplastic transformation and has been found in many human primary breast cancers. We constructed DNA expression vectors encoding the full-length neu oncogene of rat cDNA (pCMV-NeuNT), the neu extracellular domain (pCMV-ECD), or the neu extracellular and transmembrane domains (pCMV-ECD-TM). We evaluated whether i.m. injection of these plasmids induces protection against the development of mammary tumors occurring spontaneously in FVB/N neu-transgenic mice. We found that pCMV-ECD-TM induced the best protection, whereas both pCMV-ECD and pCMV-NeuNT were less effective. The coinjection with a bicistronic vector for murine IL-12 increased the efficacy of pCMV-ECD and pCMV-NeuNT plasmids, and led to the same protection obtained with pCMV-ECD-TM alone. Anti-neuECD antibodies were detected in pCMV-ECD-TM vaccinated mice and, after coinjection with pCMV-IL12 plasmids, they appeared also in animals immunized with pCMV-ECD. Our data demonstrate the effectiveness of DNA vaccination using truncated Neu plasmids in inducing antitumor protection in a spontaneous mammary tumor model.

Evasion mechanisms to tumor necrosis factor alpha (TNF-alpha) of small cell lung carcinoma and non-small cell lung carcinoma cell lines: comparison with the erythroleukaemia K-562 cell line

The tumour necrosis factor alpha (TNF-alpha) is produced by mononuclear phagocytes as a defence mechanism against malignant cells. However, these cells can evade destruction by TNF-alpha. The present study evaluates in three lung cancer cell lines (small cell carcinoma NCI-H69, adenocarcinoma A-427, squamous carcinoma SK-MES-1) and one erythroleukaemia (K-562) cell line the following evasion mechanisms: (1) inhibition of TNF-alpha production, in indirect and direct co-cultures with monocytes; (2) the expression of type I and type II receptors for TNF-alpha (TNFRI and TNFRII) by tumour cell lines, using indirect immunofluorescence and flow cytometry; (3) the sensitivity of tumour cell lines to the toxic action of recombinant human TNF-alpha (rhTNF-alpha). With the exception of cell line NCI-H69, the other tumour cell lines liberated soluble factors that inhibited TNF-alpha production in monocytes. This effect occurred even after membrane contact with the A-427 and SK-MES-1 cell lines. Erythroleukaemia K-562 cells expressed both types of receptors for TNF-alpha, whereas the NCI-H69 cells expressed only TNFRI, and the A-427 and SK-MES-1 cells expressed no receptors. Lines NCI-H69, A-427 and K-562 were insensitive to the cytotoxic action of rhTNF-alpha. In conclusion, different lung cancer cell lines may evade destruction by TNF-alpha by various mechanisms that range from blocking TNF-alpha production by monocytes to blocking the cytotoxic action of this molecule. For selecting the most effective immunotherapy, knowledge of the evasion mechanisms would be useful.

Anti-(transforming growth factor beta) antibodies with predefined specificity inhibit metastasis of highly tumorigenic human xenotransplants in nu/nu mice

Monoclonal antibodies (mAb) were prepared against conjugated transforming growth factor beta 1 (TGF beta 1) peptides: amino acid positions 48-60 and positions 86-101. Two antibodies, mAb 16-3G1 [anti-(48-60)] and mAb 5-2G6 [anti-(86-101)] cross-reacted with native TGF beta 1, -beta 2 and -beta 3 (16-3G1) or only with native TGF beta 1 (5-2G6). Both mAb were used to characterize TGF beta-mediated effects on the metastatic potential in nude mice of human carcinoma cell line SLU-1 and its metastatic subline SLU-M1. Autocrine TGF beta 1-mediated up-regulation of cell proliferation and its suppression by anti-TGF beta antibodies in vitro was recorded for SLU-M1 cells whereas SLU-1 cell proliferation in vitro appeared to be refractory to anti-TGF beta antibodies and exogenous TGF-beta 1. However, the potential of s.c. tumours to develop distant metastases in nude mice was about the same for both cell lines. Development of primary tumours and distant metastases could be suppressed by treatment of mice with anti-TGF beta antibodies. Thus we assume that the metastatic potential of tumour cells is independent of TGF beta-mediated growth-regulation effects in vitro. The anti-TGF beta-induced suppression of tumour progression and metastasis in nude mice might rather result from stimulation of the immune surveillance. TGF beta-mediated autocrine down-regulation of MHC-unrestricted cytotoxicity of activated human monocytes and CD56+ LAK cells and its reversion by anti-TGF beta antibodies could be readily demonstrated. In all our experimental series, the neutralizing potential of both anti-TGF beta antibodies, though directed against opposite sites of the TGF beta 1 molecule, was very similar.

Proinflammatory cytokines can significantly induce human mononuclear phagocytes to produce nitric oxide by a cell maturation-dependent process

The capacity of three proinflammatory cytokines, interferon-gamma (rhifn-gamma), tumour-necrosis factor-alpha (rHTNF-alpha) and interleukin-1 (rHIL-1), to induce release of nitric oxide (NO) from human mononuclear phagocytes were investigated. Peripheral blood monocytes were either used immediately or after culturing in vitro to develop into monocyte-derived macrophages (macrophages). Lipopolysaccharide (LPS) was used as second signal in all experiments. The three cytokines tested had significantly high enhancing influence on the production of nitric oxide by monocytes as well as by macrophages. However production was significantly higher by the monocytes matured in vitro to macrophages (P < 0.01). In our experimental system LPS had only marginal synergistic influence on production of NO2, and IFN-gamma demonstrated to be the most efficient of the three cytokines tested. Addition of L-arginine in the monocytes/macrophages culture further amplified production of NO2, whereas addition of NG-monomethylarginine abrogated this amplification. We conclude that human mononuclear phagocytes are capable of using inducible nitric oxide synthase pathway to produce nitric oxide.

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.

Mechanism of stimulation of human natural killer cytotoxicity by arabinogalactan from Larix occidentalis

Cultures of human peripheral blood mononuclear cells (PBMC) as well as cultures of preseparated peripheral non-adherent cells (PNAC) and monocytes showed enhancement of natural killer (NK) cytotoxicity against K562 tumor cells when pretreated with arabinogalactan from Larix occidentalis for 48-72 h. Lack of enhanced responses of PBMC (37% of donors) did not necessarily mean that PNAC and monocyte cultures were also non-responsive to arabinogalactan treatment. Moreover, PBMC, PNAC and monocytes of individual donors could exhibit various responses to arabinogalactan when cultures derived from bleedings after intervals of several months were assayed. Arabinogalactan-mediated enhancement of NK cytotoxicity was not initiated directly but was found to be governed by the cytokine network. Generally, arabinogalactan pretreatment induced an increased release of interferon gamma (IFN gamma), tumor necrosis factor alpha, interleukin-1 beta (IL-1 beta) and IL-6 but only IFN gamma was involved in enhancement of NK cytotoxicity since cytotoxicity enhancement of PBMC and PNAC but not that of monocytes could be blocked when anti-IFN gamma antibodies were present during pretreatment. The presence of anti-IL-2 antibodies completely blocked NK cytotoxicity enhancement of PBMC and only moderately that of PNAC and monocytes. This blocking effect was also observed when no detectable increase of IL-2 release could be recorded. The receptor specificity of arabinogalactan is not well characterized. Initial information obtained from comparative studies indicated that arabinogalactan presumably interacts with a receptor that showed specificity for a NK-cytotoxicity-enhancing oligo-saccharide from Viscum album extracts since the action of both components was not synergistic but rather competitive.

Augmentation of monocyte-mediated cytocidal activity by a low dose tumour necrosis factor measured by the kinetic colorimetric microplate assay

This paper describes a simple kinetic colorimetric assay for the quantitation of human peripheral blood monocyte-mediated cytotoxic activity against tumour cells. Isolated effector monocytes were cultured overnight with an increasing number of target cells in 96-well microplates. Cytotoxic activity of monocytes was determined by modified nitroblue tetrazolium (MTT) dye assay using standard ELISA reader offering possible automation. The test was performed with three different effector/target cell ratios using a fixed number of monocytes. This allowed the expression of cytotoxic activity of monocytes in cytotoxic activity units. The assay was found to be a simple method to demonstrate that low doses of TNF (1 U/ml) enhanced monocyte-mediated cytotoxicity.

The CySF-L2 factor from dialysable human leucocyte extract activates natural killer cytotoxicity by induction of interferon gamma

The mechanism of natural killer (NK) cytotoxicity activation of human peripheral blood mononuclear cells (PBMC) by CySF-L2 was elucidated. CySF-L2 is a cytotoxicity-stimulating factor isolated from dialysable human leucocyte extract, which activates NK cytotoxicity against NK-sensitive and insensitive tumour cells (K562; Daudi; Raji; MOLT4) when preincubated with effector cells for 72 h. CySF-L2-mediated activation was synergistic to interleukin-2(IL-2)-mediated activation of NK cytotoxicity. Induction of interferon gamma (IFN gamma) release was the crucial step during CySF-L2-mediated NK cytotoxicity activation since enhancement of NK activity was completely blocked when anti-IFN gamma antibodies were present during treatment of PBMC. Anti-IFN alpha, anti-TNF alpha (tumour necrosis factor alpha) anti-IL-1 and anti-IL-2 antibodies showed no blocking effect. Analysis of the supernatant culture medium after 72 h incubation of PBMC and their highly purified subpopulations demonstrated that CySF-L2 induced release of IFN gamma from CD3+T cells and CD56+CD3- NK cells and of TNF alpha and prostaglandin E2 from monocytes. CySF-L2 was also capable of activating NK cytotoxicity of highly purified (98%) CD56+CD3- NK cells as well as of monocytes (94% pure). Cell cooperation studies connected with analysis of cytokine release and enhancement of NK cytotoxicity indicated that CySF-L2 might play an essential role in the up and down regulation of NK cytotoxicity by the cytokine network.

Bronchoalveolar lavage and the immunology of lung cancer

Current concepts on the application of bronchoalveolar lavage (BAL) for the investigation of tumor markers and antitumor activities exerted by effector cells in the lung parenchyma are summarized. The evaluation of BAL cellular and humoral constituents might provide new insights into the pathogenic mechanisms taking place in lung cancer.

Chemical specificity of effector cell/tumor cell bridging by a Viscum album rhamnogalacturonan enhancing cytotoxicity of human NK cells

The component in Viscum album extract Iscador-M enhancing the NK cytotoxicity of human CD56+CD3- NK cells (87-95% enrichment) in cocultures with K562 tumor cells and increasing the formation of NK cell/tumor cell conjugates was identified as a rhamnogalacturonan. Both activities were abolished by treatment of V. album extract with poly-alpha-D-galacturonidase and alpha-rhamnosidase and both activities were inhibited in the presence of galacturonic acid and acetylated rhamnose (6-deoxymannose). Inhibition was also observed in the presence of structurally related derivatives such as acetylated mannose or acetylated mannonic acid gamma-lactone, the latter exhibiting a 5-10-fold higher inhibitory potential. The rapid formation of NK cell/tumor cell conjugates in the presence of V. album extract was based on the bridging of NK cells with tumor cells by rhamnogalacturonan. Using a specifically adapted agglutination assay, the saccharide residues of the rhamnogalacturonan interacting with NK cells and tumor cells could be identified by the formation of homologous cell conjugates induced by acetylated rhamnose or acetylated mannose conjugated to dextran and by polygalacturonic acid: terminal acetylated rhamnose or acetylated mannose bound only to NK cells in a dose-dependent manner but not to K562 tumor cells, and terminal galacturonic acid only to K562 tumor cells but not to NK cells. This type of bridging represents a novel mechanism of enhancement of NK cytotoxicity.

The in vitro development of cytotoxicity in response to granulocyte/macrophage-colony-stimulating factor or interferon gamma in the peripheral blood monocytes of patients with solid tumors: modulation by arachidonic acid metabolic inhibitors

The capacity of granulocyte/macrophage-colony-stimulating factor (GM-CSF) and interferon gamma (IFN gamma) to elicit monocyte cytotoxicity in vitro in the peripheral blood monocytes of patients with solid tumors was investigated. The cytotoxicity elicited by IFN gamma was significantly reduced in cancer patient monocytes compared to normal monocytes. The cytotoxicity elicited by GM-CSF, however, was comparable between cancer patient monocytes and normal monocytes, but was lower than that induced by IFN gamma. Indomethacin, a cyclooxygenase inhibitor, significantly augmented IFN gamma-elicited cytotoxicity in cancer patient monocytes, but not in normal monocytes. In contrast, indomethacin augmented GM-CSF-elicited cytotoxicity in both cancer patient monocytes and normal monocytes. Nordihydroguaiaretic acid (NDGA), a lipoxygenase inhibitor, was found to suppress cytotoxicity in response to IFN gamma and GM-CSF in both cancer patient monocytes and normal monocytes. The addition of leukotrienes to NDGA-treated cultures restored the development of cytotoxicity. Thus there are differences in the in vitro response of cancer patient monocytes and normal monocytes to distinct biological activators. Furthermore, these responses can be manipulated by agents that modulate arachidonic acid metabolism.

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.

Monocyte/macrophage functions in patients with squamous cell carcinoma of the oral cavity

Peripheral blood monocytes and draining lymph node macrophages from patients with squamous cell carcinoma of the oral cavity, monocytes from patients with oral leukoplakia and those from healthy donors were assessed for FcR. HLA-DR expression and interleukin-1 (IL-1) production after activation with LPS or IFN gamma. Monocyte cytotoxicity was also tested after activation with LPS, IFN gamma, IL-2 singly, or in combinations at suboptimal concentrations. The results showed that the percentage of activated monocytes expressing FcR was significantly low in untreated oral cancer patients, however, the proportion of HLA-DR positive cells was normal. The unstimulated monocytes from oral cancer patients showed spontaneous generation of IL-1. Upon activation, few patients could produce IL-1 to normal levels. The unstimulated monocytes from untreated patients and treated patients with recurrence also exhibit significantly higher tumoricidal activity. Treatment of monocytes with combinations of two modulators (IFN gamma, LPS and IL-2) induced significantly higher cytotoxicity.

Enhancement of monocyte-mediated tumoricidal activity by multiple interferon-alpha species

Twenty-one interferon (IFN)-alpha species were evaluated for their ability to enhance monocyte-mediated lysis of the human melanoma cell line, A375. A wide variation in the potency of the different species in inducing monocyte tumoricidal action was observed. In addition, many IFN-alpha species were found to induce as much or more tumoricidal activity than recombinant IFN-gamma. The degree of monocyte activation induced by the various species generally correlated with their antiviral activity. Those which were better at inducing monocyte tumoricidal action also gave the highest antiviral specific activities. Studies were conducted to determine if the relative potency of the IFN-alpha species could be changed by altering certain parameters of the cytotoxicity assay. All IFN-alpha species tested required only 30 min in culture with the monocytes to induce activation. There were no changes in the relative potency of the species when cytotoxicity was measured at different times, nor when the effector:target ratio was altered. Competitive binding studies revealed that those IFN-alpha species which induced little activity in the bioassays were also generally poor in their ability to bind the IFN-alpha receptor on human monocytes, while the IFN-alpha species which induced relatively more activity in the bioassays were better able to bind to the IFN-alpha receptor. These data indicate that there are dramatic differences in activities among the IFN-alpha species which may, in part, be explained by different binding affinities. In addition, the differences observed among the IFN-alpha species demonstrate the need for further functional and structural characterization of the individual IFN-alpha species which could lead to a more effective clinical application of IFN-alpha.

Comparative toxicity of the cardiovascular toxin allylamine to porcine aortic smooth muscle and endothelial cells

This study supports a recent hypothesis that the cardiovascular toxin, allylamine, is toxic to smooth muscle cells of large elastic arteries (aorta). Cultures of the porcine aortic smooth muscle, endothelial, and fibroblastic cells were exposed to varying concentrations of allylamine ranging from 5 microM to 340 microM. Monitored cytotoxic and cytolytic activities demonstrated that final concentrations of 60 microM allylamine decreased cell population viability of smooth muscle cells as much as 50%. Viability decreased approximately linearly with increasing concentrations of allylamine including spontaneous lysing of smooth muscle cells at 90 microM. Endothelial cells were more resistant to lower concentrations of allylamine requiring 90 microM to decrease cell population viability by 50%. In contrast, fibroblastic cells were very resistant to lower concentrations of allylamine. The specific lytic response of these cells in culture, measured by release of [3H]thymidine, gave findings parallel to the viability studies, i.e. at 100 microM allylamine smooth muscle cells demonstrated 75% specific lysis while endothelial cells showed 29%. Growth studies of cells surviving an 8-h exposure to allylamine indicate that surviving endothelial cells have better growth characteristics than surviving smooth muscle cells; both cell lines are also apparently injured at concentrations of allylamine much lower than the CT50. These studies show that of the cellular components of the vascular wall, smooth muscle cells appear to be the most sensitive to the toxic effects of allylamine.

Natural cytotoxicity of lymphocytes and monocytes and its augmentation by OK432 in melanoma patients

Lymphocytes and monocytes from the peripheral blood of 30 patients with malignant melanoma were tested for natural cytotoxicity against K562 cells in a 3-h 51Cr-release assay, and the effects of OK432 (a streptococcal preparation) on the cytotoxicity were examined. The lymphocyte cytotoxicity of melanoma patients was similar to that of normal donors and control patients with benign skin disease. Furthermore, the lymphocyte cytotoxicity of melanoma patients was not correlated to the stage of the disease. Similarly, lysis of K562 cells by monocytes isolated by adherence to autologous serum-coated plastic dishes in melanoma patients was comparable to that of controls and not associated with the stage of the disease. Positive monocyte reactions were recorded in 10 of 30 (33%) melanoma patients, seven of 21 (33%) normal donors and three of 10 (30%) control patients. There was no correlation between lymphocyte cytotoxicity and monocyte cytotoxicity. Overnight treatment of monocytes and lymphocytes with OK432 resulted in an increase in cytotoxicity. Significant augmentation of cytotoxicity by OK432 was observed in 28% of the monocyte samples and 86% of the lymphocyte samples, while partially purified human interferon augmented cytotoxicity in 63% of the monocyte samples and all the lymphocyte samples. These results suggest that neither lymphocyte nor monocyte cytotoxicities are depressed in melanoma patients as compared with normal donors and patients with benign disease and that OK432 has a stronger stimulatory effect on lymphocytes than on monocytes.

Monocyte antibody-dependent cellular cytotoxicity in cancer patients

Antibody-dependent cellular cytotoxicity (ADCC) mediated by peripheral blood monocytes was determined in 120 patients who had gastrointestinal tract (GIT), lung and breast cancer, melanoma, or Hodgkin's and non-Hodgkin's lymphoma. Results were expressed in terms of maximum cytotoxicity and cytotoxicity at E:T = 1:10 and were compared with the results obtained in 63 normal subjects. There was a significant decrease in maximal cytotoxicity for both the GIT cancer and the melanoma patient groups, but not for any of the other groups. These differences were not confirmed when results were expressed at low effector: target cell ratios, e.g., cytotoxicity at E:T = 1:10. The relationship between monocyte ADCC and disease extent was examined in those groups with sufficient numbers. Monocyte ADCC was higher in patients with GIT cancer of limited extent than in patients with extensive GIT cancer and in the control group.

Characterization by monoclonal antibodies of the cytotoxic effector cells in human peripheral blood mononuclear cells reactive against anchorage-dependent tumour cell lines

The effector cells for spontaneous cytotoxicity against anchorage-dependent human or mouse tumour cell lines in a 72-h iododeoxyuridine-release assay by normal human peripheral blood cells (PBMNC) or monocyte-enriched fractions were analysed by the use of monoclonal antibodies. PBMNC or adherent or elutriated monocyte-enriched populations of PBMNC were depleted of monoclonal antibody-reactive cells by complement-dependent lysis or separated into monoclonal-antibody-positive or -negative subsets by an indirect rosetting technique followed by Ficoll-Hypaque density gradient separation. The experimental data indicated that in both PBMNC and monocyte-enriched populations, an appreciable proportion of the effector cells with cytolytic activity against adherent human or mouse tumour target cells were positive with B73.1.1 (an antibody with a high degree of selectivity for natural killer (NK) cells), B43.4.1 (or OKM1), and with OKT11a (an antibody recognizing the receptors for sheep erythrocytes), and had the morphology of large granular cells, which have previously been shown to mediate NK activity. These effector cells were mostly negative for BRL.1, BRL.2, B52.1.1, B44.1.1, B13.4.1 and DR antigens, unlike classical monocytes. Some cells which are cytotoxic for the adherent mouse, SV-40-transformed kidney tumour line, TU-5, may bear B52.1.1 or other monocyte-like antigens. Taken together, these results indicate that, in monocyte-enriched populations, both NK cells and monocytes have cytotoxic effector activity against various human and mouse adherent target cell lines.

Spontaneous cytotoxicity by monocyte-enriched subpopulations of human peripheral blood mononuclear cells against human or mouse anchorage-dependent tumour cell lines. Contribution of NK-like cells

Human peripheral blood mononuclear cells (PBMNC) were found to be cytotoxic for mouse or human anchorage-dependent target cell lines in a 48-72 h [125I]iododeoxyuridine (IUDR) release assay. Unfractionated, adherent or nonadherent cells had significant levels of cytotoxicity, as did cells fractionated according to size into 'lymphocytes' or 'monocytes' by elutriation. Intermediate size cells, not enriched for monocytes, had high levels of cytotoxicity. In all fractions tested, including adherent populations, some cells with the morphology of large granular cells were observed. Treatment of all fractions with interferon (IFLrA, a purified, recombinant alpha-IFN) boosted cytotoxicity against four target cells lines. Treatment with lymphokines containing putative 'macrophage-activating factor' (MAF) also enhanced cytotoxicity in fractions depleted of monocytes. Culture in fetal bovine serum enhanced cytotoxicity mainly in unfractionated and nonadherent PBMNC. These experiments indicated that NK-like cells can be appreciable contaminants in elutriator-purified monocyte-enriched or adherent cell populations and thereby contribute to observed cytotoxicity, particularly after pretreatment with IFN or other stimulatory factors.

Cytotoxicity of cancer patient's macrophages for tumor cells

Monocyte derived macrophages were isolated from the peripheral blood of 66 patients with either breast, colon, gynecological or hematological cancers. The macrophages from the breast and gynecologic cancer patients generally did not acquire enhanced cytotoxicity for human tumor cells after incubation with bacterial lipopolysaccharide (LPS). However, when the macrophages isolated from colon and hematologic cancer patients were studied, more than 50% of these patients possessed cytotoxic macrophages. LPS induced macrophage mediated cytotoxicity was also found to be inhibited by factors present in many cancer patient's plasma. Twenty-three of the 50 cancer patients studied possessed a plasma inhibitor capable of suppressing macrophage mediated cytotoxicity by more than 50%. Furthermore, of these 50 patients, 47 were incapable of killing the tumor cells in vitro either because they possessed nonresponsive macrophages and/or they possessed a plasma inhibitory factor. Thus, although macrophage cytotoxic function may be normal in some patients with cancer, cytotoxicity may be inhibited in some patients by factors in autologous plasma thereby rendering the macrophages ineffective in vivo.