Biomedical subjects

T Espevik

Publications and source records attributed to T Espevik.

At least 145 records · Page 8Linked to original sources

PubMed1987

Monocyte-derived influence on growth of normal human fibroblasts. The contribution of tumour necrosis factor to growth inhibition.

The current study demonstrates that whereas high concentrations of recombinant tumour necrosis factor (rTNF, 0.05 microgram/ml) induced enhanced growth of normal human fibroblasts, supernatants from human monocytes with a similar TNF concentration induced cytostasis. This cytostasis was inhibited by an antiserum against rTNF. The TNF activity, measured as cytotoxicity against TNF-sensitive WEHI 164 cells, cochromatographed with the fibroblast growth inhibitory activity upon ion-exchange chromatography of monocyte supernatants. This indicates that TNF contributes to the fibroblast growth inhibition mediated by monocyte supernatants. Alpha interferon (IFN-alpha) abolished the growth of fibroblasts induced by rTNF, whereas rTNF in combination with gamma interferon (IFN-gamma) inhibited growth of fibroblasts. The interferon activity in the supernatants was determined to find out whether the growth-inhibitory activity of natural TNF was due to interferons present in the monocyte supernatants, which might modulate the TNF activity. Cytostasis of fibroblasts was mediated by monocyte supernatants which did not contain IFN-gamma in significant amounts. All supernatants contained IFN-alpha. An antiserum against IFN-alpha partially reduced the cytostasis induced by monocyte supernatants. This cytostasis was totally abolished by rTNF antiserum, suggesting that IFN-alpha modulates the growth-inhibitory activity of TNF in the monocyte supernatants. It appeared that the different effects of recombinant and natural TNF on fibroblast growth can probably not be attributed to monocyte-derived TNF-modulating factors alone. Thus, recombinant and natural TNF may differ in a way that affects their capacity to induce cytostasis of normal fibroblasts.

Cell Division↗

PubMed1987

Fibroblast growth-stimulatory activity released from human monocytes. The contribution of tumour necrosis factor.

Human monocytes release fibroblast growth-stimulatory activity. In this study tumour necrosis factor (TNF) has been identified as a major contributor to the monocyte-derived fibroblast growth-stimulatory activity. A neutralizing monoclonal antibody (MoAb) against recombinant TNF (rTNF) inhibited growth of FS-4 fibroblasts and skin biopsy fibroblasts induced by monocyte supernatants, indicating that TNF was involved in the stimulation. Optimal growth of FS-4 fibroblasts was induced by monocyte supernatants at dilutions which contained TNF at a concentration between 1.6 X 10(-6) and 4.0 X 10(-5) micrograms/ml, less growth being induced at higher TNF concentrations. Contrary to this, no optimal concentration interval was found for rTNF, since increasing rTNF concentrations always resulted in increased growth stimulation. It also appeared that natural TNF in the monocyte supernatants induced growth at a much lower concentration than rTNF tested in the absence of monocyte supernatant.

Antibodies, Monoclonal↗

PubMed1987

Effect of free fatty acids on the cytolytic activity of tumour necrosis factor/monocyte-derived cytotoxic factor.

The effect of different fatty acids on tumour necrosis factor (TNF)-induced cytolysis of TNF-sensitive WEHI 164 murine fibrosarcoma cells has been determined. The saturated fatty acids palmitic (16:0) and stearic (18:0) acid strongly potentiated the cytolytic activity of TNF. They also had a slight cytotoxic effect in the absence of TNF. Contrary to this, the unsaturated fatty acids oleic (18:1), linoleic (18:2), alpha-linolenic (18:3), arachidonic (20:4), and eicosapentaenoic (20:5) acid were neither cytotoxic by themselves, nor did they have any significant effect on the cytolytic activity of TNF. Addition of either of the unsaturated fatty acids 18:2 or 20:5 together with 18:0 eliminated the potentiating effect 18:0 by itself had on TNF-induced cytolysis. A mixture of fatty acids resembling that found in cell phospholipids had no cytotoxic effect by itself, nor any effect on the cytolytic activity of TNF. The potentiating effect of saturated fatty acids on TNF thus seems to depend on their relative amount compared to the amount of unsaturated acids. The results indicate that TNF does not exert its cytotoxic effect simply by suppressing hydrolysis of triglyceride, thereby inducing an insufficient cellular supply of fatty acids.

Animals↗

PubMed1987

Tumour necrosis factor-like activity on paraformaldehyde-fixed monocyte monolayers.

A tumour necrosis factor (TNF)-related protein appears to be associated in part with the monocyte surface membrane, since paraformaldehyde-fixed monocyte monolayers induced cytolysis of WEHI 164 clone 13 cells. Cytolysis was inhibited by neutralizing antisera raised against recombinant TNF (rTNF) and against the monocyte-derived cytotoxic factor, CF, which presumably is identical to natural TNF. Moreover, crude monocyte membrane preparations also contained cytotoxic activity, which was inhibited by antisera raised against rTNF and CF, and this activity was associated with particulate structures as it did not pass through filters with a pore size of 0.2 micron. Gamma-interferon (gamma-IFN)-activated monocytes fixed with paraformaldehyde had more TNF-like activity than fixed unactivated monocytes, and the crude membrane preparations from gamma-IFN-activated monocytes contained about five times more TNF-like activity than preparations from unactivated monocytes.

Cell Membrane↗

PubMed1986

A highly sensitive cell line, WEHI 164 clone 13, for measuring cytotoxic factor/tumor necrosis factor from human monocytes.

By limiting dilution of WEHI 164 mouse fibrosarcoma cells we have isolated a cell line, WEHI 164 clone 13, which is extremely sensitive to cytotoxic factor (CF) derived from human monocytes. By using WEHI 164 clone 13 in a MTT tetrazolium cytotoxicity assay it was found that CF supernatants from activated monocytes had to be diluted 10(5)-10(6) times to reach the dose which produced 50% dead cells (LD50). By comparing the LD50 of different target cells, WEHI 164 clone 13 cells were found to be approximately 10(3) times more sensitive for CF-induced cytotoxicity as compared to WEHI 164 parental cells and approximately 10(2) times more sensitive as compared to actinomycin D-treated L929 cells. Treatment of the WEHI 164 clone 13 cells with actinomycin D did not increase their sensitivity for CF-induced cytotoxicity. Recombinant tumor necrosis factor (rTNF) also mediated high cytotoxicity towards WEHI 164 clone 13 cells, with an LD50 of 2 X 10(-3) ng/ml. Neutralizing CF antiserum completely inhibited the toxic activity of rTNF. WEHI 164 clone 13 cells were highly sensitive to monocyte-mediated cytotoxicity in that 1-2 monocytes were able to kill at least 5000 of these target cells. Neutralizing TNF antiserum completely inhibited monocyte-mediated cytotoxicity. These results indicate that the high level of cytotoxicity mediated by CF supernatants and monocytes on WEHI 164 clone 13 cells is due to TNF as the effector molecule.

Animals↗

PubMed1986

Monocyte-mediated drug-dependent cellular cytotoxicity: effects on different WEHI 164 target cell lines.

The contribution of monocyte cytotoxic protein factor (CF) to monocyte-mediated drug-dependent cellular cytotoxicity (DDCC) has been investigated. Cell lines which have been derived from murine WEHI 164 cells (termed WEHI 164 parental) by selecting for high (WEHI 164 clone 3) and low (R-WEHI 164) sensitivity to CF-mediated cytotoxicity were used as target cells in DDCC. By comparing the CF doses which produced 50% dead cells (LD 50) we found that WEHI 164 clone 3 was approximately 30 times more sensitive than WEHI 164 parental which in turn was 70 times more sensitive than R-WEHI 164. Actinomycin D (Act D) treatment of WEHI 164 parental and R-WEHI 164 greatly increase susceptibility to CF-mediated cytotoxicity. The susceptibility of WEHI 164 clone 3 was apparently somewhat increased at low dilutions of CF, whereas no significant increase was observed at high dilutions. The susceptibility to DDCC of the three target cell lines (WEHI 164 parental, WEHI 164 clone 3, and R-WEHI 164) correlated with the sensitivity pattern obtained in CF-mediated cytotoxicity of Act D-treated target cells. Monocyte- and CF-mediated cytotoxicity against Act D-treated WEHI 164 clone 3 and R-WEHI 164 was inhibited by neutralizing CF antiserum. These data indicate that CF is an effector molecule in monocyte-mediated DDCC.

Animals↗

PubMed1986

Human monocyte cytotoxic factor mediates cytolysis of WEHI 164 cells.

Human monocytes can be activated to release a 40,000-Da cytostatic protein factor (CF). In this report we have investigated the cytolytic activity of CF on WEHI 164 cells which are sensitive to monocyte-mediated cytolysis. Monocyte supernatants containing CF induced cytolysis of murine WEHI 164 sarcoma cells, as determined in a 51Cr-release assay. Preincubation of WEHI 164 cells with actinomycin D enhanced cytolysis induced by supernatants containing CF, suggesting that CF may be involved in drug-dependent cellular cytotoxicity. The cytolytic activity was profoundly inhibited by a rabbit antiserum raised against purified CF, indicating that the cytolytic activity in the supernatants was in fact mediated by CF. These results indicate that CF may be an important effector molecule in monocyte-mediated cytostatic and cytolytic reactions.

Adjuvants, Immunologic↗

PubMed1986

Detection of tumour necrosis factor-like cytotoxicity in serum from patients with septicaemia but not from untreated cancer patients.

With a bioassay sensitive for recombinant tumour necrosis factor at a concentration of 10(-4) ng/ml, we were able to detect tumour necrosis factor-like cytotoxicity in serum from three patients in the initial phase of septicaemia. The cytotoxic activity corresponded to a concentration of recombinant tumour necrosis factor of 2 X 10(-2)-3 X 10(-3) ng/ml serum. The concentration in cerebrospinal fluid was estimated to be three times higher than in serum. In 23 untreated patients with malignant disease of varying origin and stage, including two patients with severe cachexia, we were not able to detect tumour necrosis factor-like cytotoxicity.

Adolescent↗

PubMed1986

The role of monocyte cytotoxic factor in monocyte-mediated lysis of tumour cells.

The role of a monocyte cytotoxic factor (CF) in monocyte-mediated lysis of leukaemia cells (K562) has been investigated using a polyclonal rabbit antiserum raised against purified CF. The CF antiserum inhibited K562 cell lysis mediated by interferon gamma (IFN-gamma)-activated monocytes. CF antiserum also inhibited monocyte-mediated lysis of antibody-coated K562 cells (AbK562). Preimmune serum at the same concentration as CF antiserum did not affect monocyte-mediated lysis, and the CF antiserum did not inhibit binding between effector and target cells, indicating that inhibition of monocyte-mediated lysis by CF antiserum was not merely a result of toxic components present in the rabbit serum, or a result of a decrease in monocyte-target cell binding. Taken together, the data suggest that CF is involved in monocyte-mediated lysis of uncoated as well as antibody-coated K562 cells.

Adult↗

PubMed1986

Role of monocyte cytotoxic factor in cytolysis of actinomycin D-treated WEHI 164 cells mediated by freshly isolated human adherent mononuclear blood cells.

The role of the monocyte cytotoxic factor (CF) in cytolysis of untreated and actinomycin D (Act D)-treated WEHI 164 cells by freshly isolated human adherent mononuclear cells has been investigated in this study. Murine WEHI 164 cells were used as target cells because of their sensitivity to lysis mediated by monocytes and their resistance to natural killer cells. Monocytes as well as monocyte supernatants mediated cytolysis of WEHI 164 cells. Cytolysis was enhanced by Act D treatment of target cells. The addition of lipopolysaccharide to monocytes accelerated the progression of cytolysis of Act D-treated WEHI 164 cells mediated by monocytes. A polyclonal rabbit antiserum against CF inhibited the cytolytic activity of monocytes and monocyte supernatants against untreated as well as Act D-treated WEHI 164 cells. At low effector:target ratios, the cytolysis was totally abrogated by CF antiserum. Depletion of natural killer cells from adherent cells by the monoclonal antibody Leu 11b and rabbit complement did not reduce cytolysis of Act D-treated WEHI 164 cells. Immunofluorescence microscopy revealed that CF antiserum stained the plasma membrane of freshly isolated monocytes, suggesting that CF is a membrane-associated molecule. Our data indicate that CF is an important effector molecule in cytolysis mediated by freshly isolated monocytes against untreated and Act D-treated WEHI 164 cells.

Animals↗

PubMed1985

IFN-gamma-induced production of monocyte cytotoxic factor.

The effect of activating human monocytes in vitro with recombinant Interferon-gamma (IFN-gamma) and lymphokines on monocyte-mediated cytotoxicity and on the production of cytotoxic protein factor(s) (CF), has been investigated. Lymphokines and IFN-gamma enhanced both cytotoxicity and CF production in a dose-dependent manner. A monoclonal antibody against human IFN-gamma abrogated the lymphokine-induced cytotoxic activity and CF production completely, indicating that the actual monocyte-activating factor in the lymphokine supernatant was IFN-gamma. At concentrations of 10(3)-10(4) U/ml, IFN-gamma induced an enhanced release of CF from the monocytes. However, IFN-gamma at concentrations (less than 100 U/ml) present in our lymphokine preparation was not sufficient to induce enhanced CF release. Since IFN-gamma at concentrations less than 100 U/ml activated monocytes for cytotoxicity, CF as an extracellular factor in the supernatant does not appear to be essential for monocyte-mediated cytotoxicity. However, using neutralizing antiserum raised against purified CF, indirect immunofluorescence microscopy revealed that IFN-gamma induced a marked accumulation of CF on the monocyte membrane. Taken together, the data shows that IFN-gamma is both necessary and sufficient at concentrations less than 100 U/ml for inducing monocyte-mediated cytotoxicity and production of CF as a membrane-associated component, but not as a released factor, suggesting that CF may function as a membrane-associated cytotoxin in monocyte-mediated cytotoxicity.

Antibodies, Monoclonal↗

PubMed1985

1,25-Dihydroxyvitamin D3-differentiated human promyelocytic leukaemia cells (HL-60) can kill antibody-coated tumour cells (K562).

The active metabolite of vitamin D3, 1 alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3), was tested for the ability to differentiate promyelocytic leukaemia cells (HL-60) and histiocytic lymphoma cells (U937) into cytotoxic effector cells against K562 leukaemia cells. A concentration of 10(-6) M 1,25(OH)2D3 differentiated HL-60 cells into substrate-adherent monocyte-like cells with cytolytic activity against antibody-coated K562 cells. These differentiated HL-60 cells were not able to lyse uncoated K562 cells in an 18-h Cr-release assay. Similar treatment of the U937 cells with 1,25(OH)2D3 did not make them cytolytic towards K562 cells. These data indicate that 1,25(OH)2D3 can differentiate HL-60 cells to mature monocytes with cytolytic activity against antibody-coated leukaemia cells.

Antibody-Dependent Cell Cytotoxicity↗

PubMed1985

Human monocyte-mediated lysis of antibody-coated tumor cells: the role of the cytoskeleton in monocytes.

Human monocytes (M phi) show high cytolytic activity towards antibody-coated tumor cells (AbK562). In this report, the relationship between the cytoskeleton in the M phi and the M phi cytolytic activity has been investigated. The actin filament inhibitors cytochalasin B and dihydrocytochalasin B (H2CB) both reduced M phi-mediated lysis of AbK562 cells by approximately 50% at a concentration of 1 microM. This concentration of H2CB did not inhibit the number of target cells bound to M phi. Dihydrocytochalasin B did not inhibit the M phi ability to release cytotoxic protein factors, suggesting that H2CB does not inhibit lysis by inhibiting release of cytotoxic protein factors. Immunofluorescence microscopy showed a rapid accumulation of actin filaments towards the contact area in more than 80% of the examined M phi-AbK562 conjugates. Exposure to H2CB did not prevent this accumulation, but caused aggregation of the accumulated actin filaments in the contact area with the target cell. Accumulation of actin filaments did not occur toward tumor cells not coated with antibodies. Scanning and thin section electron microscopy demonstrated large M phi pseudopodia directed toward the AbK562 cells, with close apposition of the effector and target cell membranes with interdigitations. The formation of the M phi pseudopodia was inhibited by exposure to H2CB. These observations indicate that M phi membrane motility toward AbK562 cells is closely related to M phi-mediated lysis of AbK562 cells. Immunofluorescence microscopy of the microtubule-organizing center (MTOC) and the Golgi apparatus revealed that both the MTOC and the Golgi apparatus in M phi reoriented towards the bound AbK562 cells in approximately 45% of the examined M phi-AbK562 conjugates. The microtubule-depolymerizing drugs colchicine and vinblastine did not inhibit M phi-mediated lysis of AbK562 cells at concentrations which disrupted the microtubule arrays in the M phi. The carboxylic ionophore monensin, which blocks Golgi-derived secretion, inhibited M phi-mediated lysis of AbK562 to a lesser extent as compared to H2CB. These results suggest that microtubule functions are of less importance in M phi-mediated lysis of AbK562 cells as compared to actin filament functions. However, the MTOC and the Golgi apparatus could participate in M phi-mediated lysis of AbK562 cells by mechanisms related to secretion of cytotoxic molecules.

Actins↗

PubMed1984

Liquid propane jet-freezing, freeze-drying and rotary replication of the cytoskeleton and plasma membrane associated structures in human monocytes.

We have studied the cytoskeleton and plasma membrane associated structures of human monocytes using liquid propane jet-freezing, freeze-drying and rotary replication. We find that the cytoskeleton of these cells consists mainly of actin filaments. The actin filaments were identified by their ability to bind myosin sub-fragment S1. A large fraction of these actin filaments radiates from dense cytoskeletal foci. The presence of such actin filament rich foci also in unfrozen cells was demonstrated using immunofluorescence light microscopic techniques. In addition to coated pits a network of thin fibrils (diameter 4-5 nm) were observed on the protoplasmic side of the plasma membrane facing the substrate. These results indicate that liquid propane jet-freezing may represent a simple, inexpensive alternative to impact freezing at liquid helium temperature for obtaining the high cooling rate necessary for successful freeze-drying and rotary replication of cytoskeletal structures.

Actins↗

PubMed1983

Toxic oxygen species in monocyte-mediated antibody-dependent cytotoxicity.

The role of toxic oxygen species in monocyte-mediated ADCC against the myelogenous cell line K-562 was investigated. Freshly isolated human monocytes caused 40% specific lysis of antibody-coated K-562 cells (Ab-K-562). Monocytes challenged with Ab-K-562 gave a small but definite luminol-dependent chemiluminescence response, indicating that a respiratory burst with generation of toxic oxygen species had been elicited. Generation of hydrogen peroxide in areas of close apposition between the monocyte and the Ab-K-562 plasma membranes was demonstrated by electron microscopy using precipitation of cerium ions as a cytochemical stain for hydrogen peroxide. Catalase inhibited the formation of cerium precipitates in the interaction zone between monocytes and Ab-K-562 cells. Despite evidence that toxic oxygen species were generated, the monocytes' cytolytic activity against Ab-K-562 was not inhibited by superoxide dismutase, catalase, or azide. Enzymatically generated fluxes of superoxide anion or hydrogen peroxide were not cytolytic to K-562 cells but did have a cytostatic effect. We conclude that toxic oxygen species are generated when human monocytes are challenged with Ab-K-562. However, these toxic oxygen species do not appear to be the major mediators of the monocytes' cytolytic activity in this experimental system.

Animals↗

PubMed1983

Human monocyte-mediated antibody dependent cytotoxicity to K-562 cells: an electron microscopic study.

Human monocyte-mediated antibody dependent cytotoxicity (ADCC) to K-562 cells has been examined using 51Cr-release assays and electron microscopy. Non-activated monocytes lysed antibody-coated K-562 cells rapidly, the observed lysis reaching a constant level of 28% after 6 h of co-culture. Lymphokine-activated monocytes mediated ADCC with a similar time course but with higher cytolysis level (42%) compared to non-activated monocytes. The cytolysis was dependent on the amount of antibody on the K-562 cells and on the number of effector cells present in the assay. Scanning electron microscopy revealed that sensitized target cells in contact with monocytes lost their microvilli. Lysis was probably extracellular, but a small number of completely engulfed intact target cells were observed. Lymphokine-activation of the monocytes led to a dissociation of the phagocytic and cytotoxic activity, indicating that phagocytosis is not directly involved in ADCC. Thin section- and freeze-fracture electron microscopy of the contact area between effector and target cells revealed no membrane specializations. The cells were always separated by a gap of 20-30 nm interrupted by characteristic invaginations in the opposing plasma membranes.

Antibody-Dependent Cell Cytotoxicity↗

PubMed1982

Human monocyte mediated cytotoxicity to K-562 cells: a freeze-fracture-, scanning- and thin section electron microscopic study.

The structural features of "natural"human monocyte-mediated cytotoxicity towards K-562 leukemia cells in vitro have been examined. Human monocytes bound K-562 cells firmly and mediated a slow cytolysis of the leukemia cells. Monocyte binding of target cells was shown to be trypsin sensitive. Freeze-fracture and thin section electron microscopy revealed that effector and target cells were separated by a irregular space larger than 20 nm. There was no evidence for the involvement of specialized membrane junctions or organelle transfer between monocytes and target cells. Scanning electron microscopy revealed that K-562 cells bound to monocytes progressively lost their microvilli. This process started in the membrane areas close to the effector-target cell interaction. The results suggest that binding of target cells by monocytes followed by action of short-range soluble cytotoxic mediators may be the mechanism for the monocyte-mediated cytotoxicity towards K-562 cells.

Animals↗

PubMed1982

Effects of cadmium on survival and morphology of cultured rat Sertoli cells.

The toxicity of different metals on isolated Sertoli cells grown in culture has been investigated. Methyl mercury (CH3HgCl) and mercury chloride (HgCl2) were more toxic than cadmium (CdCl2) which was slightly more toxic than arsenic (As2O3). Isolated peritubular cells and Sertoli cells were equally sensitive to cadmium. Cadmium reduced the Sertoli cell survival over the concentration range of 1--10 microM. Freeze-etch electron microscopy of cadmium-exposed Sertoli cells revealed circular areas of average diameter 500 nm devoid of intramembrane particles in the nuclear membrane, and general signs of degeneration such as vesiculation of the plasma membrane and intramembrane particle aggregation. However, cadmium did not dissolve junctional complexes between Sertoli cells. Isolated Sertoli cells were protected against cadmium-induced damage when the cells were preincubated for 48 h with selenium, zinc or low doses of cadmium. Preincubation with cobalt, FSH, testosterone or oestradiol did not protect against cadmium-induced damage. Cadmium bound to metallothionein had no toxic effects on isolated Sertoli cells.

Animals↗