Recombinant interferon-gamma stimulates the production of human tumor necrosis factor in vitro

Unphosphorylated STAT1 represses apoptosis in macrophages during Mycobacteriumtuberculosis infection

In murine macrophages infected with Mycobacterium tuberculosis (Mtb), the level of phosphorylated STAT1 (P-STAT1), which drives the expression of many pro-apoptosis genes, increases quickly but then declines over a period of hours. By contrast, infection induces a continued increase in the level of unphosphorylated STAT1 that persists for several days. Here, we found that the level of unphosphorylated STAT1 correlated with the intracellular bacterial burden during the later stages of infection. To investigate the significance of a high level of unphosphorylated STAT1, we increased its concentration exogenously, and found that the apoptosis rate induced by Mtb was sufficiently decreased. Further experiments confirmed that unphosphorylated STAT1 affects the expression of several immune-associated genes and lessens the sensitivity of macrophages to CD95 (FAS)-mediated apoptosis during Mtb infection. Furthermore, we characterized 149 proteins that interacted with unphosphorylated STAT1 and the interactome network. The cooperation between unphosphorylated STAT1 and STAT3 results in downregulation of CD95 expression. Additionally, we verified that unphosphorylated STAT1 and IFIT1 competed for binding to eEF1A. Taken together, our data show that the role of unphosphorylated STAT1 differs from that of P-STAT1, and represses apoptosis in macrophages to promote immune evasion during Mtb infection.

Inhibition of matrix metalloproteinase-9 by interferons and TGF-β1 through distinct signalings accounts for reduced monocyte invasiveness

Cytokines may provide signals for regulating human monocyte matrix metalloproteinase-9 (MMP-9) activity. In this study, we investigated the roles of interferons (IFN) type I/II and transforming growth factor-beta1 (TGF-beta1) in MMP-9-mediated invasiveness. MMP-9 antibody and inhibitor, IFNs and TGF-beta1 inhibited monocyte transmigration through Matrigel. IFNs and TGF-beta1 downregulated MMP-9 mRNA, protein and activity levels. The inhibitory action of IFNs was associated with the STAT1/IRF-1 pathway since the JAK inhibitor AG490 blocked STAT1 phosphorylation, IRF-1 synthesis and counteracted the blockade of MMP-9 release. TGF-beta1-mediated MMP-9 inhibition appeared STAT1/IRF-1-independent but reversed by the protein tyrosine kinase inhibitor tyrphostin 25. Our data point out the importance of IFNs and TGF-beta1 in the control of monocyte MMP-9-mediated extravasation.

Activation of JAK2/STAT1-alpha-dependent signaling events during Mycobacterium tuberculosis-induced macrophage apoptosis

Induction of apoptosis by Mycobacterium tuberculosis in murine macrophage involves TNF-alpha and nitric oxide (NO) production and caspase cascade activation; however, the intracellular signaling pathways implicated remain to be established. Our results indicate that infection of the B10R murine macrophage line with M. tuberculosis induces apoptosis independent of mycobacterial phagocytosis and that M. tuberculosis induces protein tyrosine kinase (PTK) activity, JAK2/STAT1-alpha phosphorylation, and STAT1-alpha nuclear translocation. Inhibitors of PTK (AG-126), or JAK2 (AG-490) inhibited TNF-alpha and NO production, caspase 1 activation and apoptosis, suggesting that M. tuberculosis-induction of these events depends on JAK2/STAT1-alpha activation. In addition, we have obtained evidence that ManLAM capacity to inhibit M. tuberculosis-induced apoptosis involves the activation of the PTP SHP-1. The finding that M. tuberculosis infection activate JAK2/STAT1-alpha pathway suggests that M. tuberculosis might mimic macrophage-activating stimuli.

Interferon-gamma and tumor necrosis factor-alpha induce synergistic cytolytic effects in ovarian cancer cell lines-roles of the TR60 and TR80 tumor necrosis factor receptors

OBJECTIVE

Utilizing ovarian cancer cell lines, we examined the effect of IFN-gamma on each type of TNF receptor. Additionally, we sought to determine the effect of receptor modulation on TNF-alpha-mediated cytolysis.

METHODS

Ovarian cancer cell lines Caov-3, A2780, and SK-OV-3 were employed. The number of TNF receptors was determined by a TNF-alpha binding assay utilizing 125I-labeled TNF-alpha. Monoclonal antibodies specific for the 55- to 60-kDa (TR60) and the 75- to 80-kDa (TR80) TNF receptors were used to determine the relative density of each receptor type. Northern blot analyses were performed employing cDNA probes for the TR60 and TR80 mRNAs. To elucidate which receptor(s) was responsible for mediating the signal for cytolysis, 24-h MTT cytolytic assays were performed in the presence of receptor-specific monoclonal antibodies.

RESULTS

IFN-gamma treatment resulted in an increase in TNF receptors in the cell lines A2780 and Caov-3 (P < 0.001), but not SK-OV-3. Northern blot analyses suggested distinct regulatory mechanisms for the two receptors. In Caov-3 and SK-OV-3 cells a synergistic increase in TNF-alpha-mediated cytolysis was seen when cells were pretreated with IFN-gamma. In both cell lines, pretreatment with IFN-gamma markedly enhanced the ability of the TR60 receptor to mediate cell lysis. Conversely, under similar treatment conditions, the TR80 receptor did not appear capable of generating a cytolytic signal.

CONCLUSIONS

TNF receptor modulation by IFN-gamma appears to be unique to individual cell lines. The TR60 TNF receptor plays a central role in the synergistic cytolytic effects of IFN-gamma and TNF-alpha. Sequential therapy with IFN-gamma and TNF-alpha and specific TNF receptor activation may provide novel translational strategies for the use of cytokines in the treatment of ovarian cancer.

Inactivation of the Fanconi Anemia Group C Gene Augments Interferon-γ–Induced Apoptotic Responses in Hematopoietic Cells

Hematopoietic progenitor cells (HPC) from mice nullizygous at the Fanconi anemia (FA) group C locus (FAC −/−) are hypersensitive to the mitotic inhibitory effects of interferon (IFN-γ). We tested the hypothesis that HPC from the bone marrow of Fanconi group C children are similarly hypersensitive and that the fas pathway is involved in affecting programmed cell death in response to low doses of IFN-γ. In normal human and murine HPC, IFN-γ primed the fas pathway and induced both fas and interferon response factor-1 (IRF-1) gene expression. These IFN-γ-induced apoptotic responses in HPC from the marrow of a child with FA of the C group (FA-C) and in FAC −/− mice occurred at significantly lower IFN doses (by an order of magnitude) than did the apoptotic responses of normal HPC. Treatment of FA-C CD34+ cells with low doses of recombinant IFN-γ, inhibited growth of colony forming unit granulocyte-macrophage and burst-forming unit erythroid, while treatment with blocking antibodies to fas augmented clonal growth and abrogated the clonal inhibitory effect of IFN-γ. Transfer of the normal FAC gene into FA-C B-cell lines prevented mitomycin C–induced apoptosis, but did not suppress fas expression or inhibit the primed fas pathway. However, the kinetics of Stat1-phosphate decay in IFN-γ–treated cells was prolonged in mutant cells and was normalized by transduction of the normal FAC gene. Therefore, the normal FAC protein serves, in part, to modulate IFN-γ signals. HPC bearing inactivating mutations of FAC fail to normally modulate IFN-γ signals and, as a result, undergo apoptosis executed through the fas pathway.

Inactivation of the Fanconi Anemia Group C Gene Augments Interferon-γ–Induced Apoptotic Responses in Hematopoietic Cells

Hematopoietic progenitor cells (HPC) from mice nullizygous at the Fanconi anemia (FA) group C locus (FAC −/−) are hypersensitive to the mitotic inhibitory effects of interferon (IFN-γ). We tested the hypothesis that HPC from the bone marrow of Fanconi group C children are similarly hypersensitive and that the fas pathway is involved in affecting programmed cell death in response to low doses of IFN-γ. In normal human and murine HPC, IFN-γ primed the fas pathway and induced both fas and interferon response factor-1 (IRF-1) gene expression. These IFN-γ-induced apoptotic responses in HPC from the marrow of a child with FA of the C group (FA-C) and in FAC −/− mice occurred at significantly lower IFN doses (by an order of magnitude) than did the apoptotic responses of normal HPC. Treatment of FA-C CD34+ cells with low doses of recombinant IFN-γ, inhibited growth of colony forming unit granulocyte-macrophage and burst-forming unit erythroid, while treatment with blocking antibodies to fas augmented clonal growth and abrogated the clonal inhibitory effect of IFN-γ. Transfer of the normal FAC gene into FA-C B-cell lines prevented mitomycin C–induced apoptosis, but did not suppress fas expression or inhibit the primed fas pathway. However, the kinetics of Stat1-phosphate decay in IFN-γ–treated cells was prolonged in mutant cells and was normalized by transduction of the normal FAC gene. Therefore, the normal FAC protein serves, in part, to modulate IFN-γ signals. HPC bearing inactivating mutations of FAC fail to normally modulate IFN-γ signals and, as a result, undergo apoptosis executed through the fas pathway.

Immunohistochemical localization of interferon-gamma in normal human ovary

There is increasing evidence that cytokines are important intraovarian non-steroidal regulators. The aim of the present study was to evaluate the presence in the human ovary of interferon (IFN)-gamma, a cytokine produced by T lymphocytes after mitogenic or antigenic stimulation. Very low levels of IFN-gamma (0.025-0.057 IU/ml) were found in follicular fluid of large spontaneously maturing follicles, in the ovarian vein (< 0.01-0.079 IU/ml) or peripheral blood (< 0.01-0.06 IU/ml). The avidin-biotin immunocytochemical technique, with appropriate monoclonal antibodies, was used to localize IFN-gamma-positive cells, human leukocyte antigen (HLA)-DR molecules, activated T cells, T helper/inducer cells and T cytotoxic/suppressor cells. IFN-gamma-positive cells were only detected in preovulatory follicles, associated with the follicular basal lamina, thecal vessels and interstitial tissue. In the same large follicles very few T helper/inducer cells were detected, but a high proportion of T lymphocytes expressed the CD8 phenotype in the theca, interstitial tissue and follicular cavity. No IFN-gamma-positive cells were observed in preantral and small antral follicles. The results indicate that the human ovary contains immunoreactive IFN-gamma, suggesting that the cytokine plays a paracrine role in human ovarian function.

Cathepsin-G and leukocyte elastase inactivate human tumor necrosis factor and lymphotoxin

The addition of either cathepsin-G or leukocyte elastase to endotoxin-stimulated human peripheral blood monocytes decreased the immunoreactive tumor necrosis factor (TNF) detected in culture supernatants in a concentration-dependent manner. Both enzymes also induced a loss of supernatant cytolytic activity as determined on the WEHI-164 target cell line. Incubation of recombinant human TNF and lymphotoxin (LT) with either cathepsin-G or leukocyte elastase resulted in a loss of cytokine bioactivity. Examination of enzyme-treated recombinant cytokines by gel electrophoresis revealed that cathepsin-G cleaved LT into a 12.6-kDa fragment and leukocyte elastase fragmented LT into a 14.1-kDa product. On Western blots cathepsin-G and leukocyte elastase degraded TNF into 11- and 7.6-kDa fragments, respectively. Incubating leukocyte elastase with plasma elastase inhibitor alpha-1-antitrypsin prevented the loss of recombinant TNF bioactivity and blocked the degradation of this cytokine. This study suggests that two of the most abundant neutrophil proteases, cathepsin-G and leukocyte elastase, may be important regulators of TNF and LT bioactivity.

A convenient human whole blood culture system for studying the regulation of tumour necrosis factor release by bacterial lipopolysaccharide

Bacterial lipopolysaccharide (LPS, endotoxin) induces a dose-dependent release of TNF in whole human blood which has been diluted five-fold. It is modulated by interferon-gamma, prostaglandin E2 and indomethacin in the same manner as observed with tumour necrosis factor (TNF) release from human monocyte/macrophage cells cultured in vitro. The whole blood culture system (WBCS) can provide up to 250 samples from 10 ml of venous blood and enables an individual blood to be assessed in terms of TNF inducibility and its modulation by other biological agents. The whole blood culture system was used to demonstrate the individual variation between blood donors. The results demonstrated that the information provided by induced cytokine release and its regulation in the ex vivo system would be a valuable addition to that obtained from in vitro methods.

Ability of cell-sized beads bearing tumor cell membrane proteins to stimulate LAK cells to secrete interferon-gamma and tumor necrosis factor-alpha

We recently reported that lymphokine activated killer (LAK) cells were stimulated to release both interferon-gamma (IFN-gamma) and tumor necrosis factor-alpha (TNF-alpha) when stimulated by a variety of tumor cells. We proposed then that the released cytokines may play a role in mediating tumor cell regression in vivo. In this paper, we provide further information on the nature of the signals, provided by the tumor cells (K562 erythroleukemia), that stimulate LAK cells to secrete IFN-gamma and TNF-alpha. Using a previously published protocol for coating tumor-membrane molecules onto cell-sized hydrophobic beads (also called pseudocytes), we demonstrate that the signal provided by the tumor cell is membrane associated. Beads coated with K562 membranes stimulated LAK cells to release IFN-gamma and TNF-alpha. The pretreatment of these beads with trypsin and sodium periodate eliminated the ability of these pseudocytes to stimulate cytokine release in LAK cells. The glycoproteins that stimulate LAK cells to secrete IFN-gamma and TNF-alpha were further enriched by their ability to bind concanavalin A (Con A, Jack Bean). To determine if the tumor-associated molecules that stimulate LAK cells to release IFN-gamma and TNF-alpha are also the molecules involved in mediating tumor cell lysis, we tested the ability of the Con A binding and nonbinding proteins to inhibit the LAK cell-mediated lysis of K562 cells. Our results demonstrate that molecules that inhibited LAK cell-mediated cytotoxicity were not enriched by Con A. These results are therefore consistent with the conclusion that different sets of tumor-associated molecules are involved in the stimulation of LAK cells to secrete cytokine and in the induction of LAK cells to mediate tumor cell cytolysis.

Proliferative and antiproliferative effects of interferon-gamma and tumor necrosis factor-alpha on cell lines derived from cervical and ovarian malignancies

Four human cell lines derived from cervical carcinomas (ME-180, SiHa, HT-3, and MS751) and three human cell lines derived from ovarian carcinomas (SK-OV-3, Caov-3, and NIH:OVCAR-3) were analyzed in vitro to determine the effect of recombinant interferon-gamma and recombinant human tumor necrosis factor-alpha on cell growth and survival. The effects of interferon-gamma, tumor necrosis factor-alpha, and both interferon-gamma and tumor necrosis factor-alpha on cell growth were measured after 24 and 72 hours of incubation by the incorporation of chromium 51. The results of this analysis showed that all seven cell lines were resistant to the antiproliferative action of tumor necrosis factor-alpha, that the growth of most cell lines was inhibited by interferon-gamma by 72 hours of incubation, and that after 72 hours of incubation all cell lines demonstrated a synergistic antiproliferative response to the combination of interferon-gamma and tumor necrosis factor-alpha. However, the effects of these cytokines on cell growth were found to differ among cell lines and varied with the concentration and the duration of incubation. The growth of one cell line (Caov-3) was stimulated by both tumor necrosis factor-alpha and interferon-gamma. These results suggest that the clinical effects of these cytokines on the growth of gynecologic cancers may be more complex than previously supposed.

Regulation of tumor necrosis factor secretion in leukocytes from alpha-1-antitrypsin deficient humans

Alpha-1-antitrypsin (AT) is one of several alpha-globulins which have been shown to be inhibitors of human peripheral blood monocyte TNF secretion in vitro. AT deficiency states exist, within which individuals of either the PiSS or PiZZ phenotype have reduced hepatocyte and mononuclear phagocyte AT secretion when compared to normal PiMM subjects. Here we have compared the capacity of peripheral blood monocytes of all three phenotypes to respond to both enhancers and inhibitors of TNF secretion. All monocytes exposed to lipopolysaccharide (LPS), interferon-gamma (IFN-gamma) and endotoxin, PGE2, transforming growth factor-beta 1, whole plasma alpha-globulins, purified AT and IL-6 responded equally with respect to the secretion of TNF. Our findings show that the regulation of TNF secretion in leukocytes from AT deficient humans is normal and suggest that defective AT secretion alone does not result in the aberrant regulation of TNF secretion.

Effect of interferon-gamma on the expression of HLA-DR by human melanoma cells of varying metastatic potential

Three human melanoma cell lines of varying invasive and metastatic potential were analyzed for their ability to express HLA-DR antigens on the cell surface as well as transcriptionally at the mRNA level in the presence and absence of IFN-gamma treatment. Cells of low and intermediate metastatic and invasive potential showed a high percentage of HLA-DR surface expression, both before (91.2-99.9%) and after (97.8-99.9%) IFN-gamma treatment, as quantitated by flow cytometry. In contrast, cells of high metastatic and invasive potential expressed barely detectable levels of HLA-DR-positive cells before IFN-gamma treatment (0.3-0.6%) and displayed elevated levels following treatment (42.3-89.4%). Allowing the highly metastatic cells to recover for 7 or 14 days following IFN-gamma treatment resulted in barely detectable levels of HLA-DR-positive cells. Northern blot analyses of HLA-DR transcription levels showed a strong expression in cells of low and intermediate metastatic and invasive potential. HLA-DR mRNA levels were not detectable in control cells of high metastatic potential nor in those cells which had undergone 7- and 14-day recovery periods following IFN-gamma treatment. There was, however, an induction of HLA-DR expression in the cells that had been treated with IFN-gamma for 72 hr and allowed no recovery period. In addition, a punctate, receptor-like pattern of immunofluorescence staining pattern for cell surface HLA-DR was seen after a 72 hr IFN-gamma treatment in the highly metastatic cells. In contrast, cells of low and intermediate metastatic potential expressed a homogeneous ring-like pattern of antigen expression.

Interactive effects between cytokines on PGE production by human periodontal ligament fibroblasts in vitro

Mononuclear cell production of cytokines that stimulate fibroblast production of prostaglandin E (PGE) is an important mechanism by which mononuclear cells regulate fibroblast function. The objective of this investigation was to determine the effects of the cytokines interleukin 1 beta (IL-1 beta), interleukin 1 alpha (IL-1 alpha), tumor necrosis factor alpha (TNF-alpha), and interferon gamma (IFN-gamma), alone or in paired combinations, on PGE production by near-confluent human periodontal ligament (PDL) fibroblasts in vitro. Premolars extracted in the course of orthodontic treatment were used for this study. Fibroblast cultures, free of epithelial cells, were obtained after the fourth subculture by the use of accurately-timed trypsin treatment. Cells in the fourth to sixth passage, incubated in DMEM supplemented with 10% equine serum, were used for these experiments. Cells (1 x 10(5)) were seeded in 12- x -75-mm tissue culture tubes and incubated with various doses of IL-1 beta, IL-1 alpha, TNF-alpha, and IFN-gamma, alone or in specific combinations, for 15 min, two, 12, 24, and 72 h. PGE concentrations in the media were measured by radio-immunoassay. The results showed that human PDL fibroblasts responded to the administration of cytokines by an elevation in the synthesis of PGE in a dose- and time-related fashion. The increase in PGE production was inhibited by the addition of indomethacin. The interactions between these cytokines varied in degree, depending on the particular combinations of cytokines. In addition, the administration of cytokine combinations was found to be additive, synergistic, subtractive, or suppressive on the production of PGE by PDL fibroblasts, depending on the duration of incubation. These experiments demonstrate the importance of the consideration of the interplay between cytokines produced by mononuclear cells on the mechanisms that regulate the functions of PDL fibroblasts.

Differential effects of copper and zinc on human peripheral blood monocyte cytokine secretion

The addition of copper and zinc salts to human peripheral blood leukocytes cultured in complete medium containing endotoxin and fetal calf serum stimulated tumor necrosis factor (TNF) secretion in a concentration-dependent manner. The secretion of interleukin-1 beta (IL-1 beta) and interleukin-6 (IL-6) was inhibited by copper under the same culture conditions, while zinc stimulated IL-1 beta secretion in a concentration-dependent manner and had no effect on leukocyte IL-6 release. Both copper and zinc induced increases in TNF mRNA (54 and 14%, respectively) when compared to cells cultured in complete medium alone. In serum-free, low endotoxin medium (less than 6 pg/ml), both copper and zinc failed to stimulate either TNF or IL-1 beta secretion. Under the same conditions the addition of lipopolysaccharide (LPS), at concentrations above 0.01 micrograms/ml, induced a concentration-dependent release of both cytokines. When either copper or zinc were combined with 0.01 micrograms/ml LPS, a synergistic stimulation of TNF secretion resulted. IL-1 beta secretion, unlike TNF, was not synergistically stimulated by combining metals and LPS in serum-free medium. Combining copper and zinc with inhibitors of TNF secretion, transforming growth factor beta, prostaglandin E2, and plasma alpha-globulins, resulted in a reduction of the suppressive effects of each of these agents. This study suggests that the trace metals copper and zinc may play important and possibly distinct roles in regulating leukocyte secretion of TNF, IL-1 beta, and IL-6.

Modification of the clonogenic assay for the detection of lymphokine activated killer cell activity

The soft agar clonogenic assay using [3H]thymidine uptake as an endpoint was adapted for the detection of human LAK activity against the Daudi lymphoma cell line and human tumor cells obtained by biopsy. Using Daudi cells as the target population the modified agar assay was more sensitive than the conventional 4 h 51Cr release assay. Use of a single layer agar assay allowed the assessment of LAK cytotoxic/cytostatic activity against Daudi lymphoma cells after cell to cell contact, while a two layer system permitted evaluation of the role of soluble mediators in LAK/target cell interactions. This study shows that LAK cells can either kill or inhibit the proliferation of Daudi cells by two mechanisms: one which requires cell-to-cell contact, and a second via soluble mediators. As determined by the use of neutralizing antisera, the soluble factor(s) are not tumor necrosis factor and interferon-gamma. Of the nine individual human tumor samples obtained by biopsy. 89% were sensitive to allogeneic LAK cells when the two populations were admixed. Of these nine tumors 44% were inhibited by LAK-derived soluble factors. The soft agar assay system should serve as a useful tool for determining the sensitivity of human tumors to LAK cells and for studying the mechanisms of LAK anti-tumor activity.

Tumor necrosis factor alpha production by peripheral blood mononuclear cells of patients with chronic liver disease

We investigated the production of tumor necrosis factor alpha by peripheral blood mononuclear cells of patients with chronic liver disease and its association with hepatitis activity. Tumor necrosis factor alpha production was measured with an enzyme-linked immunosorbent assay. Tumor necrosis factor alpha production by peripheral blood mononuclear cells stimulated with recombinant gamma-interferon of patients with chronic active hepatitis (5.8 +/- 4.0 units per ml, p less than 0.05) and patients with cirrhosis (4.1 +/- 2.1 units per ml, p less than 0.05) was significantly increased when compared with controls (2.5 +/- 1.6 units per ml). Tumor necrosis factor alpha production by peripheral blood mononuclear cells stimulated with a combination of recombinant gamma-interferon and recombinant interleukin 2 of patients with chronic persistent hepatitis (5.8 +/- 3.8 units per ml, p less than 0.05), patients with chronic active hepatitis (8.9 +/- 3.0 units per ml, p less than 0.001) and patients with cirrhosis (6.7 +/- 3.2 units per ml, p less than 0.05) was significantly increased in comparison with controls (3.3 +/- 1.8 units per ml). Tumor necrosis factor alpha production of patients with chronic active hepatitis was significantly higher than that of patients with chronic persistent hepatitis (p less than 0.05). There was a significant correlation (r = 0.5699, p less than 0.005) between tumor necrosis factor alpha production and histologic activity index in patients with chronic persistent hepatitis or chronic active hepatitis. These findings show that tumor necrosis factor alpha production is increased in chronic liver disease and that the increased tumor necrosis factor alpha production is related to hepatitis activity.

Characteristics of tumor necrosis factor production in rheumatoid arthritis

The biological effects of tumor necrosis factor (TNF) include the enhancement of fibroblast proliferation, the secretion of collagenase and prostaglandin E2 (PGE2) by fibroblasts, and the resorption of bone and cartilage, suggesting a role for this cytokine in arthritic conditions. To investigate this, we measured the levels of TNF in synovial fluids and evaluated its secretion by synovial fluid mononuclear cells and tissues from patients with rheumatoid arthritis, osteoarthritis, and seronegative arthritis and normals. TNF was found to be secreted in all arthritic conditions but not in normals. The levels of TNF were highest in synovial fluid and correlated with interferon-gamma (IFN-gamma) levels but not PGE2. The production of TNF was stable in a single joint for 3 to 6 months. Using immunohistochemical staining, TNF was localized to mononuclear cells in the lining layer, sublining, and perivascular areas of synovial tissue. The secretion of TNF by rheumatoid synovial fluid mononuclear cells was inhibited by PGE2, while IFN-gamma enhanced its production in those cells which were spontaneously secreting TNF. Our data suggest that TNF may play a role in various arthritic diseases.

Alpha-globulins suppress human leukocyte tumor necrosis factor secretion

The secretion of tumor necrosis factor (TNF) by human peripheral blood mononuclear cells was suppressed by either whole human plasma alpha-globulins or purified alpha 1-acid-glycoprotein, alpha 1-antitrypsin and alpha 2-macroglobulin in a concentration-dependent manner. alpha 1-Antitrypsin was found to be the most suppressive of the purified proteins tested and completely blocked TNF release at concentrations above 1.25 mg/ml. Both alpha 1-acid glycoprotein and alpha 1-antitrypsin blocked TNF secretion by leukocytes which were simultaneously stimulated with either recombinant human interferon-gamma (IFN-gamma) or lipopolysaccharide (LPS). IFN-gamma- and LPS-activated cells were also susceptible to suppression mediated by these two alpha-globulins and the inhibition produced by 5 mg/ml alpha 1-antitrypsin was greater than that caused by either 1 microM prostaglandin E2 or 10 ng/ml transforming growth factor-beta 1. The level of TNF mRNA in TNF-secreting and alpha-globulin-suppressed cells was examined and found to be equal in both groups. The suppressive effect of whole alpha-globulins was confined to the inhibition of TNF secretion and these plasma proteins had no effect on the cytolytic activity of the recombinant cytokine as measured on murine L-929 target cells. Thus the alpha-globulins, which are a major fraction of the circulating plasma proteins, may function in TNF homeostasis by controlling TNF secretion without inhibiting the biological activity of the released cytokine.

Phenotypic and functional analysis of lymphokine-activated killer (LAK) cell clones. Ability of CD3+, LAK cell clones to produce interferon-gamma and tumor necrosis factor upon stimulation with tumor targets

Lymphokine-activated killer (LAK) cells are generated by the culture of peripheral blood lymphocytes with interleukin-2 (IL-2). A variety of cells, including T-lymphocytes and natural killer (NK) cells, can be activated by IL-2 to exhibit the ability to kill multiple tumor and "modified-self" targets. Recent reports indicate that culture conditions can determine the phenotype of cells expressing LAK activity. Using limiting dilution techniques, we first generated cloned LAK cells with three culture conditions: autologous human serum (AHS) + IL-2; AHS + IL-2 + 0.1 micrograms/ml phytohemagglutinin and fetal bovine serum and IL-2. We determined that all but one of the 47 LAK cell clones generated with the three culture conditions were CD3+ and T-cell like; one NK-like clone was observed. Clones that were cytotoxic for one target could generally kill multiple targets, and the absence of phytohemagglutinin did not significantly affect the ability of the LAK cell clones to kill multiple targets. The presence of phytohemagglutinin was, however, necessary for the long-term maintenance of proliferation and cytotoxic activity of the LAK cell clones. The mechanism by which LAK cells kill tumor targets is not known. We here demonstrate that LAK cells and LAK cell clones can produce interferon-gamma and tumor necrosis factor (TNF) when stimulated with an erythroleukemia cell, K562. Five of the six CD3+, LAK cell clones tested could be stimulated by K562 cells to produce both interferon-gamma and TNF. However, the ability of the cloned LAK cells to kill K562 cells, as measured in a 4-h 51Cr-release assay, did not correlate with their ability to produce these cytokines. Furthermore, specific antibodies that neutralize the cytotoxic activity of interferon-gamma and TNF did not inhibit killing of K562 cells by LAK cells as measured with a 4-h cytotoxic assay. The cytostatic and cytotoxic activities of interferon-gamma and TNF for tumor cells are well documented, but these cytolytic activities are slower acting and exhibit their maximum effect after 48-96 h. We here propose that LAK cells kill tumor targets by a combination of cell-to-cell-mediated killing and by the release of slower acting cytostatic/cytotoxic cytokines that can inhibit the growth of tumors some distance from the effector cells.

Association between HLA-DR2 and production of tumour necrosis factor alpha and interleukin 1 by mononuclear cells activated by lipopolysaccharide

The production of tumour necrosis factor (TNF) and interleukin 1 (IL-1) by lipopolysaccharide-activated mononuclear cells from 39 healthy donors was studied in vitro by bioassay and ELISA. The donors were typed for HLA-A, -B, -C, -DR, and -DP antigens. There was no detectable production of TNF beta (lymphotoxin). The intracellular levels of bioactive TNF alpha were minimal or undetectable in all cases. Cells from HLA-DR2+ individuals secreted significantly lower amounts of TNF alpha than cells from HLA-DR2- donors [2 ng/ml (1.5-4.4) and 7.5 ng/ml (3.9-8.3) respectively (medians 25-75%); P less than 0.01]. The difference disappeared if the cells were preactivated for 2 days with 1000 U/ml of recombinant gamma interferon (rIFN-gamma). In some individuals, the TNF alpha response increased considerably after IFN-gamma priming, in particular in those possessing the HLA-DR2 antigen. In contrast, there was no detectable difference in the production of IL-1 beta between the donors, and the IL-1 beta response decreased significantly after rIFN-gamma priming in HLA-DR2+ individuals [2.3 ng/ml (1.1-8.4) versus 7.2 ng/ml (5-7.9); P less than 0.05] and in HLA-DR2- individuals [3 ng/ml (1.1-5.3) versus 5.7 ng/ml (3.9-7.5); P less than 0.01]. There was no correlation between the TNF alpha and IL-1 responses and any of the other HLA-DR, -DP, or -B antigens. There was a significant positive correlation between the levels of TNF alpha measured by ELISA and by cytotoxicity assay. However, the TNF alpha-containing supernatants from 9 out of 37 individuals appeared to contain inhibitor(s) of the biological activity of TNF alpha. The presence of inhibitor(s) was not associated with any HLA antigens.

T cell-mediated production of tumour necrosis factor-alpha by monocytes

The aim of this study was to examine the tumour necrosis factor (TNF)-alpha production by peripheral blood mononuclear cells activated by mitogens. Considerable amounts of TNF-alpha, ranging from 1.0 to 5.0 ng/ml, were present in the supernatants of cultures of human peripheral blood mononuclear cells (PBMC), stimulated with either the anti-CD3 monoclonal antibody OKT3 or the lectin phytohaemagglutinin (PHA). The amount of TNF-alpha secreted in the supernatant was closely correlated to the degree of T cell proliferation in such cultures, as measured by [3H]TdR incorporation. In the absence of proliferating T cells the mitogens did not induce secretion of TNF-alpha by monocytes. Supernatants of proliferating T cells were shown to induce TNF-alpha production by monocytes. The macrophage-activating factor gamma interferon (IFN-gamma) was also shown to induce, in the absence of endotoxin, TNF-alpha secretion by monocytes in a dose-dependent manner. The induction of TNF-alpha production by supernatants of proliferating T cells could largely be abrogated by passaging the supernatants on an anti-IFN-gamma column before adding them to the monocytes. It is therefore concluded from this study that the production of TNF-alpha by monocytes can be induced by proliferating T cells and that this induction can largely be attributed to the T cell lymphokine IFN-gamma.