Interferon beta 2/B-cell stimulatory factor type 2 shares identity with monocyte-derived hepatocyte-stimulating factor and regulates the major acute phase protein response in liver cells

Granulocyte elastase in assessment of severity of acute pancreatitis. Comparison with acute-phase proteins C-reactive protein, alpha 1-antitrypsin, and protease inhibitor alpha 2-macroglobulin

Complexes of granulocyte elastase and alpha 1-antitrypsin are markers for granulocyte activation. In 75 patients with acute pancreatitis these complexes were immunologically determined daily in plasma during the first week of hospitalization. Patients were classified into three groups: mild pancreatitis (I, less than or equal to 1 complication, N = 34), severe pancreatitis (II, greater than or equal to 2 complications, N = 29), lethal outcome (III, N = 12). Initially, granulocyte elastase (mean +/- SEM) was lower in group I (348 +/- 39 micrograms/liter) as compared to groups II (897 +/- 183 micrograms/l) and III (799 +/- 244 micrograms/liter), P less than 0.001 for I vs II + III. Initial elastase concentrations greater than 400 micrograms/liter were consistent with a severe or fatal course of the disease but did not distinguish between severe and lethal pancreatitis. In patients with mild or severe disease, mean elastase concentrations decreased continuously during the following days (197 +/- 15 micrograms/liter in mild cases, 325 +/- 30 micrograms/liter in severe cases at day 7). In patients with lethal disease, however, mean elastase concentrations even increased at day 2 and remained higher than 700 micrograms/liter during the observation period. At days 1 and 2 the predictive value for severe or lethal disease of raised (greater than 400 micrograms/liter) elastase concentrations [positive predictive value (PPV) 82%, negative predictive value (NPV) 81%] was better than that of elevated (greater than 100 mg/liter) C-reactive protein (PPV 73%, NPV 73%), elevated (greater than 4.0 g/liter) alpha 1-antitrypsin (PPV 59%, NPV 50%), or decreased (less than 1.5 g/liter) alpha 2-macroglobulin (PPV 82%, NPV 67%).(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukins and tumor necrosis factor in inflammation

Intense research efforts have been directed toward characterizing mediators that control the inflammatory response and regulate the growth, differentiation, and function of cells involved in inflammation. Tumor necrosis factor, or cachectin, and members of a heterogeneous group of peptides called interleukins exhibit a wide spectrum of activities, some of which appear to influence the evolution of inflammatory processes. This review outlines the observations that have led to our current understanding of the biology of tumor necrosis factor and the interleukins. Particular attention is directed toward the evidence suggesting that these cytokines function as mediators of inflammatory responses.

Stimulation of antibacterial macrophage activities by B-cell stimulatory factor 2 (interleukin-6)

Mononuclear phagocytes provide the major habitat of intracellular bacteria, including Mycobacterium tuberculosis and Mycobacterium bovis. The capacity of B-cell stimulatory factor 2 (interleukin-6 [IL-6]) to activate tuberculostatic functions was investigated by using murine bone marrow-derived macrophages (BMM phi). BMM phi stimulated with recombinant IL-6 and subsequently infected with M. bovis organisms failed to inhibit mycobacterial growth. In contrast, marked tuberculostasis was induced by IL-6 in BMM phi that were already infected with M. bovis, indicating that IL-6 has a macrophage-activating function.

Secretion of interleukin-6 (IL-6) by human monocytes stimulated by muramyl dipeptide and tumour necrosis factor alpha

We studied IL-6 gene expression in human monocytes stimulated by muramyl dipeptide (MDP), a synthetic immunomodulator derived from mycobacterial cell walls. In control monocytes, two IL-6 transcripts of 3.4 kb and 1.6 kb were easily detected at 2.5 hr of culture and remained stable until 18 hr. In MDP-treated monocytes, three IL-6 RNA species displayed different kinetics of accumulation: a 3.4 kb RNA whose expression already reached its maximum after 2.5 hr exposure to MDP; a 1.6 kb RNA whose expression peaked at 5 hr; and a new RNA species of 1.4 kb which was transiently induced in early time of cell stimulation. TNF-alpha co-operated with MDP to increase IL-6 gene expression and secretion of biological active protein (measured by the hybridoma plasmacytoma growth factor assay). MDP exhibits a broad spectrum of immunomodulation properties such as adjuvant activity, enhancement of macrophage cytotoxicity against tumour and induction of non-specific resistance to intracellular agents. The results reported here suggest that these properties might be linked to the stimulation by MDP of genes coding for key cytokines such as IL-6, TNF and IL-1.

IL-6 in synovial fluids, plasma and supernatants from cultured cells of patients with rheumatoid arthritis and other inflammatory arthritides

The purpose of this investigation was to measure interleukin 6 (IL-6) levels in synovial fluid (SF) and plasma from patients with rheumatoid arthritis (RA) and other inflammatory arthritides (non-RA) and to examine the in vitro production of IL-6 by T cells and monocytes from SF and peripheral blood (PB). All patients had high levels of IL-6 in SF. Although the median level was higher in the group of non-RA arthritides, the difference was not statistically significant. Supernatants from both unstimulated and stimulated highly purified CD4+ and CD8+ cells from SF and PB did not contain IL-6, while high levels of IL-6 were detectable in supernatants of mononuclear cells (MNC) and plastic adherent cells without any specific in vitro stimulant. Since IL-6 is so readily produced by normal mononuclear cells in vitro without any specific stimulant, spontaneous in vitro production by SF MNC cannot be considered as evidence for in vivo production by the same cells.

Regulation of fibronectin synthesis by interleukin-1 and interleukin-6 in rat hepatocytes

The authors have observed previously that recombinant human interleukin-1 (rhIL-1) administered into rats increased plasma fibronectin (Fn) level concomitant with the increase of Fn in the liver. Because IL-1 induces interleukin-6 (IL-6) in certain cell types, the IL-1 effect might be mediated by IL-6. To evaluate this possibility, the effect of recombinant human interleukin-6 (rhIL-6), rhIL-1 alpha, and rhIL-1 beta on Fn synthesis in cultured rat hepatocytes was studied. It was shown that rhIL-6 increased Fn synthesis in hepatocytes, in contrast, rhIL-1 alpha, rhIL-I beta and TNF did not have any effect on Fn synthesis. When we studied the interaction of IL-1 and IL-6, IL-1 did not exhibit any synergistic effect with IL-6. Conditioned medium (CM) from rhIL-1 stimulated peripheral blood monocytes (PBM) increased the Fn synthesis, and its activity was neutralized significantly by anti-rhIL-6 antibodies. The CM from rhIL-1-stimulated PBM was analyzed by enzyme linked immunosorbent assay and revealed the increase of IL-6. Furthermore, it was found that intraperitoneal administration of rhIL-1 induced IL-6 into blood. The administration of rhIL-6 into rats increased circulating Fn levels. These results strongly suggest that the in vivo effect of IL-1 on Fn synthesis is mediated by IL-6.

Interleukin 6 stimulates hepatic glucose release from prelabeled glycogen pools

Cytokines, derived from a wide variety of cell types, are now believed to initiate many of the physiological responses accompanying the inflammatory phase that follows either Gram-negative septicemia or thermal injury. Because hypoglycemia (after endotoxic challenge) and hyperglycemia (after thermal injury) represent well-characterized responses to these injuries, we sought to determine whether hepatic glycogen metabolism could be altered by specific cytokines. Cultured adult rat hepatocytes were prelabeled with [14C]glucose for 24 h, a procedure that resulted in the labeling of hepatic glycogen pools that subsequently could be depleted (with concomitant [14C]glucose release) by either glucagon or norepinephrine. After the addition of a highly concentrated human monocyte-conditioned medium (MCM) or various cytokines to these prelabeled cells, [14C]glucose release was stimulated by MCM and recombinant human interleukin 6 (IL-6) but was not stimulated by other cytokines tested. Furthermore, only antisera to IL-6 were capable of reducing the glucose-releasing factor activity found in MCM. These data therefore suggest a novel glucoregulatory role for IL-6.

Endotoxin-stimulated human macrophages produce a factor that induces polymorphonuclear leucocyte infiltration and is distinct from interleukin-1, tumour necrosis factor alpha and chemotactic factors

Previously we reported that rabbit macrophages (M phi) in the presence of nanogram quantities of endotoxin (LPS) release factors that induce polymorphonuclear leucocyte (PMNL) infiltration into the skin of rabbits following i.d. injection. The predominant factor was a de novo synthesized protein of 45,000 MW on gel filtration that was distinguishable from IL-1 but not from TNF alpha. Here we examined human monocytes, in vitro monocyte-derived M phi and peritoneal M phi for the production of an analogous protein. Upon stimulation with LPS, they all rapidly (6 hr) produced a factor(s) that caused PMNL accumulation in the skin of rabbits when injected i.d. This activity, referred to as PMNL-recruiting activity (PRA), was heat labile and its production was blocked by cycloheximide. By Sephadex-G100 chromatography the major PRA of cultured M phi or peritoneal M phi had a molecular weight (MW) of 45,000-60,000. The active fractions were free of IL-1 (less than 0.2 U/ml) and Superose-12 FPLC chromatography separated the peak of PRA, which eluted at 45,000 MW, from TNF alpha, eluting at 20,000 MW. The peak PRA was not neutralized by antisera to IL-1 alpha, IL-1 beta, TNF alpha, IL-6 or GM-CSF, indicating that it was distinct from these cytokines. The major PRA did not induce the migration of PMNL in vitro in a filter chemotaxis assay. In contrast to the M phi, the major PRA produced by LPS-stimulated monocytes eluted at 15,000-20,000 MW, contained IL-1 activity and was neutralized by antisera to IL-1 alpha and IL-1 beta. Monocytes from a few donors also produced the 45,000-60,000 MW PRA simultaneously. We conclude that human peritoneal M phi and in vitro monocyte-derived M phi exposed to LPS secrete a protein of 45,000-60,000 MW, which is a potent inducer of PMNL infiltration but is distinct from IL-1, TNF alpha, IL-6, GM-CSF and PMNL chemotactic factors.

Interleukin 1 and tumour necrosis factor increase phosphorylation of the small heat shock protein. Effects in fibroblasts, Hep G2 and U937 cells

Interleukin 1 alpha and tumour necrosis factor-alpha stimulated phosphorylation of three 27 kDa phosphoproteins in MRC-5 fibroblasts which was sustained for up to 2 h after adding the cytokines. All three phosphoproteins were immunoprecipitated by a specific antiserum to the small mammalian heat shock protein, hsp 27. The three phosphoproteins from stimulated or control cells contained phosphoserine but not phosphothreonine or phosphotyrosine. Similar increases in phosphorylation of immunoprecipitable 27 kDa proteins were seen in U937 cells stimulated by TNF alpha and Hep G2 cells stimulated by IL1 alpha.

Affinity electrophoresis for studies of mechanisms regulating glycosylation of plasma proteins

A model system for studies of mechanisms governing the alterations of glycosylation of plasma glycoproteins was developed. The system employs two human hepatoma cell lines, Hep 3B and Hep G2, as target cells and agarose affinity electrophoresis with lectins for studies of microheterogeneity of alpha 1-protease inhibitor (PI), a model glycoprotein synthesized by hepatocytes. As an example for the application of the system, the effect of cytokines on major microheterogeneity of plasma proteins is demonstrated. The results indicate that interleukin 6, transforming growth factor beta 1 and, to some extent, tumor necrosis factor alpha are directly involved in regulating the pattern of glycosylation of plasma proteins in vitro, but the major effect is obtained by using combinations of interleukin 6, transforming growth factor beta 1, tumor necrosis factor alpha and interleukin 1. In addition, the results underline the dissociation between alteration of gene expression and the changes in the pattern of plasma protein glycosylation.

Localization of interleukin 6 mRNA in human tonsils by in situ hybridization

We have investigated which areas produce interleukin 6 (IL 6) in human tonsils. This growth factor is required for the terminal differentiation of B lymphocytes into plasmocytes. Using 35S-labeled IL 6 cDNA we demonstrated IL 6 gene expression over various areas of the tonsils, with consistent exception of the follicles, by in situ hybridization. It is, therefore, proposed that B cells are stimulated during their migration out of the follicles.

Options for the treatment of serious infections with interleukin-1

In this paper, the effects of recombinant human interleukin-1 (IL-1) on non-specific resistance to infection are reviewed. In experiments in neutropenic mice, a single injection of a low dose of IL-1 (8-800 ng) appears to protect against death from lethal Pseudomonas aeruginosa and Candida albicans infections. In non-neutropenic mice protection can also be obtained with such dosages of IL-1 in infection caused by Klebsiella pneumoniae or Listeria monocytogenes. Low dosages of IL-1 are also able to prevent lethal cerebral malaria in mice. No effect has been found in murine cytomegalovirus infection. With the exception of C. albicans infection and malaria, protection is only obtained if IL-1 is given before the infection. The mechanism of protection has not been elucidated; in the Pseudomonas and Klebsiella infection, it could be demonstrated that survival was not due to a direct antibacterial effect of IL-1, not due to the action of granulocytes or increased hematopoietic recovery and not due to activation of macrophages and increased bactericidal mechanisms. In the experimental Listeria infection however, animals treated with IL-1 had lower bacterial counts in their organs. Since the cytokines interleukin-6 (IL-6) and tumor necrosis factor (TNF) are much less potent than IL-1 in these protection experiments, it is very unlikely that they are endogenous mediators of the protection induced by IL-1. The effect is not mediated via the cyclooxygenase pathway, since premedication with ibuprofen does not influence the protective effect of IL-1. Taking these data together, it is felt that IL-1 holds promise as a therapeutic agent in humans.

Nuclear factors interacting with an interleukin-6 responsive element of rat alpha 2-macroglobulin gene

During acute inflammation, a group of liver-derived plasma proteins, acute phase proteins (APPs), increase in concentration. Interleukin-6 (IL-6) is responsible for this increase via the induction of APP gene expression. We have identified an IL-6 responsive cis-acting element (IL-6RE) of gene encoding a typical APP, rat alpha 2-macroglobulin (alpha 2M). The IL-6RE contains a sequence that is conserved among the 5'-flanking regions of various APP genes. Introduction of mutations into the conserved sequence revealed that the sequence, termed IL-6RE core, is a critical and essential component of IL6-RE. Nuclear factors binding to the IL-6RE core were identified in livers of normal and inflamed rats. Mobility shift pattern and DNase I footprinting profile indicated that the factors from normal and inflamed stages recognized the same sequence but were distinct from each other. These results suggested that the regulation of alpha 2M gene expression may involve mutually exclusive interaction of stage-specific trans-acting factors.

IL-1 and IL-6 release by tumor-associated macrophages from human ovarian carcinoma

Our study was designed to investigate the production of interleukin-1 (IL-1) and IL-6 in tumor-associated macrophages (TAM) isolated from ascites (18 cases) or solid (7 cases) human ovarian carcinoma. These are pleiotropic monokines which, in addition to affecting proliferation and differentiation of lymphocytes, act on various targets, including vascular cells and liver, and may therefore be involved in the pathogenesis of certain manifestations of malignancy. IL-1 was measured by the thymocyte co-stimulator assay, under conditions in which IL-6 was inactive, and, in 8 cases, by radioimmunoassay (RIA). IL-6 was measured as hybridoma growth factor (HGF) on the 7TD1 cell line. TAM did not release appreciable levels of IL-1 spontaneously and, upon LPS stimulation, were poor producers of this monokine compared to blood monocytes. In contrast, TAM supernatants contained a high level of HGF in the absence of deliberate stimulation, and exposure to LPS either did not affect or further augmented production of this monokine. HGF activity of TAM supernatants was completely blocked by anti-IL-6 antibodies. Ascites fluid from 8 ovarian-carcinoma patients contained high levels of HGF activity, blocked by anti-IL-6 antibodies. Thus, TAM exhibit a dissociation in their capacity to release the functionally related monokines IL-1 and IL-6. IL-6 produced by TAM may account for the elevation of liver-derived acute-phase proteins associated with malignancy.

Regulation of interleukin 6 receptor expression in human monocytes and monocyte-derived macrophages. Comparison with the expression in human hepatocytes

IL-6 is a cytokine with pleiotropic biological functions, including induction of the hepatic acute phase response and differentiation of activated B cells into Ig-secreting plasma cells. We found that human peripheral blood monocytes express the IL-6-R, which is undetectable on the large majority of lymphocytes of healthy individuals. Stimulation of monocytes by endotoxin or IL-1 causes a rapid downregulation of IL-6-R mRNA levels and a concomitant enhancement of IL-6 mRNA expression. IL-6 itself was found to suppress the IL-6-R at high concentrations. A gradual decrease of IL-6-R mRNA levels was observed along in vitro maturation of monocytes into macrophages. We show that downregulation of IL-6-R mRNA levels by IL-1 and IL-6 is monocyte specific, since IL-6-R expression is stimulated by both IL-1 and IL-6 in cultured human primary hepatocytes. Our data indicate that under noninflammatory conditions, monocytes may play a role in binding of trace amounts of circulating IL-6. Repression of monocytic IL-6-R and stimulation of hepatocytic IL-6-R synthesis may represent a shift of the IL-6 tissue targets under inflammatory conditions.

Inflammatory microcrystals stimulate interleukin-6 production and secretion by human monocytes and synoviocytes

Crystal-related joint diseases are often associated with systemic inflammatory manifestations, including increased levels of acute-phase proteins, leukocytosis, and fever. Recently, interleukin-6 (IL-6) has been identified as a pluripotent mediator of inflammatory and immunologic responses and the major hepatocyte-stimulating factor. In this study, we demonstrated that monosodium urate (MSU) and calcium pyrophosphate dihydrate (CPPD) crystals, and to a lesser extent, hydroxyapatite crystals, increased IL-6 production by synoviocytes and monocytes in vitro. Immunoprecipitation experiments showed that MSU and CPPD crystals, but not hydroxyapatite crystals, were able to increase the release of newly synthesized IL-6. Crystal-induced IL-6 stimulated acute-phase protein synthesis, immunoglobulin production, and hybridoma cell proliferation, which was neutralized by a specific antibody to IL-6. High levels of IL-6 were found in synovial fluid from patients with gout and pseudogout. These results demonstrate that MSU and CPPD crystals can induce IL-6 production in synoviocytes and monocytes, and that synovial fluid from patients with gout and pseudogout contains high levels of IL-6. Crystal-induced IL-6 is likely to be an important mediator of inflammatory responses in acute gout and pseudogout.

Interleukin 6 induces a liver-specific nuclear protein that binds to the promoter of acute-phase genes

Interleukin 6 (IL-6) is responsible for a variety of biological effects related to the activation of defenses against infection or inflammation, including the immune response and the acute-phase reaction. Its mechanism of action is unknown. It has recently been shown to induce transcription of several genes encoding acute-phase proteins. Here we describe the identification of an IL-6 responsive element (IL-6RE) present in the promoter of the human hemopexin gene. This element is necessary and sufficient for the IL-6-dependent activation of transcription. The IL-6 effect does not require de novo protein synthesis. A liver-specific nuclear protein (IL-6DBP) binds to the hemopexin IL-6RE as well as to similar sequences on the promoter of other acute-phase genes. IL-6DBP DNA binding activity is induced by IL-6 via a posttranslational mechanism.

Stimulation of fibrinogen synthesis in cultured rat hepatocytes by fibrinogen degradation product fragment D

The direct stimulation of fibrinogen biosynthesis by fibrinogen degradation produces (FDPs) was studied in rat hepatocyte cultures. Pure rat FDP fragment D (FDP-D) (Mr 90,000) and FDP fragment E (FDP-E) (Mr 40,000) and mixtures of the two (FDP-DE) were added to rat hepatocytes cultured in serum-free hormonally defined medium. Hydrocortisone (20 microM) significantly increased synthesis of fibrinogen, as determined by incorporation of [35S]methionine. FDP-D and FDP-E did not increase fibrinogen synthesis in the presence of hydrocortisone. However, hepatocytes cultured without hydrocortisone displayed increased fibrinogen synthesis (2.0- to 2.8-fold) with FDP-D (2.6-6.7 microM) but not with FDP-E (5.7 microM). At these FDP concentrations the synthesis of albumin, haptoglobin, and transferrin was not increased. FDP-D-induced fibrinogen synthesis was inhibited (greater than 90%) by actinomycin D and cycloheximide, indicating that the increase in [35S]methionine incorporation was from de novo protein synthesis. The role of FDP-D was further substantiated by showing that FDP-D, but not FDP-E, bound to the hepatocytes. These data indicate that FDP-D, but not FDP-E, directly and specifically stimulates fibrinogen synthesis in rat hepatocytes; this stimulation does not require any additional serum or protein cofactors.

Interleukin-6 induced at mucosal surfaces by gram-negative bacterial infection

Interleukin-6 (IL-6) was produced in response to mucosal and systemic infection of mice with gram-negative bacteria. The IL-6 response was controlled by the lipopolysaccharide gene, Lps; in C3H/HeN mice (Lpsn/Lpsn), the urinary IL-6 levels increased within 30 min after challenge with Escherichia coli, but no response occurred in C3H/HeJ mice (Lpsd/Lpsd). In lipopolysaccharide-responder mice, the levels of local and systemic IL-6 were related to the degree of infection. The urinary response dominated after intravesical challenge, and the serum response dominated after intraperitoneal challenge. The results demonstrate that IL-6 is activated as part of lipopolysaccharide-induced mucosal and systemic responses to gram-negative bacterial infections.

Interleukin 6 decreases cell-cell association and increases motility of ductal breast carcinoma cells

Treatment of transformed breast duct epithelial cells with IL-6 produces a unique cellular phenotype characterized by diminished proliferation and increased motility. Human ductal carcinoma cells (T-47D and ZR-75-1 lines) are typically epithelioid in shape and form compact colonies in culture. Time-lapse cinemicrography shows that some untreated cells can transiently become fusiform or stellate in shape and separate from each other within a colony, but they usually rejoin their neighbors. While IL-6 suppresses the proliferation of these carcinoma cells, the IL-6-treated cells generally become stellate or fusiform and show increased motility. These changes persist as long as the cells are exposed to IL-6. This results in the dispersal of cells within colonies. The effects on cell growth, shape, and motility are reversible upon removal of IL-6. IL-6-treated T-47D cells display diminished adherens-type cell junctions, as indicated by markedly decreased vinculin-containing adhesions and intercellular desmosomal attachments. The effects on ZR-75-1 cell shape, colony number, and DNA synthesis are dependent on IL-6 concentration in the range from 0.15 to 15 ng/ml. Higher concentrations are required in T-47D cells for equivalent effects. Anti-IL-6 immune serum blocks IL-6 action. IL-6 represents a well-characterized molecule that regulates both the proliferation and junction-forming ability of breast ductal carcinoma cells.

Stimulation of rat hepatocyte fibronectin production by monocyte-conditioned medium is due to interleukin 6

In this report, conditioned media from LPS-stimulated monocytes increased rat hepatocyte production of fibronectin (Fn) in a dose-dependent manner. Preincubation of the conditioned media with anti-IL-6, but not with anti-IL-1 alpha, anti-IL-1 beta, or anti-TNF, completely neutralized the Fn-stimulating activity. 10-100 pg/ml of rIL-6 was sufficient to increase Fn production. Neither IL-1 nor TNF had an effect on Fn production. The Fn-stimulating activity of IL-6 could be specifically neutralized only with anti-IL-6, but not with anti-IL-1 or anti-TNF. The increased Fn produced was shown to be of the plasma rather than the cellular form. These results demonstrate that IL-6 is the factor in monocyte-conditioned media that stimulates Fn production, and that IL-6 is the monokine tested with such activity.

Stimulation of the acute-phase response in simian virus 40-hepatocyte cell lines

Seven simian virus 40 (SV40)-hepatocyte cell lines were characterized with respect to the ability to express eight liver acute-phase genes. cDNA clones corresponding to albumin, serum amyloid A, alpha 1-acid glycoprotein, haptoglobin, alpha-, beta-, and gamma-fibrinogen, and alpha 1-major-acute-phase protein mRNAs were used in Northern (RNA) or slot blot analyses. In the noninduced state, six of the seven cell lines showed significant (i.e., liverlike) levels of constitutive expression of all genes examined except that expression of haptoglobin mRNA was considerable lower than in the normal liver. To examine whether these immortalized liver cells can respond appropriately to inflammatory mediators, cells were treated with conditioned medium from activated human monocytes or mixed lymphocyte cultures. Results showed that these SV40-hepatocyte cell lines responded to the conditioned media in culture by down-regulating albumin gene expression and up-regulating other acute-phase genes in a time- and dose-dependent manner. These results indicate that the SV40-hepatocytes retained not only the ability to express a number of acute-phase genes but also the ability to respond to external stimuli. The usefulness of these cell lines for analysis of the molecular mechanisms involved in the regulation of these acute-phase genes is discussed.

Acute phase response to recombinant interleukin-6 and macrophage- and fibroblast-derived crude cytokine preparations in primary cultures of mouse hepatocytes

A number of acute phase proteins were determined by electroimmunoassay in media from CBA mouse hepatocytes cultured for 2 days with human recombinant IFN beta 2/IL-6, as well as with conditioned media from LPS-stimulated rat macrophages, and of murine L fibroblasts. It was found that human recombinant IL-6 caused three-fold increase in secretion of fibrinogen, while haptoglobin, complement C3 and transferrin were increased respectively, to 168 per cent, 151 per cent, and 145 per cent of the control. DEX(10(-7) M) in DMEM supplemented with 5 per cent FCS, enhanced the IL-6 effect on the three positive acute phase proteins. IL-6 elevated haptoglobin mRNA in mouse hepatocytes to a degree comparable with the concentration of the protein in the culture medium. The effect of conditioned media from murine fibroblasts and peritoneal rat macrophages was generally similar to that of recombinant IL-6. However, both natural preparations of the cytokines caused decrease in albumin and alpha-1-proteinase inhibitor secretion.

IgG1 plasmacytosis in interleukin 6 transgenic mice

Interleukin 6 (IL-6) has been suggested to be involved in the pathogenesis of polyclonal and monoclonal plasma cell abnormalities. To address this possibility, transgenic mice carrying the human IL-6 genomic gene fused with a human immunoglobulin heavy chain enhancer were generated. High concentrations of human IL-6 and polyclonal increase in IgG1 (120- to 400-fold) in sera of all transgenic mice were observed. A massive plasmacytosis in thymus, lymph node, and spleen and an infiltration of plasma cells in lung, liver, and kidney were observed. However, the plasma cells were not transplantable to syngeneic mice and were found not to contain chromosomal aberrations including c-myc gene rearrangements. The evidence indicates that deregulated gene expression of IL-6 can trigger polyclonal plasmacytosis but cannot induce plasmacytoma. It is suggested that additional genetic changes may be required for the generation of plasma cell neoplasia. Other interesting findings in these transgenic mice were the development of mesangio-proliferative glomerulonephritis and an increase in megakaryocytes in bone marrow.

Human lung fibroblast-derived granulocyte-macrophage colony stimulating factor (GM-CSF) mediates eosinophil survival in vitro

Tissue eosinophilia has been reported to occur in pulmonary fibrosis, a disease characterized by chronic inflammation and lung fibroblast proliferation. We have examined the in vitro interaction of these two cell types by determining the in vitro survival of human peripheral blood eosinophils co-cultured with human lung fibroblasts. Survival of eosinophils cultured alone was 10% at day 3 and less than 1% at day 7. In contrast, survival of eosinophils that had been co-cultured with fibroblasts was 98, 90, 73, and 69% at days 3, 7, 10, and 14, respectively. Fibroblast-conditioned medium (CM) elicited a similar result in a dose-dependent fashion. Survival of eosinophils cultured with CM which had been preincubated with a monoclonal-neutralizing antibody to human GM-CSF was inhibited in a dose-dependent manner. Human recombinant-derived GM-CSF supported eosinophil survival in the dose-dependent fashion. Survival at day 7 of eosinophils treated with one single dose of GM-CSF (10 U/ml) was 64%. The effect of fibroblast-CM on eosinophils likely represents true survival since eosinophil proliferation as determined by [3H]thymidine incorporation did not occur. We also report that freshly isolated eosinophils had normal ultrastructural, scanning and transmission electron microscopy characteristics, and were normodense. In contrast, eosinophils co-cultured for 7 days with fibroblasts acquired irregular shapes and became hypodense and partially degranulated. Thus, our results indicate that human lung fibroblast-derived GM-CSF mediates the in vitro survival of human eosinophils.(ABSTRACT TRUNCATED AT 250 WORDS)

Clinical and nutritional aspects of changes in acute-phase proteins during inflammation

1. When assessing the significance of altered plasma protein concentrations the various physiological factors, including posture and hormones which affect the amount and distribution of fluid in the body and the synthesis and catabolism of plasma proteins, must be kept in mind. 2. Although several cytokines, including IL-1 and TNF, are implicated in the acute-phase response, recent evidence is that the synthesis of the major acute-phase proteins (e.g. CRP) is induced by IL-6. 3. The positive acute-phase plasma proteins are useful non-specific indicators of tissue damage. 4. When there is evidence of an acute-phase response (e.g. increased CRP), decreased concentrations of plasma proteins such as albumin, transferrin, retinol-binding protein and pre-albumin cannot be assumed to reflect malnutrition. 5. Plasma albumin concentration can be a good indicator of prognosis.

Identification of cis-acting sequences responsible for phorbol ester induction of human serum amyloid A gene expression via a nuclear factor kappaB-like transcription factor

We have analyzed the 5'-flanking region of one of the genes coding for the human acute-phase protein, serum amyloid A (SAA). We found that SAA mRNA could be increased fivefold in transfected cells by treatment with phorbol 12-myristate 13-acetate (PMA). To analyze this observation further, we placed a 265-base-pair 5' SAA fragment upstream of the reporter chloramphenicol acetyltransferase (CAT) gene and transfected this construct into HeLa cells. PMA treatment of these transient transfectants resulted in increased CAT expression. Nuclear proteins from PMA-treated HeLa cells bound to this DNA fragment, and methylation interference analysis showed that the binding was specific to the sequence GGGACTTTCC (between -82 and -91), a sequence previously described by R. Sen and D. Baltimore (Cell 46:705-716, 1986) as the binding site for the nuclear factor NF kappa B. In a cotransfection competition experiment, we could abolish PMA-induced CAT activity by using cloned human immunodeficiency virus long-terminal-repeat DNA containing the NF kappa B-binding sequence. The same long-terminal-repeat DNA containing mutant NF kappa B-binding sequences (G. Nabel and D. Baltimore, Nature [London] 326:711-713, 1987) did not affect CAT expression, which suggested that binding by an NF kappa B-like factor is required for increased SAA transcription.

Urinary excretion of the hydroxypyridinium cross links of collagen in patients with rheumatoid arthritis

Values for urinary hydroxypyridinium cross links of collagen measured by high performance liquid chromatography in a group of 19 seropositive patients with rheumatoid arthritis (RA) were compared with 19 controls matched for age and sex. The amounts of pyridinoline, expressed relative to creatinine, were significantly higher in the RA group, but there was no significant increase in a bone specific analogue, deoxypyridinoline. There were significant positive correlations between pyridinoline excretion and both C reactive protein and erythrocyte sedimentation rate, whereas there was an inverse relation with grip strength. The data indicated that pyridinoline concentrations in urine are strongly associated with disease activity in patients with RA.

Serum amyloid A in the mouse. Sites of uptake and mRNA expression

Murine serum amyloid A1 (SAA1) and serum amyloid A2 (SAA2) are circulating, acute phase, high density apolipoproteins of unknown function. To pursue issues relating to their possible function their uptake and formation were studied. Kinetics of SAA protein distribution and gene expression after acute phase stimulation by casein or lipopolysaccharide were examined using immunocytochemistry for protein and RNA blot and in situ hybridization with probes for SAA1 and SAA2 mRNA. After casein injection, interstitial cells of testes, cells of adrenal cortex, kidney proximal convoluted tubule epithelia, and some parafollicular cells of spleen took up SAA in a time pattern related to plasma SAA levels. Extrahepatic SAA1 and SAA2 mRNA were induced by lipopolysaccharide in kidney proximal and distal convoluted tubule epithelia, and SAA1 mRNA was induced in epithelial lining the mucosa of the ileum and large intestine, indicating that there may be more than one function for the apoSAA gene family related to site of and stimulus for expression.

Elevated tumor necrosis factor alpha and interleukin-6 serum levels as markers for complicated Plasmodium falciparum malaria

PURPOSE

Tumor necrosis factor alpha (TNF-alpha) has been implicated in the pathology of experimental malaria. To establish its relevance to human malaria, we studied serum levels of two monocyte-derived cytokines, TNF-alpha and interleukin-6 (IL-6), as well as of the lymphocyte-derived mediator interferon gamma (IFN-gamma) in patients with malaria before and during antiparasitic treatment.

PATIENTS AND METHODS

One hundred twenty serum samples of 40 patients with malaria (Plasmodium falciparum [n = 32], Plasmodium vivax [n = 8]) were analyzed. IL-6 was measured by a highly sensitive and specific bioassay, TNF-alpha by immunoradiometric assay, and IFN-gamma by radioimmunoassay.

RESULTS

Elevated cytokine levels could be detected in the majority of patients with P. falciparum malaria before treatment (31 of 32, 21 of 32, and 21 of 32 for TNF-alpha, IL-6, and IFN-gamma, respectively), but only in some patients with P. vivax malaria (four of eight, one of eight, and zero of eight for TNF-alpha, IL-6, and IFN-gamma, respectively). Serum concentrations of the monokines TNF-alpha and IL-6 correlated significantly with parasitic density (p less than 0.001). No such correlation was obtained with the circulating IFN-gamma concentration. The levels of monokines TNF-alpha and IL-6 were markedly elevated in 18 P. falciparum-infected patients with complicated clinical courses (median values for TNF-alpha 172 pg/mL, for IL-6 16 U/mL, peak values: 896 pg/mL and 1,000 U/mL, respectively). The correlation between TNF-alpha and IL-6 concentrations in serum (n = 40, r = 0.56, p = 0.0002) suggests co-ordinate production of those mediators.

CONCLUSION

Organ impairment in human malaria was found to be correlated with the amount of circulating cytokine levels of TNF-alpha and IL-6. Thus, imbalances of the cytokine network in untreated P. falciparum infection serve as markers of severity of disease. Modulation of cytokine response could represent a novel approach to the treatment of severe organ dysfunctions in human malaria.

Regulation of hepatic synthesis of C3 and C4 during the acute-phase response in the rat

Following the i.p. injection of casein, rats showed increased serum levels of C4 and C3. C4 levels peaked on day 2 and returned to normal by day 4, while C3 levels peaked on day 3 before returning to normal on day 4. These changes were paralleled by changes in the hepatocyte synthesis rates of these two proteins. Macrophages, isolated from the peritoneal cavities of rats on days 1 to 7 (day-1 to day-7 macrophages) following i.p. injection of casein, were cultured in vitro, and the peritoneal macrophage-conditioned media (PMCM) assayed for their abilities to stimulate synthesis of C4 and C3 by hepatocytes from control rats. Day-2 PMCM selectively stimulated synthesis of C4, while day-3 and day-4 PMCM selectively stimulated C3 synthesis. These activities were called C4-hepatocyte stimulating factor (C4-HSF) and C3-HSF, respectively. The addition of anti-interleukin (IL) 1, tumor necrosis factor (TNF)-alpha, TNF-beta, IL 6 or interferon (IFN)-gamma antibodies to day-2 PMCM did not affect C4-HSF activity, and none had any effect on C3-HSF activity in day-4 PMCM. However, the addition of anti-IL 1 to day-4 PMCM resulted in the re-expression of C4-HSF activity as well as loss of thymocyte proliferative activity. C4-HSF activity could also be detected in day-4 PMCM by separating it from IL 1 activity using gel filtration chromatography. Furthermore the addition of recombinant IL 1 beta to day-2 PMCM prevented the expression of C4-HSF activity. Thus IL 1 appears to play a regulatory role in the acute-phase response in the rat, by preventing the expression of C4-HSF activity. The identities of C4-HSF activity and C3-HSF are still unknown but we believe that C3-HSF activity could be IL 6 as it has a similar molecular weight (30 kDa) and purified human IL 6 was more effective than IL 1, TNF-alpha or TNF-beta in stimulating C3 synthesis by rat hepatocytes. C4-HSF activity appears to be a property of a previously undescribed cytokine. It is not IL 1 alpha or beta, TNF-alpha or -beta, IL 6 or IFN-gamma.

Fate and biological action of human recombinant interleukin 1 beta in the rat in vivo

The plasma half life of recombinant human interleukin 1 beta (rhIL 1 beta) was determined in rats by measuring the disappearance of the radioactivity of 125I-labeled rhIL 1 beta from the circulation. The plasma clearance showed a biphasic behavior: an initial fast disappearance (half life of about 3 min) was followed by a second slower one (half life of about 4 h). Twenty minutes after a single-dose injection of 125I-labeled rhIL 1 beta most of the radioactivity was concentrated in kidneys, liver and intestine. rhIL 1 beta induced the synthesis of alpha 1-acid glycoprotein (AGP), alpha 1-cysteine proteinase inhibitor (CPI) and beta-fibrinogen mRNA in liver. Half maximal stimulation was elicited by approximately 3000 U of rhIL 1 beta per animal. The mRNA changes for AGP and CPI were followed by corresponding protein increases in serum. Twenty hours after rhIL 1 beta injection, serum AGP rose from 0.7 to 2.5 mg/ml. CPI increased from 0.3 to 1.9 mg/ml 25 h after administration of rhIL 1 beta. Within 20 h after rhIL 1 beta injection, albumin serum concentration showed a strong decrease, preceded by a reduction in hepatic albumin mRNA levels. Neither changes in albumin synthesis nor degradation can explain this decrease suggesting that other mechanisms such as increased transvascular permeability are involved.

Human interleukin 6 is a direct promoter of maturation of megakaryocytes in vitro

The response of cells of the murine megakaryocytic lineage to human interleukin 6 (IL-6) was assessed in serum-depleted cultures using a variety of biological assays. IL-6 alone had no influence on megakaryocytic colony formation but augmented the numbers of these colonies induced by the multipotent colony-stimulating factor interleukin 3. However, in liquid marrow cultures, IL-6 alone promoted marked increments in megakaryocytic size and the activity of acetyl-cholinesterase, a marker enzyme of the lineage. Moreover, IL-6 induced a significant shift toward higher ploidy classes when megakaryocytic DNA was quantitated by flow cytometry. To determine whether the influence of IL-6 on megakaryocytic maturation was direct, the factor was added to cultures of single megakaryocytes isolated from megakaryocytic colonies. Fifty-four percent of these cells increased in size compared with 19% of those grown without IL-6. The data show that human IL-6 is a potent direct-acting growth factor for murine megakaryocytes with activity promoting maturation of that lineage.

Participation of the cytokines interleukin 6, tumor necrosis factor-alpha, and interleukin 1-beta secreted by acute myelogenous leukemia blasts in autocrine and paracrine leukemia growth control

Autonomous in vitro growth of myeloid leukemic colony-forming cells may in part result from autocrine production of colony-stimulating factors (CSF). Some acute myeloid leukemia (AML) samples, however, fail to synthesize CSF despite growing autonomously in agar, and are therefore believed to bypass CSF requirements. Cytokines such as IL-6, tumor necrosis factor (TNF)-alpha, and IL-1, products of cells of the myeloid lineage, are known to be involved in growth control of myeloid progenitor cells. Since these molecules may also contribute to autocrine and paracrine growth regulation of myeloid leukemias, we screened a series of AML for cytokine production. In addition, possible roles of IL-6, TNF-alpha, and IL-1 in growth control of AML were investigated in vitro. We show that a substantial proportion of AML cells produce IL-6, TNF-alpha, and IL-1-beta and use these mediators to stimulate their growth by disparate mechanisms: IL-6 acts as a costimulator to enhance CSF-induced clonogenicity of AML blasts. TNF-alpha induces CSF production by endothelial cells and may therefore provide a paracrine loop to support leukemia growth.

High interleukin-6 serum levels and increased production by leucocytes in alcoholic liver cirrhosis. Correlation with IgA serum levels and lymphokines production

Hypergammaglobulinaemia and enhanced serum IgA levels are common in alcoholic liver cirrhosis. Interleukin-6 (IL-6), which is identical to B cell differentiation factor BSF2 and is implicated in various autoimmune diseases, has been studied in patients with alcoholic liver cirrhosis. Increased serum levels and spontaneous or induced production of IL-6 by peripheral blood monoclonal cells have been found. IL-6 production correlates closely with IgA serum levels and negatively with impaired interleukin-2 and interferon gamma production. This abnormality could be related to overproduction of immunoglobulins and immune disturbances observed in this disease.

Effects of monocytic products, recombinant interleukin-1, and recombinant interleukin-6 on glycosylation of alpha 1-acid glycoprotein: studies with primary human hepatocyte cultures and rats

Changes in the carbohydrate moieties of acute-phase glycoproteins (APGPs) often accompany the increase in their secretion by the liver during inflammation. In this study, we investigated whether factors known to regulate APGP gene expression are also involved in the altered glycosylation. For this purpose, the glycosylation pattern of alpha 1-acid glycoprotein (AGP) as secreted by human hepatocytes, cultured in the presence and absence of dexamethasone and monokines, was studied by crossed affino- (concanavalin A) immunoelectrophoresis (CAIE). The monokines rIL-1 and rIL-6, in the presence of dexamethasone, both stimulated AGP secretion and caused a change in glycosylation towards an increased Con A reactivity, including the appearance of two strongly reactive forms (D and E) normally not present. Dexamethasone alone did not influence either process. When tested in vivo in rats, rIL-6 also induced an increased presence of Con A-reactive forms of AGP in serum. In conclusion, the changes in secretion and glycosylation of AGP as seen during inflammation seem to be mediated by the same factor(s).

Interleukin-6 and its receptor during homeostasis, inflammation, and tumor growth

This review focuses on describing the specific role of interleukin-6 within the network of inflammatory mediators in man. Sites of interleukin-6 synthesis, regulation of its expression, and the biological functions of this molecule are here outlined. The potential role of interleukin-6 as a diagnostic monitor is discussed. Particular attention is paid to experimental evidence that interleukin-6 and its receptor may be involved in the pathogenesis of autocrine tumor growth. A recently proposed therapeutical use of cytotoxic interleukin-6 fusion proteins in order to selectively, destroy certain interleukin-6 receptor bearing tumor cells is discussed in the light of the finding, that not only hepatocytes, but also normal peripheral blood monocytes express the interleukin-6 receptor.

Interleukin-6 (IL-6) functions as an in vitro autocrine growth factor in renal cell carcinomas

Interleukin-6 (IL-6) was found to be a growth factor of renal cell carcinomas Furthermore, renal cell carcinomas freshly isolated from the patients expressed mRNA of IL-6 and secreted biologically active IL-6 under the culture conditions where the tumor cells could grow, but they did not produce IL-6 nor proliferate in the absence of fetal calf serum. The production of IL-6 by the tumor cells was also demonstrated by immunostaining of the IL-6-producing cells utilizing anti-IL-6 antiserum. Moreover, anti-IL-6 antiserum specifically inhibited the in vitro tumor growth. All data indicated that IL-6 functions as an in vitro autocrine growth factor of renal cell carcinomas.

Inhibition of endotoxin-induced activation of human monocytes by human lipoproteins

Toxicity of lipopolysaccharide (LPS) (endotoxin) is, to a large extent, mediated by the activation of monocytes/macrophages and subsequent release of monokines, such as interleukin-1 (IL-1) and tumor necrosis factor alpha (TNF-alpha). It is known that LPS binds readily to serum lipoproteins and that LPS-lipoprotein complexes are less toxic than unbound LPS. Here we present data analyzing the impact of the LPS-serum interaction at the cellular level. By measuring IL-1 TNF-alpha, and IL-6, the interaction of different LPSs or lipid A with human serum could be shown to prevent the activation of human monocytes. The amounts of LPS inactivated by normal human serum did not exceed 10 ng/ml. The LPS-inactivating capacity of serum was shown to be a function of the lipoproteins. Other serum components, such as naturally occurring anti-LPS immunoglobulin G, complement, or nutritive lipids, had no significant influence in our system. Our experiments suggest that serum lipoproteins control endotoxin-induced monocyte activation and monokine release.

Mouse bone marrow-derived IL-3-dependent mast cells and autonomous sublines produce IL-6

This study deals with the question of whether mouse bone marrow-derived mast cells are able to produce interleukin-6 (IL-6) in vitro. For this purpose, a panel of primary mast cell clones from limiting-dilution microcultures, of permanent IL-3-dependent mast cell lines and autonomous malignant sublines, was screened. All of these lines were found to produce growth factor activity for IL-6-dependent mouse hybridoma cells (7TD1), which could be completely neutralized by the monoclonal anti-IL-6-antibody 6B4. Transcriptional activity of the IL-6 gene was demonstrated in both IL-3-dependent mast cells and autonomous sublines using a mouse IL-6-specific cDNA probe.

Signal delivery by physical interaction and soluble factors from accessory cells in the induction of receptor-mediated T-cell proliferation. Synergistic effect of BSF-2/IL-6 and IL-1

Our recent study revealed that soluble factors derived from accessory cells (AC; monocytes) and physical interaction with T cells of the accessory cells are both required for the induction of the proliferation of human peripheral blood T cells by anti-CD3 antibody coupled on latex beads. The accessory cell-derived soluble factor could be replaced by IL-1 and IL-6, and the role of live macrophages for physical interaction with T cells was found to be replaceable with paraformaldehyde(PFA)-fixed macrophages, provided the macrophages were pretreated with interferon-gamma (IFN-gamma) before fixation. Quantitative analysis in the present study revealed that IL-1 and IL-6 act synergistically to induce T-cell proliferation in the above system but either one of the factors alone reveals only a marginal or weak activity. Furthermore, it was shown that the potentiating activity of the culture supernatants of monocytes was substantially inhibited by anti-IL-6 antibody. Taken together with our previous results that anti-IL-1 serum strongly inhibited the potentiating activity of the culture supernatant, these results indicate that the main responsible molecules in the culture supernatant are IL-1 and IL-6, although a presence of other effective factors is not excluded. The anti-CD3-induced thymidine uptake by T cells in the presence of IL-1 and IL-6 was significantly inhibited by anti-Tac antibody, suggesting that the proliferation of T cells in this system is mostly mediated by a IL-2-dependent pathway. Our study further showed that accessory cells seem to acquire cell surface properties necessary for the effective interaction with T cells during 6-24 hr of culture with IFN-gamma. Presumably, a certain molecule(s) required for the interaction is induced on the cell surface of the AC by IFN-gamma.

Interferon beta 2/interleukin 6 modulates synthesis of alpha 1-antitrypsin in human mononuclear phagocytes and in human hepatoma cells

The cytokine IFN beta 2/IL-6 has recently been shown to regulate the expression of genes encoding hepatic acute phase plasma proteins. INF beta 2/IL-6 has also been shown to be identical to MGI-2, a protein that induces differentiation of bone marrow precursor cells toward mature granulocytes and monocytes. Accordingly, we have examined the effect of IFN beta 2/IL-6 on expression of the IL-1- and tumor necrosis factor-unresponsive acute phase protein alpha 1-antitrypsin (alpha 1 AT) in human hepatoma-derived hepatocytes and in human mononuclear phagocytes. Purified human fibroblast and recombinant IFN beta 2/IL-6 each mediate a specific increase in steady-state levels of alpha 1 AT mRNA and a corresponding increase in net synthesis of alpha 1 AT in primary cultures of human peripheral blood monocytes as well as in HepG2 and Hep3B cells. Thus, the effect of IFN beta 2/IL-6 on alpha 1 AT gene expression in these cells is primarily due to an increase in accumulation of alpha 1 AT mRNA and can be distinguished from the direct, predominantly translational effect of bacterial lipopolysaccharide on expression of this gene in monocytes and macrophages. The results indicate that IFN beta 2/IL-6 regulates acute phase gene expression, specifically alpha 1 AT gene expression, in extrahepatic as well as hepatic cell types.

Stimulation of the acute-phase response in simian virus 40-hepatocyte cell lines

Seven simian virus 40 (SV40)-hepatocyte cell lines were characterized with respect to the ability to express eight liver acute-phase genes. cDNA clones corresponding to albumin, serum amyloid A, alpha 1-acid glycoprotein, haptoglobin, alpha-, beta-, and gamma-fibrinogen, and alpha 1-major-acute-phase protein mRNAs were used in Northern (RNA) or slot blot analyses. In the noninduced state, six of the seven cell lines showed significant (i.e., liverlike) levels of constitutive expression of all genes examined except that expression of haptoglobin mRNA was considerable lower than in the normal liver. To examine whether these immortalized liver cells can respond appropriately to inflammatory mediators, cells were treated with conditioned medium from activated human monocytes or mixed lymphocyte cultures. Results showed that these SV40-hepatocyte cell lines responded to the conditioned media in culture by down-regulating albumin gene expression and up-regulating other acute-phase genes in a time- and dose-dependent manner. These results indicate that the SV40-hepatocytes retained not only the ability to express a number of acute-phase genes but also the ability to respond to external stimuli. The usefulness of these cell lines for analysis of the molecular mechanisms involved in the regulation of these acute-phase genes is discussed.

Host defense against infections and inflammations: role of the multifunctional IL-6/IFN-beta 2 cytokine

IL-6/IFN-beta 2 appears to be one of the important mediators of the response to viral and bacterial infections and to shock. The biological effects now associated with IL-6/IFN-beta 2 include: stimulation of immunoglobulin secretion by mature B lymphocytes (BSF-2 activity), growth stimulation of plasmacytomas and hybridomas (HGF activity), activation of T cells, stimulation of hepatic acute phase protein synthesis (HSF activity), stimulation of hematopoiesis, cell differentiation (DIF activity), inhibition of tumor cell growth (AP activity) and other IFN-like effects. As a typical cytokine, IL-6/IFN-beta 2 is secreted by many cell types and acts in various combinations with other interleukins and interferons.