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

Predictive value of interleukin-5 and monocyte chemotactic protein-1 for bacteremia in children with febrile neutropenia

A variety of clinical and laboratory parameters have been used to predict bacteremia. We hypothesize that the generation of a cytokine profile could be used to identify patients at higher risk of bacteremia at the time of presentation with febrile neutropenia. We prospectively evaluated children with cancer who presented with an episode of febrile neutropenia. A multiplexed flow cytometric assay was performed which measured 15 cytokines and chemokines obtained before the initiation of antibiotics. Fifty-eight episodes of chemotherapy-induced febrile neutropenia were included in this study during which 4 patients (7%) had bacteremia. An interleukin-5 level of >8 pg/dL had a sensitivity of 67% and a specificity of 96% to predict bacteremia. An monocyte chemotactic protein-1 level >1650 pg/dL had a sensitivity of 80% and a specificity of 82% to predict bacteremia. Erythrocyte sedimentation rate, C-reactive protein, protein C, and other cytokines/chemokines were not predictive of bacteremia. Elevations of interleukin-5 and monocyte chemotactic protein-1 are predictive of bacteremia in children with cancer who have febrile neutropenia. Prospective studies should be undertaken to determine whether these parameters retain predictive value in a larger series of patients and can select children for outpatient management or early discharge.

Procalcitonin in paediatric cancer patients: its diagnostic relevance is superior to that of C-reactive protein, interleukin 6, interleukin 8, soluble interleukin 2 receptor and soluble tumour necrosis factor receptor II

Sensitive parameters of inflammation are rare in neutropenic cancer patients. In this study, procalcitonin (PCT), C-reactive protein (CRP), interleukin 6 (IL-6), IL-8, the soluble IL-2 receptor (sIL-2R) and the soluble tumour necrosis factor receptor II (sTNFRII) were evaluated for their diagnostic relevance in febrile episodes of cancer patients. Plasma or serum levels of these parameters were determined in neutropenic children with febrile episodes (n = 122) classified according to both the kind of infection [60 cases of fever of unknown origin (FUO), 28 cases of localized infection, 13 cases of pneumonia, 20 cases of bacteraemia, one case of fungaemia] and the World Health Organization (WHO) score of chemotherapy-induced mucositis. At baseline and during the febrile episodes, the highest levels of all parameters were observed in cases of gram-negative bacteraemia. However, in FUO and localized infections, low or only slightly elevated median levels of all parameters were documented. The degree of chemotherapy-induced mucositis did not influence the value of any parameter. In comparison with the other inflammatory parameters, PCT (optimum cut-off level 0.5 microg/l) was a more sensitive and more specific parameter in the diagnosis of high-risk (gram-negative bacteraemia) and low-risk (FUO) episodes, as well as in the sequential assessment of all febrile neutropenic episodes.

Interleukin-6-deficient mice refractory to IgA dysregulation but not anorexia induction by vomitoxin (deoxynivalenol) ingestion

Dietary exposure to the trichothecene vomitoxin (VT) causes feed refusal and elevates IgA production in the mouse. Based on the observations that IL-6 can cause anorexia and promote IgA production and that gene expression of this cytokine is increased in vivo and ex vivo on VT exposure, we hypothesized that IL-6 is an essential cytokine in VT-induced feed refusal and IgA dysregulation. To test this hypothesis, the effects of dietary VT on feed intake, weight gain, serum IgA levels and kidney mesangial IgA deposition in an IL-6-"knockout" mouse (B6129-IL6(tmi Kopf)) were compared to those in both a corresponding "wildtype" (B6129F2) and a previously characterized "sentinel" strain (B6C3F1) that possess the intact gene for this cytokine. IL-6 deficiency did not alter the capacity of VT to cause feed refusal or impair weight gain. VT-fed B6129F2 and B6C3F1 mice had significantly higher serum IgA concentrations than did their corresponding controls fed clean diet, whereas significant differences were not observed between IL-6 KO mice fed VT or control diets. Kidneys taken from VT-fed wild-type and sentinel mice had significantly increased mesangial IgA deposition as compared to controls. While slight increases in mesangial IgA were observed in VT-fed IL-6 KO mice, mean fluorescence intensities were significantly less than that found in the corresponding wild-type and sentinel strains. IL-6 KO mice appeared to be less prone to the development of microscopic haematuria following VT exposure than were the corresponding wild-type and sentinel strains. In total, the results suggested that IL-6-deficient mice were refractory to VT-induced dysregulation of IgA production and development of IgA nephropathy, whereas chronic VT-mediated nutritional effects related to feed intake and weight gain were unaffected.

Proinflammatory cytokines and treatment of disease

Bacterial infections in the immunocompromised host cause considerable mortality, and even recently developed antimicrobial strategies often fail to cure these infections, especially in granulocytopenic patients. Cytokines and hematopoietic growth factors have been shown to stimulate host defense mechanisms in vitro and in vivo. The possible role of the proinflammatory cytokines interleukin (IL)-1, tumor necrosis factor-alpha, IL-6, and IL-8 as modulators of host resistance to bacterial infections is discussed. Interleukin-1 has been effective in various animal models of potentially lethal bacterial infection, even during severe granulocytopenia. The protective mechanism of IL-1 may be mediated by downregulation of cytokine receptors and cytokine production and induction of acute phase proteins. Moreover, in subacute and chronic infections IL-1 interferes with microbial outgrowth via mechanisms that have only been partly elucidated.

Role of macrophages in elevated IgA and IL-6 production by Peyer's patch cultures following acute oral vomitoxin exposure

Oral vomitoxin (VT) exposure in mice results in elevated cytokine gene expression, increased production of IgA, and IgA nephropathy. To determine the potential role of macrophages (Mphi) in these effects, an ex vivo model was devised whereby Peyer's patch (PP) and spleen cells were prepared from mice 2 h after oral exposure to 0 or 25 mg/kg body wt VT, cultured, and then evaluated for IgA and cytokine IL-6 production. Both PP and, to a lesser extent, spleen cells from treatment mice produced more IgA over a 7-day period than did corresponding control cells when cultured without a costimulus or in the presence of either phorbol myristate acetate plus ionomycin (PMA + ION) or lipopolysaccharide (LPS); IgA elevation was most marked in LPS-treated cultures. The VT effect was completely ablated in PP cultures that were depleted of Mphi but not in Mphi-depleted spleen cultures. VT exposure similarly increased production of IL-6, an important helper factor for IgA secretion, in LPS-stimulated PP and spleen cell cultures. IL-6 production was also ablated by Mphi depletion. A potential costimulatory role for Mphi was further suggested because both IgA and IL-6 production increased when Mphi-depleted PP cells from VT-treated animals were cocultured with peritoneal Mphi from VT-treated animals. Similar effects were observed when an analogous ex vivo approach was used with purified PP B cells and peritoneal Mphi. PP B cells from control animals also secreted elevated levels of IgA when cocultured with splenic CD4(+) cells from VT-treated animals, thus confirming previous studies showing that T cell help also contributes to increased IgA production. Potential roles for soluble mediators and cell contact in this process were suggested when IgA production was measured in cultures of PP cells separated from VT-treated Mphi by a semipermeable membrane. Taken together, these and previous results suggest that Mphi may play a key mechanistic role in elevated IgA production and IgA nephropathy in VT-exposed mice.

Potential role for IL-5 and IL-6 in enhanced IgA secretion by Peyer's patch cells isolated from mice acutely exposed to vomitoxin

Dietary exposure to vomitoxin (VT) results in hyperelevated serum IgA and IgA nephropathy in mice. To assess the possible role of cytokines in this IgA dysregulation, the effects of a single oral exposure in B6C3F1 male mice to 0, 5 or 25 mg/kg BW VT on production of IgA and cytokines in Peyer's patch (PP) and spleen cell cultures were evaluated. IgA levels were increased significantly in PP cell cultures prepared from mice at 2 or 24 h after oral exposure to VT and subsequently stimulated with phorbol myristate acetate (PMA) and ionomycin (ION) or with lipopolysaccharide (LPS). Significant effects on IgA production were not observed in spleen cell cultures. Since cytokines such as IL-2, IL-4, IL-5 and IL-6 have been shown to promote IgA production, the effect of the same VT exposure regimen on secretion of these mediators was determined in PP and spleen cultures. Supernatant IL-2 and IL-4 levels were unaffected by the prior treatment of animals with VT. In contrast, IL-5 levels were increased significantly in 7-day PP cell cultures obtained 2 h after VT exposure both with and without PMA + ION exposure but not in other cultures. IL-6 levels were increased significantly in LPS-treated cultures prepared from PP at 2 and 24 h following exposure to VT. IL-6 levels were also elevated significantly in both PMA + ION or LPS treated cultures from spleen isolated at 2 h but not 24 h post VT exposure. To determine whether IL-5 or IL-6 play a role in IgA hyperelevation in vitro, PP and spleen cells from mice obtained 2 h after exposure to 25 mg/kg VT were cultured in the presence of neutralizing cytokine antibodies (Abs) and IgA production was monitored. Consistent with IL-5's previously documented role in IgA production, anti-IL-5 decreased IgA levels to background in cultures of both control and VT-exposed PP or spleen cells in the presence of either PMA + ION or LPS. Similar results were seen with addition of anti-IL-6. IgA levels were decreased to a lesser extent in PP cells cultured with LPS and in spleen cells cultured with PMA + ION from VT-exposed mice to which anti-IL-2 Ab was added. Thus, the potential for enhanced IgA production exists in lymphocytes as early as 2 h and as late as 24 h after a single oral exposure to VT and this may be related to the increased capacity to secrete helper cytokines of T cell and macrophage origin. Taken together, the results suggest that the superinduction of cytokine expression may, in part, be responsible for upregulation of IgA secretion in mice exposed orally to VT.

Interleukin-6-associated inflammatory processes in Alzheimer's disease: new therapeutic options

The cytokine interleukin-6 is consistently detected in the brains of Alzheimer's disease patients but not in the brains of nondemented elderly persons. Until recently it was unclear whether an interleukin-6-associated inflammatory mechanism is an early or late event in the pathological cascade of Alzheimer's disease. We investigated whether interleukin-6 could be detected in plaques of Alzheimer's disease patients prior to the onset of neuritic degeneration. We found interleukin-6 mostly in plaques where neuritic pathology has not yet developed. This indicates that the appearance of interleukin-6 may precede neuritic changes and is not just a consequence of neuritic degeneration. Therefore, one may hypothesize that activation of inflammatory mechanisms may cause neuritic degeneration in plaques. A suppression of interleukin-6 synthesis could, therefore, be of therapeutic value. Upon screening a number of substances, we found that a small number of nonsteroidal antiinflammatory drugs, including tenidap, were able to inhibit interleukin-6 synthesis in cultured human astrocytoma cells. These substances may be therapeutically useful in Alzheimer's disease and should be evaluated in clinical studies.

Evaluation of interleukin-6 in rheumatoid arthritis as an activity criterion

This study evaluated interleukin-6 levels as an activity criterion in rheumatoid arthritis (RA) and compared if with other activity criteria. We evaluated 35 patients with active RA, 31 with inactive RA, and 25 patients with osteoarthritis, in addition to 28 healthy individuals. Serum interleukin-6 levels were higher in active RA patients than in those with inactive RA, or osteoarthritis and healthy individuals (P < 0.001). Serum interleukin-6 levels of patients with active RA were positively correlated with the erythrocyte sedimentation rate, C-reactive protein, and alpha 2-globulin levels (P < 0.001), but there was a negative correlation with serum albumin levels (P < 0.05). We conclude that interleukin-6 can be responsible for both the most systemic manifestations of RA and for its local manifestations.

Regulation of interleukin-6 expression in porcine immune cells

Interleukin-6 (IL-6) is a pleiotropic cytokine that regulates the immune response, acute-phase reaction, and hematopoiesis. As a first step in studying the actions of IL-6 in pigs, the regulation of IL-6 expression was examined in various swine cells, including a fibroblast cell line, peripheral blood mononuclear cells (PBMC), and alveolar macrophages. IL-6 expression in transformed swine testicular (TST) fibroblasts was enhanced by TNF and IL-1 beta and to a lesser extent by poly(I).(C) and LPS. IL-6 was induced in porcine PBMC by either LPS or PHA; however, the combination of LPS plus PHA resulted in maximal IL-6 expression. Furthermore, in PBMC cells separated by adherence, LPS was a more potent inducer than PHA in adherent cells, whereas PHA was more potent in nonadherent cells. Alveolar macrophages collected from different pigs could be divided into low and high responders with respect to IL-6 induction by LPS. IL-6 mRNA induction by LPS could be detected in only 6 of 20 donor animals. Other inflammatory cytokines (IL-8, IL-beta, and TNF) were readily induced by LPS in alveolar macrophages from both low and high responders. Treatment of low-responder alveolar macrophages with conditioned medium containing IFN-gamma did not significantly alter the capacity of these macrophages to synthesize IL-6 mRNA in response to LPS. Comparison of IL-6 production capacity by the cell types in this study revealed the following order: PBMC = high-responder alveolar macrophages >> TST.cells > low-responder alveolar macrophages. Thus, PBMC appear to be quantitatively the most significant source of IL-6 in swine on a per cell basis.

Inflammatory mechanisms in Alzheimer's disease

In recent years many studies have indicated an involvement of inflammatory mechanisms in Alzheimer's disease (AD). Acute-phase proteins such as alpha 1-antichymotrypsin and c-reactive protein, elements of the complement system, and activated microglial and astroglial cells are consistently found in brains of AD patients. Most importantly, also cytokines such as interleukin-6 (IL-6) have been detected in the cortices of AD patients, indicating a local activation of components of the unspecific inflammatory system. Up to now it has remained unclear whether inflammatory mechanisms represent a primary event or only an unspecific reaction to brain tissue damage. Therefore, we investigated whether IL-6 immunoreactivity could be found in plaques prior to the onset of neuritic changes, or whether the presence of this cytokine is restricted to later stages of plaque pathology. We confirmed our previous observation that IL-6 is detectable in a significant proportion of plaques in the brains of demented patients. In AD patients IL-6 was found in diffuse plaques in a significant higher ratio as would have been expected from a random distribution of IL-6 among all plaque types. This observation suggests that IL-6 may precede neuritic changes, and that immunological mechanism may be involved both in the transformation from diffuse to neuritic plaques in AD and in the development of dementia.

Plasma neopterin/C-reactive protein ratio as an adjunct to the assessment of infection and cancer cachexia

Neopterin (NPT), a pteridine intermediate metabolite in the biopterine synthetic pathway, is synthesized and secreted by monocytes/macrophages upon stimulation, mainly by gamma-interferon produced by activated T cells. C-reactive protein (CRP) is one of the major acute-phase reactants and its release is thought to be mediated by interleukin-6. Plasma concentrations of NPT and CRP were synchronously analyzed in 25 determinations of 5 patients with severe infectious complications and 50 determinations of 10 cancer-burden patients representing cachexia. The mean value of NPT (pmol/ml) was 201.6 in the infection group and 16.5 in the cancer cachexia group. The mean value of CRP (mg/dl) was 12.5 in the infection group and 3.4 in the cancer cachexia group. The number of samples in which NPT alone exceeded the cut-off level were 0/25 (0%) in the infection group and 38/50 (76.0%) in the cancer cachexia group. The number of samples in which both NPT and CRP exceeded the cut-off level was 25/25 (100%) in the infection group and 12/50 (24.0%) in the cancer cachexia group. The mean ratio of NPT to CRP was 11.3 in the infection group and 30.7 in the cancer cachexia group, respectively. These results suggest that gamma-interferon could play the principal role in the pathogenesis of cancer cachexia and that interleukin-6 modified the disease status. Interleukin-6 would be the critical mediator of host responses in infectious complications.

Effects of interleukin-6 (IL-6) and transforming growth factor-beta (TGF-beta) on neutrophil elastase release

The proinflammatory cytokine interleukin-6 (IL-6) and its potential opponent, transforming growth factor-beta (TGF-beta 1), have been discussed as being involved in the regulation of inflammatory processes following trauma and infections. The aim of this study was to investigate the effect of these cytokines on the regulation of neutrophil degranulation. The posttraumatic time courses of the plasma concentrations of IL-6, and the elastase-alpha 1-proteinase-inhibitor complex as marker of degranulation in patients undergoing severe trauma were found to be highly correlated, whereas TGF-beta 1 levels were determined to be not significantly altered. The close temporal correlation of IL-6 and elastase levels could be confirmed by investigation of exudates derived from the surgical area. To prove these in vivo findings, the effect of IL-6 and TGF-beta 1 on the degranulation of isolated neutrophils of healthy donors was investigated in vitro. Pathological high IL-6 concentrations were found to be capable of inducing a significant release of lysosomal elastase in a concentration-dependent manner, whereas the degranulation was unaffected by TGF-beta 1. In conclusion, these data suggest an involvement of IL-6 in the regulation of neutrophil degranulation under pathological conditions. However, TGF-beta 1 seems to have no direct regulatory effects besides its described chemotactic function on neutrophils.

Interleukin-6 is present in early stages of plaque formation and is restricted to the brains of Alzheimer's disease patients

Interleukin-6 (IL-6) immunoreactivity has previously been shown in plaques in Alzheimer's disease (AD) and elevated IL-6 concentrations have been measured biochemically in brains of AD patients. In this study, we investigated the appearance of IL-6 immunoreactivity in AD plaques according to the stage of plaque formation. Using the Bielschowsky silver-staining method, we were able to differentiate between four types of plaques described earlier: diffuse, primitive, classic and compact. While diffuse plaques represent the early stage of plaque formation, primitive and classic plaques are thought to represent later stages of plaque development. We investigated serial sections of paraffin-embedded cortices of ten clinically diagnosed and histopathologically confirmed AD patients and ten patients with no clinical history of dementia. We found plaques in the brains of both nondemented and demented persons using the silver staining method or immunohistochemistry with antibodies against the amyloid precursor protein. In the group of clinically nondemented persons, diffuse plaques were the predominant plaque type, whereas primitive plaques formed the larger portion of lesions in the group of AD brains. IL-6 could not be detected in plaques of patients without dementia. Many IL-6-positive plaques were found in six of the AD brains and to a smaller extent in the other four AD cases. In the six cases with a large number of IL-6-positive plaques, IL-6 was found in a significantly higher ratio of diffuse plaques than expected from a random distribution of IL-6 in all plaque types.(ABSTRACT TRUNCATED AT 250 WORDS)

Interleukin-6 and selected plasma proteins in healthy persons of different ages

In the present study, interleukin-6 (IL-6) and several acute phase proteins were measured in healthy participants (23-87 years of age). A linear correlation between IL-6 and age was established with an increase of 0.016 pg/ml (0.004) per year of life. Whereas CRP remained below 0.5 mg/dl in all participants, an increase with age for fibrinogen and an inverse relation for albumin as well as transferrin were obtained. However, the increase of IL-6 did not correlate with any of these changes. IL-6 associated diseases may therefore occur more often with advancing age, but in healthy participants IL-6 does not explain the changing plasma protein pattern resembling that of an acute phase reaction.

Stimulation of chick hepatocyte fibronectin production by fibroblast-conditioned medium is due to interleukin 6

Interleukin-6 (IL6) is produced by different cell types, including monocytes and fibroblasts. We show that recombinant human IL6 (rhIL6) and chick fibroblast conditioned medium stimulate plasma fibronectin (PFn) and PFn mRNA production by cultured chick hepatocytes in a dose-dependent manner. Lipopolysaccharide (LPS) treatment of fibroblast cultures induces higher levels of the PFn stimulating activity. These effects are blocked by preincubation of either rhIL6 or LPS-stimulated chick fibroblast conditioned medium with anti-rhIL6 antibody before treatment of hepatocytes, indicating that the conditioned medium contains chick fibroblast-derived IL-6 (cfIL6). Further, LPS induces fibroblast production of a proportional increase in cfIL6 detectable by a human IL6 ELISA. cfIL6 maximally stimulates chick hepatocyte PFn production by 24 h (4.5-fold). Dexamethasone acts more rapidly, but maximal stimulation is only 2.3-fold. Hepatocyte Fn mRNA levels are even more substantially stimulated by dexamethasone and cfIL6 (up to 8.9- and 18.5-fold by 12 h, declining to 2.3 and 4.2-fold by 24 h, respectively). The effect cfIL6 with or without dexamethasone on hepatocyte PFn levels are comparable. These observations are consistent with the role of IL6 as a major mediator of acute phase protein production.

Interleukin-6 in synovial fluid is closely associated with chronic synovitis in rheumatoid arthritis

Interleukin-6 (IL-6) was detected at low levels in plasma [0.014 +/- 0.006 ng/ml (mean +/- SEM] and in high amounts in synovial fluid [SF; 2.6 +/- 2.2 ng/ml (mean +/- SEM)] of patients with rheumatoid arthritis. No correlation of IL-6 levels in plasma or SF with the ESR (n = 15) or with histological parameters of acute local synovitis (n = 10) was observed. In contrast, SF IL-6 was positively correlated with histological characteristics of chronic synovitis (n = 10; P < or = 0.01) and elevated plasma IgG concentrations (n = 15; P < or = 0.05). In vitro concentrations of IL-6 comparable to those detected in SF increased the production of both IgG and IgM by synovial membrane mononuclear cells. The present results contribute to the view that high local IL-6 concentrations in SF promote chronic synovitis in RA.

Effects of interleukin-1 and interleukin-6 on metallothionein and amyloid precursor protein expression in human neuroblastoma cells. Evidence that interleukin-6 possibly acts via a receptor different from the 80-kDa interleukin-6 receptor

Since immunohistochemical studies indicated the presence of interleukin-6 in the cortices of patients with Alzheimer's disease, we were interested in the eventual biological effects of this cytokine on neuronal cells. We found that interleukin-6 and interleukin-1 induced metallothionein expression in a human neuronal (SH-SY5Y neuroblastoma) cell line. In contrast to metallothionein, amyloid precursor protein expression was unaffected by both cytokines. When searching in the same cell line for the expression of the classical 80-kDa interleukin-6 binding protein, which is part of the dimeric interleukin-6 receptor, we were unable to detect the respective mRNA. Our findings either indicate that the interleukin-6 receptor in these cells is expressed in extremely low levels or that interleukin-6 may act upon neuronal cells via a different, yet unknown neuronal receptor.

Absence of expression of interleukin-6 (IL-6) mRNA in regenerating rat liver

The serum level of IL-6 and expression of IL-6 mRNA in hepatocytes from regenerating liver were investigated in the rat. The IL-6 level in the serum was not significantly different from that of a control group of rats submitted to an acute experimental inflammation. IL-6 mRNA expression did not occur in the liver of hepatectomized rats as judged from Northern blotting experiments using an IL-6 riboprobe. These results suggest that if IL-6 is implicated in hepatic regeneration, this cytokine is not produced by the regenerating liver and must be delivered exogenously to the liver to modulate hepatic regeneration.

Suppression and transient induction of lymphokines in cancer patients after administration of polyethylene glycolated interleukin-2

Polyethylene glycolated (pegylated) interleukin-2 (PEG IL-2) was administered as a weekly i.v. bolus to patients with metastatic cancer in a phase-I trial. Efficacy, toxicity and pharmacokinetics have been described previously. To explore mechanism of IL-2 action and discover predictors of efficacy, the levels of several lymphokines were measured in pharmacokinetic serum samples. IL-1 beta and IL-6 were elevated in many patients before PEG IL-2 administration, forming a continuous, log-normal distribution among patients. The levels of the two lymphokines were strongly correlated. However, no significant correlation could be found between these levels, clinical chemistry, or tumor regression seen after PEG IL-2 administration. Three hours after PEG IL-2 administration, IL-1 beta and IL-6 levels, if elevated, fell to normal. In all patients, independent of initial levels, IL-6 and IFN-gamma, but not IL-1 beta, increased 4 to 6 h after the injection and then fell rapidly, even though PEG IL-2 levels were high and often changed only slightly during this period. This suggests an active shut down of lymphokine synthesis, or an increase in elimination rate. After the fourth administration of PEG IL-2, the peak level of IFN-gamma was 2 to 20 times higher than after the first, while the peak level of IL-6 did not change in a consistent direction. Responding patients had typical peak levels of IL-6 and IFN-gamma. Low levels of TNF and IL-4 were occasionally seen before and after PEG IL-2 administration, but no consistent pattern was evident.

Effects of sex steroids on immunoglobulin M production by Epstein-Barr virus-transformed B-cell line SKW6-CL4

The effects of estradiol (E2), progesterone (P), and testosterone (T) on the production of immunoglobulin (Ig) M by Epstein-Barr virus-transformed B-cell line, SKW6-CL4, were investigated. Interleukin 6 (IL-6) induced IgM production by SKW6-CL4 cells in a dose-dependent manner without any significant increase in thymidine incorporation. E2 at concentrations ranging from 10(-10) to 10(-9) M enhanced IL-6-induced IgM production by SKW6-CL4 cells, whereas E2 at a high concentration of 10(-7) M inhibited both the IgM production and the growth of SKW6-CL4 cells. Time-course studies revealed that E2 acts in the early phase of differentiation of SKW6-CL4 cells in response to IL-6. On the other hand, P and T at physiological and superphysiological levels did not influence either the IgM production or the proliferation of SKW6-CL4 cells. These findings suggest a direct immunoregulatory effect of E2 on human B lineage cells and support the concept that E2 may have a role in the pathogenesis of some autoimmune diseases.

Interleukin-6 and alpha-2-macroglobulin indicate an acute-phase state in Alzheimer's disease cortices

Recent studies indicated that the formation of a major constituent of Alzheimer's disease (AD) senile plaques, called beta A4-peptide, does not result from normal processing of its precursor, amyloid precursor protein (APP). Since proteolytic cleavage of APP inside its beta A4 sequence was found to be part of APP processing the formation of the beta A4-peptide seems to be prevented under normal conditions. We considered whether in AD one of the endogenous proteinase inhibitors might interfere with APP processing. After we had recently found that cultured human neuronal cells synthesize the most potent of the known human proteinase inhibitors, alpha-2-macroglobulin (alpha 2M), upon stimulation with the inflammatory mediator interleukin-6 (IL-6) we now investigated whether alpha 2M and IL-6 could be detected in AD brains. Here we report that AD cortical senile plaques display strong alpha 2M and IL-6 immunoreactivity while no such immunoreactivity was found in age-matched control brains. Strong perinuclear alpha 2M immunoreactivity in hippocampal CA1 neurons of Alzheimer's disease brains indicates that neuronal cells are the site of alpha 2M synthesis in AD brains. We did not detect elevated IL-6 or alpha 2M levels in the cerebrospinal fluid of AD patients. Our data indicate that a sequence of immunological events which seem to be restricted to the local cortical environment is part of AD pathology.

[Hepatology. New research results in its significance for the understanding of liver diseases]

By two exemplary clinical situations--acute viral hepatitis, acute-phase reaction of the liver--the significance of basic research for the understanding of clinical phenomena and for the development of new diagnostic and therapeutic procedures is demonstrated. The very different phenomena following infection with the hepatitis-B-virus can be explained by the variation in the interactions of virus and liver cell, by the immune reaction of the host, and by mutants of the virus. The reaction of the liver to an extrahepatic infection is mediated by interleukin-6, and characterized by an alteration in protein metabolism. The synthesis of acute-phase proteins is increased. The proteins confine the local injury and establish the homeostasis of the organism.

Interleukin-6 in clinical medicine

This article covers the basic biological functions of interleukin-6 (IL-6) in man. Three major topics are addressed more closely: the involvement of IL-6 in various disease states, particularly those of hematopoietic origin; the diagnostic usefulness of IL-6 measurements in biological fluids; the possible use of IL-6, IL-6 antagonists or IL-6 derivatives as therapeutic means.

Alpha-2-macroglobulin decreases parallel to albumin and haemoglobin after elective surgery

Plasma levels of the plasma protease inhibitor alpha-2-macroglobulin (alpha 2-M) were followed for 7 days in 90 patients subjected to various surgical procedures. Alpha 2-M was found to decrease strictly in parallel with the decrease seen for haemoglobin and albumin levels in all patients. Changes were most pronounced after extensive operations; total hip replacement (n = 7), pulmonary resection (n = 11), extensive colo-rectal resection (n = 15), and less pronounced after 'minor' operations; mastectomy (n = 23) proximal gastric vagotomy (n = 5) and moderate colo-rectal resection (n = 29). Levels were lowest on the second to third postoperative day, whereafter they slowly returned to normal, preoperative levels during the 7-day study period. Functional and quantitative alpha 2-M levels almost paralleled each other throughout the 7 days studied. Chromogenic peptide substrate assays indicated circulating plasmin-alpha 2-M complexes, while no protease-alpha 2-M complexes could be demonstrated using sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) or isoelectric focusing (IEF) analyses. Local accumulation and consumption of proteins within wounded tissues, together with haemodilution, were probably the major factors responsible for the decreased plasma levels seen. It is concluded that the plasma levels of alpha 2-M decrease after major elective surgery strictly in parallel with the decrease seen in haemoglobin and albumin levels, and that circulating plasmin-alpha 2-M complexes are probable. The decrease seems to be graded, that is, proportional to the extent of the operative trauma, similar to the postoperative increase seen in positive acute-phase proteins. Thus, alpha 2-M cannot be used as an internal, unchanged plasma protein standard for other protein changes seen after trauma.

Alpha 2-macroglobulin synthesis in interleukin-6-stimulated human neuronal (SH-SY5Y neuroblastoma) cells. Potential significance for the processing of Alzheimer beta-amyloid precursor protein

Cultured human neuronal (SH-SY5Y neuroblastoma) cells synthesize and secrete the potent protease inhibitor alpha 2-macroglobulin (a2M) upon stimulation with interleukin-6 (IL-6) indicating that alpha 2-macroglobulin behaves as an acute-phase protein in the human central nervous system. Exogenous addition of a2M to the cultured neuronal cells resulted in only a slight inhibition of Alzheimer beta A4-amyloid precursor protein (APP) synthesis, but markedly inhibited its secretion pointing to the possibility that a2M may affect the proteolytic APP processing. Evidence is provided that IL-6 and a2M are involved in Alzheimer's disease pathogenesis.

Effects of cytokines on the liver

Cytokines are essential for the communication not only between the liver and extrahepatic sites but also within the liver itself. Cytokines regulate the intermediary metabolism of amino acids, proteins, carbohydrates, lipids and minerals. Cytokines partially interact with classical hormones such as glucocorticoids, resulting in a complex network of mutual control. Since many cytokines exert growth factor-like activities in addition to their specific proinflammatory effects, the distinction between cytokines and growth factors is somewhat artificial. The liver is an important site of synthesis and the major clearance organ for several cytokines. In liver disease, cytokines are involved in the onset of intrahepatic immune responses (e.g., during viral hepatitis), in liver regeneration (e.g., after partial hepatectomy) and in the fibrotic and cirrhotic transformation of the liver such as chronic chemical injury or viral infection. Further studies of cytokine actions may lead to a better understanding of liver diseases and to the development of new immunomodulating therapeutic options.

Interleukin-6 production by thyroid epithelial cells. Enhancement by interleukin-1

Interleukin-1 is a potent inhibitor of thyroglobulin and cAMP production in human thyroid cells and the inhibitory effect is enhanced by tumor necrosis factor-alpha and interferon-gamma. In the present study secondary cultures of human thyroid cells produced interleukin-6 and the production was significantly increased after exposure of the cells to recombinant interleukin-1 alpha and -1 beta. This increase was dose-dependent and concomitant of the IL-1 induced decrease in cAMP and thyroglobulin production. Both tumor necrosis factor-alpha and -beta also augmented interleukin-6 production, but less potently than interleukin-1. Interferon-gamma did not affect the production of interleukin-6. The rat thyroid cell line FRTL-5 produced interleukin-6 spontaneously, and the production was enhanced after addition of recombinant interleukin-1 beta. A pathogenetic role of interleukin-6 in autoimmune thyroid disease is suggested.

Gene regulation by interleukin 6

Interleukin 6 (IL-6) is a central alarm hormone of the mammalian body. During acute and chronic inflammations, it induces acute phase plasma protein synthesis by liver hepatocytes, modulates the immune response and participates in the regulation of body temperature (fever). In addition, it is a growth factor for certain tumor cells, such as myeloma cells. The details of the IL-6 signal transduction mechanism are unknown. We have contributed to this problem at 2 levels: (a), we have mapped an IL-6-response element (IL-6-RE) in the 5' flanking region of the alpha 2-macroglobulin gene (alpha 2M), a prototype rat liver acute phase gene. This element, CTGGGA, serves as a binding site for nuclear factors that facilitate hormone induced transcription. We have begun to characterize these factors from hepatic cells and demonstrated that they undergo characteristic IL-6-induced changes. Similar factors were also discovered in human Burkitt tumor derived cell lines (B cells). These bound at the IL-6-RE of the rat alpha 1M gene and formed indistinguishable protein DNA complexes, as the corresponding hepatic factors. Thus, common elements probably operate in the IL-6 signal transduction cascade in liver cells and B cells; (b), we have cloned the rat liver IL-6 receptor (IL-6-R) and derived its amino acid sequence. It was 53% identical to the human leukocyte IL-6-R and all functional domains were highly conserved. Therefore, the cell-type specific responses to IL-6 in liver cells and lymphocytes were probably not due to cell-type specific forms of the receptor, but to other so far unknown elements of the signal transduction cascade.(ABSTRACT TRUNCATED AT 250 WORDS)

Induction of hepatocyte mitosis in intact adult rat by interleukin-1 alpha and interleukin-6

In the adult rat the liver is normally quiescent, but it proliferates rapidly in response to partial hepatectomy (PH). A hepatectomized rat is subjected to stress by the operation. We have examined the effects of acute phase cytokines. To investigate the mediation of hepatocyte growth, recombinant human interleukin-1 alpha (IL-1) and interleukin-6 (IL-6) were injected into male rats. Administration of IL-1 or IL-6 followed by NH4Cl and glucagon could induce hepatocyte mitosis 30 h after the first injection. This activity was lost when interleukins were exposed to 90 degrees C for 30 minutes. NH4Cl augmented the effects of IL-1 and IL-6. These results suggest that the IL-1 and IL-6 are important mediators of liver regeneration after PH. We present a hypothesis for the triggering mechanism of hepatocyte proliferation.

Cellular targets and receptors for interleukin-6. I. In vivo and in vitro uptake of IL-6 in liver and hepatocytes

Interleukin-6 (IL-6) is a potent stimulator of the hepatic synthesis of acute-phase proteins. 125I-labelled IL-6 disappeared from the blood of rats with an overall half-time of about 1.5 min; 41% of the injected tracer dose was recovered in the liver by 15 min. The clearance was biphasic. The simultaneous injection of tracer and an excess of unlabelled IL-6 eliminated the initial rapid phase, and reduced the hepatic uptake to 14%. Light microscopic autoradiography showed 5% of the grains over non-hepatocytes, and 80% over hepatocytes, accumulating in areas around the bile canaliculi. Thereafter, degradation products accumulated in the bile. At 4 degrees C, isolated rat hepatocytes bound IL-6 with an apparent Kd of 39 pmol l-1 to a uniform class of 4500 receptors per cell with an apparent molar mass of 115-120 kg mol-1. The HepG2 human hepatocellular cell line bound IL-6 with an apparent Kd of 21 pmol l-1 to a uniform class of 1200 receptors per cell with an apparent molar mass of 155-160 kg mol-1. At 37 degrees C, both cell types endocytosed the bound ligand slowly, and degradation products appeared in the medium after a relatively long lag period (40 min in hepatocytes and 1 h in HepG2 cells).

Serum interleukin 6, C-reactive protein and pancreatic secretory trypsin inhibitor (PSTI) as acute phase reactants after major thoraco-abdominal surgery

We measured serum immunoreactive interleukin 6 (IL-6) levels in patients after major thoraco-abdominal surgery and compared them with changes in serum C-reactive protein (CRP) and pancreatic secretory trypsin inhibitor (PSTI) levels. Serum IL-6 levels were elevated earlier than serum CRP or PSTI. There were significant relationships between the peak levels of serum IL-6 and the operation time (p less than 0.05) or the volume of blood loss during surgery (p less than 0.05), showing that serum IL-6 can be a useful laboratory test for the evaluation of tissue injuries due to surgical intervention. Though there was a significant relationship between the peak levels of IL-6 and CRP (p less than 0.01), there was no relationship between the peak levels of IL-6 and PSTI.

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.