Circulating interleukin-8 concentrations in patients with multiple organ failure of septic and nonseptic origin

OBJECTIVES

Interleukin (IL)-8, a pro-inflammatory cytokine, is a potent chemoattractant factor and an activator of neutrophils produced by many cell types after stimulation by IL-1, tumor necrosis factor (TNF), or microbial products such as endotoxins. We investigated whether the presence of measurable IL-8 in plasma was associated with the clinical status of severely ill septic or nonseptic patients susceptible to the development of multiple organ failure.

DESIGN

Cohort study.

SETTING

A collaborative study between an intensive care unit and a research laboratory.

SUBJECTS

Circulating IL-8 concentrations were measured in the plasma of 27 patients with sepsis syndrome and in 16 patients with noninfectious shock because these two conditions put patients at risk for the development of multiple organ failure. Sixteen of 27 patients with severe infection and 13 of 16 patients with noninfectious pathologies developed multiple organ failure.

MEASUREMENTS AND MAIN RESULTS

A specific enzyme-linked immunosorbent assay (ELISA) for IL-8 was set up with a monoclonal and a rabbit polyclonal antihuman IL-8 using a sandwich technique. High concentrations of circulating IL-8 were found in the plasma of patients with sepsis syndrome. Among septic patients, a significant difference was observed between concentrations of IL-8 in survivors (n = 16) and nonsurvivors (n = 11) (81 +/- 13 pg/mL vs. 3326 +/- 1219 pg/mL, respectively; p = .001). A correlation was noticed between plasma IL-8 and IL-6 concentrations (r2 = .42; p = .001), while no correlation was observed between IL-8 and TNF-alpha values, or between IL-8 and IL-1 beta. Although the mortality rate of nonseptic, multiple organ failure patients was 92%, low plasma concentrations of IL-8 were found (78 +/- 34 pg/mL), while high plasma concentrations were measured in septic, multiple organ failure patients (mortality rate 69%) who were sampled at a similar stage. By contrast, increased IL-6 values were observed in both septic and nonseptic, multiple organ failure patients.

CONCLUSIONS

In septic patients, high amounts of circulating IL-8 concentrations correlate with fatal outcome, whereas only low plasma concentrations of IL-8 are present in patients with nonseptic, multiple organ failure. This finding suggests that the signals involved in the exacerbation of IL-8 production are different, depending on infectious or noninfectious etiology.

Correlation between the capacity to activate macrophages in vitro and the antitumor activity in vivo of lipopolysaccharides from different bacterial species

The correlation between the activation of macrophages by lipopolysaccharides (LPS) from four different bacterial species and their antitumor effect in a rat model of colon cancer was investigated. The efficacy of LPS from Neisseria meningitidis (Nm), Salmonella minnesota (Sm), Escherichia coli (Ec) and Bordetella pertussis (Bp) was evaluated as the smallest concentration inducing rat peritoneal macrophages (pm psi) to produce tumor necrosis factor (TNF), interleukin-1 (IL-1), IL-6 and nitric oxide (NO). The cytokine production was measured in bioassays and NO production quantitatively with Griess reactant. Nm was the most effective LPS with concentrations of 1 ng/10(6) pm psi for the induction of TNF, IL-1 and IL-6 activities and 0.01 ng/10(6) pm psi for the induction of NO production. The range between efficacy of different LPS was broad from 1 to 10(4)-10(5) for TNF activity, 1 to 10(2)-10(3) for NO production and IL-6 activity and 1 to 10-10(2) for IL-1 activity. In vivo antitumor effect was evaluated on the growth of peritoneal carcinomatosis. Complete tumor regressions were observed, the LPS rating with respect to decreasing efficacy was Nm, Sm, Ec then Bp; Nm, Sm and Ec were very closed while Bp was not effective. These results show the correlation between the antitumor effect in vivo of LPS and their capacity to induce in vitro IL-1 activity, but not between their ability to induce NO production, TNF and IL-6 activities.

Cytokines and macrophages

Macrophages, within the cytokine network, are a major source of many cytokines involved in immune response, hematopoiesis, inflammation and many other homeostatic processes. Upon stimulation by micro-organisms, microbial products or endogenous factors including cytokines, macrophages can de novo synthesize and release a large variety of cytokines (ie IL-1, IL-1ra, IL-6, IL-8, IL-10, IL-12, TNF alpha, IFN alpha, IFN gamma, MCP-1, MCP-3, MIF, M-CSF, G-CSF, GM-CSF, MIP-1, MIP-2, LIF, OSM, TGF beta). Some cytokines can upregulate the production of cytokines by macrophages (IL-3, GM-CSF, IFN gamma) while others can inhibit it (IL-4, IL-10, IL-13, TGF beta). In addition, these cytokines can modulate most of the macrophage functions and cell surface marker expression. Other cytokines (the chemokines such as MCP-1,2,3, MIP-1,2 and RANTES) contribute to the recruitment of circulating monocytes within tissues. It is worth noting that macrophages can be their own source of regulatory cytokines.

A novel granulocyte-derived peptide with lipopolysaccharide-neutralizing activity

Rabbit CAP18 (cationic antimicrobial protein, 18 kDa) is a leukocyte protein identified and purified using as an assay its capacity to bind and inhibit various activities of LPS. Oligonucleotide probes designed from the putative N-terminal protein sequence were used to obtain the corresponding cDNA from a rabbit bone marrow cDNA library. Examination of the cDNA sequence revealed that the protein fragment of the putative N-terminus was actually a 37-amino-acid C-terminal fragment. This fragment, designated CAP18(106-142), inhibits many activities of LPS. In the present studies, synthetic CAP18(106-142) is shown to: 1) bind to erythrocytes coated with diverse strains of LPS; 2) inhibit LPS-induced release of cytokines (TNF, IL-1, IL-6) and nitric oxide from macrophages; 3) inhibit LPS-induced LAL coagulation and 4) protect mice from LPS lethality. CAP18(106-142) may have therapeutic utility for conditions associated with elevated concentrations of LPS.

A novel granulocyte-derived peptide with lipopolysaccharide-neutralizing activity

Rabbit CAP18 (cationic antimicrobial protein, 18 kDa) is a leukocyte protein identified and purified using as an assay its capacity to bind and inhibit various activities of LPS. Oligonucleotide probes designed from the putative N-terminal protein sequence were used to obtain the corresponding cDNA from a rabbit bone marrow cDNA library. Examination of the cDNA sequence revealed that the protein fragment of the putative N-terminus was actually a 37-amino-acid C-terminal fragment. This fragment, designated CAP18(106-142), inhibits many activities of LPS. In the present studies, synthetic CAP18(106-142) is shown to: 1) bind to erythrocytes coated with diverse strains of LPS; 2) inhibit LPS-induced release of cytokines (TNF, IL-1, IL-6) and nitric oxide from macrophages; 3) inhibit LPS-induced LAL coagulation and 4) protect mice from LPS lethality. CAP18(106-142) may have therapeutic utility for conditions associated with elevated concentrations of LPS.

[Contribution of cytokines to inflammatory mechanisms]

A large number of cytokines are found within foci of inflammation. Two of these cytokines, namely interleukin-1 (IL-1) and tumor necrosis factor (TNF), play a key role in orchestrating the mechanisms responsible for inflammation. These two cytokines induce production by many cells of lipid mediators, proteases, and free radicals, all of which play a direct role in development of the deleterious effects of inflammation. IL-1 and/or TNF exert cytotoxic effects on the vascular endothelium, cartilage, bone, muscle, or pancreatic beta-cell islets. Cytokines, including interferon gamma (IFN), IL-3 and granulocyte-macrophage colony-stimulating factor (GM-CSF), amplify the inflammatory response by increasing production of IL-1 and TNF by macrophages. Macrophages also produce other cytokines, such as IL-8 and macrophage chemoattractant protein-1 (MCP-1), with chemoattractant properties that contribute to draw leucocytes to the site of inflammation. IL-6, produced in large amounts during inflammatory processes, induces the production of acute phase proteins by hepatocytes. IL-1, TNF, IL-11, leukemia inhibitory factor (LIF), and transforming growth factor beta (TGF beta) share this effect. TGF beta also has a number of anti-inflammatory effects. TGF beta, IL-4, and IL-10 inhibit production of IL-1 and TNF. Glucocorticoids also have this effect. Glucocorticoids can be produced as a result of a chain of events initiated by IL-1, TNF, and IL-6 and involving the neuro-endocrine axis. Other substances, such as IL-1 receptor antagonist (IL-1 ra) or soluble forms of the TNF receptors, can specifically inhibit the effects of IL-1 and TNF. Cascade production of cytokines, inhibition, negative feed-back, and synergistic mechanisms are parameters that illustrate the concept of "cytokine network" and aptly characterize the role of these mediators in the mechanisms of inflammation.

High levels of portal TNF-alpha during abdominal aortic surgery in man

During shock or multiple organ dysfunction syndrome, translocation of bacteria and/or lipopolysaccharide (LPS) from the ischaemic gut might occur and could explain the excess of cytokine production detectable in plasma. To test this hypothesis, we studied a model of mild gut ischaemia due to bowel manipulation and aortic clamping in patients undergoing abdominal aortic surgery (n = 14). Per-operative levels of LPS and cytokines were measured before clamping and after reperfusion, and compared in systemic and portal blood. Systemic levels of LPS and cytokines were measured in a control group of patients undergoing internal carotid surgery (n = 7). Portal LPS was detectable (i.e., > 12 pg/ml) in 36% of the patients undergoing aortic surgery after bowel manipulation, and in 71% after clamp release. Similar levels of LPS were observed in portal and systemic blood after clamp release. Circulating tumour necrosis factor alpha (TNF-alpha) was observed in all patients undergoing aortic surgery. Levels of portal TNF-alpha were higher than those in systemic blood after bowel manipulation as well as after reperfusion (P = 0.02 and 0.007, respectively). LPS was never detected in control patients and TNF-alpha was detectable in only two out of seven patients. Mean levels of IL-6 were similar in the two groups, with a peak on the day following surgery, confirming that circulating IL-6 is associated with any surgical procedures. Our data indicate that bowel manipulation, aortic clamping and reperfusion lead to similar levels of portal and systemic circulating LPS.(ABSTRACT TRUNCATED AT 250 WORDS)

[Cytokines and inflammation]

Numerous cytokines are present in inflammatory foci. Two of them, interleukin-1 (IL-1) and tumour necrosis factor (TNF), play a major role in coordinating mechanisms which command inflammation. Under their action many cells produce lipidic mediators, proteolytic enzymes or free radicals, all factors that are directly responsible for the noxious effects observed. IL-1 and/or TNF exert cytotoxic activities on vascular epithelium, cartilage, bone, muscle or beta cells of pancreatic islets. Such cytokines as interferon gamma (IFN gamma), IL-3 or granulocyte-macrophage colony stimulating factor (GM-CSF) amplify the inflammatory response by increasing the production of IL-1 and TNF by macrophages. GM-CSF also produces other cytokines, such as IL-8 and the macrophage chemoattractant protein 1 (MCP-1), the chemotactic properties of which participate in the recruitment of leucocytes within the focus of inflammation. IL-6 abounds in inflammatory processes and induces the production by hepatocytes of acute inflammation phase proteins. The same applies to IL-1, TNF, IL-11, the leukaemia inhibitory factor (LIF) or the transforming growth factor beta (TGF beta). The latter also possesses a number of anti-inflammatory activities and, like IL-4 and IL-10, can inhibit IL-1 and TNF production. Glucocorticoids have this potential activity, and they may be produced by a cascade of events initiated by IL-1, TNF and IL-6, involving the neuroendocrine system. The concept of "cytokine network", therefore, perfectly illustrates the participation of these mediators in inflammatory mechanisms.

Assessment of ability of murine and human anti-lipid A monoclonal antibodies to bind and neutralize lipopolysaccharide

The use of monoclonal antibodies (mAbs) directed to lipid A for the therapy of gram-negative sepsis is controversial. In an attempt to understand their biologic basis of action, we used a fluid-phase radioimmunoassay to measure binding between bacterial lipopolysaccharide (LPS) and two IgM mAbs directed to lipid A that are being evaluated for the treatment of gram-negative bacterial sepsis. Both antibodies bound 3H-LPS prepared from multiple strains of gram-negative bacteria when large excesses of antibody were used, although binding was modest and only slightly greater than control preparations. We also studied the ability of each anti-lipid A antibody to neutralize some of the biological effects of LPS in vitro. Despite large molar excesses, neither antibody neutralized LPS as assessed by the limulus lysate test, by a mitogenic assay for murine splenocytes, or by the production of cytokines interleukin (IL)-1, IL-6, or tumor necrosis factor from human monocytes in culture medium or in whole blood. Our experiments do not support the hypothesis that either of these anti-lipid A mAbs function by neutralizing the toxic effects of LPS.

Cytokine production by murine cells activated by erythrogenic toxin type A superantigen of Streptococcus pyogenes

The mode of pathogenic action of the Steptococcus pyogenes superantigen erythrogenic toxin type A (ETA) in causing toxic shock-like syndrome in humans is thought to be mediated by massive release of cytokines by patients immune cells. The cytokine-inducing capacity of ETA as an extracellular protein was compared with that of lipopolysaccharide (LPS), a component of cell wall of gram-negative bacteria. Peritoneal macrophages and splenocytes of BALB/c and C3H/HeJ mice were stimulated by ETA and LPS. Tumor necrosis factor (TNF), interleukin 3 (IL-3) and interleukin 6 (IL-6) activities in the supernatants of stimulated cells were evaluated. In contrast to LPS, ETA induced only low amounts of IL-6 and no detectable TNF activities in peritoneal macrophage supernatants. ETA-triggered BALB/c and C3H/HeJ splenocytes produced great amounts of IL-6. ETA triggered the production of IL-3 by both mice strains splenocytes in a dose dependent manner. The amounts of IL-3 in supernatants were comparable to those induced by concanavalin A. The simultaneous presence of ETA and LPS in macrophage and splenocyte cultures induced a slight enhancement above an additive value after 72-96 h. Challenge of BALB/c mice with ETA 6 h before the harvest of peritoneal macrophages led to an enhanced production of IL-6 upon stimulation with ETA as well as with LPS. Splenocytes of nude BALB/c mice did not produce IL-6 upon stimulation with ETA, whereas LPS-induced IL-6 production was similar in these mice and in their littermates. The pathogenic effect of ETA on host's immune cells could most likely be explained as a consequence of T cell activation. The results confirm also that LPS- and ETA-induced shock is mediated by different cell types.

Influence of surgery on in-vitro cytokine production by human monocytes

Surgery leads to significant modulation of the immune system, in which cytokines play a major role. Circulating interleukin 6 (IL-6) and IL-1 have been reported following surgery whereas tumor necrosis factor alpha (TNF-alpha) is only found in gut ischemia-associated surgery. We have investigated the consequences of surgery on in-vitro cytokine production by human monocytes stimulated by lipopolysaccharide (LPS) and staphylococcal toxic shock syndrome toxin-1 (TSST-1). Comparisons were made between the responsiveness of cells obtained the day before (D-1), during (D0) and after (D1, D2, D3) surgery. Patients undergoing abdominal aortic surgery (N = 9), carotid surgery (N = 4) and spinal surgery (N = 4) have been studied. A significant decrease of TNF-alpha, IL-1 beta and IL-1 alpha production by monocytes prepared from blood samples taken during the surgery was noticed, whereas IL-6 production was not significantly modified. On D2 a significant increase of monocyte responsiveness was observed and levels of cytokine productions rose back to initial values by the end of the follow up. The diminished in-vitro cytokine production observed during surgery might be the consequence of the effects of anaesthetic drugs, whereas the enhancement observed on D2 might reflect the surgical stress, leading to in-vivo priming of circulating monocytes.

Circulating cytokines: the tip of the iceberg?

Circulating cytokines, particularly TNF alpha, IL-1, IL-6 and IL-8, can be detected during severe infections consecutively to an exacerbate release by activated cells. The presence or absence of cytokines within biological fluids reflects a rather complex balance between enhancing and inhibitory signals acting on producer cells, between production and catabolism, and between their binding to the target cells and the modulation of their receptors on the cell surface. Furthermore, their presence does not necessarily parallel their activity and a possible interplay between the cytokines and their corresponding inhibitors should be considered. On the contrary, the absence of detectable circulating cytokines does not indicate an absence of production by activated cells. We discuss the concept that circulating cytokines represent the tip of the iceberg.

Serum interleukin-6 in long-term hemodialyzed patients

The generation of compounds such as interleukin 1 (IL-1), tumor necrosis factor alpha (TNF alpha), and the possible encounter of circulating cells with endotoxin (LPS) have been demonstrated during hemodialysis. All these factors are able to induce the production of IL-6 by human monocytes. Anaphylatoxins can be generated following complement activation by cellulosic membrane dialysis. C5a is known to potentiate the LPS-induced production of IL-1 and TNF alpha, and we established that recombinant human C5a was able to act synergistically with LPS in the induction of IL-6 by human monocytes. We investigated whether IL-6 could be detected in the serum of long-term hemodialyzed and uremic patients. Using the very sensitive 7TD1 cell line bioassay, we demonstrated that circulating IL-6 activity was present in the serum of all 14 tested patients, whereas it was occasionally present in normal sera. The presence of serum IL-6 was confirmed using an anti-IL-6 antibody and a specific ELISA (109 +/- 36 pg/ml). Most patients had a reproducible level of IL-6 activity throughout a period of 10 days. The dialysis session did not significantly modify these levels and patients had similar serum IL-6 activity at the start, during or the at end of the dialysis session. The different parameters of the dialysis session (i.e. standard or filtrated dialyzates, complement-activating or nonactivating membranes) did not significantly influence the levels of IL-6. Elevated levels of IL-6 were also observed in uremic patients compared to normal donors, although significantly lower than in hemodialyzed patients (p = 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Dysregulation of in vitro cytokine production by monocytes during sepsis

The production by monocytes of interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta), interleukin-6 (IL-6), and tumor necrosis factor alpha (TNF alpha) in intensive care unit (ICU) patients with sepsis syndrome (n = 23) or noninfectious shock (n = 6) is reported. Plasma cytokines, cell-associated cytokines within freshly isolated monocytes and LPS-induced in vitro cytokine production were assessed at admission and at regular intervals during ICU stay. TNF alpha and IL-6 were the most frequently detected circulating cytokines. Despite the fact that IL-1 alpha is the main cytokine found within monocytes upon in vitro activation of cells from healthy individuals, it was very rarely detected within freshly isolated monocytes from septic patients, and levels of cell-associated IL-1 beta were lower than those of TNF alpha. Cell-associated IL-1 beta and TNF alpha were not correlated with corresponding levels in plasma. Upon LPS stimulation, we observed a profound decrease of in vitro IL-1 alpha production by monocytes in all patients, and of IL-1 beta, IL-6, and TNF alpha in septic patients. This reduced LPS-induced production of cytokines was most pronounced in patients with gram-negative infections. Finally, monocytes from survival patients, but not from nonsurvival ones recovered their capacity to produce normal amounts of cytokines upon LPS stimulation. In conclusion, our data indicate an in vivo activation of circulating monocytes during sepsis as well as in noninfectious shock and suggest that complex regulatory mechanisms can downregulate the production of cytokines by monocytes during severe infections.

Dissociation between plasma and monocyte-associated cytokines during sepsis

We report our investigations of circulating interleukin (IL) 1 beta, IL 6 and tumor necrosis factor (TNF)-alpha, as well as cell-associated IL 1 alpha, IL 1 beta and TNF-alpha in plasma and monocytes of 21 patients with sepsis syndrome and 6 patients with non-septic shock. Longitudinal studies reveal that (a) the most frequent detectable plasma cytokines were TNF-alpha and IL 6, (b) the presence and the kinetics of circulating cytokines were independent of one other, (c) detectable levels of cytokines could be found for a long period of time, and (d) significantly higher levels of IL 6 were found for non-surviving patients. Because of the in vivo half-life of cytokines and of the existence of numerous specific high-affinity receptors, it is quite probable that detectable plasma cytokines represent the excess of produced mediators which have not been trapped by the target cells. TNF-alpha (410 +/- 65 pg/10(6) monocytes) and IL 1 beta (153 +/- 60 pg/10(6) monocytes) were frequently found associated to monocyte lysates (88% and 50%, respectively). Despite the fact that IL 1 alpha is the most abundant cytokine found associated to monocytes following in vitro activation, IL 1 alpha was rarely found in monocytes of intensive care unit patients (29%). No correlation was found to exist between the levels of plasma cytokines and cell-associated cytokines. Some patients had plasma TNF-alpha or IL 1 beta in the absence of the corresponding monocyte-associated cytokine. This observation suggests that cells other than monocytes can participate in the production of circulating cytokines. At the end of the longitudinal study (day 14 +/- 2), only 2/12 surviving patients still had plasma TNF-alpha, whereas 8/12 had monocyte-associated TNF-alpha. These results indicate that activation of monocytes still occurs in patients for whom no plasma cytokines can be detected. Thus, in addition to the measurement of plasma cytokine, measurement of cell-associated cytokine appears useful to assess cytokine production and monocyte activation in vivo.

Interleukin-3 enhances cytokine production by LPS-stimulated macrophages

In addition to its hematopoietic activities, interleukin-3 (IL-3) can modulate macrophage functions. We have studied the production of interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor (TNF) by mouse peritoneal macrophages triggered by lipopolysaccharide (LPS) in the presence or absence of IL-3. Interleukin-3 at the concentration used (i.e., 100 U/ml) did not induce the production of any cytokines, whereas it enhanced significantly the secretion of IL-1, IL-6 and TNF by LPS-stimulated macrophages. The synergistic activity of IL-3 was observed over a wide range of Escherichia coli or Salmonella enteritidis LPS concentrations. No additive effect was noticed between IL-3 and granulocyte/macrophage colony-stimulating factor (GM-CSF), another factor able to enhance LPS-induced IL-1 production. Thus, IL-3 can potentiate the inflammatory response induced by endotoxin from Gram-negative bacteria through a potentiation of cytokine production.

Induction of interleukin-3 by interleukin-1 in the absence of other exogenous stimuli

We have previously reported that lipopolysaccharide (LPS) could induce the production of interleukin-3 (IL-3) by mouse spleen cells. In the present study, we show that recombinant human interleukin-1, in the absence of other stimuli, is able to induce the production of IL-3. IL-3 was detected in the supernatants of adult, although neither in young nor in nude mouse splenocytes and was assessed by its capacity to support the growth of the IL-3-dependent FDC-P2 cell line. The presence of IL-3 was antigenically confirmed with a monoclonal anti-IL-3 antibody. Both recombinant IL-1 alpha and IL-1 beta had similar potential for inducing IL-3 production. IL-3 activity was detected in the supernatants of cells cultured in the presence of 100 pg/ml IL-1; maximal IL-3 levels were obtained with 10-30 ng/ml IL-1. Kinetic studies of IL-1-induced IL-3 production indicated that 4-6 days of culture were required for optimal production, whereas 1-2 days were sufficient in cultures stimulated with concanavalin A. Recombinant IL-6 failed to induce significant amounts of IL-3, and TNF alpha induced only weak IL-3 production. GM-CSF but not M-CSF could lead to the appearance of IL-3 in spleen cell culture supernatants. Removal of macrophages decreased the production of IL-3 induced by LPS and GMF-CSF though did not affect the IL-3 production induced by IL-1. This observation suggests that IL-1 production might be an intermediate event in IL-3 production induced by LPS and GM-CSF through the activation of macrophages. IL-3 was detected in culture supernatants of B-cell-depleted splenocytes indicating that T-cells were the source of IL-3. Surprisingly T-cell-depleted populations could also produce IL-3 upon IL-1 stimulation. Preliminary experiments with an autoreactive CD4- CD8- V beta 8+ clone suggested that these cells might also be involved in the described IL-3 production.

Cytokine response by monocytes and macrophages to free and lipoprotein-bound lipopolysaccharide

Recent evidence suggests that bacterial lipopolysaccharide binds to serum lipoproteins in vitro and in vivo and that lipopolysaccharide in the form that is bound to lipoprotein is less biologically active in several experimental models. In order to study the mechanism of this apparent detoxification, we compared the ability of free and lipoprotein-bound lipopolysaccharide from Escherichia coli O18 to stimulate interleukin-1, interleukin-6, and tumor necrosis factor from elicited murine peritoneal macrophages and circulating human monocytes. Lipopolysaccharide bound to lipoprotein was 20- to 1,000-fold less active than the unbound form in inducing the release of each cytokine. We also studied the binding of each form of lipopolysaccharide to the macrophage surface. Lipopolysaccharide complexed to lipoprotein was unable to compete for the binding of radiolabeled heterologous lipopolysaccharide to murine macrophages, and radiolabeled lipopolysaccharide-lipoprotein complexes bound poorly compared with molar equivalents of free lipopolysaccharide. Our experiments suggest that in the process of binding to lipoproteins, lipopolysaccharide may be rendered less toxic through a mechanism of decreased ability to induce monocytes and macrophages to release cytokines, perhaps because of an altered interaction at the cell surface.

Lipopolysaccharide-induced production of cytokines by bone marrow-derived macrophages: dissociation between intracellular interleukin 1 production and interleukin 1 release

We investigated the capacity of mouse bone marrow-derived macrophages (BMDM) to produce interleukin 1 (IL 1), interleukin-6 (IL 6), and tumor necrosis factor (TNF) upon lipopolysaccharide (LPS) stimulation. BMDM were allowed to differentiate either in the presence of conditioned medium (from WEHI-3 or L cells), or in the presence of recombinant cytokines (IL 3, macrophage-colony stimulating factor [M-CSF], or granulocyte/macrophage-colony stimulating factor [GM-CSF]). Cells were maintained in culture up to 3 weeks and tested at different times. Significant spontaneous cytokine production was never observed. BMDM rapidly acquired the capacity to elaborate cytokine upon LPS activation. LPS-triggered BMDM were able to produce IL 1, IL 6, and TNF, throughout the culture period, although 2- to 3-week-old cells lost their ability to release IL 1 while accumulation of intracellular IL 1 remained unchanged. The dissociation between synthesis and release of IL 1 was not correlated with a significant modification of the specific binding of LPS onto the cell surface.

High in vitro spontaneous histamine release in long-term hemodialyzed patients

Adverse reactions, such as skin flush and pruritus, have been observed among hemodialyzed (HD) patients. A potential relationship between hemodialysis and allergic phenomena prompted us to investigate some allergologic parameters. Total IgE, specific IgE antiethylene oxide and anti-isocyanate toluene diisocyanate, and in vitro spontaneous histamine release (SHR) were measured in 105 long-term stable HD patients. Thirty-two of the patients had occasionally developed skin flush reactions and/or pruritus during dialysis sessions. Blood samples were taken at the start of dialysis, sera were kept frozen until assay, and in vitro SHR was performed on washed leukocytes at 37 degrees C for 40 minutes. A high (range, 20% to 80%) and reproducible in vitro SHR was observed among 24% of patients. No correlation was found between SHR and the type of dialysis membrane used (copolymer of acrylonitrile-methallyl-sodium sulfonate, cuprophan, and polysulfone). High SHR (i.e., greater than 20%) was observed mainly among patients with detectable antiethylene oxide IgE antibodies (p less than 0.001). High levels of IgE (greater than 300 ng/ml), specific IgE antibodies, and a high in vitro SHR were all observed concomitantly in 26% of the patients with skin flush reactions and/or pruritus, whereas all three of these parameters together were present in only 3% of the symptom-free patients. To our knowledge, this is the first time that a high in vitro SHR has been described among HD patients, and putative correlations with in vivo phenomena are discussed.

Recombinant C5a enhances interleukin 1 and tumor necrosis factor release by lipopolysaccharide-stimulated monocytes and macrophages

Lipopolysaccharide (LPS) is a potent inducer of interleukin 1 (IL 1) synthesis and release, and of tumor necrosis factor (TNF) secretion. Many signals can enhance the LPS-induced production of these cytokines. We have previously observed that addition of low amounts of normal human serum to the culture medium enhances IL 1 production. Among serum factors, anaphylatoxins C3a and C5a and/or their desArg derivatives have been shown to enhance LPS-induced IL 1 and TNF production. However, the capacity of natural anaphylatoxins to induce by themselves the production of cytokines remains a controversial issue. We have investigated the capacity of human recombinant C5a (hrC5a) to induce IL 1 and TNF production. Despite its lack of direct triggering, hrC5a was able to act synergistically with LPS, leading to higher IL 1 and TNF release by human monocytes and mouse peritoneal macrophages. As assessed by the comitogenic assay, hrC5a increased IL 1 release, whereas cell-associated IL 1 activity was not significantly modified. Measurement by enzyme-linked immunosorbent assay of human IL 1 beta led to similar conclusions, whereas measurement of IL 1 alpha by radioimmunoassay indicated, in addition, an increase in intracellular IL 1 alpha.