Adherence of airway neutrophils and inflammatory response are increased in CF airway epithelial cell-neutrophil interactions

Persistent presence of PMN in airways is the hallmark of CF. Our aim was to assess PMN adherence, percentage of apoptotic airway PMN (aPMN), and IL-6 and IL-8 production when aPMN are in contact with airway epithelial cells. Before coculture, freshly isolated CF aPMN have greater spontaneous and TNF-alpha-induced apoptosis compared with blood PMN from the same CF patients and from aPMN of non-CF patients. We then examined cocultures of PMN isolated from CF and non-CF airways with bronchial epithelial cells bearing mutated cftr compared with cftr-corrected bronchial epithelial cells. After 18-h coculture, the number of CF aPMN adhered on cftr-deficient bronchial epithelial cells was 2.3-fold higher compared with the coculture of non-CF aPMN adhered on cftr-corrected bronchial epithelial cells. The percentage of CF apoptotic aPMN (9.5 +/- 0.2%) adhered on cftr-deficient bronchial epithelial cells was similar to the percentage of non-CF apoptotic aPMN adhered on cftr-corrected bronchial epithelial cells (10.3 +/- 0.7%). IL-6 and IL-8 levels were enhanced 6.5- and 2.9-fold, respectively, in coculture of CF aPMN adhered on cftr-deficient bronchial epithelial cells compared with coculture of non-CF aPMN adhered on cftr-corrected bronchial epithelial cells. Moreover, blocking surface adhesion molecules ICAM-1, VCAM-1, and E-selectin on cftr-deficient bronchial epithelial cells with specific MAbs inhibited the adherence of CF aPMN by 64, 51, and 50%, respectively. Our data suggest that in CF patients a high number of nonapoptotic PMN adhered on airway epithelium associated with elevated IL-6 and IL-8 levels may contribute to sustained and exaggerated inflammatory response in CF airways.

Investigation of a potential effect of exogenous interleukin 10 on lipopolysaccharide mediated tolerance to lipopolysaccharide in rabbits

Background

Postoperative immunosuppression is a risk factor for postoperative infection and sepsis. The lipopolysaccharide (LPS) sensitivity of circulating leucocytes is diminished in the postoperative course. A similar state of LPS tolerance can be induced in the experimental setting by injection of low doses of LPS. This tolerance may be mediated by cytokines which are released following LPS injection. In the presence of interleukin (IL) 10 the LPS-induced production of numerous cytokines is diminished in leucocytes. The aim of the study was to investigate the effect of exogenous IL-10 on LPS-induced tolerance to LPS in rabbits.

Methods

Rabbits were injected intravenously with LPS 5 μg kg−1 or human recombinant IL-10 (hrIL-10) 5 μg kg−1 or with sodium chloride or hrIL-10 1 h before LPS. Blood was drawn thereafter repeatedly up to the fifth day and incubated without or with LPS (10 ng ml−1, 1000 ng ml−1) for 20 h. Tumour necrosis factor (TNF) α was assayed in plasma supernatants using the L929 bioassay and hrIL-10 was detected in serum samples by enzyme-linked immunosorbent assay. Rectal temperature was measured at the indicated time points.

Results

Injection of LPS transiently (3 days) caused a biphasic fever and a LPS-tolerant state. IL-10, like LPS, transiently diminished the capacity for TNF-α production. The administration of IL-10 1 h before the injection of LPS neither affected the LPS-induced suppression of TNF-α production, nor modified the duration of tolerance. Likewise, fever curves were no different.

Conclusion

This pilot study shows that, despite IL-10-induced reduction of the capacity for (proinflammatory) cytokine production, LPS tolerance following LPS injection was not altered. Thus systemic cytokine production seems not to be responsible for the induction of fever and LPS tolerance.

Structural and functional analyses of bacterial lipopolysaccharides

Bacterial lipopolysaccharides (LPSs) are powerful immunomodulators in infected hosts, and may cause endotoxic shock. Most of them share a common architecture but vary considerably in structural motifs from one genus, species, and strain to another. Cells of the innate immune response recognize evolutionarily conserved LPS molecular patterns of endotoxins and structural details thereby greatly influencing their response.

Immunodepression in sepsis and SIRS assessed by ex vivo cytokine production is not a generalized phenomenon: a review

Sepsis and non-infectious systemic inflammatory response syndrome (SIRS) are paradoxically associated with an exacerbated production of cytokines, as assessed by their presence in biological fluids, and a diminished ability of circulating leukocytes to produce cytokine upon in vitro activation. In this review, we depict that the observed cellular hyporeactivity is not a global phenomenon and that some signalling pathways are unaltered and allow the cells to respond normally to certain stimuli. Furthermore, we illustrate that during sepsis and SIRS, cells derived from tissues are either fully responsive to ex vivo stimuli or even primed, in contrast to cells derived from hematopoietic compartments (blood, spleen, etc.) which are hyporeactive. In addition to cytokine production, nuclear factor-kappa B (NF-kappa B) status within leukocytes can be used as a useful marker of hypo- or hyper-reactivity. We illustrate that the immune-depression reported in sepsis and SIRS patients, often revealed by a diminished capacity of leukocytes to respond to lipopolysaccharide, is not a generalized phenomenon and that SIRS is associated with a compartmentalized responsiveness which involves either anergic or primed cells.

Mitochondrial membrane potential and apoptosis peripheral blood monocytes in severe human sepsis

Reduced mitochondrial membrane potential (Delta(Psi)m), which is considered as an initial and irreversible step towards apoptosis, as well as cell death regulating proteins, such as Fas, Hsp70, or Bcl-2, may play an important role in sepsis. We studied the relationship between sepsis severity and peripheral blood monocyte Delta(Psi)m, cell death (necrosis and apoptosis), soluble Fas ligand, Hsp70, and Bcl-2 expression over time in 18 patients with sepsis, and compared these data with those of a group of 17 healthy control subjects. All measurements were performed within 3 d of the onset of severe sepsis (T1), then 7 to 10 d later (T2), and finally at hospital discharge (T3). Delta(Psi)m was expressed as the percent monocytes with altered Delta(Psi)m (%Delta(Psi)m). Patients with sepsis had greater %Delta(Psi)m at T1 and T2 but not at T3 (14.6 +/- 2.6% and 15.9 +/- 2%, respectively, versus control 6.6 +/- 0.2%, p < 0.01). Septic patients exhibited greater cell death in their monocytes and had greater Hsp70 expression only at T1. Bcl-2 levels were similar in septic and control subjects. Comparing survivors with non-survivors of sepsis, nonsurvivors had a greater %Delta(Psi)m at T1 (26.4 +/- 5.3% versus 10.1 +/- 2.7%, p < 0.01) and a significant decrease in Bcl-2 expression, whereas no difference was found in Hsp70 levels. These results indicate that mitochondrial dysfunction and subsequent cell death occur in severe sepsis and suggest that %Delta(Psi)m is a marker of severity in human sepsis.

KEYWORDS

mitochondria; apoptosis; sepsis; heat-shock protein 70; proto-oncogene protein c-Bcl-2

Long-term-impaired expression of nuclear factor-kappa B and I kappa B alpha in peripheral blood mononuclear cells of trauma patients

Nuclear factor (NF)-kappa B expression and dimer characteristics were studied in peripheral blood mononuclear cells (PBMCs) of major-trauma patients and healthy controls. Analysis of PBMCs on days 1, 3, 5, and 10 after trauma revealed that expression of both p65p50 heterodimers and p50p50 homodimers was significantly reduced compared with that in controls. In vitro lipopolysaccharide (LPS) stimulation of PBMCs induced NF-kappa B translocation. However, throughout the survey, p65p50 activation remained significantly lower in trauma patients than in controls. After LPS stimulation in vitro, the p65p50/p50p50 ratio was significantly lower in PBMCs from trauma patients than from healthy controls. The ex vivo expression of I kappa B alpha was higher in PBMCs of controls than of trauma patients. LPS did not induce I kappa B expression in PBMCs from trauma patients, but strong induction was obtained with staphylococci, suggesting that this defect is not universal and depends on the nature of the activating signal. Although no direct correlation was found between levels of interleukin-10 or transforming growth factor-beta and NF-kappa B, these immunosuppressive cytokines were significantly elevated in trauma patients by 10 days after admission. The long-term low-basal and LPS-induced nuclear translocation of NF-kappa B recalled long-term immunoparalysis observed in patients with severe inflammatory stress such as trauma.

Pyrogenicity and cytokine-inducing properties of Streptococcus pyogenes superantigens: comparative study of streptococcal mitogenic exotoxin Z and pyrogenic exotoxin A

Streptococcal mitogenic exotoxin Z (SMEZ), a superantigen derived from Streptococcus pyogenes, provoked expansion of human lymphocytes expressing the Vbeta 2, 4, 7 and 8 motifs of T-cell receptor. SMEZ was pyrogenic in rabbits and stimulated the expression of the T-cell activation markers CD69 and cutaneous lymphocyte-associated antigen. A variety of cytokines was released by human mononuclear leukocytes stimulated with SMEZ, which was 10-fold more active than streptococcal pyrogenic exotoxin A. Th2-derived cytokines were elicited only by superantigens and not by streptococcal cells.

Pro- versus anti-inflammatory cytokines: myth or reality

Inflammation is characterized by an interplay between pro- and anti-inflammatory cytokines. Cytokines are commonly classified in one or the other category: interleukin-1 (IL-1), tumor necrosis factor (TNF), gamma-interferon (IFN-gamma), IL-12, IL-18 and granulocyte-macrophage colony stimulating factor are well characterized as pro-inflammatory cytokines whereas IL4, IL-10, IL-13, IFN-alpha and transforming growth factor-beta are recognized as anti-inflammatory cytokines. In this review, we point out that this classification is far too simplistic and we provide numerous examples illustrating that a given cytokine may behave as a pro- as well as an anti-inflammatory cytokine. Indeed, the cytokine amount, the nature of the target cell, the nature of the activating signal, the nature of produced cytokines, the timing, the sequence of cytokine action and even the experimental model are parameters which greatly influence cytokine properties.

Immune mediators in cerebrospinal fluid during cryptococcosis are influenced by meningeal involvement and human immunodeficiency virus serostatus

Pro- and anti-inflammatory mediators (tumor necrosis factor [TNF]-alpha, interleukin [IL]-6, IL-8, IL-10, and soluble TNF receptor II [sTNFR] II) were measured in cerebrospinal fluid (CSF) before treatment (day 0), and after 2 weeks and 3 months of antifungal therapy in 51 human immunodeficiency virus (HIV)-positive and 7 HIV-negative patients with culture-confirmed cryptococcosis. On day 0, all mediator concentrations, except IL-10 in HIV-positive patients, were higher in patients with meningeal, rather than extrameningeal cryptococcosis or in control subjects (P<.05). For meningitis patients, all mediator levels, except sTNFR II, were higher in HIV-negative than HIV-positive patients (P<.05). Day 0 CSF IL-8 levels were higher in HIV-positive patients receiving antiretroviral therapy than in untreated persons (P<.02). Day 0 sTNFR II levels were higher in HIV-positive survivors at 3 months, and elevated levels were sustained in HIV-positive patients with meningitis. Overall, these data support the idea that inflammatory responses are crucial to the eradication of cryptococcal infections in the central nervous system.

NF-kappaB expression in mononuclear cells of patients with sepsis resembles that observed in lipopolysaccharide tolerance

The expression of NF-kappaB was studied in freshly isolated peripheral blood mononuclear cells (PBMC) of patients with severe sepsis and major trauma. The expression of p65p50 heterodimer, the active form of NF-kappaB, was significantly reduced for all patients as compared with control subjects. The p50p50 homodimer, an inhibitory form of NF-kappaB, was reduced in the survivors of sepsis and in patients with trauma. Subsequent in vitro stimulation of PBMC with lipopolysaccharide (LPS) did not induce further NF-kappaB nuclear translocation: the survivors of sepsis and trauma patients showed low expression of both p65p50 and p50p50, whereas nonsurvivors of sepsis showed a predominance of the inactive homodimer and a low p65p50/p50p50 ratio when compared with control subjects. In the later group of patients there was a reverse correlation between plasma IL-10 levels and the p65p50/p50p50 ratio after in vitro LPS stimulation (r = -0.8, p = 0.04). The reduced expression of nuclear NF-kappaB was not due to its inhibition by IkappaBalpha, as very low expression of IkappaBalpha, as well as low levels of p65 and p50 were found in the cytoplasm of PBMC from patients with sepsis and trauma when compared with control subjects. These results demonstrate that upon LPS activation, PBMC of patients with systemic inflammatory response syndrome show patterns of NF-kappaB expression that resemble those reported during LPS tolerance: global down-regulation of NF-kappaB in survivors of sepsis and trauma patients and the presence of large amounts of the inactive homodimer in the nonsurvivors of sepsis.

Immunological surrogate parameters in a prognostic model for multi-organ failure and death

OBJECTIVE

To assess the ability of clinical or biochemical parameters to predict outcome (survival or non-survival; severe or moderate/no complication) using multiple regression analyses.

DESIGN

Prospective, descriptive cohort study with no interventions

SETTING

12 surgical intensive care units of university hospitals and large community hospitals; four medical school research laboratories in eight European countries

PATIENTS

128 surgical patients with major intra-abdominal surgery admitted for at least two days to an intensive care unit

MAIN OUTCOME MEASURES

Prediction of complications or survival based on analysis of clinical (Multiple Organ Dysfunction Score, Multi-Organ-Failure Score, Acute Physiology and Chronic Health Evaluation II scores) and immunological (plasma levels of endotoxin, endotoxin neutralizing capacity, IL-6, IL-8, cell associated IL-8, Fc-receptor polymorphism, soluble CD-14) parameters, with comparison of predicted and actual outcomes.

RESULTS

APACHE II, MODS score, MOF score, platelets, IL-6, IL-8, ENC, cell ass. IL-8 were significantly different between survivors and non-survivors and patients with/without severe complications by univariate analysis. By multivariate analysis only MOF, MODS score, IL-6, platelets, comorbidity predicted complications with a sensitivity of 82% and a specificity of 87%. Multivariate analysis demonstrated that only APACHE II score, plasma IL-8 and complications predicted death (sensitivity 84%; specificity 90%).

CONCLUSION

Immunological surrogate parameters may predict complications and death of surgical ICU patients. The use of several parameters may add to increase sensitivity and specificity in a prognostic model.

Interleukin-1 receptor antagonist production during infectious and noninfectious systemic inflammatory response syndrome

OBJECTIVE

To analyze the levels of circulating and cell-associated forms of interleukin-1 receptor antagonist (IL-1ra) and the spontaneous and the lipopolysaccharide- or streptococcus-induced ex vivo production of IL-1ra by isolated neutrophils.

DESIGN

Cohort study.

SETTING

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

PATIENTS

Septic patients (those with infectious systemic inflammatory response syndrome [SIRS]) and patients undergoing cardiac surgery with cardiopulmonary bypass (noninfectious SIRS).

MEASUREMENTS AND MAIN RESULTS

Both noninfectious and infectious SIRS patients had enhanced levels of plasma IL-1ra. In septic patients, the increased level of IL-1ra associated with circulating leukocytes reflected the higher number of circulating neutrophils, because these cells, as well as peripheral blood mononuclear cells, contained similar levels of cell-associated forms of IL-1ra than those found at homeostasis in healthy controls. The analysis of the in vitro production of IL-1ra by neutrophils showed a decreased capacity of these cells to release the secreted form of IL-1ra on activation in all patients when compared with that capacity in healthy controls. In contrast, the production of the intracellular forms of IL-1ra was not altered in septic patients, but it was diminished in post-cardiopulmonary bypass patients.

CONCLUSIONS

The capacity of releasing IL-1ra by activated neutrophils from infectious or noninfectious SIRS patients was diminished. In contrast, the accumulation of intracellular IL-1ra in septic patients was not modified when compared with that in healthy controls. These ex vivo data illustrate that a different gene regulation of the secreted and intracellular forms of IL-1 ra occurs during a pathologic situation like sepsis.

Administration of endotoxin associated with lipopolysaccharide tolerance protects mice against fungal infection

Lipopolysaccharide (LPS) pretreatment of mice resulted in a significantly enhanced survival after disseminated Cryptococcus neoformans infection. The survival was associated with reduced fungal burden in tissues. LPS-pretreated mice had lower levels of cytokines in blood, spleen, and lungs and higher levels in brain. Pentoxifylline abolished the beneficial effect of LPS pretreatment.

Coupled plasma filtration-adsorption in a rabbit model of endotoxic shock

OBJECTIVE

To test the hypothesis that nonselective adsorption by a hydrophobic resin of cytokines and other proinflammatory mediators could improve 72-hr survival in a rabbit model of endotoxic shock.

DESIGN

Prospective, randomized, controlled animal trial.

SETTING

Animal care facility at a research institution.

SUBJECTS

A total of 109 New Zealand white male rabbits.

INTERVENTIONS

Anesthetized rabbits were cannulated with indwelling femoral arterial and venous lines. Septic shock was induced by a single intravenous injection of Escherichia coli lipopolysaccharide. The dose was experimentally assessed in 40 rabbits receiving 1.0, 0.5, 0.1, and 0.05 mg/kg body weight to determine LD80 at 72 hrs. Extracorporeal circulation consisted of plasma filtration coupled with passage of the plasma filtrate through a hydrophobic sorbent and reinfusion into the venous line. The extracorporeal treatment lasted for 3 hrs. Rabbits injected with endotoxin (0.05 mg/kg) were submitted to plasma filtration with (19 rabbits) or without (20 rabbits) sorbent adsorption. As controls, rabbits injected with vehicle alone were treated with plasma filtration (ten rabbits) or without (ten rabbits) sorbent adsorption. Ten rabbits were monitored under anesthesia to determine basal survival.

MEASUREMENTS AND MAIN RESULTS

Plasma concentrations of endotoxin, bioactive tumor necrosis factor, resin-adsorbed platelet-activating factor, mean arterial pressure, base excess, and white cell count were assessed and a global severity score was established. At 72 hrs, cumulative survival was significantly (p = .0041) improved in septic rabbits treated with coupled plasma filtration-adsorption. Circulating tumor necrosis factor bioactivity remained similar in control and treated rabbits. Biologically significant amounts of platelet activating factor were eluted from the sorbent during the entire treatment time. The severity score inversely correlated with survival (p < .001).

CONCLUSIONS

Coupled plasma filtration-adsorption improved survival in a rabbit model of endotoxic shock. Coupled plasma filtration-adsorption may be an extracorporeal treatment capable of removing structurally different inflammatory mediators associated with sepsis.

Ex vivo T-lymphocyte derived cytokine production in SIRS patients is influenced by experimental procedures

Ex vivo production of interleukin-2 (IL-2), IL-4, IL-5, and IL-10 by peripheral blood mononuclear cells (PBMC) was studied in 13 septic patients with infectious systemic inflammatory response syndrome (SIRS) and 13 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB) (noninfectious SIRS). We have investigated the levels of cytokines after activation by either concanavalin A (ConA), phytohemagglutinin (PHA), or anti-CD3 antibodies. In whole blood assays, ConA-induced IL-10 was significantly reduced in both groups of patients compared with healthy controls. In sepsis patients, IL-2, IL-5, and IL-10 productions by isolated PBMC were diminished on ConA-induced activation but not in response to PHA and anti-CD3; in CPB patients, only anti-CD3-induced IL-10 production was significantly reduced. Our data indicate that subtle modifications of the reactivity of circulating cells occur during infectious and noninfectious SIRS. Production of both Th1 and Th2 cytokines can be down-regulated; however, the nature of the SIRS, of the cell population, and of the activator may influence the observation.

Interleukin 8 production in whole blood assays: Is interleukin 10 responsible for the downregulation observed in sepsis?

Reduced cytokine production in ex vivo cultures has been regularly reported in patients suffering from sepsis syndrome. Using whole blood assays, we have now demonstrated that in sepsis patients, normal production of IL-8 was achieved with the higher concentration of lipopolysaccharide (LPS; 1 microg/ml) and with heat-killed streptococci, whereas the IL-8 production induced by lower LPS concentration (0.1 microg/ml) was significantly reduced as compared to healthy controls. In contrast, in patients undergoing cardiac surgery associated with cardio-pulmonary bypass, a group of patients with inflammation in the absence of infectious insult, none of the studied IL-8 productions were affected. Among the various anti-inflammatory cytokines known to regulate IL-8 production which we tested (i.e. IL-4, IL-10, IL-13, TGF-beta), IL-10 was the most active inhibitory cytokine in whole blood assays performed with blood samples from healthy subjects. However, its activity was not influenced by the amounts of LPS used. In addition, IL-10 also inhibited the heat-killed streptococci-induced IL-8 production and was the only cytokine to inhibit the release of IL-8 when TNF was added to LPS. It is worth noting that IL-13 which also inhibited the heat-killed streptococci-induced IL-8 production, failed to do so when the TNF production was analysed. Together, these data suggest that while circulating IL-10 in septic patients may be responsible for the hyporeactivity of circulating leukocytes, its presence is not sufficient to explain the observed dysregulation which occurs in septic patients.

Cytokine profiles of AIDS patients are similar to those of mice with disseminated Cryptococcus neoformans infection

Cryptococcosis is an hematogenously disseminated meningoencephalitis during which the relationship between the disease severity and the immune response remains unclear. We thus analyzed, by enzyme-linked immunosorbent assay, proinflammatory (tumor necrosis factor alpha [TNF-alpha] and interleukin-6 [IL-6]) and anti-inflammatory (IL-10) cytokine levels in plasma at the time of diagnosis in 51 AIDS patients with culture-proven cryptococcosis. We used a murine model to determine the correlation between cytokine levels and fungal burden in blood and tissues and the kinetics of the immune response and of the formation of cerebral lesions. In AIDS patients, plasma TNF-alpha and IL-10, but not IL-6, levels were significantly higher in the case of fungemia or disseminated infection than in their absence, whereas the presence of meningitis had no influence on these levels. In mice, none of these cytokines were detected within the first day after inoculation. Later on, TNF-alpha and IL-10, but not IL-6, levels in plasma correlated significantly with the fungal burden in the blood and spleen but not the brain. In the brain, cytokine levels were low compared to those in other compartments, and tissue lesions and a degree of infection similar to those observed in humans were seen, further suggesting the relevance of this experimental model. Thus, AIDS patients with cryptococcosis produce an immune response that reflects the dissemination but not the meningeal involvement. This murine model of disseminated cryptococcosis can be used to investigate the pathophysiology of cryptococcosis and new therapeutic approaches.

Enhanced sensitivity of tumor necrosis factor/lymphotoxin-alpha-deficient mice to Cryptococcus neoformans infection despite increased levels of nitrite/nitrate, interferon-gamma, and interleukin-12

The cytokine network and infection severity were characterized during disseminated cryptococcosis in tumor necrosis factor (TNF)- and lymphotoxin (Lt)-alpha-deficient mice. On day 16, the fungus burden was higher and median survival time was reduced, as was polymorphonuclear leukocyte infiltrate in the brains of knockout mice. TNF/Lt-alpha-deficient mice had lower levels of interleukin (IL)-6 in lungs and brains, IL-1beta, and the chemokine KC in brain and spleen and of the chemokine monocyte chemoattractant protein (MCP)-1 in spleen than control animals. In contrast, higher levels of IL-6, IL-10, and MCP-1 in plasma and higher levels of IL-12, interferon (IFN)-gamma, and nitrite/nitrate were found in all compartments of TNF/Lt-alpha-deficient mice. These data confirm that TNF or Lt-alpha is a key cytokine for the anticryptococcal response and demonstrate its major role for the induction of IL-1beta, IL-6, and KC in the brain; however, its presence is not a prerequisite for IL-12, IFN-gamma, and nitrite/nitrate production.

Distinct sputum cytokine profiles in cystic fibrosis and other chronic inflammatory airway disease

The dominant role of inflammation in airways disease progression in cystic fibrosis (CF) is now well established and, based on recent findings, the possibility of an inappropriate inflammatory response in the lung of patients with CF has emerged. In order to characterize this response, the aim of the present work was to evaluate the levels of a number of pro- and anti-inflammatory cytokines in the sputum of CF children and to compare these levels to those observed in the sputum from non-CF children with diffuse bronchiectasis (DB). Three groups of patients were investigated: a group of 25 CF children (mean age: 12.2 yrs), a group of 10 non-CF children with DB (mean age 11.5 yrs), and a group of five healthy young adults (mean age 24 yrs). Elevated concentrations of pro-inflammatory cytokines, tumour necrosis factor (TNF)-alpha, interleukin (IL)-1beta and IL-8 were found in children with CF and in non-CF children with DB, with significantly higher concentrations of IL-1beta in CF children. Analysis of the natural anti-inflammatory cytokine IL-1 receptor antagonist (IL-1ra) and type II TNF soluble receptor (sTNFRII) concentrations showed distinct patterns, with elevated levels of both inhibitors in CF patients, whereas only sTNFRII was found to be increased in non-CF children with DB. IL-10 data indicated low concentrations in the CF group. In all CF children, the concentrations of IL-6 in the airways were extremely low, independent of the clinical, bacteriological or functional status. By contrast, significantly increased IL-6 levels were found in non-CF children with DB. These results document distinct cytokine profiles in cystic fibrosis patients and noncystic fibrosis patients. They also suggest that impairment of interleukin-6 expression may represent an important component of the excessive inflammatory response observed in cystic fibrosis.

Paradoxical priming effects of IL-10 on cytokine production

IL-10 is a well-known immunosuppressive and/or anti-inflammatory cytokine. However, we report in vitro experimental studies in which IL-10 primed leukocytes and led to an enhanced production of tumor necrosis factor (TNF) upon further stimulation by lipopolysaccharide (LPS). Monocytes and peripheral blood mononuclear cells (PBMC) prepared from whole blood maintained for 20 h at 37 degrees C in the presence of recombinant human IL-10 had an enhanced capacity to produce TNF in response to LPS. In addition to TNF, LPS-induced IL-6 and spontaneous IL-1ra production were also enhanced. When isolated PBMC were first cultured for 20 h in the presence of IL-10 on Teflon to prevent adherence, washed to remove IL-10 and then further cultured in plastic dishes for an additional 20 h in the presence of LPS or IL-1beta, an enhanced release of TNF was observed. This was not the case when PBMC were pre-cultured in plastic multidishes in the presence of IL-10. TNF mRNA expression induced by LPS was decreased when the pre-treatment of PBMC with IL-10 was performed on plastic, whereas this was not the case when cells were pre-cultured with IL-10 on Teflon. Furthermore, NFkappaB translocation following LPS activation was higher after IL-10 pre-treatment on Teflon than on plastic. Interestingly, an enhanced frequency of CD16 and CD68(+) cells among the CD14(+) cells was observed in the presence of IL-10, independently of the pre-culture conditions of the PBMC. Altogether, these results indicate that the IL-10-induced up-regulation of cytokine production depends on the prevention of monocyte adherence by red cells in the whole blood assays or by cultures of PBMC on Teflon. In contrast, the adherence parameter has no effect on the IL-10-induced modulation of some monocyte surface markers.

Removal of cytokines and activated complement components in an experimental model of continuous plasma filtration coupled with sorbent adsorption

BACKGROUND

Sepsis is associated with enhanced cytokine production. Here, we examined the in vitro removal of plasma cytokines during continuous plasmafiltration coupled with sorbent adsorption.

METHODS

Proinflammatory (tumour necrosis factor-alpha, interleukins-1, -8) and anti-inflammatory (interleukin 1 receptor antagonist, soluble tumour necrosis factor receptor type I and II) cytokines in whole blood spiked with Escherichia coli endotoxin were determined during 2-h recirculation in the ultrafiltrate (condition A), plasma filtrate (condition B), before and after different sorbents (of the Amberlite-, Amberchrome- Ambersorb -type and charcoal). We studied the maximal adsorbing capacity, the 1% leakage test for cytokines and C3a des Arg and the adsorption of complement-dependent leukocyte chemiluminescence. Plasma proteins eluted from the resins were examined by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting with an anti-human alpha2-macroglobulin.

RESULTS

In condition B, we observed a 40- and 121-fold % increase (vs condition A) in the removed mass and clearance of tumour necrosis factor-alpha. For all other cytokines, the removed mass and the clearance increased from 2.3- up to 6-fold. The Amberchrome but not the Amberlite or Ambersorb resins could remove the highest amount of cytokines and could reduce complement-dependent chemiluminescence. Two protein bands of approximately 400,000 D and 200,000 D were eluted only from Amberchrome resins and immunoprecipitated by anti-human alpha2-macroglobulin and anti-human C3c antibodies, respectively.

CONCLUSIONS

These studies suggest an efficient removal of cytokines in continuous plasmafiltration with sorbent adsorption. The binding of alpha2-macroglobulin, a carrier of cytokines in plasma, might be a additional mechanism in the removal of cytokines from plasma.

Reduced ex vivo interleukin-8 production by neutrophils in septic and nonseptic systemic inflammatory response syndrome

Ex vivo cytokine production by circulating lymphocytes and monocytes is reduced in patients with infectious or noninfectious systemic inflammatory response syndrome. Very few studies have addressed the reactivity of polymorphonuclear cells (PMN). To analyze further the relative contribution of systemic inflammatory response syndrome alone or in combination with infection we studied the interleukin-8 (IL-8) production by PMN isolated from patients who had undergone cardiac surgery with cardiopulmonary bypass (CPB) and patients with sepsis. Cells were activated with either lipopolysaccharide (LPS) or heat-killed streptococci. Compared with healthy controls, the release of IL-8 by PMN in both groups of patients was significantly reduced whether activated by LPS, independently of its concentration and origin, or by heat-killed streptococci. These observations suggest that stressful conditions related to inflammation, independently of infection, rapidly dampened the reactivity of circulating PMN. We investigated whether the observed diminished reactivity of PMN might reflect an endotoxin tolerance phenomenon. Our in vitro experiments with PMN from healthy controls indicated that PMN could not be rendered tolerant stricto sensu. However, our data suggested that LPS-induced mediators such as IL-10 may be responsible for the observed anergy in patients.

Continuous plasma filtration coupled with sorbents

An in vitro system composed of a plasma separation membrane coupled with natural (charcoal) or synthetic (Amberlite, Amberchrome) types of sorbents was evaluated for the simultaneous removal of proinflammatory cytokines (TNF-alpha, IL-1 beta and IL-8) and cytokine antagonists [interleukin (IL)-1 receptor antagonist (IL-1Ra), soluble tumor necrosis factor-alpha (TNF-alpha) receptor I and II (sTNFR I and II)] in whole blood spiked with bacterial lipopolysaccharide (LPS). These studies showed that plasma filtration rather than ultrafiltration significantly increased the clearance of all cytokines, particularly TNF-alpha, and the synthetic (Amberlite-type of resin) but not natural (uncoated charcoal) membrane could extensively absorb almost 100% of plasma filtered IL-Ra, IL-1 beta and IL-8, but only 40% of TNF-alpha. Other synthetic (Amberchrome) membranes could also effectively (80%) remove TNF-alpha. In the complex scenario of sepsis, the simultaneous removal of excess proinflammatory and/or immunomodulatory mediators may play a role in reducing the hemodynamic alterations, thus resulting in enhanced patient survival. Whether this occurs in the human setting awaits the results of an ongoing clinical investigation.

Lipopolysaccharide-induced cytokine cascade and lethality in LT alpha/TNF alpha-deficient mice

BACKGROUND

Tumor necrosis factor alpha (TNF-alpha) is often considered the main proinflammatory cytokine induced by lipopolysaccharide (LPS) and consequently the critical mediator of the lethality associated with septic shock.

MATERIALS AND METHODS

We used mice carrying a deletion of both the lymphotoxin alpha (LT-alpha) and TNF-alpha genes to assess the role of TNF in the cytokine cascade and lethality induced by LPS.

RESULTS

Initial production of IL-1 alpha, IL-1 beta, IL-6, and IL-10 is comparable in wild-type and mutant mice. However, at later times, expression of IL-1 alpha, IL-1 beta, and IL-10 is prolonged, whereas that of IL-6 decreases in mutant mice. Expression of IFN-gamma is almost completely abrogated in mutants, which is in agreement with a more significant alteration of the late phase of the cytokine cascade. We measured similar LD50 (600 micrograms) for the intravenous injection of LPS in mice of the three genotypes (+/+, +/-, -/-), demonstrating that the absence of TNF does not confer long-term protection from lethality. However, death occurred much more slowly in mutant mice, who were protected more efficiently from death by CNI 1493, an inhibitor of proinflammatory cytokine production, than were wild-type mice.

DISCUSSION

Thus, while TNF-alpha is not required for the induction of these cytokines by LPS, it modulates the kinetics of their expression. The lethality studies simultaneously confirm a role for TNF as a mediator of early lethality and establish that, in the absence of these cytokines, other mediators take over, resulting in the absence of long-term protection from LPS toxicity.

Variations of cytokine levels and production in CAPD patients

Macrophages, predominant cells in dialysates of patients on CAPD without peritonitis, produce a wide variety of substances including cytokines. The aim of this study was to examine the cytokine production in five uninfected patients. This work investigated the presence in dialysates of interleukin-1beta, interleukin-6, interleukin-8, tumor necrosis factor alpha and the ability of peritoneal macrophages to produce these cytokines. These results were compared with values obtained from control group in non-uremic conditions (peritoneal lavage with isotonic saline or dialysis fluid). All cytokines were detectable in dialysates. Interindividual variations in cytokine concentration in dialysates were wider than variations of production of cytokines ex vivo by stimulated and unstimulated cells. In control group, dialysis fluid inhibited the cytokine production and with isotonic saline, cells produced less cytokines than dialysis patients' cells. The highest levels of interleukin-1 and tumor necrosis factor in dialysates and the highest capacity to respond to LPS were observed in patients having the shortest duration of dialysis. The variability observed did not seem to be due to cells themselves but to their environment.

Trophic effect of human pericardial fluid on adult cardiac myocytes. Differential role of fibroblast growth factor-2 and factors related to ventricular hypertrophy

Pericardial fluid (PF) may contain myocardial growth factors that exert paracrine actions on cardiac myocytes. The aims of this study were (1) to investigate the effects of human PF and serum, collected from patients undergoing cardiac surgery, on the growth of cultured adult rat cardiac myocytes and (2) to relate the growth activity of both fluids to the adaptive changes in overloaded human hearts. Both PF and serum increased the rate of protein synthesis, measured by [14C]phenylalanine incorporation in adult rat cardiomyocytes (PF, +71.9 +/- 8.2% [n = 17]; serum, +14.9 +/- 6.5% [n = 13]; both P < .01 versus control medium). The effects of both PF and serum on cardiomyocyte growth correlated positively with the respective left ventricular (LV) mass. However, the magnitude of change with PF was 3-fold greater than with serum (P < .01). These trophic effects of PF were mimicked by exogenous basic fibroblast growth factor (FGF2) and inhibited by anti-FGF2 antibodies and transforming growth factor-beta (TGF-beta), suggesting a relationship to FGF2. In addition, FGF2 concentration in PF was 20 times greater than in serum. On the other hand, the LV mass-dependent trophic effect, present in both fluids, was independent of FGF2 concentration or other factors, such as angiotensin II, atrial natriuretic factor, and TGF-beta. These data suggest that FGF2 in human PF is a major determining factor in normal myocyte growth, whereas unidentified LV mass-dependent factor(s), present in both PF and serum, participates in the development of ventricular hypertrophy.

Cytokines and soluble cytokine receptors in pleural effusions from septic and nonseptic patients

The balance between proinflammatory cytokines and their inhibitors has rarely been investigated in pleural effusions of nonmalignant or noninfectious origin. To evaluate the impact of a lung and/or intrathoracic infection in such a circumstance, we compared the levels of proinflammatory cytokines (interleukin-8 [IL-8]); tumor necrosis factor-alpha (TNF-alpha); the cytokine antagonists and inhibitors (IL-1 receptor antagonist [IL-1ra]) and soluble TNF receptors Types I and II (sTNFRI, sTNFRII); and antiinflammatory cytokines (transforming growth factor-beta [TGF-beta]) in pleural effusion and plasma from septic (n = 15) and nonseptic (n = 9) patients. In addition, we analyzed the levels of IL-6 and its soluble receptor (sIL-6R). Bronchoalveolar lavage fluids (BALFs) were also studied in a few septic patients. High and nonsignificantly different levels of cytokines and inhibitors were detected in both groups of patients. The levels of IL-6 and sTNFRI and sTNFRII in pleural effusion were higher than in plasma, whereas the levels of IL-1ra and sIL-6R were higher in plasma. The levels of sIL-6R influenced the bioactivity of IL-6. There was no correlation between the levels of cytokines in plasma and in pleural effusion. In contrast, a significant correlation was observed for the soluble receptors sIL-6R (r = 0.67, p < 0.001), sTNFRI (r = 0.76, p < 0.001) and sTNFRII (r = 0.66, p = 0.001). Furthermore, a high correlation was found between the levels of both forms of sTNFRs in plasma (r = 0.95, p < 0.001) and in pleural effusion (r = 0.79, p < 0.001). In addition, a correlation was observed between the levels of TGF-beta in pleural effusion and in BALF. The highest levels of some markers in plasma and of others in pleura argue in favor of both a systemic and a compartmentalized response, independently of the presence of infection. Because cytokines can be trapped by the surrounding cells in their environment, measurable levels of cytokines in biologic fluids represent the "tip of the iceberg," which is not the case for soluble receptors. The correlations of these latter markers between plasma and pleura strongly suggest that exchanges between both compartments can occur in both directions.

Mice heterozygous for a deletion of the tumor necrosis factor-alpha and lymphotoxin-alpha genes: biological importance of a nonlinear response of tumor necrosis factor-alpha to gene dosage

The tumor necrosis factors (TNF-alpha and lymphotoxin, or LT-alpha) are important mediators of the immune and inflammatory responses, and it has been proposed that a positive feedback loop could boost the expression of the TNF to sufficiently high levels to fend off infections. To investigate this phenomenon and its biological consequences, we have generated LT-alpha/TNF-alpha knockout mice and compared mice having one or two functional LT-alpha/TNF-alpha alleles. In response to lipopolysaccharide (LPS) stimulation, TNF-alpha levels in the circulation or in the supernatant of macrophage cultures were 20- to 100-fold lower in heterozygous samples than in their wild-type counterparts. This differential increased with the intensity of stimulation and throughout the response, supporting the involvement of a positive feedback loop. Moreover, the heterozygous mice had an increased bacterial load following Listeria monocytogenes infection and exhibited a bimodal response to the association of D-galactosamine and LPS which was similar to that of wild-type mice at low doses of LPS and more like that of homozygous mutants at high doses. These results therefore establish the biological importance of the nonlinear response of TNF-alpha levels to gene dosage, and these mice provide a unique tool to study how the propensity to produce TNF can determine the immunological fitness of individuals.

Presence of high levels of leukocyte-associated interleukin-8 upon cell activation and in patients with sepsis syndrome

In inflammatory and infectious diseases, the presence of circulating cytokines in plasma strongly suggests, following their exacerbated production, that saturation of specific binding sites has occurred or that an equilibrium between receptor-bound and free cytokines has been reached. In this report, we demonstrate that in addition to circulating interleukin-8 (IL-8), high levels of cell-associated IL-8 were detected in blood samples from patients with sepsis syndrome. The following analysis will reveal that in addition to erythrocytes, which have been dubbed a "sink" for IL-8, peripheral blood mononuclear cells (PBMC) and polymorphonuclear cells (PMN) contributed to the detection of cell-associated IL-8. On a per cell basis, 2,000 to 7,000 times the amount of IL-8 was found associated with PMN than with erythrocytes. In addition, circulating cells may well be the source of the leukocyte-associated form of IL-8. Similarly, in vitro experiments, such as whole-blood stimulation assays or the addition of exogenous IL-8 in blood samples, demonstrated that a large proportion of the IL-8 was associated with leukocytes. This suggests that the trapping of free cytokines onto the cell surface and the internalization of the IL-8 bound to its receptor, occurring both in vitro and in vivo, allows the detection of this cell-associated form. This analysis of cell-associated cytokines was extended to IL-1ra, another component of the inflammatory response, which, in contrast to IL-8, has been demonstrated to exist as an intracellular form. Indeed, cell-associated IL-1ra was also detected in septic patients. The measurement of cell-associated proinflammatory and anti-inflammatory cytokines in patients is clearly a more reliable reflection of their production than is the simple measurement in plasma and may provide useful indication to further understand the inflammatory process.

Human pro- and anti-inflammatory cytokine patterns induced by Streptococcus pyogenes erythrogenic (pyrogenic) exotoxin A and C superantigens

The superantigenic streptococcal erythrogenic toxins A and C (ETA/SPEA and ETC/SPEC) elicit the production by human peripheral blood mononuclear cells of substantial amounts of Th1-derived cytokines (interleukin-2 [IL-2] and gamma interferon) as well as anti-inflammatory cytokines (IL-10 and IL-1 receptor antagonist). In contrast, very low levels of IL-4 and no alpha interferon were induced. The production of these cytokines after stimulation with Streptococcus pyogenes heat-killed bacteria and lipopolysaccharide from gram negative bacteria differed qualitatively and quantitatively from that elicited by the superantigens.

IL-10 and IL-4 synergize with TNF-alpha to induce IL-1ra production by human neutrophils

The anti-inflammatory properties of IL-4, IL-10, IL-13 and TGF-beta are associated with their ability to repress the production of pro-inflammatory cytokines and to favour the release of interleukin-1 receptor antagonist (IL-1ra). Here, we investigate their actions on activated human polymorphonuclear cells (PMN). IL-4 and TGF-beta were able to increase the production of IL-1ra, however only IL-4 were able to further increase IL-1ra production in the presence of LPS. When IL-1ra production by PMN was induced by tumour necrosis factor-alpha (TNF-alpha), IL-10 and IL-4 both amplified its release and its presence as a cell-associated form. In conclusion, IL-10 which was unable to induce IL-1ra by itself or to amplify the LPS-induced production by PMN, was able to increase its release when TNF-alpha, is the triggering signal. IL-4 was active in the different combinations tested; IL-13 and TGF-beta did not further modulate LPS- and TNF-alpha-induced IL-1ra production by PMN.

Variable estimates of cytokine levels produced by commercial ELISA kits: results using international cytokine standards

Commercially available ELISA kits now make it possible to measure cytokines in biological samples and cell culture supernatants. We have compared the levels of IL-1 beta, IL-6, IL-8 and TNF-alpha in various pathological plasma and synovial fluids, and in supernatants of human monocytes activated by lipopolysaccharide (LPS). Measurements were performed using ELISA kits from different companies. A wide variation in values was obtained when measurements were deduced from the standard curves formed with the standard provided by the manufacturers. We also performed calibration curves for all ELISA kits, using the international standards provided by the NIBSC (UK). The coefficients of variation were then significantly improved for IL-6 and IL-8 measurements but not for IL-1 beta and TNF alpha assays. However, despite this attempt to obtain uniform measurements, none of the kits gave similar values for individual samples. These results suggest that the nature of the different pairs of monoclonal antibodies employed in each ELISA does not permit comparable recognition of cytokines in samples. Further work with the various kits is required to establish whether (i) denaturation of the recognized epitope within the natural cytokine, (ii) fragmentation of the cytokine following enzymatic cleavage, (iii) depolymerization, (iv) binding of cytokines to undefined ligands, (v) variable glycosylation of the natural cytokines (vi) recognition of precursor forms, interferes with the measurements.

Monoclonal immunoglobulin A antibody directed against serotype-specific epitope of Shigella flexneri lipopolysaccharide protects against murine experimental shigellosis

To determine the role of humoral mucosal immune response in protection against shigellosis, we have obtained a monoclonal dimeric immunoglobulin A (IgA) antibody specific for Shigella flexneri serotype 5a lipopolysaccharide (mIgA) and used a murine pulmonary infection model that mimics the lesions occurring in natural intestinal infection. Adult BALB/c mice challenged with 10(7) S. flexneri organisms developed a rapid inflammatory response characterized by polymorphonuclear cell infiltration around and within the bronchi and strong systemic interleukin 6 response. Implantation of hybridoma cells in the back of mice, resulting in the development of a myeloma tumor producing mIgA in the serum and subsequently secretory mIgA in local secretions, or direct intranasal administration of these antibodies, protected the animals against subsequent intranasal challenge with S. flexneri serotype 5a. Absence of histopathological lesion and significant decrease in bacterial load of the lungs and of systemic interleukin 6 response were the three major criteria of protection. This protection was shown to be serotype-specific and dependent on local concentration of mIgA. These data demonstrate that mucosal antibodies directed against a single polysaccharidic surface epitope of Shigella can protect against the disease.

Role of interleukin-1 in the pathogenesis of experimental shigellosis

The effect of human recombinant interleukin-1 receptor antagonist on intestinal inflammation, tissue destruction, and bacterial invasion during experimental shigellosis caused by Shigella flexneri was studied in the rabbit-ligated loop infection model. Intravenous infusion of the inhibitor at a dose of 2 mg/kg per h, was initiated 30 min before intestinal loops were ligated and infected, and continued during the 8-h period of infection. The animals treated with IL-1 receptor antagonist showed a striking decrease in inflammation, destruction, and bacterial invasion of their tissues, both at the level of the villous intestine and Peyer's patches. This is conclusive evidence that interleukin-1 plays a critical role in the pathogenesis of shigellosis. This proinflammatory cytokine is here proposed as a major trigger of the inflammatory reaction which is characteristic of this invasive disease of the intestine, due to the particular interaction existing between S. flexneri and macrophages.

The nonspecific nature of endotoxin tolerance

Re-exposure of organisms or cells to endotoxin after a previous challenge is not accompanied by the profound metabolic changes that are induced by the first encounter with endotoxin. Endotoxin tolerance is not specific to the action of lipopolysaccharide, and crossreactivity with other exogenous stimuli occurs. Various cytokines can mimic the effects of endotoxin in vivo and/or in vitro.

Selective induction of interleukin-1 receptor antagonist and interleukin-8 in human monocytes by normal polyspecific IgG (intravenous immunoglobulin)

We have investigated the effects of intravenous immunoglobulin (IVIg), a therapeutic preparation of normal human polyspecific IgG, on the synthesis and release of cytokines by peripheral blood monocytes. IVIg was found to selectively induce gene transcription and secretion of interleukin-1 receptor antagonist (IL-1ra) and IL-8 in cultures of normal human monocytes. The addition of IVIg to cultures of purified monocytes induced a dose-dependent secretion of IL-1ra and IL-8 without stimulating the production of IL-1 alpha, IL-1 beta, tumor necrosis factor-alpha or IL-6. The effects of IVIg required both the Fc and F(ab')2 portions of IgG. IVIg-induced production of IL-8 by monocytes was enhanced by lipopolysaccharide (LPS), although LPS inhibited the secretion of IL-1ra, suggesting that IVIg and LPS stimulate distinct intracellular pathways in monocytes. Induction of IL-1ra and IL-8 by IVIg was enhanced in the presence of autologous T lymphocytes. Our observations document the selectivity of the effects of IVIg on the synthesis of cytokines and cytokine antagonists by human monocytes. Induction of IL-1ra and IL-8 by IVIg may contribute to the anti-inflammatory effects of immunoglobulin therapy in patients with autoimmune and systemic inflammatory disorders.

[Cytokines in inflammation]

Numerous cytokines are present within inflammatory foci. Interleukin-1 (IL-1) and tumour necrosis factor (TNF) play a major role in coordinating mechanisms which command inflammation. Upon their action, many different cells produce lipidic mediators, proteolytic enzymes, and free radicals, all directly responsible for the noxious effects observed. IL-1 and TNF exert cytotoxic effects on vascular endothelium, cartilage, bone and muscle. Such cytokines as interferon-gamma, IL-3 or granulocyte-macrophage colony stimulating factor amplify the inflammatory response by increasing the production of IL-1 and TNF. The latest trigger the release of chemokines such as IL-8 and macrophage chemoattractant protein-1, the chemotactic activity of which participates in the recruitment of leukocytes within the foci of inflammation. IL-6, abounds in inflammatory processes and induces the production by hepatocytes of acute phase proteins. The same applies to IL-1, TNF, IL-11, the leucocyte inhibitory factor, and the transforming growth factor-beta. The later also processes a number of anti-inflammatory activities and, like IL-4, IL-10 and IL-13, can inhibit IL-1 and TNF production. Such property has also been mentioned for interferon-alpha. These anti-inflammatory cytokines can also counteract some of the IL-1 and TNF activities such as those reported during the coagulation process. Furthermore, these anti-inflammatory cytokines can induce the production of the IL-1 receptor antagonist which prevents the activities initiated by IL-1. Soluble TNF receptors, released during inflammation, are the direct inhibitors for TNF. Glucocorticoids, produced following a cascade of events initiated by IL-1, TNF and IL-6, involving the neuroendocrine axis, also inhibit proinflammatory cytokine productions. The concept of "cytokine network" therefore, perfectly illustrates the participation of these mediators in inflammation mechanisms.

Synthetic peptides that mimic the binding site of horseshoe crab antilipopolysaccharide factor

Tachypleus antilipopolysaccharide (LPS) factor (TALF) is a protein of 102 amino acids in the lysate of amebocytes of Tachypleus tridentatus that binds bacterial LPS with high affinity and blocks its biologic activity in numerous assays. To elucidate the minimal sequences that bind LPS, overlapping synthetic peptides based on the sequence of TALF were assessed for the ability to bind and neutralize LPS. TALF41-53 was the minimal sequence that bound LPS, as assessed by a slot blot capture assay. TALF29-59 bound LPS with the highest potency. TALF29-59 decreased LPS-induced coagulation of limulus amebocyte lysate, induction of cytokines from human monocytes, and LPS-induced lethality in sensitized mice. Synthetic peptides based on TALF or other LPS-binding proteins may be useful for the design of drugs for treatment of endotoxemia.

Comparative study of cytokine release by human peripheral blood mononuclear cells stimulated with Streptococcus pyogenes superantigenic erythrogenic toxins, heat-killed streptococci, and lipopolysaccharide

The differences between toxic or septic shocks in humans during infections by streptococci and gram-negative bacteria remain to be fully characterized. For this purpose, a quantitative study of the cytokine-inducing capacity of Streptococcus pyogenes erythrogenic (pyrogenic) exotoxins (ETs) A and C, heat-killed S. pyogenes bacteria, and Neisseria meningitidis endotoxin (lipopolysaccharide [LPS]) on human peripheral blood mononuclear cells (PBMC) and monocytes has been undertaken. The levels of interleukin-1 alpha (IL-1 alpha), IL-1 beta, IL-6, IL-8, tumor necrosis factor alpha (TNF-alpha), and TNF-beta induced by these bacterial products and bacteria were determined by using cell supernatants. The capacity of ETs to elicit the monocyte-derived cytokines IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha was found to depend on the presence of T lymphocytes, because of the failure of purified monocytes to produce significant amounts of these cytokines in response to ETs. PMBC elicited large amounts of these cytokines, as well as IL-8 and TNF-beta, with an optimal release after 48 to 96 h. The most abundant cytokine produced in response to ETA was IL-8. In contrast to the superantigens ETA and ETC, LPS and heat-killed streptococci stimulated the production of significant amounts of IL-1 alpha, IL-1 beta, IL-6, and TNF-alpha, with optimal production after 24 to 48 h in monocytes, indicating no significant involvement of T cells in the process. ETs, but neither LPS nor streptococci, were potent inducers of TNF-beta in PBMC. This study outlines the differences in the pathophysiological features of shock evoked by endotoxins and superantigens during infection by gram-negative bacteria and group A streptococci, respectively. The production of TNF-alpha was a common pathway for LPS, streptococcal cells, and ETs, although cell requirements and kinetics of cytokine release were different.

Acute inflammation causes epithelial invasion and mucosal destruction in experimental shigellosis

The gram-negative pathogen Shigella flexneri causes bacillary dysentery, an invasive disease of the human colonic mucosa. A major characteristic of the infectious process is the occurrence of an acute inflammatory reaction of mucosal tissues which is generally consequence of primary invasion and destruction of colonic epithelial cells by the pathogen. Confirming in vitro demonstration that S. flexneri is unable to invade the apical pole of colonic cells and that polymorphonuclear (PMN) cells may assist them in reaching the basal side of epithelial cells where they can invade, we have provided here in vivo evidence that S. flexneri enters the epithelial barrier essentially through the dome of lymphoid follicles at the early stage of infection and that subsequent invasion and destruction of the epithelium is primarily due to immigration of leukocytes, particularly PMN that destroy cohesion of the epithelial barrier. These conclusions are based on experiments carried out in infected rabbit ligated intestinal loops, with some animals treated by an anti-CD18 monoclonal antibody that blocked immigration of leukocytes into infected tissues.

Interleukin 1 is released by murine macrophages during apoptosis induced by Shigella flexneri

Peritoneal macrophages undergoing apoptosis induced by Shigella flexneri infection release the inflammatory cytokine interleukin 1 (IL-1), but not IL-6 or tumor necrosis factor alpha (TNF alpha). Wild type shigella causes a very fast and significant release of IL-1 from prestimulated peritoneal macrophages, before the cell's integrity is compromised. Both IL-1 alpha and IL-1 beta are released, IL-1 beta in its mature processed form. IL-1 is released from presynthesized cytoplasmic pools. These results demonstrate that bacteria-induced apoptosis of macrophages may play an active role in vivo by releasing IL-1, which in turn mediates an early inflammatory response in epithelial tissues.