Dynamics of blood cytokine concentrations in patients with bacteremic infections

The granulocyte colony-stimulating factor produced during Streptococcus suis infection controls neutrophil recruitment in the blood without affecting bacterial clearance

Streptococcus suis causes diseases in pigs and has emerged as a zoonotic agent. When infected, the host develops an exacerbated inflammation that can lead to septic shock and meningitis. Although neutrophils greatly infiltrate the lesions, their dynamics during S. suis infection remain poorly described. Moreover, very few studies reported on the production and role of a key factor in the regulation of neutrophils: the colony-stimulating granulocyte factor (G-CSF). In this study, we characterized the G-CSF-neutrophil axis in the pathogenesis of S. suis induced disease. Using a mouse model of S. suis infection, we first evaluated the recruitment of neutrophils and their activation profile by flow cytometry. We found that infection provokes a massive neutrophil recruitment from the bone marrow to the blood and spleen. In both compartments, neutrophils displayed multiple activation markers. In parallel, we observed high systemic levels of G-CSF, with a peak of production coinciding with that of neutrophil recruitment. We then neutralized the effects of G-CSF and highlighted its role in the release of neutrophils from the bone marrow to the blood. However, it did not affect bacteremia nor the cytokine storm induced by S. suis. In conclusion, systemic G-CSF induces the release of neutrophils from the bone marrow to the blood, but its role in inflammation or bacterial clearance seems to be compensated by unknown factors. A better understanding of the role of neutrophils and inflammatory mediators could lead to better strategies for controlling the infection caused by S. suis.

Down-regulation of TNF-α via macrophage-targeted RNAi system for the treatment of acute inflammatory sepsis

Sepsis is a systemic inflammatory response syndrome caused by bacterial infection. The sepsis therapy has involved prescription of adequate antibiotics, requiring several days to determine the proper type without reducing the inflammatory response. Thus, it is necessary to rapidly decrease fundamental inflammation, which can induce serious organ damage. In the inflammatory mechanism, tumor necrosis factor-alpha (TNF-α) produced by macrophages has an important role in infiltration of macrophages into infected sites and as a trigger for secretion of pro-inflammatory cytokines. However, commercialized TNF-α antibody medicines have limits such as fibrosis, cytokine storms, and high production costs. There is a growing need for anti-inflammatory sepsis treatment free from side effects. For this reason, TNF-α converting enzyme (TACE) could be an innovative target to break the positive feedback loop of inflammatory mediators (TNF-α) since it converts the inactive TNF-α membrane bound form to the activated soluble form in macrophages. A non-viral gene delivery system was developed in this study to deliver siRNA into inflammation-mediated macrophages without toxicity. The peptide-based gene carrier created by conjugating positively-charged nine arginine (9R) and the TKPR (Thr-Lys-Pro-Arg) sequence from the Fc region of Immunoglobulin G (IgG) specifically binds to the neuropilin-1 (NRP-1) receptor on the macrophage surface. Our results demonstrated that siTACE/TKPR-9R complexes were internalized in macrophages and successfully down-regulated TACE mRNA level. Finally, RNA interference with cell-targeted peptide carriers indicates a fundamental therapy for acute inflammatory sepsis free of off-target effects.

Bacterial and fungal infections in acute-on-chronic liver failure: prevalence, characteristics and impact on prognosis

Bacterial infection is a frequent trigger of acute-on-chronic liver failure (ACLF), syndrome that could also increase the risk of infection. This investigation evaluated prevalence and characteristics of bacterial and fungal infections causing and complicating ACLF, predictors of follow-up bacterial infections and impact of bacterial infections on survival.

PATIENTS

407 patients with ACLF and 235 patients with acute decompensation (AD).

RESULTS

152 patients (37%) presented bacterial infections at ACLF diagnosis; 46%(n=117) of the remaining 255 patients with ACLF developed bacterial infections during follow-up (4 weeks). The corresponding figures in patients with AD were 25% and 18% (p<0.001). Severe infections (spontaneous bacterial peritonitis, pneumonia, severe sepsis/shock, nosocomial infections and infections caused by multiresistant organisms) were more prevalent in patients with ACLF. Patients with ACLF and bacterial infections (either at diagnosis or during follow-up) showed higher grade of systemic inflammation at diagnosis of the syndrome, worse clinical course (ACLF 2-3 at final assessment: 47% vs 26%; p<0.001) and lower 90-day probability of survival (49% vs 72.5%;p<0.001) than patients with ACLF without infection. Bacterial infections were independently associated with mortality in patients with ACLF-1 and ACLF-2. Fungal infections developed in 9 patients with ACLF (2%) and in none with AD, occurred mainly after ACLF diagnosis (78%) and had high 90-day mortality (71%).

CONCLUSION

Bacterial infections are extremely frequent in ACLF. They are severe and associated with intense systemic inflammation, poor clinical course and high mortality. Patients with ACLF are highly predisposed to develop bacterial infections within a short follow-up period and could benefit from prophylactic strategies.

Mathematical modeling of postcoinfection with influenza A virus and Streptococcus pneumoniae, with implications for pneumonia and COPD-risk assessment

Background

The interaction between influenza and pneumococcus is important for understanding how coinfection may exacerbate pneumonia. Secondary pneumococcal pneumonia associated with influenza infection is more likely to increase respiratory morbidity and mortality. This study aimed to assess exacerbated inflammatory effects posed by secondary pneumococcal pneumonia, given prior influenza infection.

Materials and methods

A well-derived mathematical within-host dynamic model of coinfection with influenza A virus and Streptococcus pneumoniae (SP) integrated with dose–response relationships composed of previously published mouse experimental data and clinical studies was implemented to study potentially exacerbated inflammatory responses in pneumonia based on a probabilistic approach.

Results

We found that TNFα is likely to be the most sensitive biomarker reflecting inflammatory response during coinfection among three explored cytokines. We showed that the worst inflammatory effects would occur at day 7 SP coinfection, with risk probability of 50% (likely) to develop severe inflammatory responses. Our model also showed that the day of secondary SP infection had much more impact on the severity of inflammatory responses in pneumonia compared to the effects caused by initial virus titers and bacteria loads.

Conclusion

People and health care workers should be wary of secondary SP infection on day 7 post-influenza infection for prompt and proper control-measure implementation. Our quantitative risk-assessment framework can provide new insights into improvements in respiratory health especially, predominantly due to chronic obstructive pulmonary disease (COPD).

Systemic inflammation in decompensated cirrhosis: Characterization and role in acute-on-chronic liver failure

Acute-on-chronic liver failure (ACLF) in cirrhosis is characterized by acute decompensation (AD), organ failure(s), and high short-term mortality. Recently, we have proposed (systemic inflammation [SI] hypothesis) that ACLF is the expression of an acute exacerbation of the SI already present in decompensated cirrhosis. This study was aimed at testing this hypothesis and included 522 patients with decompensated cirrhosis (237 with ACLF) and 40 healthy subjects. SI was assessed by measuring 29 cytokines and the redox state of circulating albumin (HNA2), a marker of systemic oxidative stress. Systemic circulatory dysfunction (SCD) was estimated by plasma renin (PRC) and copeptin (PCC) concentrations. Measurements were performed at enrollment (baseline) in all patients and sequentially during hospitalization in 255. The main findings of this study were: (1) Patients with AD without ACLF showed very high baseline levels of inflammatory cytokines, HNA2, PRC, and PCC. Patients with ACLF showed significantly higher levels of these markers than those without ACLF; (2) different cytokine profiles were identified according to the type of ACLF precipitating event (active alcoholism/acute alcoholic hepatitis, bacterial infection, and others); (3) severity of SI and frequency and severity of ACLF at enrollment were strongly associated. The course of SI and the course of ACLF (improvement, no change, or worsening) during hospitalization and short-term mortality were also strongly associated; and (4) the strength of association of ACLF with SI was higher than with SCD.

CONCLUSION

These data support SI as the primary driver of ACLF in cirrhosis. (Hepatology 2016;64:1249-1264).

Angiotensin-Converting Enzyme Inhibitors and Active Tuberculosis: A Population-Based Study

Numerous epidemiological data suggest that the use of angiotensin-converting enzyme inhibitors (ACEis) can improve the clinical outcomes of pneumonia. Tuberculosis (TB) is an airborne bacteria like pneumonia, and we aimed to find out whether the use of ACEis can decrease the risk of active TB.We conducted a nested case-control analysis by using a 1 million longitudinally followed cohort, from Taiwan national health insurance research database. The rate ratios (RRs) for TB were estimated by conditional logistic regression, and adjusted using a TB-specific disease risk score (DRS) with 71 TB-related covariates.From January, 1997 to December, 2011, a total of 75,536 users of ACEis, and 7720 cases of new active TB were identified. Current use (DRS adjusted RR, 0.87 [95% CI, 0.78-0.97]), but not recent and past use of ACEis, was associated with a decrease in risk of active TB. Interestingly, it was found that chronic use (>90 days) of ACEis was associated with a further decrease in the risk of TB (aRR, 0.74, [95% CI, 0.66-0.83]). There was also a duration response effect, correlating decrease in TB risk with longer duration of ACEis use. The decrease in TB risk was also consistent across all patient subgroups (age, sex, heart failure, cerebrovascular diseases, myocardial infraction, renal diseases, and diabetes) and patients receiving other cardiovascular medicine.In this large population-based study, we found that subjects with recent and chronic use of ACEis were associated with decrease in TB risk.

Skeletal muscle wasting in cachexia and sarcopenia: molecular pathophysiology and impact of exercise training

Skeletal muscle provides a fundamental basis for human function, enabling locomotion and respiration. Transmission of external stimuli to intracellular effector proteins via signalling pathways is a highly regulated and controlled process that determines muscle mass by balancing protein synthesis and protein degradation. An impaired balance between protein synthesis and breakdown leads to the development of specific myopathies. Sarcopenia and cachexia represent two distinct muscle wasting diseases characterized by inflammation and oxidative stress, where specific regulating molecules associated with wasting are either activated (e.g. members of the ubiquitin-proteasome system and myostatin) or repressed (e.g. insulin-like growth factor 1 and PGC-1α). At present, no therapeutic interventions are established to successfully treat muscle wasting in sarcopenia and cachexia. Exercise training, however, represents an intervention that can attenuate or even reverse the process of muscle wasting, by exerting anti-inflammatory and anti-oxidative effects that are able to attenuate signalling pathways associated with protein degradation and activate molecules associated with protein synthesis. This review will therefore discuss the molecular mechanisms associated with the pathology of muscle wasting in both sarcopenia and cachexia, as well as highlighting the intracellular effects of exercise training in attenuating the debilitating loss of muscle mass in these specific conditions.

Cytokine screening identifies NICU patients with Gram-negative bacteremia

INTRODUCTION

Biomarkers and physiomarkers may be useful adjunct tests for sepsis detection in neonatal intensive care unit (NICU) patients. We studied whether measuring plasma cytokines at the time of suspected sepsis could identify patients with bacteremia in centers in which patients were undergoing continuous physiomarker screening using a heart rate characteristics (HRC) index monitor.

RESULTS

Six cytokines were higher in Gram-negative bacteremia (GNB) than in Gram-positive bacteremia or candidemia (GPBC). A cytokine score using thresholds for granulocyte colony-stimulating factor (G-CSF), interleukin (IL)-6, IL-8, and tumor necrosis factor (TNF)-α had 100% sensitivity and 69% positive predictive value (PPV) for GNB. A single cytokine marker, IL-6 < 130 pg/ml, had 100% sensitivity and 52% PPV for sepsis ruled out (SRO). The average HRC index was abnormal in this cohort of patients with clinical suspicion of sepsis and did not discriminate between the final sepsis designations.

DISCUSSION

In summary, in NICU patients with suspected late-onset sepsis, plasma cytokines can identify those with SRO and those with GNB, potentially aiding in decisions regarding therapy.

METHODS

Seven cytokines were measured in 226 plasma samples from patients >3 d old with sepsis suspected based on clinical signs, abnormal HRC index, or both. Cases were classified as SRO, clinical sepsis (CS), GPBC, or GNB.

Phagocytosis and digestion of pH-sensitive fluorescent dye (Eos-FP) transfected E. coli in whole blood assays from patients with severe sepsis and septic shock

The function of phagocytic and antigen presenting cells is of crucial importance to sustain immune competence against infectious agents as well as malignancies. We here describe a reproducible procedure for the quantification of phagocytosis by leukocytes in whole blood. For this, a pH-sensitive green-fluorescent protein- (GFP) like dye (Eos-FP) is transfected into infectious microroganisms. After UV-irradiation, the transfected bacteria emit green (≈5160 nm) and red (≈581 nm) fluorescent light at 490 nm excitation. Since the red fluorescent light is sensitive to acidic pH, the phagocytosed bacteria stop emitting red fluorescent light as soon as the phagosomes fuse with lysosomes. The green fluorescence is maintained in the phagolysosome until pathogen degradation is completed. Fluorescence emission can be followed by flow cytometry with filter settings documenting fluorescence 1 (FL 1, FITC) and fluorescence 2 (FL 2, phycoerythrin, PE). Eos-FP transfected bacteria can also be traced within phagocytes using microscopical techniques. A standardized assay has been developed which is suitable for clinical studies by providing clinicians with syringes pre-filled with fixed and appropriately UV-irradiated Eos-FP E. coli (TruCulture™). After adding blood or body fluids to these containers and starting the incubation at 37°C, phagocytosis by granulocytes proceeds over time. Cultures can be terminated at a given time by lysing red blood cells followed by flow cytometry. A pilot study demonstrated that Eos-FP E. coli phagocytosis and digestion was up-regulated in the majority of patients with either severe sepsis or septic shock as compared to healthy donors (p < 0.0001 after o/n incubation). Following treatment with recombinant human granulocyte colony-stimulating factor (rhG-CSF) in selected patients with sepsis, phagolysosome fusion appeared to be accelerated.

Structure-activity relationships of antimicrobial and lipoteichoic acid-sequestering properties in polyamine sulfonamides

We have recently confirmed that lipoteichoic acid (LTA), a major constituent of the gram-positive bacterial surface, is the endotoxin of gram-positive bacteria that induces proinflammatory molecules in a Toll-like receptor 2 (TLR2)-dependent manner. LTA is an anionic amphipath whose physicochemical properties are similar to those of lipopolysaccharide (LPS), which is found on the outer leaflet of the outer membranes of gram-negative organisms. Hypothesizing that compounds that sequester LPS could also bind to and inhibit LTA-induced cellular activation, we screened congeneric series of polyamine sulfonamides which we had previously shown effectively neutralized LPS both in vitro and in animal models of endotoxemia. We observed that these compounds do bind to and neutralize LTA, as reflected by the inhibition of TLR2-mediated NF-kappaB induction in reporter gene assays. Structure-activity studies showed a clear dependence of the acyl chain length on activity against LTA in compounds with spermine and homospermine scaffolds. We then sought to examine possible correlations between the neutralizing potency toward LTA and antimicrobial activity in Staphylococcus aureus. A linear relationship between LTA sequestration activity and antimicrobial activity for compounds with a spermine backbone was observed, while all compounds with a homospermine backbone were equally active against S. aureus, regardless of their neutralizing potency toward LTA. These results suggest that the number of protonatable charges is a key determinant of the activity toward the membranes of gram-positive bacteria. The development of resistance to membrane-active antibiotics has been relatively slower than that to conventional antibiotics, and it is possible that compounds such as the acylpolyamines may be useful clinically, provided that they have an acceptable safety profile and margin of safety. A more detailed understanding of the mechanisms of interactions of these compounds with LPS and LTA, as well as the gram-negative and -positive bacterial cell surfaces, will be instructive and should allow the rational design of analogues which combine antisepsis and antibacterial properties.

Clinical evaluation of proinflammatory cytokine inhibitors (sTNFR I, sTNFR II, IL-1 ra), anti-inflammatory cytokines (IL-10, IL-13) and activation of neutrophils after burn-induced inflammation

The study was aimed at evaluating the involvement of sTNFR I, sTNFR II, IL-1 ra, IL-10, IL-13 and reactive oxygen species (ROS) in systemic inflammatory response syndrome (SIRS) development in severely burned children and at assessing the prognostic value of the immunological markers studied. The study comprised 37 patients (17 burned children and 20 controls). Serum levels of the markers determined by means of ELISA and respiratory burst of neutrophils as well as p55 and p75 tumour necrosis factor-alpha (TNF-alpha) receptor expression using flow cytometry were evaluated twice. The burned children presented significantly higher levels of IL-10 and cytokine inhibitors within the first 6-24 h after injury compared with controls (P < 0.05). The decreased oxygen metabolism of neutrophils and increased TNF-alpha receptor expression were found on admission. Moreover, a significant decrease in initially high sTNFR I, sTNFR II, IL-1 ra, IL-10, IL-13 concentrations (P < 0.05) and reduced expression of TNF-alpha receptors (P < 0.05) were observed after burn therapy, whereas ROS generation evidently augmented (P < 0.05). Four of our children who developed hypovolaemic shock revealed a significantly lower ROS generation and higher concentrations of soluble TNF-alpha receptors and IL-1 ra together with IL-10, IL-13 compared with children with good outcome (P < 0.05). Our results revealed the involvement of both ROS, soluble TNF-alpha receptors and IL-1 ra in the development of SIRS in burned children; their monitoring allows for an assessment of the systemic inflammatory reaction activity. The neutrophil BURSTTEST and IL-1 ra might have been clinically helpful markers of SIRS prognosis.

Comparison of the immunostimulatory and proinflammatory activities of candidate Gram-positive endotoxins, lipoteichoic acid, peptidoglycan, and lipopeptides, in murine and human cells

The role of lipopolysaccharide (LPS) in the pathogenesis of Gram-negative septic shock is well established. The corresponding proinflammatory and immunostimulatory molecule(s) on the Gram-positive bacteria is less well understood, and its identification and characterization would be a key prerequisite in designing specific sequestrants of the Gram-positive endotoxin(s). We report in this paper the comparison of NF-kappaB-, cytokine- and chemokine-inducing activities of the TLR2 ligands, lipoteichoic acid (LTA), peptidoglycan (PGN), and lipopeptides, to LPS, a prototype TLR4 agonist, in murine macrophage cell-lines as well as in human blood. In murine cells, di- and triacyl liopopeptides are equipotent in their NF-kappaB inducing activity relative to LPS, but elicit much lower proinflammatory cytokines. However, both LPS and the lipopeptides potently induce the secretion of a pattern of chemokines that is suggestive of the engagement of a TLR4-independent TRIF pathway. In human blood, although the lipopeptides induce p38 MAP kinase phosphorylation and CD11b upregulation in granulocytes at ng/ml concentrations, they do not elicit proinflammatory cytokine production even at very high doses; LTA, however, activates neutrophils and induces cytokine secretion, although its potency is considerably lower than that of LPS, presumably due to its binding to plasma proteins. We conclude that, in human blood, the pattern of immunostimulation and proinflammatory mediator production elicited by LTA parallels that of LPS.

In vitro effect of recombinant human granulocyte colony-stimulating factor on canine neutrophil apoptosis

Apoptosis is essential in eliminating neutrophils (polymorphonuclear leukocytes: PMNs) in animals. The suppression of PMN apoptosis is believed to be beneficial in eradicating pathogens and is implicated in the pathogenesis of human inflammatory diseases. In the present study, canine PMNs were stimulated with recombinant human granulocyte colony-stimulating factor (rhG-CSF) to investigate the in vitro effect on the apoptosis of canine PMNs. Apoptotic cell rates were assessed by flow cytometry in relation to the ability of PMNs to produce reactive oxygen species (ROS). Canine PMN apoptosis was markedly suppressed by rhG-CSF treatment, in association with the retention of the PMN ability to produce ROS. The addition of cycloheximide abolished this suppression by rhG-CSF. Moreover, canine PMNs, which were stimulated by rhG-CSF, expressed high levels of anti-apoptotic mcl-1 gene mRNA, as quantified by real-time polymerase chain reaction method. The results suggest that PMNs, stimulated by G-CSF, could work effectively over a longer period to eliminate pathogens, and that the prolongation of the PMN life-span might occasionally aggravate tissue injuries in dogs. In addition, the suppression of PMN apoptosis seems to be mediated by the induction of anti-apoptotic mcl-1 gene expression.

Epidural Analgesia Prevents Endotoxin-Induced Gut Mucosal Injury in Rabbits

In the present study, we evaluated the effect of epidural analgesia on the alterations of gut barrier function elicited by endotoxin in rabbits. After the placement of an epidural catheter, 28 male rabbits were randomized into either 0.5% lidocaine (group E) or saline (group C) group. The solutions (0.4 mL/kg) were epidurally injected, followed by continuous infusion (0.1 mL . kg(-1) . h(-1)) throughout the study period. Under a continuous infusion of lipopolysaccharide (15 microg . kg(-1) . h(-1)), mean arterial blood pressure, intramucosal pH, and plasma thrombomodulin concentrations were measured. At 4 h, mean arterial blood pressure was lower (P < 0.05), intramucosal pH was higher (P < 0.01), and the progression of hemodilution more profound (P < 0.05) in group E versus group C, whereas plasma thrombomodulin levels were increased to a similar extent between the groups. With less wet-to-dry weight ratio of ileum, histopathological injury scores of gut mucosa were significantly less in group E versus group C (P < 0.01). In a separate series of experiments (n = 10 each group), mucosal permeability in group E was significantly less compared with group C (P < 0.05). Collectively, these studies showed that despite a significant decrease of perfusion pressure and arterial oxygen content, epidural analgesia minimized endotoxin-induced functional and structural injury of gut mucosa possibly through endothelium-independent mechanisms.

Interleukin-6 Causes Myocardial Failure and Skeletal Muscle Atrophy in Rats

Background— The impact of interleukin (IL)-6 on skeletal muscle function remains the subject of controversy.

Methods and Results— The effects of 7-day subcutaneous administration of recombinant human IL-6 were examined at 3 doses, 50, 100, or 250 μg · kg −1 · d −1 , in rats. Skeletal muscle mass decreased dose-dependently (with increasing dose: in the diaphragm, −10%, P =NS; −15%, P =0.0561; and −15% P <0.05; and in the gastrocnemius, −9%, P =NS; −9%, P =NS; and −18%, P <0.005) because of decreases in cross-sectional area of all fiber types without alterations in diaphragm contractile properties. Cardiovascular variables showed a dose-dependent heart dilatation (for end-diastolic volume: control, 78 μL; moderate dose, 123 μL; and high dose, 137 μL, P <0.001), reduced end-systolic pressure (control, 113 mm Hg; moderate dose, 87 mm Hg; and high dose, 90 mm Hg; P =0.037), and decreased myocardial contractility (for preload recruitable stroke work: control, 79 mm Hg; moderate dose, 67 mm Hg; and high dose, 48 mm Hg; P <0.001). Lung edema was confirmed by an increased wet-to-dry ratio (control, 4.2; moderate dose, 4.6; and high dose, 4.5; P <0.001) and microscopy findings. These cardiovascular alterations led to decreases in organ blood flow, particularly in the diaphragm (control, 0.56 mL · min −1 · g −1 ; moderate dose, 0.21 mL · min −1 · g −1 ; and high dose, 0.23 mL · min −1 · g −1 ; P =0.037). In vitro recombinant human IL-6 administration did not cause any alterations in diaphragm force or endurance capacity.

Conclusions— IL-6 clearly caused ventilatory and peripheral skeletal muscle atrophy, even after short-term administration. Blood flow redistribution, resulting from the myocardial failure induced by IL-6, was likely responsible for this muscle atrophy, because IL-6 did not exert any direct effect on the diaphragm.

Inflammatory response associated with pulmonary complications in non-HIV immunocompromised patients

BACKGROUND

A study was undertaken to evaluate the local and systemic inflammatory response associated with pulmonary complications in immunocompromised patients and potential implications regarding severity and prognosis.

METHODS

Levels of different inflammatory mediators were measured in the bronchoalveolar lavage (BAL) fluid and serum on days 1 and 4 after the identification of the pulmonary complication in 127 patients with different immunosuppressive conditions.

RESULTS

Pulmonary complications were characterised by a high percentage of neutrophils and increased levels of tumour necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-8 and IL-10 in the BAL fluid and high serum levels of TNF-alpha, IL-6, and plasma C-reactive protein (CRP). The inflammatory response was similar in the different groups of immunocompromised patients evaluated. The levels of proinflammatory cytokines were higher in patients with pulmonary infections, particularly those of bacterial aetiology. Patients with a more severe pulmonary infection had a more intense local and systemic inflammatory response. A BAL fluid IL-6 level of >40 pg/ml was an independent predictor of mortality (OR 4.65, 95% CI 1.3 to 16.1), together with a need for mechanical ventilation (OR 13.5, 95% CI 3.2 to 57.3). Patients who died had persistently high levels of CRP on day 4.

CONCLUSIONS

The evaluation of the inflammatory response, particularly the determination of IL-6 levels in the BAL fluid and CRP in the serum, may be useful for deciding the appropriate management of pulmonary complications in immunocompromised patients.

High concentrations of alpha-defensins in plasma and bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

alpha-Defensins, antimicrobial peptides localized in neutrophils, participate in tissue damage through their cytotoxic effects in neutrophil-mediated pulmonary diseases. Neutrophils play an important role in the pathogenesis of acute respiratory distress syndrome (ARDS). We measured alpha-defensins levels in plasma and bronchoalveolar lavage fluid (BALF) of ARDS patients to assess the kinetics of alpha-defensins in ARDS. Plasma alpha-defensins levels were higher in ARDS patients than in control subjects, and BALF levels were also higher in ARDS patients than in control subjects. In ARDS, BALF alpha-defensins levels correlated with those of interleukin (IL)-8, and plasma alpha-defensins levels also correlated with Lung Injury Score. Peripheral neutrophil alpha-defensins contents were higher in ARDS than the control. IL-8 dose-dependently stimulated alpha-defensins release from cultured neutrophils and these levels were higher in ARDS than the control. Reverse-phase high performance liquid chromatography showed high plasma levels of pro-defensins, precursors of alpha-defensins from the bone marrow in ARDS, although alpha-defensins in peripheral and BALF neutrophils were mature type. In conclusion, high plasma alpha-defensins in ARDS patients result from the release of pro-defensins from bone marrow, rather than mature alpha-defensins from neutrophils that accumulate in the alveolar space. The alpha-defensins contents of peripheral neutrophils in ARDS are higher and easier to release than control.

Similar inflammatory response in human whole blood to live Streptococcus pneumoniae of different serotypes

Differences in inflammatory responses in human adult whole blood to live pneumococcal serotypes 3, 7F, 9V and 23F were investigated. Using flow cytometry and ELISA, oxidative burst, expression of activation markers CD11b/CD18, and in-vitro production of tumour necrosis factor-alpha, interleukin-6 (IL-6) and interleukin-8 were measured. There was no significant difference between the serotypes regarding any of the variables investigated, although there was a trend towards higher concentrations of IL-6 induced by serotypes 9V and 23F. In the present experimental model, the serotypes of Streptococcus pneumoniae shown previously to cause different degrees of inflammation were found to cause a similar inflammatory response in human whole blood.

Effects of exogenous recombinant human granulocyte colony-stimulating factor (filgrastim, rhG-CSF) on neutrophils of critically ill patients with systemic inflammatory response syndrome depend on endogenous G-CSF plasma concentrations on admission

OBJECTIVE

To investigate the effects of exogenous recombinant human granulocyte colony-stimulating factor (rhG-CSF; filgrastim) application on the neutrophils of patients at risk of sepsis following major trauma or operation.

DESIGN

Randomized controlled trial.

SETTING

Surgical intensive care unit and research laboratory of a university hospital.

PATIENTS

Twenty-seven patients with systemic inflammatory response syndrome (SIRS).

INTERVENTIONS

Thirteen patients were treated with filgrastim (1 micro g.kg.24 h) for 10 days as a continuous infusion. Fourteen patients served as controls.

MEASUREMENTS AND RESULTS

Surface expression of FcgammaR type I (CD64), phagocytosis of E. coli, and the E. coli-induced oxidative burst of neutrophils were tested by flow cytometry. On the first postoperative/posttraumatic day, endogenous G-CSF plasma concentrations were <300 pg/ml in seven controls (subgroup 1) and nine filgrastim patients (subgroup 3), and were already elevated with >500 pg/ml in seven controls (subgroup 2) and four filgrastim patients (subgroup 4). G-CSF values ( P=0.0026, subgroup 1/3; P=0.0167, 2/4), neutrophil counts ( P=0.0026, 1/3; P=0.0167, 2/4), and CD64 expression ( P=0.0013, 1/3) were higher in filgrastim-treated than non-treated subgroups, but not phagocytic and burst activities. From day zero to day 1, phagocytosis decreased in subgroups 1 (5/7 patients) and 3 (5/9), but increased in subgroups 2 (5/7) and 4 (3/4), and respiratory burst activity decreased in subgroup 3 (8/9).

CONCLUSIONS

Besides activation of neutrophil maturation, low-dose rhG-CSF application in postoperative patients with SIRS has different effects on neutrophil functions, in part depending on already endogenously produced G-CSF.

How to leverage an endogenous immune defense mechanism: the example of granulocyte colony-stimulating factor

Our understanding of host defense has exploded during the past two decades. It is temping to take advantage of this knowledge by considering the modulation and control of these mechanisms as therapeutic options. In intensive care medicine, the aim is usually to block an overwhelming inflammatory response, which represents the "bad" side of the double-edged sword of host defense. The obvious danger of such treatment strategies is that impairing the inflammatory reaction means impairing host defense in patients exposed to infectious agents. The alternative approach, i.e., strengthening or supplementing favorable host defense mechanism, has so far been little explored clinically. Granulocyte colony-stimulating factor, the granulocyte colony-stimulating factor, combines the unique properties of an anti-infectious and an anti-inflammatory factor. This attractive profile has led us to various approaches to exploit these immunomodulatory activities. In a recently terminated, placebo-controlled, randomized study, we investigated if prophylactic treatment with rh granulocyte colony-stimulating factor (Filgrastim), at the time a risk can be anticipated such as before an operation, may offer protection from immunoinflammatory dyshomeostasis and thus lower the incidence of postoperative sepsis. Perioperative rh granulocyte colony-stimulating factor administration, compared with placebo treatment, resulted in the prevention of postoperative monocyte deactivation, conservation of an adequate Th1/Th2 ratio, as well as a considerable alleviation of the acute phase response. In parallel, there was a clear tendency toward lowering the rate of postoperative septic complications under the administration of Filgrastim.

Brain cytokines and disease

Cytokines (e.g. various interleukins and subfamily members, tumor necrosis factors, interferons, chemokines and growth factors) act in the brain as immunoregulators and neuromodulators. Over a decade ago, the integrative article 'Immunoregulators in the Nervous System' (Neurosci Biobehav Rev 1991; 15: 185-215) provided a comprehensive framework of pivotal issues on cytokines and the nervous system that recently have been extensively studied. Cytokine profiles in the brain, including cytokine generation and action, have been studied in multiple models associated with neuropathophysiological conditions. These include: (1) acute conditions and disorders such as stroke (cerebral ischemia or infarction and intracranial hemorrhage), traumatic brain injury, spinal cord injury and acute neuropathies; (2) chronic neurodegenerative disorders and chronic conditions, including Alzheimer's disease, Parkinson's disease, neuropathic pain, epilepsy and chronic neuropathies; (3) brain infections, including bacterial meningitis and encephalitis; (4) brain tumors; (5) neuroimmunological disorders per se, such as multiple sclerosis; (5) psychiatric disorders, including schizophrenia and depression; (6) neurological and neuropsychiatric manifestations associated with non- central nervous system (CNS) disorders such as peripheral cancer, liver, kidney and metabolic compromise, and peripheral infectious and inflammatory conditions; and (7) cytokine immunotherapy, which can be accompanied by neuropsychiatric manifestations when administered either via peripheral or brain routes. Cytokine profiles have also been studied in multiple animal models challenged with inflammatory, infectious, chemical, malignant and stressor insults. Essentially data show that cytokines play a pivotal role in multiple neuropathophysiological processes associated with different types of disorders and insults. Cytokine expression and action in the brain shows a different profile across conditions, but some similarities exist. Under a defined temporal sequence, cytokine involvement in neuroprotection or the induction of a deleterious pathophysiological cascade and in resolution/healing is proposed depending on the type of cytokine. In the brain, functional interactions among cytokines, balance between pro-inflammatory and anti-inflammatory cytokines and functional interactions with neurotransmitters and neuropeptides play a pivotal role in the overall cytokine profile, pattern of neuropathophysiological cascades, and quality and magnitude of neuropsychiatric manifestations. In this brief review various selected cytokine-related issues with relevance to the brain are discussed.

Induction and regulation of endogenous granulocyte colony-stimulating factor formation

Granulocyte colony-stimulating factor (G-CSF) is one of the most prominent endogenous proteins in broad clinical use. While its biological and clinical effects are relatively well studied, little is known about its endogenous formation in health and disease. However, such knowledge is crucial to decide in which situations G-CSF should be applied efficiently in the clinic, ie. when endogenous production does not suffice. The dramatic changes induced by G-CSF in the differential blood cell count are directly immunomodulatory, strengthening the innate defence by multiplying neutrophilic granulocytes. A multitude of further immunomodulatory effects contribute to the regulation of the concerted host defence. In this review, following a short introduction into the biology of G-CSF, the available data on endogenous formation in a number of animal models and human diseases is compiled. The cellular sources and inducers of G-CSF formation are reviewed and the regulation of G-CSF expression on both the transcriptional and translational level are discussed. The emerging understanding of the role and regulation of endogenous G-CSF formation opens up possibilities to define therapeutic windows as well as targets for diagnostics or drug development. Lastly, the modulation of G-CSF formation by various pharmacological agents alerts to putative side effects of these drug treatments.

Peaks of endogenous G-CSF serum concentrations are followed by an increase in respiratory burst activity of granulocytes in patients with septic shock

The relationship between peaks of G-CSF serum concentrations and respiratory burst activity of polymorphonuclear cells (PMN) was investigated in patients with postoperative or post-traumatic severe sepsis and septic shock. Over a 12 month period, a longitudinal analysis of G-CSF, TNF-alpha and IFN-gamma serum concentrations, burst activity of PMN, and expression of CD64 on the surface of PMN, were performed by ELISA technique and flow cytometric analysis, respectively, in 58 patients admitted to the intensive care unit (ICU) on a daily basis until discharge from the ICU or death. Out of these 58 patients, 27 with proven infections were in septic shock for at least 4 days' duration. Seventeen of these patients survived, whereas ten died. In 15 out of these 27 patients, 26 episodes of G-CSF peaks were observed, which were followed in most patients (13/15) by an increase in PMN burst activity, from 28% up to 540% (median 188%). Following the G-CSF peaks, CD64 expression on PMN remained at an increased level, followed by a marked decline 3 days later. TNF-alpha serum concentrations were elevated in most episodes (22/26), whereas IFN-gamma serum concentrations were below the detection level in 23/26 episodes. Taken together, peaks in G-CSF serum concentrations are followed by enhanced CD64 expression and increased burst activity of PMN in most patients with severe sepsis and septic shock. Thus, endogenous G-CSF increases neutrophil function in patients with severe sepsis and septic shock, necessary for resolution of bacterial infections in these patients.

Immunomodulation in Septic Shock: Hydrocortisone Differentially Regulates Cytokine Responses

Abstract. Cortisol is known to be an immunomodulatory hormone that exerts suppressive and permissive effects on the immune response. Little is known regarding the evolution of the cytokine response in human septic shock in the presence of hypercortisolemia induced by infusion of stress doses of hydrocortisone. Twenty-four consecutive patients with high-out-put circulatory failure (cardiac index, >4 liters/min per m2) who met the American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference Committee criteria for septic shock were enrolled in a prospective, double-blind study. The severity of illness at the time of enrollment was graded using the Acute Physiology and Chronic Health Evaluation II system, and the evolution of sepsis-induced organ dysfunction syndrome was assessed using Sepsis-Related Organ Failure Assessment scores. After randomization, hyper-cortisolemia was induced in 12 patients by infusion of 100 mg of hydrocortisone, followed by continuous infusion of 0.18 mg/kg per h. Levels of the circulating cytokines tumor necrosis factor α (TNF), interleukin 6 (IL-6), IL-8, and IL-10 were serially measured at prospectively defined time points during the first 5 d after randomization. The infusion of hydrocortisone was associated with significant reductions in serum IL-6 and IL-8 levels and with earlier resolution of the sepsis-induced organ dysfunction syndrome. IL-6 levels started to differ between the groups on day 5. The TNF and IL-10 responses were not altered by hydrocortisone infusion. Hydrocortisone infusion in septic shock differentially regulated the cytokine responses. IL-6 and IL-8 levels decreased significantly and IL-6 levels differed between the groups, whereas TNF and IL-10 levels were not affected by hydrocortisone. Stress doses of hydrocortisone may be a valuable immunomodulatory therapy for septic shock.

Dissociation of LPS-induced monocytic ex vivo production of granulocyte colony-stimulating factor (G-CSF) and TNF-alpha in patients with septic shock

Over a 6 month period, in 192 patients admitted to the intensive care unit (ICU), a longitudinal analysis of whole blood lipopolysaccharide (LPS)-induced ex vivo cytokine production was performed on a daily basis until discharge from the ICU or death. Twenty-one patients with proven infections were in septic shock for the first time and for at least 3 days' duration. Ex vivo LPS-inducible release of granulocyte colony-stimulating factor (G-CSF) was upregulated and that of TNF-alpha was downregulated in patients with septic shock, regardless whether they survived or died. In conclusion, LPS-induced ex vivo TNF-alpha and G-CSF cytokine release by monocytes is regulated differentially in patients with septic shock. Since upregulation of LPS-induced production of G-CSF occurred earlier in survivors than in non-survivors, rapidly elevated and sustained G-CSF responsiveness may contribute to survival in septic shock.

Plasma granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor levels in critical illness including sepsis and septic shock: relation to disease severity, multiple organ dysfunction, and mortality

OBJECTIVE

To define the circulating levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) during critical illness and to determine their relationship to the severity of illness as measured by the Acute Physiology and Chronic Health Evaluation (APACHE) II score, the development of multiple organ dysfunction, or mortality.

DESIGN

Prospective cohort study.

SETTING

University hospital intensive care unit.

PATIENTS

A total of 82 critically ill adult patients in four clinically defined groups, namely septic shock (n = 29), sepsis without shock (n = 17), shock without sepsis (n = 22), and nonseptic, nonshock controls (n = 14).

INTERVENTIONS

None.

MEASUREMENT AND MAIN RESULTS

During day 1 of septic shock, peak plasma levels of G-CSF, interleukin (IL)-6, and leukemia inhibitory factor (LIF), but not GM-CSF, were greater than in sepsis or shock alone (p < .001), and were correlated among themselves (rs = 0.44-0.77; p < .02) and with the APACHE II score (rs = 0.25-0.40; p = .03 to .18). G-CSF, IL-6, and UF, and sepsis, shock, septic shock, and APACHE II scores were strongly associated with organ dysfunction or 5-day mortality by univariate analysis. However, multiple logistic regression analysis showed that only septic shock remained significantly associated with organ dysfunction and only APACHE II scores and shock with 5-day mortality. Similarly, peak G-CSF, IL-6, and LIF were poorly predictive of 30-day mortality.

CONCLUSIONS

Plasma levels of G-CSF, IL-6, and LIF are greatly elevated in critical illness, including septic shock, and are correlated with one another and with the severity of illness. However, they are not independently predictive of mortality, or the development of multiple organ dysfunction. GM-CSF was rarely elevated, suggesting different roles for G-CSF and GM-CSF in human septic shock.

An improved clinically relevant sepsis model in the conscious rat

OBJECTIVE

To develop an improved small animal experimental paradigm that more closely mimics human sepsis.

DESIGN

Prospective, randomized, controlled animal study.

SETTING

Medical school research laboratory.

SUBJECTS

Male Sprague-Dawley rats (280-320 g).

INTERVENTIONS

We monitored the hemodynamic, hematologic, and biochemical consequences of abdominal sepsis produced by intraperitoneal implantation of a fibrin clot containing Escherichia coli in conscious, antibiotic-treated, rats.

MEASUREMENTS AND MAIN RESULTS

Similar to human sepsis, the implanted, infected clot (LD50 = 5-7 x 10(8) colony forming units/mL, n = 6) elevated cardiac index (>7% vs. sterile clot, p < .05, at 4 hrs), whereas mean arterial pressure and heart rate remained unaffected. The total peripheral resistance index and stroke volume index tended to decrease and increase, respectively. In contrast, an intravenous bolus injection of endotoxin (LD50 of E. coli lipopolysaccharide = 5.6 mg/kg, n = 7), the most commonly used sepsis model, induced profound hypodynamic responses manifested by a 27% decrease (vs. endotoxin vehicle, p < .01) in cardiac index, a 28% increase in the total peripheral resistance index (p < .01), and a 33% decrease in the stroke volume index (P < .01). The infectious peritonitis model also displayed dose-dependent thrombocytopenia (<61%, p < .05), leukopenia (<60%, p < .05), and mortality rate (50% at 5-7 x 10(8) colony forming units/mL, p < .05) with a minimally elevated serum tumor necrosis factor-alpha level (145 vs. 12 +/- 6 pg/mL in controls, p < .05).

CONCLUSION

This rodent model of antibiotic-treated, intra-abdominal infection features key characteristics of clinical sepsis. Although the hyperdynamic response observed in septic patients undergoing resuscitation was not clearly elicited, this paradigm better mimics clinical sepsis compared with the commonly used endotoxin model. Thus, utilization of this paradigm may provide additional opportunities to explore mechanisms of sepsis and to examine novel therapeutics.

Plasma cytokine response in mice with bacterial infection

BACKGROUND

Exposure to microorganisms elicts the production of cytokines. These soluble factors enhance several innate immune functions and regulate the ensuing specific immune response aimed at limiting the spread of infection.

AIM

This study was undertaken to quantify the plasma levels of pro-inflammatory cytokines during the course of primary Listeria monocytogenes and Campylobacter jejuni infection. Using an in vivo infection the relationship between endogenous cytokines and the bacterial number in the liver of infected animals was examined.

METHODS

C57BL/6 mice were infected by the intraperitoneal route. At different time points we determined the number of colony-forming units of bacteria in the liver of infected animals and paralled these with the plasma levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) measured by enzyme immunoassays.

RESULTS

L. monocytogenes infection lasted 10-11 days. IFN-gamma production occurred in the early phase but was more pronounced after day 4, following the appearance of specific immunity. The duration of experimental campylobacteriosis was 15 days. Early IFN-gamma production was not significant but a progressive rise of this cytokine in plasma was seen during the second week post infection. Mice produced measurable amounts of plasma TNF-alpha immediately after being given viable L. monocytogenes, peaking on day 2-3 when the greatest number of bacteria was present in the examined organs. During C. jejuni infection plasma TNF-alpha was produced in a similar manner, but the highest concentrations were found a few days later than in listeriosis, in correlation with the different course of campylobacteriosis. The quantity of IL-6 increased and decreased in concordance with clearance of L monocytogenes and the clinical status of the animals. C. jejuni did not promote the induction of this cytokine. This is to some extent an unusual finding. With respect to the role of IL-6 in Th2 responses and antibody production, the appearance of this cytokine in campylobacteriosis was more expected.

DISCUSSION

During systemic bacterial infection, a network of pro-inflammatory cytokines is activated and blood levels of these cytokines are elevated, albeit inconsistently, with large individual variations and depending on microbial characteristics and structure.

Occult bacteremia in young febrile children

The evaluation of nontoxic-appearing, young, febrile children has been a subject of considerable debate. Of young, nontoxic-appearing children aged 3 to 36 months with temperatures of 39 degrees C or more and no clear source, approximately 2% to 3% have occult bacteremia. Of these bacteremias, approximately 90% are caused by S. pneumoniae, 5% by nontyphoidal Salmonella sp., and 1% by N. meningitidis. Most children with occult pneumococcal bacteremia improve spontaneously, but approximately 25% of untreated patients have persistent bacteremia or develop new focal infections, including 3% to 6% who develop meningitis. Occult meningococcal bacteremia, although rare, has frequent complications, including meningitis in approximately 40% and death in approximately 4%. Less is known about the natural history of untreated occult nontyphoidal Salmonella bacteremia. Empiric antibiotic treatment of children with occult bacteremia decreases the rate of complications, including meningitis. Few disagree that febrile, young children at risk for occult bacteremia require a careful clinical evaluation and close follow-up. The benefits of laboratory screening and selective empiric antibiotic treatment of febrile children at risk for occult bacteremia have to be weighed against the costs of screening tests and blood cultures, inconvenience, temporary discomfort to patients, risk for side effects of antibiotics, and the role of antibiotics in the development of bacterial resistance. Although great debate exists concerning the role of empiric antibiotics, a strategy for obtaining blood cultures and empirically administering antibiotics on the basis of an increased ANC, in addition to close clinical follow-up, may be effective in reducing the frequency and severity of uncommon but adverse sequelae. A highly effective S. pneumoniae bacterial conjugate vaccine will soon be available, which will benefit all children, and will alter the ways that clinicians evaluate fully immunized young, febrile children.

Immune determinants of organism and outcome in febrile hospitalized Thai patients with bloodstream infections

Opportunistic infections (OI) and the human immunodeficiency virus (HIV) cause significant morbidity and mortality in developing countries. Immune cell and cytokine profiles may be related to the type and course of OI and to the OI-HIV interaction. Examining cell-specific cytokine production ex vivo has only recently become feasible. In Thailand, 53 febrile, hospitalized adults were enrolled in a study of the immune correlates of bloodstream infections (BSI). On site, blood cells were stimulated ex vivo. Cell-surface antigens and eight intracellular cytokines were subsequently analyzed using flow cytometry to determine associations with mortality and the organism causing the BSI. By logistic regression analysis, the percentage of CD3(+) CD16/56(+) cells making tumor necrosis factor alpha (TNF-alpha) (P = 0.033) and the percentage of CD3(-) CD16/56(+) cells (NK) (P = 0.032) were related to HIV positivity. Lymph node enlargement with HIV infection and the percentage of CD3(+) CD16/56(+) making TNF-alpha were predictive of death. A lower percentage of CD3(+) CD8(+) lymphocytes making interleukin-8 (IL-8) (P = 0.005), fewer monocytes expressing CD14 (P = 0.009), and the percentage of CD3(+) CD8(+) cells producing gamma interferon (P = 0. 011) were associated with blood culture positivity and the causative organism. For every one point decrease in the percentage of CD3(+) CD8(+) cells making IL-8, the likelihood of a positive culture increased 23%; for every one point decrease in the percentage of monocytes expressing CD14, the likelihood of a positive culture increased by 5%. Only a few immune cell types and three of their related cytokines were significantly associated with HIV disease outcome or the BSI organism. These cell types did not include CD3(+) CD8(-) cells (a surrogate for CD4(+) cells), nor did they involve cytokines associated with a type I to type II cytokine shift, which might occur with advancing HIV infection. These associations support the premise that CD8(+) and CD16/56(+) lymphocytes play significant roles in HIV and type I infections.

Cytokines as markers for infections and their effect on growth performance and well-being in the pig

Exposure to micro-organisms commonly elicit the production of cytokines. These soluble factors enhance several innate immune functions that aim to limit the spread of infection. Further, many of the pro-inflammatory cytokines regulate the ensuing specific immune response. In addition to their effects on cells of the immune system, cytokines also are important regulators in the so called immune-neuroendocrine network. The microbial structures that are necessary for induction of cytokine production are not conclusively determined but in general, bacteria preferentially induce the production of IL-1, TNF-alpha, IL-6, and IL-8, whereas virus induce the production of Type 1 interferons (IFN-alpha/beta). The onset of production of these cytokines is rapid, and several of them may reach systemic levels during a short period after infection. Thus, cytokines can serve as markers for ongoing infections and be used for discrimination between infections of bacterial or viral origin. Results from experimental and field studies show that serum IFN-alpha and IL-6 seem to be useful markers for ongoing (subclinical) viral and bacterial infections, respectively, in the pig. Consequently, demonstration of these cytokines can be valuable tools in heard health monitoring programs.

Evaluation of various cytokines (IL-6, IFN-alpha, IFN-gamma, TNF-alpha) as markers for acute bacterial infection in swine--a possible role for serum interleukin-6

A total of 64 specific pathogen free pigs were divided into eight experimental groups. Pigs in Group I served as non-infected controls while the other 56 pigs were infected intranasally with approximately 7 x 10(8) CFU of Actinobacillus pleuropneumoniae serotype 2 (strain 700/89) in 1 ml saline. When more than 25% of the infected animals showed clinical signs of disease, i.e. 20 h post infection, 48 of the infected pigs were treated with different antibiotics (8 pigs per group), leaving 8 infected animals untreated. Serum samples collected 0, 10, 20, 28 and 44 h, and 3, 4, 7, 13 and 17 days post infection were analysed for their content of interferon (IFN)-alpha, IFN-gamma, tumor necrosis factor (TNF)-alpha by immunoassays and interleukin-6 (IL-6) by a bioassay. In addition, the development of specific antibodies was determined in sera. Among the cytokines analysed, the experimental infection only induced detectable serum levels of IL-6. The appearance of IL-6 positive animals coincided with the onset of clinical signs of disease and increased body temperatures. Varying levels of IL-6 (range, 1-220 U ml-1) were detected in serum from a majority of the infected pigs (80%). In general, the highest levels of IL-6 were detected in serum collected for 10 or 20 h after infection. Among the animals not treated with antibiotics, the number of pigs displaying IL-6 in serum continued to increase until 28 h post infection and then declined. The duration of the IL-6 response varied between individuals and lasted from eight hours to three days. Treatment with antibiotics that ceased the infection also terminated the IL-6 production in most of the pigs. In a pilot field survey, IL-6 was detected in an approximately 30% of serum samples collected from conventional reared pigs before allocation to finishing units. Thus, serum IL-6 seems to be a potential marker for ongoing bacterial infections in swine.

Interleukin-6 Production by Human Neutrophils After Fc-Receptor Cross-Linking or Exposure to Granulocyte Colony-Stimulating Factor

Polymorphonuclear neutrophils (PMNs) are essential effector cells in host defense and tissue inflammatory responses. These responses may be initiated after cross-linking of cell surface Fc receptors that bind the constant portion of IgG (FcγR). We evaluated the effect of cross-linking FcγRI or FcγRII on interleukin-6 (IL-6) production by purified PMNs from normal donors or from patients being treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF). In PMNs from normal donors, IL-6 mRNA was detected by reverse transcriptase-polymerase chain reaction only after FcγRI or FcγRII cross-linking. We also found that IL-6 mRNA could be detected in PMNs after either in vitro or in vivo rhG-CSF treatment in the absence of FcγR cross-linking. IL-6 protein was found to be produced intracellularly and secreted by PMNs after cross-linking FcγRI or FcγRII or after rhG-CSF stimulation. Cross-linking FcγRI or FcγRII on PMNs from patients treated with rhG-CSF resulted in a synergistic increase in IL-6 secretion. Upregulation of IL-6 production by PMNs after rhG-CSF treatment may contribute to a clinical engraftment syndrome that occurs during periods of rapid increase in PMN numbers in patients receiving rhG-CSF.

Interleukin-6 Production by Human Neutrophils After Fc-Receptor Cross-Linking or Exposure to Granulocyte Colony-Stimulating Factor

Polymorphonuclear neutrophils (PMNs) are essential effector cells in host defense and tissue inflammatory responses. These responses may be initiated after cross-linking of cell surface Fc receptors that bind the constant portion of IgG (FcγR). We evaluated the effect of cross-linking FcγRI or FcγRII on interleukin-6 (IL-6) production by purified PMNs from normal donors or from patients being treated with recombinant human granulocyte colony-stimulating factor (rhG-CSF). In PMNs from normal donors, IL-6 mRNA was detected by reverse transcriptase-polymerase chain reaction only after FcγRI or FcγRII cross-linking. We also found that IL-6 mRNA could be detected in PMNs after either in vitro or in vivo rhG-CSF treatment in the absence of FcγR cross-linking. IL-6 protein was found to be produced intracellularly and secreted by PMNs after cross-linking FcγRI or FcγRII or after rhG-CSF stimulation. Cross-linking FcγRI or FcγRII on PMNs from patients treated with rhG-CSF resulted in a synergistic increase in IL-6 secretion. Upregulation of IL-6 production by PMNs after rhG-CSF treatment may contribute to a clinical engraftment syndrome that occurs during periods of rapid increase in PMN numbers in patients receiving rhG-CSF.

Production of tumor necrosis factor-alpha and interleukin-6 in whole blood stimulated by live Gram-negative and Gram-positive bacteria

OBJECTIVE: To investigate the production of tumor necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6) induced by live Gram-negative and Gram-positive bacteria in whole blood in vitro. METHODS: In all, 49 different isolates were studied. Each of the 49 different isolates was incubated for 4 h with whole blood at a ratio of one monocyte per 1--5 bacteria. Plasma was then separated and frozen, and the concentrations of TNF-alpha and IL-6 were measured by enzyme immunoassays. RESULTS: There was a positive correlation between TNF-alpha and IL-6 values, r=0.9. Gram-negative bacteria induced higher levels of both TNF-alpha and IL-6 than Gram-positive bacteria. Group G streptococci (GGS) induced higher levels of TNF-alpha than Streptococcus pneumoniae, Staphylococcus aureus, Staphylococcus epidermidis and group A streptococci (GAS). Klebsiella pneumoniae induced higher levels of TNF-alpha than Haemophilus influenzae, Escherichia coli and Neisseria meningitidis. GGS induced higher levels of IL-6 than Staphylococcus epidermidis, Staphylococcus aureus and GAS. When the relative amounts of cytokine induced by the strains were compared to serum concentrations measured on admission in patients with bacteremia caused by the same bacterial isolates there was no significant correlation. CONCLUSION: Species- and strain-related differences in cytokine-inducing properties were found which may have significance in clinical infections.