Impaired ex vivo lipopolysaccharide-stimulated whole blood tumor necrosis factor production may identify "septic" intensive care unit patients

The Expression Levels and Concentrations of PD-1 and PD-L1 Proteins in Septic Patients: A Systematic Review

Sepsis is a series of life-threatening organ dysfunction caused by an impaired host response to infection. A large number of molecular studies of sepsis have revealed complex interactions between infectious agents and hosts that result in heterogeneous manifestations of sepsis. Sepsis can cause immunosuppression and increase the expression of checkpoint inhibitor molecules, including programmed death protein (PD-1) and programmed death ligand 1 (PD-L1), and thus PD-1 and PD-L1 are thought to be useful as diagnostic and prognostic tools for sepsis. PD-1 is an inhibitor of both adaptive and innate immune responses, and is expressed on activated T lymphocytes, natural killer (NK) cells, B lymphocytes, macrophages, dendritic cells (DCs), and monocytes, whereas PD-L1 is expressed on macrophages, some activated T and B cells, and mesenchymal stem cells as well as various non-hematopoietic cells. This systematic review aims to assess the PD-1 and PD-L1 protein expression levels and concentrations in septic and other infectious patients.

The role of nitric oxide in sepsis-associated kidney injury

Sepsis is one of the leading causes of acute kidney injury (AKI), and several mechanisms including microcirculatory alterations, oxidative stress, and endothelial cell dysfunction are involved. Nitric oxide (NO) is one of the common elements to all these mechanisms. Although all three nitric oxide synthase (NOS) isoforms are constitutively expressed within the kidneys, they contribute in different ways to nitrergic signaling. While the endothelial (eNOS) and neuronal (nNOS) isoforms are likely to be the main sources of NO under basal conditions and participate in the regulation of renal hemodynamics, the inducible isoform (iNOS) is dramatically increased in conditions such as sepsis. The overexpression of iNOS in the renal cortex causes a shunting of blood to this region, with consequent medullary ischemia in sepsis. Differences in the vascular reactivity among different vascular beds may also help to explain renal failure in this condition. While most of the vessels present vasoplegia and do not respond to vasoconstrictors, renal microcirculation behaves differently from nonrenal vascular beds, displaying similar constrictor responses in control and septic conditions. The selective inhibition of iNOS, without affecting other isoforms, has been described as the ideal scenario. However, iNOS is also constitutively expressed in the kidneys and the NO produced by this isoform is important for immune defense. In this sense, instead of a direct iNOS inhibition, targeting the NO effectors such as guanylate cyclase, potassium channels, peroxynitrite, and S-nitrosothiols, may be a more interesting approach in sepsis-AKI and further investigation is warranted.

The Urosepsis-A Literature Review

Urosepsis is a very serious condition with a high mortality rate. The immune response is in the center of pathophysiology. The therapeutic management of these patients includes surgical treatment of the source of infection, antibiotic therapy and life support. The management of this pathology is multidisciplinary and requires good collaboration between the urology, intensive care, imaging and laboratory medicine departments. An imbalance of pro and anti-inflammatory cytokines produced during sepsis plays an important role in pathogenesis. The study of cytokines in sepsis has important implications for understanding pathophysiology and for development of other therapeutic solutions. If not treated adequately, urosepsis may lead to serious septic complications and organ sequelae, even to a lethal outcome.

A Whole Blood Enzyme-Linked Immunospot Assay for Functional Immune Endotyping of Septic Patients

Sepsis initiates simultaneous pro- and anti-inflammatory processes, the pattern and intensity of which vary over time. The inability to evaluate the immune status of patients with sepsis in a rapid and quantifiable manner has undoubtedly been a major reason for the failure of many therapeutic trials. Although there has been considerable effort to immunophenotype septic patients, these methods have often not accurately assessed the functional state of host immunity, lack dynamic range, and are more reflective of molecular processes rather than host immunity. In contrast, ELISpot assay measures the number and intensity of cytokine-secreting cells and has excellent dynamic range with rapid turnaround. We investigated the ability of a (to our knowledge) novel whole blood ELISpot assay and compared it with a more traditional ELISpot assay using PBMCs in sepsis. IFN-γ and TNF-α ELISpot assays on whole blood and PBMCs were undertaken in control, critically ill nonseptic, and septic patients. Whole blood ELISpot was easy to perform, and results were generally comparable to PBMC-based ELISpot. However, the whole blood ELISpot assay revealed that nonmonocyte, myeloid populations are a significant source of ex vivo TNF-α production. Septic patients who died had early, profound, and sustained suppression of innate and adaptive immunity. A cohort of septic patients had increased cytokine production compared with controls consistent with either an appropriate or excessive immune response. IL-7 restored ex vivo IFN-γ production in septic patients. The whole blood ELISpot assay offers a significant advance in the ability to immunophenotype patients with sepsis and to guide potential new immunotherapies.

The relationship between immune status as measured by stimulated ex-vivo tumour necrosis factor alpha levels and the acquisition of nosocomial infections in critically ill mechanically ventilated patients

Introduction

Immunological dysfunction is common in critically ill patients but its clinical significance and the optimal method to measure it are unknown. The level of tumor necrosis factor alpha (TNF-α) after ex-vivo whole blood stimulation with lipopolysaccharide (LPS) has been proposed as a possible method to quantify immunological function. We hypothesized that in a cohort of critically ill patients, those with a lower post-stimulation TNF-α level would have increased rates of nosocomial infections (NIs) and worse clinical outcomes.

Methods

A secondary analysis of a phase 2 randomized, multi-centre, double-blinded placebo-controlled trial. As there was no difference between treatment and control arms in outcomes and NI rate, all the patients were analyzed as one cohort. On enrolment, day 4, 7, and weekly until day 28, whole blood was incubated with LPS ex-vivo and subsequent TNF-α level was measured. Patients were grouped in tertiles according to delta and peak TNF-α level. The primary outcome was the association between NIs and tertiles of TNF-α level post LPS stimulation; secondary outcomes included ICU and 90-day mortality, and ICU and hospital length of stay.

Results

Data was available for 201 patients. Neither the post LPS stimulation delta TNF-α group nor the peak TNF-α post-stimulation group were associated with the development of NIs or clinical outcomes. Patients in the highest tertile for post LPS stimulation delta TNF-α compared to the lowest tertile were younger [61.1 years ± 15.7 vs. 68.6 years ± 12.8 standard deviations (SD) in the lowest tertile], had lower acuity of illness (APACHE II 25.0 ± 9.7 vs. 26.7 ± 6.1) and had lower baseline TNF-α (9.9 pg/mL ± 19.0 vs. 31.0 pg/mL ± 68.5). When grouped according to peak post-stimulation TNF-α levels, patients in the highest tertile had higher serum TNF-α at baseline (21.3 pg/mL ± 66.7 compared to 6.5 pg/mL ± 9.0 in the lowest tertile).

Conclusion

In this prospective multicenter study, ex-vivo stimulated TNF-α level was not associated with the occurrence of NIs or clinical outcomes. Further study is required to better ascertain whether TNF levels and ex-vivo stimulation can be used to characterize immune function in critical illness and if other assays might be better suited to this task.

Immunosuppression is Inappropriately Qualifying the Immune Status of Septic and SIRS Patients

Immunosuppression is the most commonly used concept to qualify the immune status of patients with either sterile systemic inflammatory response syndrome (SIRS) or sepsis. In this review we attempt to demonstrate that the concept of immunosuppression is an oversimplification of the complex anti-inflammatory response that occurs in patients dealing with a severe sterile or infectious insult. Particularly, the immune status of leukocytes varies greatly depending on the compartment from where they are derived from. Furthermore, although certain functions of immune cells present in the blood stream or in the hematopoietic organs can be significantly diminished, other functions are either unchanged or even enhanced. This juxtaposition illustrates that there is no global defect. The mechanisms called reprogramming or trained innate immunity are probably aimed at preventing a generalized deleterious inflammatory reaction, and work to maintain the defense mechanisms at their due levels.

Sepsis: The evolution in definition, pathophysiology, and management

There has been a significant evolution in the definition and management of sepsis over the last three decades. This is driven in part due to the advances made in our understanding of its pathophysiology. There is evidence to show that the manifestations of sepsis can no longer be attributed only to the infectious agent and the immune response it engenders, but also to significant alterations in coagulation, immunosuppression, and organ dysfunction. A revolutionary change in the way we manage sepsis has been the adoption of early goal-directed therapy. This involves the early identification of at-risk patients and prompt treatment with antibiotics, hemodynamic optimization, and appropriate supportive care. This has contributed significantly to the overall improved outcomes with sepsis. Investigation into clinically relevant biomarkers of sepsis are ongoing and have yet to yield effective results. Scoring systems such as the sequential organ failure assessment and Acute Physiology and Chronic Health Evaluation help risk-stratify patients with sepsis. Advances in precision medicine techniques and the development of targeted therapy directed at limiting the excesses of the inflammatory and coagulatory cascades offer potentially viable avenues for future research. This review summarizes the progress made in the diagnosis and management of sepsis over the past two decades and examines promising avenues for future research.

Precision Immunotherapy for Sepsis

Decades of sepsis research into a specific immune system-targeting adjunctive therapy have not resulted in the discovery of an effective compound. Apart from antibiotics, source control, resuscitation and organ support, not a single adjunctive treatment is used in current clinical practice. The inability to determine the prevailing immunological phenotype of patients and the related large heterogeneity of study populations are regarded by many as the most important factors behind the disappointing results of past clinical trials. While the therapeutic focus has long been on immunosuppressive strategies, increased appreciation of the importance of sepsis-induced immunoparalysis in causing morbidity and mortality in sepsis patients has resulted in a paradigm shift in the sepsis research field towards strategies aimed at enhancing the immune response. However, similar to immunosuppressive therapies, precision medicine is imperative for future trials with immunostimulatory compounds to succeed. As such, identifying those patients with a severely suppressed or hyperactive immune system who will most likely benefit from either immunostimulatory or immunosuppressive therapy, and accurate monitoring of both the immune and treatment response is crucial. This review provides an overview of the challenges lying ahead on the path towards precision immunotherapy for patients suffering from sepsis.

Impact of intraoperative blood salvage on monocyte subsets alteration and intracellular tumor necrosis factor-α production

Intraoperative salvaged blood is used to reduce allogeneic blood transfusion in orthopedic surgery patients. However, salvaged blood reinfusion may lead to immune reactions. Salvaged and venous blood from 20 patients undergoing hip arthroplasty was processed. The salvaged samples were mixed with patients' venous blood and incubated in absence or presence of lipopolysaccharide.

SAMPLES

Venous: venous patient blood (n = 20). Native: mixed salvaged native blood (n = 20). Filtered: mixed salvaged leukocyte filtered blood (n = 20). Irradiated: mixed salvaged irradiated blood (n = 20). The frequency of the surface receptors CD14, HLA-DR, and intracellular tumor necrosis factor (TNF)-α on peripheral blood mononuclear cells was analyzed by fluorescence-activated cell sorting analysis. The frequency of unstimulated CD14^low and CD14^high cells as well as unstimulated HLA-DR and TNF-α positive monocytes was comparable between venous and filtered salvaged blood. However, native and irradiated salvaged blood increased compared with venous (p < 0.05) and filtered salvaged blood (p < 0.05) for unstimulated CD14^low cells, HLA-DR, and TNF-α positive monocytes. Stimulated intracellular TNF-α positive monocytes were decreased in native, filtered, and irradiated salvaged blood compared with venous blood (p < 0.05). Processing perioperative salvaged blood with leukofiltration minimizes the influence on monocytes activation compared with native and irradiated salvaged blood. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 815-821, 2018.

Tolerance and Cross-Tolerance following Toll-Like Receptor (TLR)-4 and -9 Activation Are Mediated by IRAK-M and Modulated by IL-7 in Murine Splenocytes

Objective

Immune suppression during critical illness predisposes to serious infections. We sought to determine the mechanisms regulating tolerance and cross-tolerance to common pro-inflammatory danger signals in a model that recapitulates the intact in vivo immune response.

Materials and Methods

Flt3-expanded splenocytes obtained from wild-type or matching IRAK-M knockout (IRAK-M-/-), C57BL/6, male mice (8–10 weeks old) were treated repeatedly or alternately with either LPS or CpGA DNA, agonists of Toll-like receptor (TLR)-4 and -9, respectively, over successive 24-hour periods. Supernatants were collected following each 24-hour period with cytokine release (ELISA) and splenocyte IRAK-M expression (Western blot) determined. Tolerance and cross-tolerance were assessed in the absence or presence of programmed death receptor (PD)-1 blocking antibody or IL-7 pre-treatment.

Main Results

Splenocytes notably exhibited both tolerance and cross-tolerance to subsequent treatments with either LPS or CpGA DNA. The character of tolerance and cross-tolerance in this model was distinct following initial LPS or CpGA treatment in that TNFα and IFNγ release (not IL-10) were suppressed following LPS; whereas, initial CpGA treatment suppressed TNFα, IFNγ and IL-10 release in response to subsequent stimulation (LPS or CpGA). Tolerance and cross-tolerance were unrelated to IL-10 release or PD-1 but were attenuated in IRAK-M-/- splenocytes. IL-7 significantly suppressed IRAK-M expression and restored TNFα and IFNγ production without influencing IL-10 release.

Conclusions

In summary, acute immune tolerance and cross-tolerance in response to LPS or CpGA were distinct in that LPS selectively suppressed pro-inflammatory cytokine responses; whereas, CpGA suppressed both pro- and anti-inflammatory responses. The induction of tolerance and cross-tolerance in response to common danger signals was mechanistically unrelated to IL-10 or PD-1 but was directly influenced by IRAK-M expression. IL-7 reduced IRAK-M expression and attenuated immune tolerance induced by either LPS or CpGA, and thus may be useful for reversal of immune tolerance in the setting of critical illness.

Thymosin alpha1 based immunomodulatory therapy for sepsis: a systematic review and meta-analysis

OBJECTIVES

Thymosin alpha1 (Tα1) is considered a promising immunomodulatory drug. However, it is still unclear whether Tα1 should be recommended for the management of sepsis. Here we conducted a systematic review and meta-analysis to assess the efficacy of Tα1 based immunomodulatory therapy on the clinical outcomes of septic patients.

METHODS

We searched for relevant clinical trials published before Dec. 12, 2014 through electronic databases. All articles about Tα1 based immunomodulatory therapy for sepsis were included regardless of language. Two authors independently selected studies, extracted data and assessed the quality of each included study. We polled the data related to all-cause mortality with Review Manager 5.1.

RESULTS

Twelve controlled trials were evaluated in all. Tα1 based immunomodulatory therapy had a significant trend toward lower all-cause mortality among patients with sepsis (pooled risk ratio 0.68, 95%CI 0.59-0.78, p<0.00001, 12 trials, n=1480).

CONCLUSIONS

Tα1 based immunomodulatory therapy was associated with a lower mortality in septic patients. Nevertheless, these findings should be interpreted cautiously because of the poor quality and small number of participants of the included trials. More well-designed worldwide multicenter clinical trials are needed to provide a conclusive guideline for clinical practice.

Impact of intraoperatively salvaged and washed blood on stimulated cytokine release in vitro

BACKGROUND

Intraoperative blood salvage and processing it with commercially available devices is a widespread standard procedure to reduce allogeneic blood transfusion in patients undergoing major orthopedic surgery. The aim of this study was to investigate the impact of such processed blood on the immune system by measuring pro- and anti-inflammatory cytokines.

STUDY DESIGN AND METHODS

Salvaged blood from 20 patients undergoing hip arthroplasty was processed with a continuous autotransfusion system. One part of the processed blood was left without further treatment, one part was additionally leukoreduced, one part was irradiated, and one part was separated into its cellular and soluble fraction by centrifugation. Specimens from each part were mixed in vitro with venous blood from the patient in ratios of 3:1, 1:1, and 1:3 and incubated with endotoxin for 24 hours. Tumor necrosis factor (TNF)-α and interleukin (IL)-10 were measured in cell culture supernatants by enzyme-linked immunosorbent assay.

RESULTS

All parts of the salvaged blood were without a significant influence on TNF-α release. In contrast, IL-10 was significantly increased, independently of the admixtured salvaged blood being plain, additionally irradiated, or additionally leukoreduced. This IL-10 increase was also found with the cellular fraction of the plain salvaged blood, whereas the soluble fraction had no influence on IL-10 release.

CONCLUSION

Intraoperative salvaged blood is not immunologically inert. We observed a significant increase in the anti-inflammatory IL-10 response without affecting the proinflammatory TNF-α release. Neither leukofiltration nor gamma irradiation eliminated this effect that was limited only to the cellular fraction of the salvaged blood, suggesting red blood cells to be responsible for the observed immunomodulation.

Uncontrolled sepsis: a systematic review of translational immunology studies in intensive care medicine

BACKGROUND

The design of clinical immunology studies in sepsis presents several fundamental challenges to improving the translational understanding of pathologic mechanisms. We undertook a systematic review of bed-to-benchside studies to test the hypothesis that variable clinical design methodologies used to investigate immunologic function in sepsis contribute to apparently conflicting laboratory data, and identify potential alternatives that overcome various obstacles to improve experimental design.

METHODS

We performed a systematic review of the design methodology employed to study neutrophil function (respiratory burst), monocyte endotoxin tolerance and lymphocyte apoptosis in the intensive care setting, over the past 15 years. We specifically focussed on how control samples were defined, taking into account age, gender, ethnicity, concomitant therapies, timing of sample collection and the criteria used to diagnose sepsis.

RESULTS

We identified 57 eligible studies, the majority of which (74%) used case-control methodology. Healthy volunteers represented the control population selected in 83% of studies. Comprehensive demographic data on age, gender and ethnicity were provided in ≤48% of case control studies. Documentation of diseases associated with immunosuppression, malignancy and immunomodulatory therapies was rare. Less than half (44%) of studies undertook independent adjudication for the diagnosis of sepsis while 68% provided microbiological data. The timing of sample collection was defined by highly variable clinical criteria. By contrast, surgical studies avoided many such confounders, although only one study in surgical patients monitored the study group for development of sepsis.

CONCLUSIONS

We found several important and common limitations in the clinical design of translational immunologic studies in human sepsis. Major elective surgery overcame many of these methodological limitations. The failure of adequate clinical design in mechanistic studies may contribute to the lack of translational therapeutic progress in intensive care medicine.

Relation of signal in mononuclear cell with endotoxin response and clinical outcome after trauma

BACKGROUND

We investigated the correlation of proinflammatory transcript nuclear factor κB (NF-κB) and antioxidative gene transcript nuclear factor-erythroid 2-related factor 2 (Nrf2) expressions in peripheral blood mononuclear cells (PBMCs) with the tumor necrosis factor α (TNF-α) response after endotoxin stimulation and the clinical outcome of severely injured patients.

METHODS

Thirty-two severe blunt trauma patients (injury severity score>16) with systemic inflammatory response syndrome were enrolled. Age- and sex-matched healthy persons were the controls. Patients' blood samples were obtained at 24 and 72 hours after injury. Peripheral blood mononuclear cells were isolated, and measurements for NF-κB p65 translocation, Nrf2 and phosphorylated inhibitory κB-α expressions, and TNF-α levels were assayed after endotoxin stimulation.

RESULTS

In the trauma patients, TNF-α hyporesponse, depressed NF-κB p65 translocation, and phosphorylated inhibitory κB-α expression in PBMCs were found at 24 and 72 hours after injury; the Nrf2 expressions in PBMCs were not significantly different between patients and controls. The TNF-α levels had significant correlation with the NF-κB translocation and the trend of negative correlation with Nrf2 expression. Fifteen patients had critical injury (injury severity score≥25). Patients with critical injury had a lower NF-κB signal and a lower TNF-α response than did the counter group. Twelve patients developed organ failure; their Nrf2 expressions were significantly lower than those of patients without organ failure.

CONCLUSIONS

The endotoxin hyporesponse associated with NF-κB and Nrf2 signal alternations in PBMCs of injured patients develops early after injury. The hyporesponse of PBMCs with a lower TNF-α level correlates with a lower NF-κB signal and is associated with critical injury, whereas a depressed Nrf2 expression in PBMCs is associated with later organ failure in trauma patients.

Chronic pulmonary LPS tolerance induces selective immunosuppression while maintaining the neutrophilic response

LPS challenge causes potent activation of innate immunity. Because LPS is ubiquitously present in ambient air, repeated inhalation may lead to activation of the pulmonary immune response. If this activation is unregulated, chronic LPS inhalation would lead to persistent inflammation and organ damage. We hypothesized that the lung uses the mechanism of LPS tolerance to maintain the balance between hypoinflammatory and hyperinflammatory states. We developed a model of chronic pulmonary LPS tolerance induced by pulmonary exposure to 1 microg LPS for 4 consecutive days. Mice were challenged with 10 microg of LPS 24 h later. TNF-alpha protein was significantly decreased in the bronchoalveolar lavage fluid of tolerant versus nontolerant mice, whereas IL-6 levels were significantly increased in the tolerant group. Tolerant mice were also protected from airway hyperresponsiveness. M2 and M3 muscarinic receptor mRNA was significantly decreased in the lungs of tolerant mice, suggesting a mechanism for the decreased airway hyperresponsiveness. CXCL2 was significantly reduced in tolerant mice, but CXCL1 was equivalent between groups. No difference was seen in neutrophil recruitment to the alveolar space. Interestingly, LPS tolerance does not confer cross-tolerance to the Toll-like receptor (TLR) 2 stimulus Pam3Cys. TNF-alpha and IL-6 concentrations were significantly increased in LPS-tolerant mice challenged with Pam3Cys; however, chemokine concentrations were unaffected. Our data show that repeated LPS inhalation results in differential regulation of cytokines but does not inhibit neutrophil recruitment. This unrestricted neutrophil recruitment may represent a mechanism by which individuals may be protected from pulmonary bacterial infection and pneumonia.

Spleen artery embolization aggravates endotoxin hyporesponse of peripheral blood mononuclear cells in patients with spleen injury

BACKGROUND

: Spleen artery embolization (SAE) increases the success of nonoperative management of spleen injury; however, the immune alternation after SAE is unclear. This study searched the endotoxin responses of peripheral blood mononuclear cells (PBMCs) in injured patients who received SAE.

METHODS

: Patients were subsequently enrolled when their spleen injuries were confirmed by computed tomographic scan. Peripheral blood samples were obtained within first, at third, fifth, and seventh postinjury days. PBMCs were isolated; nuclear factor (NF)-kB translocations, phosphorylated I-kB expressions, and in vitro tumor necrosis factor (TNF)-alpha levels were assayed after endotoxin stimulation (ES).

RESULTS

: Sixteen patients who received nonoperative managements were enrolled. Five patients received SAE (embolized patients) and 11 patients did not (nonembolized patients). Compared with those in controls, NF-kB translocations, phosphorylated I-kB expressions, and TNF-alpha levels after ES decreased significantly early in injured patients. NF-kB translocation and TNF-alpha levels after ES were indifferent at seventh day between nonembolized patients and controls, whereas significantly lower NF-kB p65 translocation and TNF-alpha levels after ES were found at seventh postinjury day in embolized patients than in controls. Compared with nonembolized patients, embolized patients had significantly lower levels of NF-kBp50 translocations after ES from first to third postinjury days and lower levels of NF-kB p65 translocations, TNF-alpha, and phosphorylated I-kB expressions after ES from first to fifth postinjury days.

CONCLUSIONS

: SAE dysregulates the NF-kB system and aggravates the cytokine hyporesponse upon ES of PBMCs in patients with spleen injury. These results implicate that SAE alters immune response and may increase susceptibility to infections in injured patients.

Perioperative gene expression analysis for prediction of postoperative sepsis

BACKGROUND

Postoperative sepsis is one of the main causes of death after major abdominal surgery; however, the immunologic factors contributing to the development of sepsis are not completely understood. In this study, we evaluated gene expression in patients who developed postoperative sepsis and in patients with an uncomplicated postoperative course.

METHODS

We enrolled 220 patients in a retrospective matched-pair, case-control pilot study to investigate the perioperative expression of 23 inflammation-related genes regarding their properties for predicting postoperative sepsis. Twenty patients exhibiting symptoms of sepsis in the first 14 days after surgery (case group) were matched with 20 control patients with an uncomplicated postoperative course. Matching criteria were sex, age, main diagnosis, type of surgery, and concomitant diseases. Blood samples were drawn before surgery and on the first and second postoperative days. Relative gene expression was analyzed with real-time reverse-transcription PCR.

RESULTS

Significant differences (P < 0.005) in gene expression between the 2 groups were observed for IL1B (interleukin 1, beta), TNF [tumor necrosis factor (TNF superfamily, member 2)], CD3D [CD3d molecule, delta (CD3-TCR complex)], and PRF1 [perforin 1 (pore forming protein)]. Logistic regression analysis and a subsequent ROC curve analysis revealed that the combination of TNF, IL1B, and CD3D expression had a specificity and specificity of 90% and 85%, respectively, and predicted exclusion of postoperative sepsis with an estimated negative predictive value of 98.1%.

CONCLUSIONS

These data suggest that gene expression analysis may be an effective tool for differentiating patients at high and low risk for sepsis after abdominal surgery.

Lipopolysaccharide-stimulated whole blood cytokine production does not predict the inflammatory response in human endotoxemia

A widely applied method to study the activation of the innate immune system is in vitro stimulation of whole blood using lipopolysaccharide (LPS). However, it is unclear if in vitro cytokine production relates to in vivo cytokine levels elicited during experimental endotoxemia or sepsis. To determine the correlation between in vitro cytokine production and the in vivo inflammatory response, blood was obtained from 15 healthy volunteers for in vitro incubation with Escherichia coli LPS, immediately followed by experimental E. coli endotoxemia. Correlations of in vitro and peak in vivo cytokine concentrations were determined using Pearson correlation coefficient. In stimulated whole blood, tumor necrosis factor (TNF)-α, Interleukin (IL)-1β, IL-6, IL-10 and interferon (IFN)-γ were induced to 279 ± 53, 392 ± 64, 5312 ± 624, 83 ± 20 and 343 ± 85 pg/ml, respectively, whereas in vivo cytokine induction led to cytokine levels of 603 ± 123, 11 ± 1, 4999 ± 1228, 167 ± 25 and 194 ± 40 pg/ml, respectively. Correlation coefficients between the in vitro and in vivo cytokine concentrations were for TNF-α, IL-1β, IL-6, IL-10 and IFN-γ -0.10 (P = 0.7), 0.09 (P = 0.8), 0.36 (P = 0.2), 0.19 (P = 0.5) and 0.40 (P = 0.1), respectively. Comparison between in vitro and in vivo stimulation with LPS shows no correlation between the amount of cytokines produced. In vitro cytokine production, therefore, does not predict the in vivo inflammatory response.

[Influence of gender on stimulated cytokine response in patients with severe sepsis]

AIM

Studies suggest that female mice have lower mortality rates than males after sepsis or trauma-hemorrhage. This study investigated the impact of gender and disease severity on monocyte hyporesponsiveness in severe human sepsis.

METHODS

We prospectively investigated 49 (male n=28, female n=21) consecutive patients with severe sepsis. Tumor necrosis factor-alpha (TNF-alpha) and interleukin-10 (IL-10) were assayed by ELISA in unstimulated whole blood cultures or after stimulation with lipopolysaccharide (LPS; E. coli 0111:B4) or Staph. aureus Cowan strain I (SAC-I) lysate at days 1, 2, 3, 4, and 8 after enrollment. Testosterone and estradiol levels were quantified by electrochemoluminescence immunoassays.

RESULTS

Mortality was similar for males (35.7%) and females (42.9%). While disease severity was also comparable, septic patients showed a substantial suppression in stimulated TNF-alpha response compared to healthy controls who recovered within 8 days in surviving patients. Stimulated cytokine response recovered in female non-surviving patients, while it remained suppressed in non-surviving male patients and was significantly different compared to female non-surviving patients. Testosterone levels were substantially suppressed in male but not female septic patients compared to normal values but did not differ between surviving and non-surviving patients. Estradiol levels were elevated in female and male septic patients. Addition of different concentrations of testosterone and estradiol to whole blood obtained from younger (<35 years old) and older (>60 years old) male as well as from younger (proestrous premenopausal) and older (postmenopausal) female non-septic volunteers revealed no effect on LPS-stimulated TNF-alpha and IL-10 release.

CONCLUSION

Severe sepsis leads to a substantial suppression of stimulated cytokine response. Prolonged suppression may serve as a marker of unfavourable outcome in male but not in female individuals suffering from severe sepsis. Furthermore, our data suggest that gender differences in cellular immunity described for young, sexually mature animals obviously persist in typical postmenopausal intensive care unit patients, although a direct interaction between testosterone or estradiol and LPS-stimulated cytokine response could not be demonstrated.

Acute pulmonary lipopolysaccharide tolerance decreases TNF-alpha without reducing neutrophil recruitment

Pulmonary LPS exposure plays a key role in exacerbation of lung diseases such as chronic obstructive pulmonary disease and asthma. However, little is known about the effects of repeated LPS exposure in the lung microenvironment. We have developed a novel murine model of pulmonary LPS tolerance induced by intratracheal (i.t.) administration of LPS. First, we show that pulmonary LPS exposure does not induce whole-body refractoriness to systemic LPS, because i.t. administration followed by i.p. administration did not decrease plasma TNF-alpha. However, a local refractory state can be induced with two i.t. LPS exposures. Pulmonary LPS tolerance was induced by i.t. administration of 100 ng LPS at time 0 and 48 h. Nontolerant mice received PBS at time 0 and LPS at 48 h. Bronchoalveolar lavage levels of TNF-alpha were significantly attenuated in tolerant mice vs nontolerant mice (1597 pg/ml vs 7261 pg/ml). TNF-alpha mRNA was significantly reduced in bronchoalveolar lavage cells (5-fold) and lung tissue (10-fold). No reduction was seen in neutrophil numbers in the bronchoalveolar lavage fluid, myeloperoxidase activity, or expression of neutrophil chemoattractants CXCL1 and CXCL2, reflecting the specificity of the response. The reduction in TNF-alpha was accompanied by a significant increase in soluble receptors, TNF-SRI (159 pg/ml vs 206 pg/ml) and TNF-SRII (1366 pg/m vs 2695 pg/ml). In conclusion, pulmonary LPS tolerance results in a specific reduction in TNF-alpha expression, while the neutrophilic response is unaffected. This response may be a mechanism to limit tissue damage by reducing TNF-alpha levels, while still maintaining the antimicrobial capacity of the lung.

Induction of endotoxin tolerance enhances bacterial clearance and survival in murine polymicrobial sepsis

The fundamental mechanisms that underlie endotoxin tolerance remain to be elucidated, and the clinical significance of endotoxin tolerance in the context of active systemic infection remains in question. We hypothesized that the endotoxin tolerance phenotype would result in decreased inflammation at the expense of altered bacterial clearance and, thus, higher mortality in a murine model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). Endotoxin tolerance was induced in C57Bl/6 mice with 5 mg/kg LPS or vehicle 18 h before subsequent CLP. Lung tissue, peritoneal fluid, and blood were collected at 1, 3, 6, and 18 h after surgery for subsequent analysis. Peritoneal macrophages were isolated for ex vivo phagocytosis assay. In separate experiments, mice were allowed to recover, and survival was monitored for 7 days. Endotoxin tolerance attenuated plasma TNF-alpha and IL-6 at 6 h after CLP. Peritoneal fluid cytokines were significantly attenuated as well. Endotoxin tolerance significantly improved bacterial clearance in both blood and peritoneal fluid after CLP. Similarly, ex vivo phagocytosis by primary peritoneal macrophages and RAW264.7 murine peritoneal macrophages was significantly improved after induction of the endotoxin tolerance phenotype. Contrary to our original hypothesis, we conclude that endotoxin tolerance significantly attenuates the host inflammatory response, augments bacterial clearance, and improves survival in this murine model of polymicrobial sepsis.

Behavioral tolerance to endotoxin is enhanced by adaptation to winter photoperiods

Seasonal changes in day length enhance or suppress aspects of immune function in mammals. Following adaptation to short, winter-like short photoperiods, cytokine and behavioral responses to lipopolysaccharide (LPS)-induced simulated infections are attenuated in LPS-naive Siberian hamsters. This experiment examined whether diminished initial responses to LPS in short days (SDs) are accompanied by decrements in the development of innate immunological memory that leads to endotoxin tolerance. Male hamsters exposed to SDs (9h-light/day) or kept in their natal long-day (LD) photoperiod (15h-light/day) for 12-13 weeks were injected with bacterial LPS (625microg/kg, i.p.) or sterile saline. Ten days later all hamsters were challenged with LPS (625microg/kg, i.p.), and behavioral sickness responses (anorexia and reductions in nest building) were assessed. In LD hamsters, behavioral responses to the second LPS injection were markedly attenuated but still evident, indicative of partial tolerance. SD hamsters, in contrast, failed to exhibit anorexic or thermoregulatory responses to the second LPS injection, indicative of complete behavioral tolerance to LPS. Thus despite engaging greater naive responses to LPS, LD hamsters exhibited incomplete LPS tolerance relative to SD hamsters. The expression of behavioral tolerance to endotoxin is relatively diminished during the breeding season, a time of year when naive responses to endotoxin are at their greatest. During winter, enhancements in behavioral endotoxin tolerance may conserve energy and facilitate survival in the face of energetically challenging conditions.

Immune reconstitution inflammatory syndrome in association with HIV/AIDS and tuberculosis: views over hidden possibilities

Gut immune components are severely compromised among persons with AIDS, which allows increased translocation of bacterial lipopolysaccharides (LPS) into the systemic circulation. These microbial LPS are reportedly increased in chronically HIV-infected individuals and findings have correlated convincingly with measures of immune activation. Immune reconstitution inflammatory syndrome (IRIS) is an adverse consequence of the restoration of pathogen-specific immune responses in a subset of HIV-infected subjects with underlying latent infections during the initial months of highly active antiretroviral treatment (HAART). Whether IRIS is the result of a response to a high antigen burden, an excessive response by the recovering immune system, exacerbated production of pro-inflammatory cytokines or a lack of immune regulation due to inability to produce regulatory cytokines remains to be determined. We theorize that those who develop IRIS have a high burden of proinflammatory cytokines produced also in response to systemic bacterial LPS that nonspecifically act on latent mycobacterial antigens. We also hypothesize that subjects that do not develop IRIS could have developed either tolerance (anergy) to persistent LPS/tubercle antigens or could have normal FOXP3+ gene and that those with defective FOXP3+ gene or those with enormous plasma LPS could be vulnerable to IRIS. The measure of microbial LPS, anti-LPS antibodies and nonspecific plasma cytokines in subjects on HAART shall predict the role of these components in IRIS.

Origin of immunomodulation after soft tissue trauma: potential involvement of extracellular heat-shock proteins

Severe injury may lead to immunosuppression, multiple organ failure, and death. The aim of the study was to investigate the direct impact of soft tissue destruction on the development of trauma-associated immunomodulation. Hip surgery was considered to represent an isolated soft tissue trauma that allowed for the examination of changes taking place locally at the site of trauma or systemically with regard to monocyte function and leukocyte redistribution. Peripheral blood and wound fluid collected from the drains of 21 patients after hip surgery were analyzed to determine the cellular composition and/or the responsiveness of mononuclear cells (MNCs) to lipopolysaccharide (LPS). Different factors present in the wound fluids were tested for their capacity to modulate the MNC of healthy individuals with regard to cytokine and chemokine secretion. We found that various factors, including heat-shock protein (HSP) 60 and HSP70, were locally released at the site of soft tissue trauma and could be detected in wound fluids. The wound fluid-derived MNC (but not the peripheral blood-derived MNC) showed an impaired capacity to release TNF-alpha after LPS stimulation. Cell-free wound fluid suppressed in healthy individuals the LPS-induced TNF-alpha secretion by MNC. After surgery, granulocytosis was found in peripheral blood and in wound fluids, but monocytopenia was restricted to wound fluids. In parallel, wound fluids induced in healthy individuals the release by MNC of distinct chemokines specific for granulocytes and monocytes. These wound fluid-mediated effects of TNF-alpha suppression and chemokine induction could be mimicked by recombinant human HSP70 and, in part, by HSP60. Thus, tissue-derived factors, such as HSP70 released after injury, suppress monocyte function and, therefore, might favor the development of immunosuppression after severe injury.

The cytokine response of circulating peripheral blood mononuclear cells is changed after intravenous injection of lipopolysaccharide in cattle

The aim of the study was to investigate lipopolysaccharide (LPS)-induced short and long term changes in capacity for intracellular cytokine-production of bovine circulating peripheral blood mononuclear cells (PBMCs). Eight dairy cows each received three intravenous injections of Escherichia coli LPS (10, 100 and 1000ng/kg, consecutively) at 3week intervals. Intracellular cytokine production was determined by flow cytometry in PBMCs obtained 0, 2, 6 and 24h after each LPS challenge. After LPS administration, proportions of monocytes producing tumour necrosis factor (TNF) alpha, interleukin (IL)-1beta and IL-8, as well as proportions of circulating lymphocytes producing interferon (IFN) gamma, decreased significantly. Within 24h, proportions had returned to or increased above pre-injection levels. Proportions of lymphocytes producing IL-4 and IL-10 increased significantly after injection of 1000ng LPS/kg. This study demonstrated that cytokine profiles shift quickly, but temporarily, to favour the anti-inflammatory response immediately after LPS exposure. The long term response to LPS was opposite to the immediate response, as cytokine profiles shifted in the 3weeks between challenges towards a pro-inflammatory response. Proportions of monocytes producing IL-1beta and TNFalpha determined immediately before the second and/or third LPS injection were higher than proportions determined before the first injection, whereas pre-injection proportions of lymphocytes producing IL-4 decreased with each challenge. These changes may result in a quicker host response to invading pathogens.

Pathophysiology of sepsis

Sepsis remains a critical problem with significant morbidity and mortality even in the modern era of critical care management. Multiple derangements exist in sepsis involving several different organs and systems, although controversies exist over their individual contribution to the disease process. Septic patients have substantial, life-threatening alterations in their coagulation system, and currently, there is an approved therapy with a component of the coagulation system (activated protein C) to treat patients with severe sepsis. Previously, it was believed that sepsis merely represented an exaggerated, hyperinflammatory response with patients dying from inflammation-induced organ injury. More recent data indicate that substantial heterogeneity exists in septic patients' inflammatory response, with some appearing immuno-stimulated, whereas others appear suppressed. Cellular changes continue the theme of heterogeneity. Some cells work too well such as neutrophils that remain activated for an extended time. Other cellular changes become accelerated in a detrimental fashion including lymphocyte apoptosis. Metabolic changes are clearly present, requiring close and individualized monitoring. At this point in time, the literature richly illustrates that no single mediator/system/pathway/pathogen drives the pathophysiology of sepsis. This review will briefly discuss many of the important alterations that account for the pathophysiology of sepsis.

Up-regulation of MyD88s and SIGIRR, molecules inhibiting Toll-like receptor signaling, in monocytes from septic patients*

OBJECTIVE

Immune status is altered during systemic inflammatory response syndrome and sepsis. Reduced ex vivo tumor necrosis factor production has been regularly reported with lipopolysaccharide-activated monocytes. In this study, we addressed the specificity of this hyporeactivity and investigated some of the possible associated mechanistic events.

DESIGN

Ex vivo study.

SETTING

Academic research laboratory.

PATIENTS

Healthy controls, septic patients, and resuscitated patients after cardiac arrest (RCA). This latter group presents a systemic inflammatory response syndrome of noninfectious origin.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

We investigated the reactivity of patients' monocytes in terms of cytokine production, after stimulation with a Toll-like receptor (TLR) 2 (Pam3CysSK4), a TLR4 (lipopolysaccharide), a Nod2 agonist (muramyl dipeptide), or heat-killed bacteria. We also investigated the contribution of phagocytosis in cytokine production, studied the expression of intracellular bacterial peptidoglycan sensors (Nod1 and Nod2), and analyzed the messenger RNA expression of inhibitors of TLR signaling: Toll interacting protein (Tollip), suppressor of cytokine signaling-1 (SOCS1), myeloid differentiation 88 short (MyD88s), and single immunoglobulin interleukin-1 receptor-related molecule (SIGIRR). In sepsis, tumor necrosis factor production in response to lipopolysaccharide and Pam3CysSK4 was reduced, whereas interleukin-10 production was enhanced. The responsiveness to Staphylococcus aureus, Escherichia coli, and muramyl dipeptide and the expression of Nod1 and Nod2 were similar to those obtained for healthy donors. The messenger RNA expression of Tollip and SOCS1 was unchanged, whereas that of MyD88s and SIGIRR was significantly enhanced compared with healthy controls. Monocytes from RCA patients showed a reduced production of tumor necrosis factor in response to lipopolysaccharide but neither to Pam3CysSK4 nor to heat-killed bacteria. They displayed an increased expression of SIGIRR but not of MyD88s. We showed that TLR2-dependent nuclear factor-kappaB activation was inhibited by MyD88s but not by SIGIRR. This result may explain the normal tumor necrosis factor production through TLR2 observed for monocytes of RCA patients.

CONCLUSION

There is a "reprogramming" of monocyte reactivity, and not a global hyporeactivity, during systemic inflammation, which differs in septic and RCA patients.

Optimization of analytical and pre-analytical variables associated with an ex vivo cytokine secretion assay

PURPOSE

Measurements of cytokine release in whole blood after ex vivo stimulation are useful in drug development. The components contributing to variation within such assays have not been clearly defined. Therefore, we characterized the sources of variability within an ex vivo stimulation assay for TNF-alpha release.

METHOD

Fresh whole blood or mononuclear cells from a cell preparation tube were added to silanized, screw-top tubes with a final concentration of 1 microg/mL lipopolysaccharide (LPS). Each tube was purged with 95% air/5%CO2 and incubated 4 or 6 h at 37 degrees C in a metabolic water bath. Plasma TNF-alpha was next measured in supernatants by immunoassay. Total method variability was assessed in 10 normal donors each drawn in the morning and afternoon over 3 days. Four additional samples were pre-treated with dexamethasone to investigate inhibition of TNF-alpha release.

RESULTS

Our analysis indicated precise temperature control, the timing and duration of stimulation, and the surface properties of the stimulation vessel most significantly influenced assay performance. A comparison of multiple anticoagulants indicated that careful consideration should be taken in selecting the optimal anticoagulant. The estimated total assay CV for all anticoagulants tested was less than 33.81%. The analytical variability (stimulation and measurement) was less than 25.88% CV. The one exception was mononuclear cells collected in sodium heparin. The total variability estimate incorporated day-to-day, diurnal, inter-donor, tube-to-tube and immunoassay variability. Using our optimized conditions, TNF-alpha release was inhibited by dexamethasone with a mean IC50 of 33.3 +/- 4.6 nM.

CONCLUSIONS

We have described an optimal set of conditions for collection, storage and processing of an ex vivo cytokine stimulation assay. These conditions were selected for operational feasibility, minimal imprecision and elimination of potential confounding factors. The end result is a more robust method that can be applied to clinical drug development.

Reprogramming of circulatory cells in sepsis and SIRS

Immune status is altered in patients with sepsis or non-infectious systemic inflammatory response syndrome (SIRS). Reduced ex-vivo TNF production by endotoxin-activated monocytes has been regularly reported. This observation is reminiscent of the phenomenon of endotoxin tolerance, and the term 'leukocyte reprogramming' well defines this phenomenon. This review will outline that the hyporesponsiveness of circulating leukocytes is not a generalized phenomenon in sepsis and SIRS. Indeed, the nature of the insult (i.e. infectious versus non-infectious SIRS; under anesthesia [surgery] or not [trauma, burn]), the nature of the activator used to trigger leukocytes (i.e. different Toll-like receptor ligands or whole bacteria), the nature of the cell culture (i.e. isolated monocytes versus peripheral blood mononuclear cells versus whole blood assays), and the nature of the analyzed cytokines (e.g. IL-1beta versus IL-1ra; TNF versus IL-10) have a profound influence on the outcome of the response.

The induction of super-resistance using synthetic lipopolysaccharide receptor agonist rescues fatal endotoxemia in rats without excessive immunosuppression

Endotoxin tolerance provides protection against mortality under various conditions of stress. However, the induction of endotoxin tolerance thus far has no clinical application because of endotoxin toxicity and the excessive immune suppression that follows the tolerance induction. In this study, we examined whether a novel, synthetic lipopolysaccharide (LPS) receptor agonist, ER-803058 (ER) can induce endotoxin tolerance with accompanying low toxicity. The stimulative effects of ER on tumor necrosis factor (TNF)-alpha production from RAW264 cells were 50% to 70% lower than those of the corresponding quantities of LPS. ER pretreatment also diminished TNF-alpha secretion induced by a subsequent LPS shock. However, the degree of desensitization with ER pretreatment (10 ng/mL, 55.5% +/- 6.7%; 100 ng/mL, 42.3 +/- 4.9%) was modest in contrast with that measured for the corresponding LPS pretreatment (10 ng/mL, 36.7% +/- 3.7%; 100 ng/mL, 20.0% +/- 3.6%). The minimum in vivo dose (0.02 mg/kg/body weight) of ER-induced negligible production of TNF-alpha and interleukin (IL)-6 in rats, and resulted in a modest endotoxin tolerance with respect to TNF-alpha secretion. Although the plasma TNF-alpha level after ER pretreatment was decreased (48.2% +/- 1.1%), the suppression was not statistically significant. Interestingly, even this minimal quantity of ER pretreatment evoked a dramatic improvement in survival (90% survival) against administration of a lethal dose of LPS, which is inconsistent with the modest TNF-alpha suppression. Furthermore, ER pretreatment preserved normal plasma albumin levels and prevented the increase of plasma blood urea nitrogen levels seen with LPS. These results indicate that pretreatment with ER can effectively induce endotoxin tolerance, with a consequent improvement in mortality without toxicity and without subsequent excessive immunosuppression.

Neutrophils as firemen, production of anti-inflammatory mediators by neutrophils in a mixed cell environment

Neutrophils represent critical components of the innate immune system that bear primary responsibility for phagocytosis and killing of invading pathogens. Following stimulation of human whole blood, robust production of multiple cytokines and cytokine inhibitors occurs. We attempted to define the cell population responsible for the synthesis of different mediators by first stimulating whole blood and then isolating pure populations of granulocytes and monocytes. Monocytes produced mRNA coding for the classic pro-inflammatory cytokines tumor necrosis factor-alpha (TNF-alpha), interleukin-1beta (IL-1beta), and IL-6, while mRNA for these cytokines was not detectable in the isolated neutrophils. In contrast, neutrophils produce significant quantities of cytokine inhibitors such as the type 2 TNF soluble receptor and the IL-1 receptor antagonist. Both neutrophils and monocytes produced mRNA coding for IL-8. These data indicate that following stimulation of a mixed cell population the monocytes primarily produce pro-inflammatory mediators while the neutrophils synthesize a significant portion of the anti-inflammatory mediators. The neutrophils may be compared to firemen who bring the resources necessary to put out the flame of acute inflammation.

Enhancement of dendritic cell production by fms-like tyrosine kinase-3 ligand increases the resistance of mice to a burn wound infection

Fms-like tyrosine kinase-3 ligand (Flt3L) is a hemopoietic cytokine that stimulates the production of dendritic cells. This study evaluated the ability of Flt3L-enhanced dendritic cell production to increase the resistance of mice to a burn wound infection with Pseudomonas aeruginosa, a common source of infections in burn patients that have impaired immunity and are susceptible to opportunistic microorganisms. Treatment of mice with Flt3L for 5 days caused a significant increase in dendritic cell numbers in the spleen and significantly increased survival upon a subsequent burn wound infection. Improved survival in Flt3L-treated mice was associated with limited bacterial growth and spread within the burn wounds and a decrease in systemic dissemination of P. aeruginosa. Resistance to burn wound infection could also be conferred to recipient mice by the adoptive transfer of dendritic cells that had been isolated from spleens of Flt3L-treated mice. Adoptive transfer of the same number of splenic dendritic cells from nontreated mice did not confer resistance to burn wound infection. These data indicate that Flt3L can increase the resistance of mice to a P. aeruginosa burn wound infection through both stimulation of dendritic cell production and enhancement of dendritic cell function.

Diminished bacterial clearance is associated with decreased IL-12 and interferon-gamma production but a sustained proinflammatory response in a murine model of postseptic immunosuppression

After a major illness or injury, immune status in critically ill patients may fluctuate between a marked proinflammatory response and an immunosuppressed state. Postinflammatory immunosuppression can result in increased susceptibility to infection. Alterations of cytokine production, such as suppression of IFNgamma and elevation of the anti-inflammatory cytokine IL-10, are believed to contribute to postinflammatory immunosuppression. We examined antimicrobial immunity in mice that had previously been subjected to a sublethal cecal ligation and puncture (CLP) as a model of major injury. Mice were challenged with Pseudomonas aeruginosa (5 x 10(7) CFU i.v.) on day 5 after CLP or sham surgery. Bacterial clearance in mice after CLP was impaired and associated with decreased production of IFNgamma and increased production of IL-10 in the early response to the Pseudomonas challenge. Pseudomonas-induced production of the IFNgamma-inducing factor IL-12 was also decreased in post-CLP mice. However, splenocytes from post-CLP mice remained responsive to exogenous stimulation with the IFNgamma-inducing cytokines IL-12, IL-15, and IL-18 as well as T-cell receptor activation. Furthermore, production of the proinflammatory cytokines TNF-alpha, IL-1beta, and IL-6 were as high, or higher, in the post-CLP group compared with sham mice after P. aeruginosa challenge. Blockade of IL-10 did not reverse IL-12 and IFNgamma suppression in splenocytes from post-CLP mice. These studies show that suppressed bacterial clearance in post-CLP mice is associated with decreased production of IFNgamma and IL-12 and with increased production of IL-10 and proinflammatory cytokines.

MAGNOLOL ALTERS THE COURSE OF ENDOTOXIN TOLERANCE AND PROVIDES EARLY PROTECTION AGAINST ENDOTOXIN CHALLENGE FOLLOWING SUBLETHAL HEMORRHAGE IN RATS

The endotoxin tolerance induced by sublethal hemorrhage (SLH) is associated with an initial surge of proinflammatory cytokines such as TNF-alpha. Magnolol, a potent antioxidative herb, is hypothesized to suppress TNF-alpha production after SLH and to alter or attenuate subsequent endotoxin tolerance. A prospective, randomized experimental study was performed. Male Sprague-Dawley rats were randomly segregated into one of four groups. Rats in the Sham/Veh and Sham/Mag groups received a sham operation for SLH and treatment with vehicle or magnolol, respectively. Rats in the SLH/Veh and SLH/Mag groups received SLH and treatment with vehicle or magnolol, respectively. Animals were subjected to endotoxin challenge (EC) at 12, 24, or 36 h after these procedures. Cytokines (TNF-alpha and IL-10), lipid peroxidation, and superoxide dismutase (SOD) activity were measured in lung tissue following SLH. Plasma cytokines were assessed after SLH or EC at different time points, and survival analyses were performed after EC. Plasma and tissue TNF-alpha increased after SLH; this increase was significantly suppressed by magnolol. Additionally, a significant increase in plasma and tissue IL-10 after SLH was observed in the SLH/Mag group. Lipid peroxidation and SOD activity increased after SLH; magnolol suppressed the lipid peroxidation but not the SOD activity. If EC was performed 12 or 24 h after SLH, greater survival with decreased TNF-alpha and increased IL-10 in plasma was observed in the SLH/Mag group. If EC was performed 24 or 36 h after SLH, greater survival with decreased plasma TNF-alpha was observed in the SLH/Veh group. In conclusion, magnolol induces an antiinflammatory response and provides early protection against EC following SLH; however, magnolol attenuates the protraction of endotoxin tolerance and inhibits late protection against EC following SLH.

Immune monitoring of patients with septic shock by measurement of intraleukocyte cytokines

OBJECTIVE

To assess the immune competence of patients presenting with septic shock by measuring on-line the production of intracellular cytokines by circulating leukocytes.

DESIGN AND SETTING

Prospective study in a 18-bed medical intensive care unit of a university hospital.

PATIENTS AND PARTICIPANTS

21 patients with septic shock, and 11 volunteers.

INTERVENTIONS

Single-step isolation of leukocytes from whole blood obtained within the first 24 h after admission. Leukocytes were fixed immediately or after treatment with lipopolysaccharide (LPS) and/or heterologous plasma.

MEASUREMENTS AND RESULTS

Leukocytes were permeabilized, and the intracellular cytokine expression of TNF-alpha and IL-10 was quantified by immunostaining and flow cytometry. LPS treatment significantly increased monocyte intracellular cytokine TNF-alpha and IL-10 as well as lymphocyte intracellular cytokine IL-10 in normal leukocytes. Septic monocytes and granulocytes had nonstimulated intracellular cytokine TNF-alpha concentrations lower than those measured in volunteers and were severely hyporesponsive to LPS. These phenotypic changes were correlated with disease severity and could be reproduced by treatment of normal leukocytes with plasma from patients with septic shock.

CONCLUSIONS

Intracellular cytokine staining is a simple and rapid method to assess in situ and on-line the inflammatory balance and responsiveness of leukocyte subpopulations and could therefore represent a useful monitoring tool to assess the immune competence of critically ill patients. This study identifies the cellular source of cytokines in whole blood and confirms prior reports showing that septic phagocytes are characterized by a predominant anti-inflammatory phenotype, with hyporesponsiveness to LPS, depending on a plasma deactivation factor.

[Clinical course and prognostic significance of immunological and functional parameters after severe trauma]

Generalized severe trauma leads to an increased incidence of SIRS, sepsis, and MOF. The aim of this prospective study was to investigate the immunological parameters in terms of their predictive value for multiple organ failure (MOF).HLA-DR expression on peripheral monocytes was analyzed by flow cytometry, the ex vivo endotoxin-stimulated TNFalpha synthesis of whole blood, and the serum levels of IL-6, IL-10, procalcitonin (PCT), and CRP were analyzed by ELISA in 16 severely injured patients with an ISS >25. Initially after trauma elevated serum levels of IL-6, IL-10, and PCT were found, while TNFalpha-producing capacity and HLA-DR expression on monocytes decreased. In patients with MOF a further decrease of HLA-DR expression on days 3-4 after injury was observed accompanied by elevated levels of IL-10 at this time point. However, the TNFalpha-producing capacity was even enhanced in patients with MOF in the 2nd week after trauma. Later PCT levels were also higher in patients with MOF.Monitoring of immunological parameters after severe injury is useful to identify mediator constellations that are associated with the development and clinical course of MOF even in extremely injured patients.

Pathogenesis of malaria and clinically similar conditions

There is now wide acceptance of the concept that the similarity between many acute infectious diseases, be they viral, bacterial, or parasitic in origin, is caused by the overproduction of inflammatory cytokines initiated when the organism interacts with the innate immune system. This is also true of certain noninfectious states, such as the tissue injury syndromes. This review discusses the historical origins of these ideas, which began with tumor necrosis factor (TNF) and spread from their origins in malaria research to other fields. As well the more established proinflammatory mediators, such as TNF, interleukin-1, and lymphotoxin, the roles of nitric oxide and carbon monoxide, which are chiefly inhibitory, are discussed. The established and potential roles of two more recently recognized contributors, overactivity of the enzyme poly(ADP-ribose) polymerase 1 (PARP-1) and the escape of high-mobility-group box 1 (HMGB1) protein from its normal location into the circulation, are also put in context. The pathogenesis of the disease caused by falciparum malaria is then considered in the light of what has been learned about the roles of these mediators in these other diseases, as well as in malaria itself.

Differential regulation of membrane CD14 expression and endotoxin-tolerance in alveolar macrophages

CD14 is important in the clearance of bacterial pathogens from lungs. However, the mechanisms that regulate the expression of membrane CD14 (mCD14) on alveolar macrophages (AM) have not been studied in detail. This study examines the regulation of mCD14 on AM exposed to Escherichia coli in vivo and in vitro, and explores the consequences of changes in mCD14 expression. The expression of mCD14 was decreased on AM exposed to E. coli in vivo and AM incubated with lipopolysaccharide (LPS) or E. coli in vitro. Polymyxin B abolished LPS effects, but only partially blocked the effects of E. coli. Blockade of extracellular signal-regulated kinase pathways attenuated LPS and E. coli-induced decrease in mCD14 expression. Inhibition of proteases abrogated the LPS-induced decrease in mCD14 expression on AM and the release of sCD14 into the supernatants, but did not affect the response to E. coli. The production of tumor necrosis factor-alpha in response to a second challenge with Staphylococcus aureus or zymosan was decreased in AM after incubation with E. coli but not LPS. These studies show that distinct mechanisms regulate the expression of mCD14 and the induction of endotoxin tolerance in AM, and suggest that AM function is impaired at sites of bacterial infection.

Paradoxical Cytoskeleton and Microparticle Formation Changes in Monocytes and Polymorphonuclear Leukocytes in Severe Systemic Inflammatory Response Syndrome Patients

BACKGROUND

Circulating monocytes and polymorphonuclear leukocytes (PMNLs) are considered as central regulators controlling systemic inflammatory response after severe insults. Recently, activated monocytes and PMNLs have been reported to produce microparticles (MPs) in vitro. The objective of this study was to evaluate production of MPs and changes of cytoskeleton in monocytes from severe systemic inflammatory response syndrome (SIRS) patients, and to compare them with those in PMNLs.

METHODS

Twenty severe SIRS patients (SIRS criteria and serum C-reactive protein > 10 mg/dL) and 15 healthy volunteers were included. MP formation and F-actin content in monocytes and PMNLs were measured by flow cytometry in the presence or absence of lipopolysaccharide or formylmethionyl-leucyl-phenylalanine (FMLP). The membrane expression of human leukocyte antigen-DR and CD64 in monocytes and O2- production in PMNLs were also measured by flow cytometry.

RESULTS

In severe SIRS patients, MP formation with and without lipopolysaccharide in monocytes significantly decreased in comparison with those in normal controls (p < 0.05), whereas those with and without FMLP in PMNLs increased (p < 0.05). F-actin content with and without FMLP in monocytes also significantly decreased in patients (p < 0.05), whereas those in PMNLs increased as compared with normal controls (p < 0.05). The expression of human leukocyte antigen-DR in monocytes significantly decreased in patients (p < 0.05), which indicated monocyte modulation. The O2- production in PMNLs increased in patients (p < 0.05), which showed PMNL activation.

CONCLUSION

The changes of MP formation and cytoskeleton in circulating monocytes and PMNLs were paradoxically different in severe SIRS patients.

Modulation of the Lipopolysaccharide Receptor Complex (CD14, TLR4, MD-2) and Toll-Like Receptor 2 in Systemic Inflammatory Response Syndrome-Positive Patients With and Without Infection: Relationship to Tolerance

The lipopolysaccharide (LPS) receptor complex consists of two interacting receptors (CD14 and TLR4) and an associated protein (MD-2). When engaged by LPS, as in gram-negative infection, this complex transduces a signal detected by MyD88 and passed onward by a cascade of the IRAKs, TRAF6, and NIK, resulting in activation of NF-kappaB. A similar cascade, mediated by TLR2, occurs with ligands derived from gram-positive bacteria. In vitro studies of human monocytes have shown that TLR4 mRNA is paradoxically upregulated in response to "tolerizing" doses of LPS. This study evaluated changes in vivo of blood monocyte CD14, TLR4, TLR2, and MD-2 mRNA by reverse transcription followed by real-time polymerase chain reaction in surgical intensive care unit patients and in normal controls. In addition cell-surface receptor expression of TLR2, TLR4, and CD14 was assessed by flow cytometry in patients and normal controls. Inflammation-induced acute tolerance to LPS was evaluated by ex vivo whole blood tumor necrosis factor alpha production and was significantly reduced in patients compared with controls, confirming LPS hyporesponsiveness. Monocyte mRNA and cell-surface receptor expression of TLR4 were increased 2.4-fold (P < 0.05) and 1.7-fold (P <.002), respectively, in patients compared with normal controls. Monocyte TLR2 mRNA, MD-2 mRNA and CD14 and TLR2 cell-surface expression were not significantly changed compared with controls. The present study suggests that the acute inflammatory condition associated with peripheral cellular LPS hyporesponsiveness is neither specific to prior infectious challenge nor can be ascribed to significant alterations in expression of the cell-surface LPS binding complex proteins.

Lower levels of whole blood LPS-stimulated cytokine release are associated with poorer clinical outcomes in surgical ICU patients

BACKGROUND

In vitro pretreatment of human monocytes with lipopolysaccharide (LPS) induces "endotoxin tolerance" with blunted TNF and IL-6 release to rechallenge with LPS. The pro-inflammatory cytokines TNF and IL-6 are important mediators in sepsis. A high IL-6 concentration has been used as a marker of infection severity, but IL-6 may also have beneficial effects as an acute-phase protein. We sought to address two questions: (a) What is the relationship between TNF and IL-6 release? (b) Is the clinical outcome different for intensive care unit (ICU) patients with ex vivo characteristics of endotoxin tolerance (low levels of ex vivo LPS-stimulated cytokine release)?

MATERIALS AND METHODS

Heparinized whole blood was obtained from 62 surgical ICU patients and 15 control subjects and incubated for 3 h at 37 degrees C in the presence or absence of 10 ng/mL LPS. Concentrations of TNF and IL-6 were measured in plasma samples using an enzyme-linked immunosorbent assay (pg/mL). Clinical data on ICU length of stay (LOS), ventilator days, white blood cell count (WBC), and documented clinical infection were obtained by chart review. Outcome parameters for patients with low ex vivo LPS-stimulated cytokine release (low = IL-6 < 3000 pg/mL and TNF <2100 pg/mL) were compared to patients with Normal/High concentrations of cytokines.

RESULTS

Cytokines were essentially undetectable in ICU patients or controls without LPS stimulation, however a range of values was measured for LPS-stimulated release in both ICU patients (IL-6, 7847 +/- 857 pg/mL; TNF, 4390 +/- 457 pg/mL) and controls (IL-6, 7704 +/- 793 pg/mL; TNF, 6706 +/- 715 pg/mL). There were no differences in age between High/Normal concentrations of cytokines compared to the Low cytokine group, however there were significant differences in WBC, cytokine concentrations, ICU LOS, incidence of clinical infection, and mortality. The Low group also required an average of 6.9 more days of mechanical ventilation (p < 0.05). LPS-stimulated TNF release seemed to correlate better with the observed mortality than did IL-6 release.

CONCLUSION

The data suggest that ICU patients with characteristics of endotoxin tolerance (low LPS-stimulated cytokine release capacity) have significantly poorer clinical outcomes. Ex vivo LPS-stimulated whole blood cytokine production may be useful to identify ICU patients with severe sepsis.