Reprogramming of circulatory cells in sepsis and SIRS

A dual negative regulation model of Toll-like receptor 4 signaling for endotoxin preconditioning in human endotoxemia

We discuss a model illustrating how the outcome of repeated endotoxin administration experiments can emerge as a natural consequence of the tightly regulated signaling pathways and also highlight the importance of a dual negative feedback regulation including PI3K/Akt and IRAK-M (IRAK3). We identify the relative time scales of the onset and the magnitude of the stimulus as key determinants of outcome in repeated administration experiments. The results of our simulations involve potentiated response, tolerance, and protective tolerance. Moreover, the knockout of negative regulators shows that IRAK-M is a necessary and sufficient factor for generation of endotoxin tolerance (ET). The effects of the knockout of IRAK-M gene or administration of PI3K inhibitor do yield predictions that have been verified experimentally. Finally, the pretreatment with PI3K inhibitor reveals the interaction between these two negative regulations.

A multicentre evaluation of the accuracy and performance of IP-10 for the diagnosis of infection with M. tuberculosis

IP-10 has potential as a diagnostic marker for infection with Mycobacterium tuberculosis, with comparable accuracy to QuantiFERON-TB Gold In-Tube test (QFT-IT). The aims were to assess the sensitivity and specificity of IP-10, and to evaluate the impact of co-morbidity on IP-10 and QFT-IT. 168 cases with active TB, 101 healthy controls and 175 non-TB patients were included. IP-10 and IFN-γ were measured in plasma of QFT-IT stimulated whole blood and analyzed using previously determined algorithms. A subgroup of 48 patients and 70 healthy controls was tested in parallel with T-SPOT.TB IP-10 and QFT-IT had comparable accuracy. Sensitivity was 81% and 84% with a specificity of 97% and 100%, respectively. Combining IP-10 and QFT-IT improved sensitivity to 87% (p < 0.0005), with a specificity of 97%. T-SPOT.TB was more sensitive than QFT-IT, but not IP-10. Among non-TB patients IP-10 had a higher rate of positive responders (35% vs 27%, p < 0.02) and for both tests a positive response was associated with relevant risk factors. IFN-γ but not IP-10 responses to mitogen stimulation were reduced in patients with TB and non-TB infection. This study confirms and validates previous findings and adds substance to IP-10 as a novel diagnostic marker for infection with M. tuberculosis. IP-10 appeared less influenced by infections other than TB; further studies are needed to test the clinical impact of these findings.

Genetic aspects of pancreatitis

Acute pancreatitis and chronic pancreatitis are complex inflammatory disorders of the pancreas with unpredictable severity, complications, and clinical courses. Growing evidence for genetic risk and modifying factors, plus strong evidence that only a minority of patients with these disorders are heavy alcohol drinkers, has revolutionized our concept of these diseases. Once considered a self-inflicted injury, pancreatitis is now recognized as a complex inflammatory condition like inflammatory bowel disease. Genetic linkage and candidate gene studies have identified six pancreas-targeting factors that are associated with changes in susceptibility to acute and/or chronic pancreatitis, including cationic trypsinogen (PRSS1), anionic trypsinogen (PRSS2), serine protease inhibitor Kazal 1 (SPINK1), cystic fibrosis transmembrane conductance regulator (CFTR), chymotrypsinogen C (CTRC) and calcium-sensing receptor (CASR). Patients with mutations in these genes are at increased risk of pancreatitis caused by a variety of stresses including hyperlipidemia and hypercalcemia. Multiple studies are reporting new polymorphisms, as well as complex gene x gene and gene x environmental interactions.

Immunosuppressive CD14+HLA-DRlow/- monocytes in prostate cancer

OBJECTIVE

To determine if the levels of circulating myeloid-derived suppressor cells increase with progression of prostate cancer (PCa); to determine if such cells could contribute to the relative inefficiency of PCa immunotherapy.

MATERIALS AND METHODS

We analyzed peripheral blood mononuclear cells isolated from untreated PCa patients (uPCa; N = 18; mean age +/- SD: 72.1 +/- 6.9 years), tPCa (N = 22; 72.8 +/- 9.8 years) and age matched controls (AMC; N = 12; 68.8 +/- 7.5 years). We quantified surface marker phenotype, differentiation potential, effects on T cell proliferation and intracellular cytokines.

RESULTS

We observed an unexpectedly high percentage of a type of myeloid-derived suppressor cells, CD14(+)HLA-DR(low/-) monocytes, in tPCa (30.7 +/- 15.0% of CD14(+) cells) relative to AMC (4.1 +/- 6.5%, P < 0.0001) and uPCa (10.6 +/- 14.3%, P = 0.0001). The levels of CD14(+) HLA-DR(low/-) cells were significantly correlated with circulating PSA levels and treatment with LHRH-agonist leuprolide in combination with either an antiandrogen or dexamethasone. Monocytes from tPCa inhibited autologous T cell proliferation statistically significantly more effectively than AMC monocytes and were defective in their ability to differentiate into phenotypically mature dendritic cells. Isolated CD14(+)HLA-DR(low/-) cells expressed higher levels of intracellular interleukin-10 and suppressed T cell proliferation more effectively than isolated CD14(+)HLA-DR(+) cells.

CONCLUSIONS

This is the first report of CD14(+) cells exhibiting reduced expression of HLA-DR molecules in PCa patients. These cells suppress immune cell function in vitro and, plausibly, in vivo, a finding that must be factored into the design of immunotherapy protocols for PCa patients.

CD14 inhibition efficiently attenuates early inflammatory and hemostatic responses in Escherichia coli sepsis in pigs

Sepsis is a severe infection-induced systemic inflammatory syndrome. Inhibition of downstream inflammatory mediators of sepsis, e.g., TNF-alpha, has failed in clinical trials. The aim of this study was to investigate the effects of inhibiting CD14, a key upstream innate immunity molecule, on the early inflammatory and hemostatic responses in a pig model of gram-negative sepsis. The study comprised two arms, whole live Escherichia coli bacteria and E. coli lipopolysaccharide (LPS) (n=25 and n=9 animals, respectively). The animals were allocated into treatment (anti-CD14) and control (IgG isotype or saline) groups. Inflammatory, hemostatic, physiological, and microbiological parameters were measured. The proinflammatory cytokines TNF-alpha, IL-1beta, IL-6, and IL-8, but not the anti-inflammatory cytokine IL-10, were efficiently inhibited by anti-CD14. Furthermore, anti-CD14 preserved the leukocyte count and significantly reduced granulocyte enzyme matrix metalloproteinase-9 release and expression of the granulocyte membrane activation molecule wCD11R3 (pig CD11b). The hemostatic markers thrombin-antithrombin III complexes and plasminogen activator inhibitor-1 were significantly attenuated. Anti-CD14 did not affect LPS or E. coli DNA levels. This study documents that CD14 inhibition efficiently attenuates the proinflammatory cytokine response and granulocyte activation and reverses the procoagulant state but does not interfere with LPS levels or bacterial counts in E. coli-induced sepsis.-Thorgersen, E. B., Hellerud, B. C., Nielsen, E. W., Barratt-Due, A., Fure, H., Lindstad, J. K., Pharo, A., Fosse, E., Tønnessen, T. I., Johansen, H. T., Castellheim, A., Mollnes, T. E. CD14 inhibition efficiently attenuates early inflammatory and hemostatic responses in Escherichia coli sepsis in pigs.

Endotoxin tolerance: new mechanisms, molecules and clinical significance

Prior exposure of innate immune cells like monocytes/macrophages to minute amounts of endotoxin cause them to become refractory to subsequent endotoxin challenge, a phenomenon called "endotoxin tolerance". Clinically, this state is associated with monocytes/macrophages in sepsis patients where they contribute to "immunosuppression" and mortality. The molecular mechanisms underlying endotoxin tolerance remain elusive. The recent appreciation of inflammation as a self-regulating process, the relative contribution of MyD88 versus TRIF signaling pathways in inducing activation or tolerance, plasticity of NF-kappaB function and the role of chromatin modification and microRNAs in LPS-induced gene reprogramming urges a re-evaluation of endotoxin tolerance. This review integrates these new findings into an up-to-date account of endotoxin tolerance, its molecular basis and clinical implications in different pathologies.

Tolerance and M2 (alternative) macrophage polarization are related processes orchestrated by p50 nuclear factor kappaB

Cells of the monocyte-macrophage lineage play a central role in the orchestration and resolution of inflammation. Plasticity is a hallmark of mononuclear phagocytes, and in response to environmental signals these cells undergo different forms of polarized activation, the extremes of which are called classic or M1 and alternative or M2. NF-kappaB is a key regulator of inflammation and resolution, and its activation is subject to multiple levels of regulation, including inhibitory, which finely tune macrophage functions. Here we identify the p50 subunit of NF-kappaB as a key regulator of M2-driven inflammatory reactions in vitro and in vivo. p50 NF-kappaB inhibits NF-kappaB-driven, M1-polarizing, IFN-beta production. Accordingly, p50-deficient mice show exacerbated M1-driven inflammation and defective capacity to mount allergy and helminth-driven M2-polarized inflammatory reactions. Thus, NF-kappaB p50 is a key component in the orchestration of M2-driven inflammatory reactions.

The stressed host response to infection: the disruptive signals and rhythms of systemic inflammation

The cognate signals from sterile or pathogen-induced sources converge on the same recognition or response pathways. In the surgical patient, a systemic response to infection most often occurs in the context of ongoing inflammatory stress. Such an inflammatory response is modulated initially by the magnitude of injury and by patient-specific (endogenous) factors, such as confounding illness, age, and genetic variation. Over an extended period of stress, treatmentrelated (exogenous) factors add unpredictability to host responses to subsequent challenges, such as acquired infection. The host response is discussed in the context of how existing sterile stressors may modify the response to acquired infection in surgical patients.

Innate immune responses to danger signals in systemic inflammatory response syndrome and sepsis

The systemic immune response induced by non-infectious agents is called systemic inflammatory response syndrome (SIRS) and infection-induced systemic immune response is called sepsis. The host inflammatory response in SIRS and sepsis is similar and may lead to multiple organ dysfunction syndrome (MODS) and ultimately death. The mortality and morbidity in SIRS and sepsis (i.e. critical illness) remain high despite advances in diagnostic and organ supporting possibilities in intensive care units. In critical illness, the acute immune response is organized and executed by innate immunity influenced by the neuroendocrine system. This response starts with sensing of danger by pattern-recognition receptors on the immune competent cells and endothelium. The sensed danger signals, through specific signalling pathways, activate nuclear transcription factor kappaB and other transcription factors and gene regulatory systems which up-regulate the expression of pro-inflammatory mediators. The plasma cascades are also activated which together with the produced pro-inflammatory mediators stimulate further the production of inflammatory biomarkers. The acute inflammatory response underlies the pathophysiological mechanisms involved in the development of MODS. The inflammatory mediators directly affect organ function and cause a decline in remote organ function by mediating the production of nitric oxide leading to mitochondrial anergy and cytopathic hypoxia, a condition of cellular inability to use oxygen. Understanding the mechanisms of acute immune responses in critical illness is necessary for the development of urgently needed therapeutics. The aim of this review is to provide a description of the key components and mechanisms involved in the immune response in SIRS and sepsis.

Hsp70 and cardiac surgery: molecular chaperone and inflammatory regulator with compartmentalized effects

Open heart surgery is a unique model to study the interplay between cellular injury, regulation of inflammatory responses and tissue repair. Stress-inducible heat shock protein 70-kDa (Hsp70) provides a molecular link between these events. In addition to molecular chaperoning, Hsp70 exerts modulatory effects on endothelial cells and leukocytes involved in inflammatory networks. Hsp70 residing in the intracellular compartment is part of an inhibitory feedback loop that acts on nuclear factor kappaB (NF-kappaB). In contrast, extracellular Hsp70 is recognized by multiple germline-encoded immune receptors, e.g., Toll-like receptor (TLR) 2, TLR4, LOX-1, CD91, CD94, CCR5 and CD40. Hsp70 is thereby able to enhance chemotaxis, phagocytosis and cytolytic activity of innate immune cells and stimulate antigen-specific responses. These apparent contradictory pro- and anti-inflammatory effects of endogenous Hsp70 in the context of cardiac surgery are still not fully understood. An all-embracing model of the compartmentalized effects of endogenous Hsp70 in the orchestration of inflammatory responses in cardiac surgery is proposed.

Invited review: deterioration of the immune system after trauma: signals and cellular mechanisms

Multiple trauma leads to a deterioration of the immune system. On the one hand, hyperinflammation mediates remote organ damage and may lead to multi-organ failure. On the other hand, immunosuppression develops and promotes an enhanced risk to acquire infectious complications after trauma. The mechanisms that underlie these opposing consequences of trauma are not yet completely understood. There is increasing evidence that endogenous danger signals that derive from destroyed tissues play a role in trauma-induced immune dysfunction. Here, we give an overview on the common animal models that are used to investigate trauma-induced pathology, potential signals and cellular mechanisms that support the imbalance between inflammation and counter-regulation after trauma.

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.

A simple mathematical model of signaling resulting from the binding of lipopolysaccharide with Toll-like receptor 4 demonstrates inherent preconditioning behavior

The complex biology of Gram-negative bacterial lipopolysaccharide (LPS) is central to the acute inflammatory response in sepsis and related diseases. Repeated treatment with LPS can lead to desensitization or enhancement of subsequent responses both in vitro and in vivo (a phenomenon known as preconditioning). Previous computational studies have demonstrated a role for anti-inflammatory influences in this process (J. Day, J. Rubin, Y. Vodovotz, C.C. Chow, A. Reynolds, G. Clermont, A reduced mathematical model of the acute inflammatory response: II. Capturing scenarios of repeated endotoxin administration. J. Theor. Biol. 242 (2006) 237). Since LPS signals via Toll-like receptor 4 (TLR4), we created a simple mathematical model in order to address the role of this receptor in both the normal and preconditioned response to LPS. We created a non-linear system of ordinary differential equations, consisting of free LPS, free TLR4, bound complex LPS-TLR4, and an intracellular signaling cascade (lumped into a single variable). We simulate the effects of preconditioning by small and large repeated doses of LPS on the system, varying the timing of the doses as well as the rate of expression of TLR4. Our simulations suggest that a simplified model of LPS/TLR4 signaling can account for complex preconditioning phenomena without invoking a specific signaling inhibition mechanism, but rather based on the dynamics of the signaling response itself, as well as the timing and magnitude of the LPS stimuli.

Prognostic value of phagocytic activity of neutrophils and monocytes in sepsis. Correlation to CD64 and CD14 antigen expression

The role of the phagocytic function of monocytes and neutrophils in sepsis has been poorly investigated. The present study evaluated the impact of the phagocytic activity of neutrophils and monocytes on the outcome of patients with severe sepsis. Thirty-one patients and 30 healthy individuals were enrolled in the study. The phagocytic activity of monocytes and neutrophils was evaluated during 24 h after admission and the results were correlated to the expression of CD64 on neutrophils and monocytes, CD14 antigen on monocytes, the Simplified Acute Physiology Score II and the patients' survival. A reduced phagocytic activity of neutrophils during the first 24 h after admission was a negative predictor for survival. Increased expression of CD64 antigen on polymorphonuclear cells (PMNs) and monocytes was favourably correlated to the patients' survival. In multivariate analysis the phagocytic activity of PMNs was the only independent predictor factor for survival. Patients with PMN phagocytic activity <37% had lower expression of CD64 on monocytes and PMNs and worse outcome, while those with phagocytic activity >37% had higher expression of CD64 on monocytes and PMNs and better outcome. Reduced phagocytic activity of neutrophils may represent a state of neutrophil inactivation similar to that previously described for monocytes during the compensatory anti-inflammatory response.

Effect of major abdominal surgery on endotoxin release and expression of Toll-like receptors 2/4

BACKGROUND

Surgery can cause endotoxemia, and endotoxin aggregates to Toll-like receptors and acts proinflammatory; repetitive endotoxin application can cause tolerance. The objective of the study is to characterize early inflammatory response and expression of TLR2/4 during major abdominal surgery.

MATERIALS AND METHODS

A prospective controlled study of 20 patients with elective major abdominal surgery was performed. Blood samples were collected before and at a defined time after surgery. Endotoxemia, capability of plasma to inactivate endotoxin, cytokine release of LPS-stimulated mononuclear cells, quantitative TLR mRNA expression, and plasma concentrations of TNFalpha, IL-6, C-reactive protein (CRP), alpha(1)-acid glycoprotein, transferrin, and albumin were measured.

RESULTS

Surgery caused endotoxemia (p = 0.053), and the capability of plasma to inactivate endotoxin was reduced (p = 0.0002). Two hours postoperatively, the plasma concentrations of TNFalpha and IL-6 peaked significantly, but the liberation capacity of mononuclear cells for cytokines (TNFalpha, IL-1beta, IL-6) was significantly reduced. The concentration of CRP and alpha(1)-acid glycoprotein peaked 48 h postoperatively, but those of transferrin and albumin were significantly decreased (p < 0.001, respectively). Median mRNA expression of TLR2 and TLR4 of mononuclear cells was not altered, and there was no obvious trend over time.

CONCLUSION

Major abdominal surgery is associated with endotoxemia, reduced capability of plasma to inactivate endotoxin, cytokine kinetics resembling those of healthy man after experimentally given LPS, and substantial acute-phase reaction. The cytokine liberation of mononuclear cells suggests a state of postoperative endotoxin tolerance. Despite these substantial changes, trends in TLR2/4 expression are not obvious.

Endotoxemia and endotoxin tolerance in patients with ARDS

BACKGROUND

The significance of endotoxemia in man is controversial, induces cytokine release and stimulates the immune system. Exaggerated cytokine release of mononuclear cells was observed in acute lung injury/acute respiratory distress syndrome (ALI/ARDS). However, repetitive administration of endotoxin can cause tolerance.

OBJECTIVE

To investigate endotoxemia, plasma TNFalpha, IL-1beta, IL-6, the liberation capacity of those cytokines from mononuclear cells after LPS challenge (Delta values), and plasma antibodies to endotoxins and alpha-hemolysin of Staphylococcus aureus in ALI/ARDS.

DESIGN

A prospective clinical study was conducted.

SETTING

The study was carried out at the University Hospital Ulm, Ulm, Germany.

SUBJECTS

The respondents were 23 patients with ALI/ARDS.

INTERVENTIONS

ALI/ARDS was defined according to the American-European Consensus Conference on ARDS. Blood was collected periodically. Parameters were measured by LAL or ELISA.

RESULTS

ARDS (P(a)O(2)/F(i)O(2) < 200) revealed higher endotoxemia (0.22-0.46 [0.06-1.15] EU/mL vs 0.05-0.14 [0.02-0.63] EU/mL) than ALI (P(a)O(2)/F(i)O(2) > 200) but lower DeltaIL-6 (124-209 [10-1214] pg/mL vs 298-746 [5-1797] pg/mL), DeltaTNFalpha (50-100 [6-660] pg/mL vs 143-243 [12-2795] pg/mL), and DeltaIL-1 (2-3 [0-26] pg/mL vs 2-14 [0-99] pg/mL). Endotoxemia correlated negative with P(a)O(2)/F(i)O(2) (r, -0.44 to -0.50). All patients presented antibodies to lipopolysaccharides and alpha-hemolysin, but the level did not correlate with P(a)O(2)/F(i)O(2).

CONCLUSIONS

ALI/ARDS is associated with endotoxemia. The more severe the disease, the more intense is endotoxemia but the lower is the capacity of mononuclear cells to release cytokines (tolerance). Antibodies against Gram-positive and Gram-negative bacteria are detectable in the plasma but without relation to P(a)O(2)/F(i)O(2).

Immunoparalysis after multiple trauma

The immunological sequelae following multiple trauma constitute an ongoing challenge in critical care management. The overall immune response to multiple trauma is a multilevel complex interdependently involving neurohormonal, cellular and haemodynamic factors. Immunoparalysis is characterised by a reduced capacity to present antigens via downregulated HLA-DR and an unbalanced monocyte-T cell interaction. Trauma-induced death of functionally conducive immune cells in the early recovery phase is significant in the emergence of posttraumatic multiple organ dysfunction or failure. Novel findings may contribute to more appropriate immunomonitoring and improved treatment. We must consider the preservation and support of immune function as the ultimate therapeutic goal, which may override the current strategy of simply antagonising excessive pro- or anti-inflammatory immune responses of the severely injured person. This review focuses on the injury-induced conduct of key immune effector cells and associated effects promoting immunoparalysis after multiple trauma.

Mechanisms of sepsis-induced organ dysfunction

BACKGROUND

The past several years have seen remarkable advances in understanding the basic cellular and physiologic mechanisms underlying organ dysfunction and recovery relating to sepsis. Although several new therapeutic approaches have improved outcome in septic patients, the far-reaching potential of these new insights into sepsis-associated mechanisms is only beginning to be realized.

AIM

The Brussels Round Table Conference in 2006 convened >30 experts in the field of inflammation and sepsis to review recent advances involving sepsis and to discuss directions that the field is likely to take in the near future.

FINDINGS

Current understanding of the pathophysiology underlying sepsis-induced multiple organ dysfunction highlights the multiple cell populations and cell-signaling pathways involved in this complex condition. There is an increasing appreciation of interactions existing between different cells and organs affected by the septic process. The intricate cross-talk provided by temporal changes in mediators, hormones, metabolites, neural signaling, alterations in oxygen delivery and utilization, and by modifications in cell phenotypes underlines the adaptive and even coordinated processes beyond the dysregulated chaos in which sepsis was once perceived. Many pathologic processes previously considered to be detrimental are now viewed as potentially protective. Applying systems approaches to these complex processes will permit better appreciation of the effectiveness or harm of treatments, both present and future, and also will allow development not only of better directed, but also of more appropriately timed, strategies to improve outcomes from this still highly lethal condition.

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.

Rebuilding immunity in cancer patients

Rebuilding and maintaining immunity are paramount to the success of cancer immunotherapy and hematopoietic stem cell transplantation. If immune surveillance indeed can protect from cancer, the very manifestation of malignancy means that the disease has prevailed over immunity. Yet, often, tumor-specific T cells can be found in cancer patients irrespective of vaccination. Interestingly, patients suffering from malignancy often harbor unexpectedly high levels of immature CD14(+)HLA-DR(-) monocytes, although the abundance of CD4(+) cells, CD8(+) cells and CD4(+)CD25(high) cells may be normal. It is plausible that in cancer such cells suppress T cell function, analogous to CD14(+)HLA-DR(-) cells in sepsis and major trauma, in addition to their likely failure to re-present tumor-associated antigens once dendritic cells have initiated the T cell response. Recent evidence indicates that tumor-borne adenosine, lactate and hypoxia in the tumor environment may modulate tumor-specific immunity to a significant extent, but their effects on myeloid cell function are unclear. Thus, understanding and controlling these factors may appreciably impact the success of rebuilding and maintaining immunity in cancer patients.

Immune response of severely injured patients--influence of surgical intervention and therapeutic impact

BACKGROUND

[corrected] Severe injury leads to a severe deterioration of the patients' immune response. The changes of the immune response after severe injury include a broad range of immune functions and may result in a status of immunosuppression, which could favor infectious complications. Therefore, immunostimulating therapies have been introduced in the therapy for severely injured patients in clinical and experimental settings.

OBJECTIVES

The article summarizes actual immunomodulating approaches in the treatment of trauma patients and therapeutic strategies avoiding additional immune deteriorations.

RESULTS

Examples for an immunostimulating approach in trauma patients are interferon gamma and the granulocyte macrophage-colony-stimulating factor (GM-CSF), which are summarized in this review in detail. However, the effect of such an interference in the patients' immune response with all its different cellular targets is not yet clearly understood, and most studies focus on the reaction of circulating monocytes. In addition, further immunomodulating strategies, including nutritional support, are addressed. However, clinically established therapeutic immunomodulating strategies in trauma care so far do not exist. The impact of the accidental and also an additional surgical trauma on the immune response has been clearly demonstrated. Therefore, the idea of a "damage control orthopedic surgery" (DCOS) is not only necessary to prevent further deterioration of the homeostasis of, e.g., the coagulating system, but is also desirable in terms of minimizing the burden on the immune system. In addition, also the timing of secondary surgical treatment in trauma patient care should include an evaluation of the immune response, although the most reliable markers still need to be identified.

CONCLUSION

Immunomodulating therapies in trauma patients exist on an experimental level with inconsistent results. The general management of trauma patients includes strategies that have been developed also on the basis of immunological considerations.

Rosiglitazone, a PPAR-gamma ligand, protects against burn-induced oxidative injury of remote organs

Severe burn induces the activation of an inflammatory cascade that contributes to the development of subsequent immunosuppression, increased susceptibility to sepsis, as well as generation of reactive oxygen radicals and lipid peroxidation, leading to multiple organ failure. In the present study, we investigated whether rosiglitazone, a peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand is protective against burn-induced remote organ injury. Under brief ether anaesthesia, shaved dorsum of the rats were exposed to 90 degrees C (burn group) or 25 degrees C (control group) water bath for 10s. Rosiglitazone (4 mg/kg) or saline was administered intraperitoneally immediately after and at the 12th hour of the burn. Rats were decapitated 24h after injury and the tissue samples from lung, liver, and kidney were taken for the determination of malondialdehyde (MDA) and glutathione (GSH) levels, myeloperoxidase (MPO) activity and collagen contents. Serum aspartate aminotransferase (AST), alanine aminotransferase (ALT) levels, and creatinine, blood urea concentrations (BUN) were determined to assess liver and kidney function, respectively. Serum levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta) and lactate dehydrogenase (LDH) were also assayed. Severe skin scald injury (30% of total body surface area) caused a significant decrease in GSH level, and significant increases in MDA level, MPO activity and collagen content of tissues. Similarly, serum ALT, AST and BUN levels, as well as LDH, IL-1 beta and TNF-alpha were elevated in the burn group as compared to the control group. Rosiglitazone treatment reversed all these biochemical indices. According to the findings of the present study, rosiglitazone possesses a anti-inflammatory effect that prevents burn-induced damage in remote organs and protects against organ damage.

Human CD4+CD25+ regulatory T lymphocytes inhibit lipopolysaccharide-induced monocyte survival through a Fas/Fas ligand-dependent mechanism

Although it is known that septic shock induces immunosuppression, the mechanism for this phenomenon is not well understood. Monocytes play a central role in septic shock pathophysiology, which is also characterized by an increased proportion of natural regulatory T (Treg) cells. We therefore investigated whether Treg could be involved in the decreased monocyte expression of CD14 and HLA-DR observed during septic shock. We demonstrated that human Treg inhibit LPS-induced retention of monocyte CD14. Because loss of CD14 is a hallmark of monocyte apoptosis, this suggests that Treg inhibit monocyte survival. This effect was largely mediated through the release of a soluble mediator that was not identical with either IL-10 or IL-4. The Fas/FasL pathway participated in the effect as it was blocked by anti-FasL Abs and reproduced by Fas agonist and recombinant soluble FasL. Furthermore, expression of FasL was much higher on Treg than on their CD25(-) counterparts. Collectively, these results indicate that Treg act on monocytes by inhibiting their LPS-induced survival through a proapoptotic mechanism involving the Fas/FasL pathway. This may be an important mechanism for septic shock-induced immunosuppression and may offer new perspectives for the treatment of this deadly disease.

MyD88 and Src are differentially regulated in Kupffer cells of males and proestrus females following hypoxia

Hypoxia produces sex dimorphic immune responses in males and proestrus females. Because Kupffer cells are the major source of proinflammatory cytokines, studies were conducted to discern IL-6 production in mouse Kupffer cells following hypoxia. Hypoxia enhances TLR4 expression in Kupffer cells irrespective of sex. However, MyD88 and Src expression in Kupffer cells decreased significantly after hypoxia in proestrus females, whereas Src protein expression and phosphorylation increased in males in concurrence with differences in IL-6 production. 17beta-estradiol administration elevated MyD88 and Src expression in males to levels in normoxic proestrus females. Administration of Src inhibitor in hypoxic males prevented increased IL-6 production. Thus, differential regulation of MyD88 and Src in males and females plays an important role in sex-specific immune response following hypoxia.