Spontaneous in contrast to CD95-induced neutrophil apoptosis is independent of caspase activity.

BACKGROUND: The influence of caspase inhibitors on spontaneous and on CD95-triggered apoptosis was investigated in neutrophils from healthy volunteers and compared with neutrophils from patients with severe sepsis. METHODS: To further elucidate the mechanisms of neutrophil apoptosis, isolated neutrophils from healthy volunteers (n = 9) were either stimulated with the agonistic anti-CD95 antibody (100 ng/mL) or left unstimulated in the presence or absence of the caspase inhibitors zIETD-fmk (10 micromol/L), zDEVD-fmk (10 micromol/L), or zVAD-fmk (20 micromol/L). Apoptosis was determined by measuring DNA fragmentation and Annexin-V binding in FACS, and caspase-3-like activity by DEVD-afc cleavage assay. Results were compared with those from patients with severe sepsis (n = 15). RESULTS: Reduced spontaneous neutrophil apoptosis in patients with sepsis (-48.7%) was completely restored by incubation with agonistic anti-CD95 antibody (p < 0.05). Inhibition of caspases did not influence spontaneous neutrophil apoptosis in both groups. However, zVAD-fmk reduced anti-CD95 antibody-induced apoptosis in neutrophils from controls by -22.6% (p < 0.05) and in patients with sepsis by -43.1% (p < 0.05). CONCLUSION: These results indicate that spontaneous in contrast to CD95-induced neutrophil apoptosis is independent of caspase activity.

Interleukin-18 plasma levels are increased in patients with sepsis compared to severely injured patients.

Interleukin-18 (IL-18) appears to play a critical role in cytokine-induced organ failure during endotoxemia in animal models. Therefore, plasma samples from patients with severe trauma and sepsis were examined for the presence of IL-18. Significantly elevated plasma IL-18 concentrations were found in patients with sepsis compared to severely injured patients and healthy humans. Septic patients who died and patients with septic shock exhibited higher levels of IL-18 than survivors and septic patients without shock. In addition, septic patients with gram-positive infections had significantly higher IL-18 plasma levels than patients with gram-negative infection. These findings were confirmed by whole blood assay from healthy humans where Staphylococcus aureus markedly (P < 0.05) increased the release of IL-18 in whole blood ex vivo, while endotoxin was ineffective. Although obtained from a small patient group, these results suggest that IL-18 production may discriminate between gram-positive and gram-negative sepsis, and that increased IL-18 appearance may be associated with an adverse outcome in septic patients.

Differential effect of caspase inhibition on proinflammatory cytokine release in septic patients.

The interleukins (IL)-1beta and IL-18 represent potent players in the proinflammatory cytokine cascade. Their activation is regulated predominantly through the IL-1-converting enzyme (ICE)/caspase-1. The role of caspases in the secretion of IL-1beta and IL-18, as well as in the release of the secondary-induced cytokines IL-12 and interferon (IFN)-gamma in whole blood from septic patients compared to healthy controls, was studied. Inhibition of caspase activity by Z-VAD significantly reduced lipopolysaccharide (LPS) and Staphylococcus aureus (SAC) induced release of mature IL-1beta in septic patients and controls. In contrast, in whole blood from septic patients significantly elevated basal level of IL-18 were found, which could neither be further increased by LPS or SAC, nor be inhibited by Z-VAD. Release of IL-12 p40 was significantly lower in septic patients compared to controls and was not affected by Z-VAD. Despite high levels of IL-18, IFN-gamma was not detected in whole blood from septic patients even after stimulation with SAC or LPS. Thus, during sepsis, caspases participate in the processing of IL-1beta, whereas maturation of IL-18 during sepsis appears to be independent of caspases. The lack of IFN-gamma release seen in septic patients could be attributed to low IL-12 release rather than to diminished IL-18 release.

Sepsis after severe injury interrupts caspase-dependent processing of interleukin-18.

BACKGROUND: Cysteine proteases (caspases) participate in the activation process of interleukin-18 (IL-18), a key cytokine for septic organ failure. This study evaluates the influence of caspase blockade on secretion of IL-18 into whole blood in patients with multiple injuries and in patients with severe sepsis. METHODS: Heparinized blood was collected from patients with multiple injuries, from septic patients, as well as from healthy humans. Whole blood was stimulated for 24 hours with lipopolysaccharide (LPS) or Staphylococcus aureus in the presence or absence of the caspase inhibitors Z-VAD and Z-DEVD. IL-18 was measured by enzyme-linked immunosorbent assay. RESULTS: S. aureus Cowan strain differentially increased the release of IL-18 in the three study populations, whereas LPS was ineffective. Z-VAD and to a lesser degree Z-DEVD decreased (p < 0.05) S. aureus Cowan strain I-induced secretion of IL-18 into whole blood from control subjects and trauma patients. Caspase inhibitors did not influence release of IL-18 into whole blood from septic patients. CONCLUSION: Secretion of IL-18 into whole blood from healthy humans and trauma patients can be effectively controlled through blockade of caspase activity. In contrast, during sepsis, alternative mechanisms may regulate secretion of IL-18.

Relationship between procalcitonin plasma levels and severity of injury, sepsis, organ failure, and mortality in injured patients.

OBJECTIVE: To compare procalcitonin (PCT) plasma levels of injured patients with the incidence and severity of systemic inflammatory response syndrome (SIRS), infection, and multiple organ dysfunction syndrome (MODS) and to assess the predictive value of PCT for these posttraumatic complications. DESIGN: Retrospective study comparing patients with mechanical trauma in terms of severity of injury, development of infectious complications, and organ dysfunctions. SETTING: Level I trauma center with emergency room, intensive care unit, and research laboratory. PATIENTS: Four hundred five injured patients with an Injury Severity Score of > or =9 points were enrolled in this study from January 1994 to February 1996. INTERVENTIONS: Blood samples were collected on the day of admission and on days 1, 3, 5, 7, 10, 14, and 21 thereafter. MEASUREMENTS AND MAIN RESULTS: We determined PCT serum levels using a specific immunoluminometric assay. We retrospectively evaluated the occurrence of SIRS, sepsis, and MODS using patients' charts. Mechanical trauma led to increased PCT plasma levels dependent on the severity of injury, with peak values on days 1 and 3 (p < .05) and a continuous decrease within 21 days after trauma. Patients who developed SIRS demonstrated a significant (p < .05) increase of peak PCT plasma levels compared with patients without SIRS. The highest PCT plasma concentrations early after injury were observed in patients with sepsis (6.9+/-2.5 ng/mL; day 1) or severe MODS (5.7+/-2.2 ng/mL; day 1) with a sustained increase (p < .05) for 14 days compared with patients with an uneventful posttraumatic course (1.1+/-0.2 ng/mL). Moreover, these increased PCT plasma levels during the first 3 days after trauma predicted (p < .0001; logistic regression analysis) severe SIRS, sepsis, and MODS. CONCLUSIONS: These data indicate that PCT represents a sensitive and predictive indicator of sepsis and severe MODS in injured patients. Routine analysis of PCT levels seems to aid early recognition of these posttraumatic complications. Thus, PCT may represent a useful marker to monitor the inflammatory status of injured patients at risk.

Incidence of septic complications and multiple organ failure in severely injured patients is sex specific.

BACKGROUND: Sexual hormones are potent regulators of various immune functions. Although androgens are immunosuppressive, estrogens protect against septic challenges in animal models. This study correlates sexual dimorphism with the incidence of posttraumatic complications in severely injured patients. METHODS: From January of 1991 to February of 1996, 1,276 consecutive injured patients (Injury Severity Score [ISS] > or = 9 points) were studied. Males (n = 911) did not differ from females (n = 365) with regard to severity of injury (ISS) and injury pattern. RESULTS: The incidence of posttraumatic sepsis (30.7%) and multiple organ dysfunction syndrome (29.6%) was significantly increased in severely injured males with ISS > or = 25 points in comparison to the equivalent group of females (sepsis, 17.0%; multiple organ dysfunction syndrome, 16.0%). No difference was found in patients with ISS < 25 points. Moreover, plasma levels of procalcitonin and interleukin-6 were elevated (p < 0.05) in severely injured males compared with females. CONCLUSION: Sex influences posttraumatic morbidity in severely injured patients and supports the concept that females are immunologically better positioned toward a septic challenge.

Circulating mediators in serum of injured patients with septic complications inhibit neutrophil apoptosis through up-regulation of protein-tyrosine phosphorylation.

BACKGROUND: The accumulation of neutrophils at inflammatory sites results in excessive release of toxic metabolites causing tissue injury. Proinflammatory cytokines may cause the breakdown of homeostasis of neutrophil numbers through inhibition of apoptosis. METHODS: Neutrophils were isolated from healthy humans and from patients with multiple injuries on day of admission and during septic complications. Apoptosis was quantitated using propidium iodide fluorescence and the TUNEL method. Tyrosine phosphorylation was measured by flow cytometry. RESULTS: Neutrophil apoptosis was decreased (33.3 +/- 5.5%; p < 0.05) in injured patients with sepsis compared with healthy humans (87.2 +/- 3.0%) and injured patients without sepsis (76.0 +/- 2.0%). Serum from injured patients with sepsis inhibited (p < 0.05) apoptosis of neutrophils from healthy humans in a dose-dependent manner. Serum from healthy humans and from injured patients at admission was ineffective. Neutralization of granulocyte-colony stimulating factor, but not of granulocyte-macrophage-colony stimulating factor, in serum of injured patients with sepsis partially abrogated (+51.2%) serum induced prolongation of neutrophil life span. Reduction of neutrophil apoptosis was concomitant with increased tyrosine phosphorylation. CONCLUSIONS: Septic complications, but not the injury itself, result in inhibition of spontaneous neutrophil apoptosis. Circulating mediators seem to reduce neutrophil apoptosis through up-regulation of tyrosine phosphorylation.

Chloroquine inhibits proinflammatory cytokine release into human whole blood.

Excessive synthesis and release of proinflammatory cytokines during endotoxemia causes severe pathophysiological derangements and organ failure. Because the lysosomotropic agent chloroquine has been effective in the treatment of diseases associated with increased secretion of proinflammatory cytokines such as malaria or rheumatoid arthritis, this study evaluates the potential effect of chloroquine on endotoxin-induced cytokinemia using human whole blood from healthy volunteers. Chloroquine revealed a dose-dependent inhibitory effect on endotoxin-induced secretion of tumor necrosis factor-alpha, interleukin-1 beta, and interleukin-6 that was associated with reduced cytokine mRNA expression. Moreover, ammonia and methylamine, which react as weak bases like chloroquine, reduced synthesis and secretion of proinflammatory cytokines. These data indicate a potent anti-inflammatory effect of chloroquine on endotoxin-induced synthesis of proinflammatory cytokines that may be due to its weak base effect. Thus chloroquine may be of therapeutic benefit not only, during chronic inflammation but also in diseases that are related to bacteria-induced inflammation.

[Predictive role of IL-6 for multi-organ dysfunction syndrome MODS) in severely injured patients in the early intensive care phase]. / Prädiktive Rolle von IL-6 für das Multiorgan-Dysfunktionssyndrom (MODS) bei schwerverletzten Patienten in der frühen Intensivpflegephase.

Interleukin-6 seems to have a predictive value for the multiple organ dysfunction syndrome (MODS) in the early period after trauma.

[Severe trauma leads to damaged signal transduction with inhibited secretion of cytokines]. / Das schwere Trauma führt zu einer Störung der Signaltransduktion mit einer gehemmten Sekretion von Zytokinen.

The reduced secretion if IL-1 beta after severe injury seems to be due to disturbances in signal transduction pathways. Protein-tyrosine kinases are necessary for endotoxin-induced secretion of IL-1 beta, while protein kinase C antagonizes this effect.

Detectable concentrations of Fas ligand in cerebrospinal fluid after severe head injury.

When the cell surface molecule Fas is triggered by its agonist Fas ligand the result is apoptosis of these cells and tissue destruction. To elucidate the pathophysiological relevance of Fas ligand in patients with cerebral oedema caused by trauma, we examined its concentrations in cerebrospinal fluid in 18 patients using specific ELISA. Serum and cerebrospinal fluid from healthy people and injured patients without head trauma did not contain detectable Fas ligand. In contrast, cerebrospinal fluid from patients with severe brain injury contained high concentrations of Fas ligand without detectable concentrations in serum. Soluble Fas ligand concentrations in cerebrospinal fluid correlated significantly with severity of brain injury. The Fas-Fas ligand-system may have a pivotal role in causing oedema and local tissue destruction in the brain after severe head injury.

Interleukin-10 counterregulates proinflammatory cytokine-induced inhibition of neutrophil apoptosis during severe sepsis.

Neutrophils play a key role in the pathophysiology of septic multiple organ dysfunction syndrome (MODS) through excessive release of toxic granule components and reactive oxygen metabolites with consequent tissue destruction. The increase of senescent neutrophils during sepsis indicates a potential breakdown of autoregulatory mechanisms including apoptotic processes to remove activated neutrophils from inflammatory sites. Therefore, neutrophil apoptosis of patients with severe sepsis and its regulatory mechanisms were investigated. Spontaneous neutrophil apoptosis from patients with severe sepsis was significantly reduced in comparison to healthy individuals. Cytokines detected in the circulation during sepsis (tumor necrosis factor-alpha [TNF-alpha], interferon-gamma [IFN-gamma], granulocyte colony-stimulating factor [G-CSF], granulocyte-macrophage colony-stimulating factor [GM-CSF]) inhibited neutrophil apoptosis in both groups, though the effect was more distinct in neutrophils from healthy humans. Addition of lipopolysaccharide (LPS) to neutrophils from healthy humans markedly (P < .05) reduced apoptosis which was partially restored through addition of anti-TNF-antibody. Interleukin-10 (IL-10) counteracted (P < .05) inhibition of neutrophil apoptosis induced by LPS, recombinant human (rh) TNF-alpha, rhIFN-gamma, rhG-CSF, and rhGM-CSF, whereas rhIL-4 or rhIL-13 were ineffective. Reduced neutrophil apoptosis during sepsis was concomitant with increased tyrosine phosphorylation, while IL-10 markedly inhibited tyrosine phosphorylation in LPS-stimulated neutrophils. These results identify proinflammatory cytokines and IL-10 as strong regulators of spontaneous neutrophil apoptosis during sepsis. Inhibition as well as acceleration of neutrophil apoptosis seems to be associated with alterations of signal transduction pathways.

Relationship of interleukin-10 plasma levels to severity of injury and clinical outcome in injured patients.

Interleukin-10 (IL-10) markedly inhibits lymphocyte and phagocytic functions, which are essential for an adequate immune response to invading microbes. Although various animal and clinical studies revealed an increased release of IL-10 during sepsis, alterations of circulating IL-10 after injury and potential relationships to severity of injury and clinical outcome are unknown. Injured patients (n = 417) showed elevated (p < 0.001) IL-10 levels throughout the observation period of 21 days compared with healthy volunteers (n = 137). Patients with severe injury (Injury Severity Score > or = 25 points) demonstrated significantly increased IL-10 levels compared with patients with minor trauma (Injury Severity Score < 25 points). Patients who died from injury or developed posttraumatic complications (sepsis, multiple organ dysfunction syndrome) revealed elevated IL-10 levels in comparison with injured patients with uneventful posttraumatic course. Thus, trauma causes an enhanced release of IL-10 dependent on the severity of injury. Because increased IL-10 levels are significantly related to posttraumatic complications, IL-10 may be involved in their pathogenesis.

Inhibition of the defense system stimulating interleukin-12 interferon-gamma pathway during critical Illness.

Interleukin-12 (IL-12) and interferon-gamma (IFN-gamma) exert protective effects during experimental endotoxemia through upregulation of cellular immunity and phagocytic functions. They are part of a positive regulatory feedback loop that enhances the production of the other. Because critically ill patients show a marked suppression of T-cell and macrophage functions with a high susceptibility to infection, potential defects in the immunity/inflammation upregulating IL-12 IFN-gamma pathway were studied. As an ex vivo model of endotoxemia, lipopolysaccharide (LPS) stimulated whole blood from 25 critically ill patients and 12 healthy individuals was incubated with either recombinant human (rh) IL-12 or rhIFN-gamma, respectively. IFN-gamma dose-dependently (P < .05) increased the release of IL-12 p40 and p70 into LPS-stimulated whole blood from healthy humans without effect in whole blood from critically ill patients. RhIL-12 p70 enhanced (P < .05) the secretion of IFN-gamma in controls, while it was ineffective in LPS-stimulated whole blood from critically ill patients. The observed inhibition of the IL-12 IFN-gamma pathway is not specific to LPS, since Staphylococcus aureus Cowan strain I (SAC)-stimulated whole blood from critically ill patients showed similar suppression. The secretion of IL-12 and IFN-gamma was less reduced in critically ill patients when using isolated cultures of adherent cells or lymphocytes. Although preculture of whole blood from healthy humans with IL-10, but not with IL-4, mimicked suppression of the IL-12 IFN-gamma pathway similar to that observed during critical illness, the release of antiinflammatory reacting cytokines (IL-4, IL-10, transforming growth factor [TGF]-beta 1) was decreased into LPS-stimulated whole blood from critically ill patients. These results indicate at least two mechanisms responsible for dramatic disturbances of the IL-12 IFN-gamma pathway during critical illness: (1) deactivation of IL-12 and IFN-gamma producing leukocytes in vivo early after the primary insult, and (2) presence of serum suppressive factors different from IL-4, IL-10, or TGF-beta 1. Because IL-12 and IFN-gamma upregulate essential immune functions, the marked inhibition of IL-12 and IFN-gamma release may be pivotal for high susceptibility of critically ill patients to infection.

Transforming growth factor-beta 1 inhibits synthesis of cytokines in endotoxin-stimulated human whole blood.

OBJECTIVE: To determine the potency of transforming growth factor-beta (TGF-beta) for inhibiting proinflammatory cytokine synthesis in endotoxin-stimulated human whole blood. DESIGN: Endotoxin-stimulated whole blood from healthy volunteers as an ex vivo model of endotoxemia was incubated with different concentrations of TGF-beta 1. Cytokine levels in plasma with a bioassay (for tumor necrosis factor alpha) or an enzyme-linked immunosorbent assay (for interleukin [IL]-1 beta and IL-6), messenger RNA (mRNA) expression with northern blotting, and protein levels with Western blotting were determined. RESULTS: High TGF-beta 1 concentrations (> 100 pg/mL) inhibited (P < .05) secretion of tumor necrosis factor alpha, IL-1 beta, and IL-6 into lipopolysaccharide-stimulated whole blood, while low concentrations (< 50 pg/mL) were ineffective. Moreover, TGF-beta 1 inhibited mRNA expression of tumor necrosis factor alpha and IL-6 in a dose-dependent manner. In contrast, neither IL-1 beta mRNA expression nor IL-1 beta protein synthesis were attenuated by TGF-beta 1. CONCLUSION: Transforming growth factor-beta 1, with its downregulatory effect on the synthesis and release of proinflammatory cytokines by phagocytic cells, represents an inhibitor of endotoxin-induced inflammatory reactions.

Endotoxin tolerance after severe injury and its regulatory mechanisms.

OBJECTIVE: To study the responsiveness of peripheral blood mononuclear cells to lipopolysaccharide (LPS) after severe trauma and its regulatory mechanisms. MATERIALS AND METHODS: The release of proinflammatory reacting cytokines (tumor necrosis factor-alpha, interleukin (IL)-1 beta, IL-6, IL-8, interferon (IFN)-gamma) into whole blood from 12 patients on day 1, 5, 10, and 14 after severe trauma (Injury Severity Score, 39.3 +/- 2.8 points) and 10 healthy volunteers was studied after stimulation with LPS, concanavalin A, phorbol myristate acetate (PMA), and the addition of recombinant IFN-gamma. MAIN RESULTS: Trauma caused a significant reduction of LPS and concanavalin A induced release of inflammation activating cytokines into whole blood, including IFN-gamma. However, the diminished release of proinflammatory cytokines could be increased with recombinant IFN-gamma or even attenuated after stimulation of peripheral blood mononuclear cells with the protein kinase C activator PMA. CONCLUSIONS: Trauma leads to reduced responsiveness of blood monocytes to LPS and a decreased secretion of proinflammatory reacting lymphokines. Because activation of the protein kinase C pathway with PMA or the addition of IFN-gamma significantly increased cytokine response, endotoxin tolerance is not caused by inhibition of protein synthesis, but to disturbances in the signal transduction pathway and its regulating mediators.

Different pattern of local and systemic release of proinflammatory and anti-inflammatory mediators in severely injured patients with chest trauma.

BACKGROUND: Excessive release of proinflammatory cytokines has been involved in pathogenesis of acute respiratory distress syndrome. DESIGN: Since injured patients with chest trauma reveal a high risk for posttraumatic acute respiratory distress syndrome, local and systemic release of proinflammatory cytokines and their naturally occurring inhibitors were determined in the early posttraumatic period. MATERIALS AND METHODS: Proinflammatory and anti-inflammatory mediators were measured in plasma and bronchoalveolar lavage fluid (BALF) from 16 patients with multiple injuries including severe chest injury (Injury Severity Score of 34.4 +/- 2.3 points) and compared with healthy volunteers (n = 17). RESULTS: Tumor necrosis factor-alpha was detectable neither in plasma nor in BALF. Interleukin-1beta and interleukin-8 were significantly increased in BALF from injured patients, while plasma levels were similar in both groups. Soluble tumor necrosis factor receptors p55 and p75 and interleukin-1ra were markedly elevated in plasma (p < or = 0.01) and BALF (p < or = 0.001) from injured patients compared with controls. CONCLUSION: Highly increased concentrations of proinflammatory cytokines in BALF, but not in circulation, indicate a strong local inflammatory response early after multiple injuries combined with chest injury rather than severe systemic inflammation. In contrast, anti-inflammatory mechanisms seem to be activated locally and systemically.

Interleukin-10 attenuates the release of proinflammatory cytokines but depresses splenocyte functions in murine endotoxemia.

OBJECTIVE: To determine whether interleukin (IL)-10, besides its potent anti-inflammatory properties, causes depression of splenocyte functions in a murine model of gram-negative endotoxemia. DESIGN: Mice (strain C3H/HeN) were injected intravenously with 1 mg of Escherichia coli lipopolysaccharide at 15 minutes after intravenous injection of either 200 U of recombinant murine IL-10 or saline solution. Serum levels of tumor necrosis factor alpha, IL-6, and IL-1 alpha were determined at 90 minutes and 12 hours after lipopolysaccharide challenge. In addition, splenocyte proliferation and lymphokine release (IL-2, IL-6, and interferon gamma) were measured. RESULTS: Pretreatment with IL-10 markedly reduced (P < .05) serum levels of tumor necrosis factor alpha (-79%), IL-6 (-94%), and IL-1 alpha (-69%), but it significantly inhibited splenocyte proliferation (-32%) and IL-2 (-40%), IL-6 (-49%), and interferon gamma (-54%) release of splenocytes. CONCLUSIONS: Interleukin-10 prevents E coli lipopolysaccharide-induced cytokinemia but dampens antigen-driven cellular immune responses. Although IL-10 protects against the detrimental effects of proinflammatory cytokines by deactivation of macrophages, its immunosuppressive effect may augment susceptibility to repeated or continuous invasion of microorganisms, as it is observed during clinical sepsis.

Interleukin-1, -6 and tumor necrosis factor-alpha release is down-regulated in whole blood from septic patients.

Proinflammatory cytokines are important mediators during endotoxemia. In experimental models, injection of lipopolysaccharide (LPS) activates macrophages leading to excessive secretion of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1 beta and IL-6; infusion of high dose of these mediators results in organ failure and death. Natural infection may be different, because it persists over days or even weeks, with repeated endotoxin challenge to macrophages. Little is known about the capacity of peripheral blood mononuclear cells (PBMCs) to release proinflammatory cytokines under these conditions. Therefore, as an ex vivo model of sepsis, the expression of proinflammatory cytokines after stimulation of whole blood with LPS was studied. A high LPS dose (1 microgram/ml) maximally increased TNF-alpha, IL-1 beta and IL-6 secretion in controls, but a marked depression was observed in septic patients (p < 0.01; 15 patients with severe sepsis versus 20 control patients without infection). This reduction persisted for up to 10 days after diagnosis of sepsis. The release of TNF-alpha, IL-1 beta and IL-6 was markedly decreased in the septic group even when a lower and physiologically more relevant LPS concentration (1 ng/ml) was used. IL-1 beta mRNA was similar to controls, but a down-regulation was observed in TNF-alpha and IL-6 transcript levels in PBMCs from the blood of septic patients. This was at least in part due to a marked reduction in TNF and IL-6 mRNA half-life. These results indicate that different mechanisms down-regulate proinflammatory cytokine release in the whole blood of septic patients. Although excessive secretion is known to be deleterious, low concentrations of these cytokines are involved in regulating essential cellular and humoral immune functions. Thus, the reduced capacity to express and release adequate amounts of proinflammatory cytokines after exposure to endotoxin, as observed in whole-blood PBMCs from septic patients, may contribute to the development of immunodeficiency.

Release of anti-inflammatory mediators after mechanical trauma correlates with severity of injury and clinical outcome.

Excessive synthesis of proinflammatory cytokines [tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 beta] after trauma has been correlated with poor outcome. Recently, naturally occurring inhibitors of TNF-alpha and IL-1 beta have been characterized such as soluble TNF receptors (sTNFRs) and IL-1 receptor antagonist (IL-1ra). The present study was undertaken to determine whether injury results in a rise of circulating sTNFRs and IL-1ra. If so, whether plasma levels of these anti-inflammatory mediators correlate with severity of injury and clinical outcome of these patients. Injured patients (n = 213) showed significantly increased sTNFR and IL-1ra plasma levels throughout the observation period of 14 days, compared with healthy volunteers (n = 127). Patients with severe injury (Injury Severity Score > 16 points) revealed higher levels (p < 0.05) of sTNFRs and IL-1ra than patients with minor trauma (Injury Severity Score < or = 16 points). Patients who died from injury demonstrated increased (p < 0.05) sTNFR p55 and IL-1ra plasma levels, compared with survivors. Thus, anti-inflammatory mechanisms are activated after trauma dependent on severity of injury. Because increased plasma levels of anti-inflammatory reacting proteins portended poorly for patient survival, these mediators may contribute to prediction of outcome after severe injury.