Critical role of cRel subunit of NF-κB in sepsis survival

NF-κB c-Rel Dictates the Inflammatory Threshold by Acting as a Transcriptional Repressor

NF-κB/Rel family of transcription factors plays a central role in initiation and resolution of inflammatory responses. Here, we identified a function of the NF-κB subunit c-Rel as a transcriptional repressor of inflammatory genes. Genetic deletion of c-Rel substantially potentiates the expression of several TNF-α-induced RelA-dependent mediators of inflammation. v-Rel, the viral homologue of c-Rel, but not RelB, also possesses this repressive function. Mechanistically, we found that c-Rel selectively binds to the co-repressor HDAC1 and competitively binds to the DNA mediating HDAC1 recruitment to the promoters of inflammatory genes. A specific point mutation at tyrosine25 in c-Rel's DNA-binding domain, for which a missense single nucleotide variation (Y25H) exists in humans, completely abrogated its ability to bind DNA and repress TNF-α-induced, RelA-mediated transcription. Our findings reveal that the transactivator NF-κB subunit c-Rel also plays a role as a transcriptional repressor in the maintenance of inflammatory homeostasis.

Linkage of lncRNA CRNDE sponging miR-181a-5p with aggravated inflammation underlying sepsis

This investigation was performed to verify whether lncRNA CRNDE sponging miR-181a-5p was involved with sepsis-relevant inflammatory dysfunctions. Aggregately 136 sepsis patients and 151 healthy people were recruited, and their fasting peripheral blood was gathered to detect expressions of CRNDE and miR-181a-5p. In addition, THP-1 cells were transfected with si-CRNDE, miR-181a-5p mimic, pcDNA3.1-TLR4 and si-TLR4, and then sepsis-specific inflammatory cytokines within the cells were quantified. The sponging relationships between CRNDE and miR-181a-5p, as well as between miR-181a-5p and TLR4, were ascertained by means of luciferase reporter gene assay. The experimental results revealed that over-expressed CRNDE and under-expressed miR-181a-5p were associated with shortened lifespan of sepsis patients. Mechanically, si-CRNDE-1 and miR-181a-5p mimic were able to reverse the promoting effects of LPS on production of NF-kB, TNF-α, IL-1β and IL-6 by THP-1 cells. Moreover, the expressional change of miR-181a-5p in THP-1 cells was in part owing to its being sponged by CRNDE. Lastly, TLR4, subjected to targeted modification of miR-181a-5p, was capable of disturbing the contribution of CRNDE and miR-181a-5p to THP-1 cells’ release of NF-kB, TNF-α, IL-1β and IL-6. Collectively, the CRNDE/miR-181a-5p/TLR4 axis seemed to have potential in modifying sepsis-related inflammatory pathogenesis, which offered a direction for sepsis diagnosis and treatment.

Metagenomic analysis of the effects of toll-like receptors on bacterial infection in the peritoneal cavity following cecum ligation and puncture in mice

Objective

To establish the composition of bacteria in mice following cecum ligation and puncture (CLP) through metagenomic analysis and investigate the role of TLRs on the composition of bacteria.

Methods

Total DNA extraction was done from the ascites, blood, and fecal samples from C57BL/6 mice sacrificed at 0, 4, 8, and 16 h, as well as from Tlr2^–/–, Tlr4^–/–, Tlr5^–/–, and NF-κB^–/–mice sacrificed at 16 h following CLP. Amplification of the V3–V4 regions of the bacterial 16S rRNA genes by PCR and the Illumina MiSeq sequencer was used for deep sequencing. Hierarchical clustering of the isolates was performed with Ward’s method using Euclidean distances. The relative abundance according to operational taxonomic unit (OTU) number or taxa was used to compare the richness among subgroups in the experiments.

Results

There were 18 taxa that had significantly different abundances among the different samples of the C57BL/6 mice at 16 h following CLP. Various dynamic changes in the infectious bacteria inside the peritoneal cavity after CLP were found. While knockout of Tlr5 and NF-κB impaired the ability of bacterial clearance inside the peritoneal cavity for some kinds of bacteria found in the C57BL/6 mice, the knockout of Tlr4 enhanced clearance for other kinds of bacteria, and they presented excessive abundance in the peritoneal cavity despite their scarce abundance in the stool.

Conclusion

NF-κB and TLRs are involved in bacterial clearance and in the expression pattern of the bacterial abundance inside the peritoneal cavity during polymicrobial infection.

Mesenchymal stem cells attenuate sepsis-induced liver injury via inhibiting M1 polarization of Kupffer cells

Sepsis is a leading cause of death in intensive care units that can result in acute hepatic damage. Animal experiments and clinical trials have shown that mesenchymal stem cell (MSC) therapy has some beneficial in several liver diseases. However, the protective effects of MSC therapy on sepsis-induced hepatic damage and associated mechanisms are not completely understood. The aim of the present study was to investigate the effects of MSCs on sepsis-induced liver injury and underlying mechanisms. A rat model of sepsis-induced liver injury was established by cecal ligation and puncture, and serum alanine aminotransferase and aspartate transaminase activities as well as liver histological changes were measured. Inflammatory cytokines, Kupffer cell M1 phenotype markers, and associated signal molecules were also determined in septic rats and in lipopolysaccharide (LPS)-treated Kupffer cells. Our results showed that injection of MSCs attenuated sepsis-induced liver injury. Treatment with MSCs inhibited activation of Kupffer cells towards M1 phenotype, attenuated TNF-α and IL-6 expression, and promoted IL-4 and IL-10 expression in septic rats and LPS-treated Kupffer cells. Furthermore, MSCs also inhibited the nuclear translocation of nuclear factor-kappa B in LPS-challenged Kupffer cells and the liver of septic rats. These results indicated that MSCs attenuated sepsis-induced liver injury through suppressing M1 polarization of Kupffer cells.

Disease Tolerance as an Inherent Component of Immunity

Pathogenic organisms exert a negative impact on host health, revealed by the clinical signs of infectious diseases. Immunity limits the severity of infectious diseases through resistance mechanisms that sense and target pathogens for containment, killing, or expulsion. These resistance mechanisms are viewed as the prevailing function of immunity. Under pathophysiologic conditions, however, immunity arises in response to infections that carry health and fitness costs to the host. Therefore, additional defense mechanisms are required to limit these costs, before immunity becomes operational as well as thereafter to avoid immunopathology. These are tissue damage control mechanisms that adjust the metabolic output of host tissues to different forms of stress and damage associated with infection. Disease tolerance is the term used to define this defense strategy, which does not exert a direct impact on pathogens but is essential to limit the health and fitness costs of infection. Under this argument, we propose that disease tolerance is an inherent component of immunity.

Understanding the Cellular Origin of the Mononuclear Phagocyte System Sheds Light on the Myeloid Postulate of Immune Paralysis in Sepsis

Sepsis, in essence, is a serious clinical condition that can subsequently result in death as a consequence of a systemic inflammatory response syndrome including febrile leukopenia, hypotension, and multiple organ failures. To date, such life-threatening organ dysfunction remains one of the leading causes of death in intensive care units, with an increasing incidence rate worldwide and particularly within the rapidly growing senior population. While most of the clinical trials are aimed at dampening the overwhelming immune response to infection that spreads through the bloodstream, based on several human immunological investigations, it is now widely accepted that susceptibility to nosocomial infections and long-term sepsis mortality involves an immunosuppressive phase that is characterized by a decrease in some subsets of dendritic cells (DCs). Only recently substantial advances have been made in terms of the origin of the mononuclear phagocyte system that is now likely to allow for a better understanding of how the paralysis of DCs leads to sepsis-related death. Indeed, the unifying view of each subset of DCs has already improved our understanding of the pivotal pathways that contribute to the shift in commitment of their progenitors that originate from the bone marrow. It is quite plausible that this anomaly in sepsis may occur at the single level of DC-committed precursors, and elucidating the immunological basis for such a derangement during the ontogeny of each subset of DCs is now of particular importance for restoring an adequate cell fate decision to their vulnerable progenitors. Last but not least, it provides a direct perspective on the development of sophisticated myelopoiesis-based strategies that are currently being considered for the treatment of immunosenescence within different tissue microenvironments, such as the kidney and the spleen.

Multidimensional pooled shRNA screens in human THP-1 cells identify candidate modulators of macrophage polarization

Macrophages are key cell types of the innate immune system regulating host defense, inflammation, tissue homeostasis and cancer. Within this functional spectrum diverse and often opposing phenotypes are displayed which are dictated by environmental clues and depend on highly plastic transcriptional programs. Among these the 'classical' (M1) and 'alternative' (M2) macrophage polarization phenotypes are the best characterized. Understanding macrophage polarization in humans may reveal novel therapeutic intervention possibilities for chronic inflammation, wound healing and cancer. Systematic loss of function screening in human primary macrophages is limited due to lack of robust gene delivery methods and limited sample availability. To overcome these hurdles we developed cell-autonomous assays using the THP-1 cell line allowing genetic screens for human macrophage phenotypes. We screened 648 chromatin and signaling regulators with a pooled shRNA library for M1 and M2 polarization modulators. Validation experiments confirmed the primary screening results and identified OGT (O-linked N-acetylglucosamine (GlcNAc) transferase) as a novel mediator of M2 polarization in human macrophages. Our approach offers a possible avenue to utilize comprehensive genetic tools to identify novel candidate genes regulating macrophage polarization in humans.

Association of REL polymorphisms and outcome of patients with septic shock

Background

cRel, a subunit of NF-κB, is implicated in the inflammatory response observed in autoimmune disease. Hence, knocked-out mice for cRel had a significantly higher mortality, providing new and important functions of cRel in the physiopathology of septic shock. Whether genetic variants in the human REL gene are associated with severity of septic shock is unknown.

Methods

We genotyped a population of 1040 ICU patients with septic shock and 855 ICU controls for two known polymorphisms of REL; REL rs842647 and REL rs13031237. Outcome of patients according to the presence of REL variant alleles was compared.

Results

The distribution of REL variant alleles was not significantly different between patients and controls. Among the septic shock group, REL rs13031237*T minor allele was not associated with worse outcome. In contrast, REL rs842647*G minor allele was significantly associated with more multi-organ failure and early death [OR 1.4; 95 % CI (1.02–1.8)].

Conclusion

In a large ICU population, we report a significant clinical association between a variation in the human REL gene and severity and mortality of septic shock, suggesting for the first time a new insight into the role of cRel in response to infection in humans.

Endotoxemia Induces IκBβ/NF-κB-Dependent Endothelin-1 Expression in Hepatic Macrophages

Elevated serum concentrations of the vasoactive protein endothelin-1 (ET-1) occur in the setting of systemic inflammatory response syndrome and contribute to distal organ hypoperfusion and pulmonary hypertension. Thus, understanding the cellular source and transcriptional regulation of systemic inflammatory stress-induced ET-1 expression may reveal therapeutic targets. Using a murine model of LPS-induced septic shock, we demonstrate that the hepatic macrophage is the primary source of elevated circulating ET-1, rather than the endothelium as previously proposed. Using pharmacologic inhibitors, ET-1 promoter luciferase assays, and by silencing and overexpressing NF-κB inhibitory protein IκB expression, we demonstrate that LPS-induced ET-1 expression occurs via an NF-κB-dependent pathway. Finally, the specific role of the cRel/p65 inhibitory protein IκBβ was evaluated. Although cytoplasmic IκBβ inhibits activity of cRel-containing NF-κB dimers, nuclear IκBβ stabilizes NF-κB/DNA binding and enhances gene expression. Using targeted pharmacologic therapies to specifically prevent IκBβ/NF-κB signaling, as well as mice genetically modified to overexpress IκBβ, we show that nuclear IκBβ is both necessary and sufficient to drive LPS-induced ET-1 expression. Together, these results mechanistically link the innate immune response mediated by IκBβ/NF-κB to ET-1 expression and potentially reveal therapeutic targets for patients with Gram-negative septic shock.

Treatment of low molecular weight heparin inhibits systemic inflammation and prevents endotoxin-induced acute lung injury in rats

To determine whether low molecular weight heparin (LMWH) is able to reduce pulmonary inflammation and improve the survival in rats with endotoxin-induced acute lung injury (ALI). Rat ALI model was reproduced by injection of lipopolysaccharide (LPS) into tail vein. Rats were divided randomly into three groups: control group, ALI group, LMWH-treated group. Blood was collected and lung tissue was harvested at the designated time points for analysis. The lung specimens were harvested for morphological studies, streptavidin-peroxidase immunohistochemistry examination. Lung tissue edema was evaluated by tissue water content. The levels of lung tissue myeloperoxidase (MPO) were determined. Meanwhile, the nuclear factor-kappa B (NF-κB) activation, tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) levels and high mobility group box 1 (HMGB1) and intercellular adhesion molecule-1 (ICAM-1) protein levels in the lung were studied. In survival studies, a separate group of rats were treated with LMWH or sterile saline after LPS administration. Then, the mortality was recorded. Treatment with LMWH after ALI was associated with a reduction in the severity of LPS-induced lung injury. Treatment with LMWH significantly decreased the expression of TNF-α, IL-1β, HMGB1 and ICAM-1 in the lung of ALI rats. Similarly, treatment with LMWH dramatically diminished LPS-induced neutrophil sequestration and markedly reduced the enhanced lung permeability. In the present study, LMWH administration inhibited the nuclear translocation of NF-κB in the lung. Survival was significantly higher among the LMWH-treated group compared with the ALI group. These data suggest that LMWH attenuates inflammation and prevents lethality in endotoxemic rats.

Inhibiting IκBβ-NFκB signaling attenuates the expression of select pro-inflammatory genes

Multiple mediators of septic shock are regulated by the transcription factor nuclear factor κB (NFκB). However, complete NFκB inhibition can exacerbate disease, necessitating evaluation of targeted strategies to attenuate the pro-inflammatory response. Here, we demonstrate that in murine macrophages, low-dose NFκB inhibitors specifically attenuates lipopolysaccharide (LPS)-induced IκBβ degradation and the expression of a select subset of target genes (encoding IL1β, IL6, IL12β). Gain- and loss-of-function experiments demonstrate the necessary and sufficient role of inhibitor of NFκB family member IκBβ (also known as NFKBIB) in the expression of these genes. Furthermore, both fibroblasts and macrophages isolated from IκBβ overexpressing mice demonstrate attenuated LPS-induced IκBβ-NFκB signaling and IL1β, IL6 and IL12β expression. Further confirming the role of IκBβ and its NFκB subunit binding partner cRel in LPS-induced gene expression, pre-treatment of wild-type mouse embryonic fibroblasts with a cell-permeable peptide containing the cRel nuclear localization sequence attenuated IL6 expression. We prove that LPS-induced IκBβ-NFκB signaling can be selectively modulated to attenuate the expression of select pro-inflammatory target genes, thus providing therapeutic insights for patients exposed to systemic inflammatory stress.

Identification of haplotype tag single nucleotide polymorphisms within the nuclear factor-κB family genes and their clinical relevance in patients with major trauma

Introduction

Nuclear factor-κB (NF-κB) family plays an important role in the development of sepsis in critically ill patients. Although several single nucleotide polymorphisms (SNPs) have been identified in the NF-κB family genes, only a few SNPs have been studied.

Methods

A total of 753 patients with major blunt trauma were included in this study. Tag SNPs (tSNPs) were selected from the NF-κB family genes (NFKB1, NFKB2, RELA, RELB and REL) through construction of haplotype blocks. The SNPs selected from genes within the canonical NF-κB pathway (including NFKB1, RELA and REL), which played a critical role in innate immune responses were genotyped using pyrosequencing method and analyzed in relation to the risk of development of sepsis and multiple organ dysfunction (MOD) syndrome. Moreover, the rs842647 polymorphism was analyzed in relation to tumor necrosis factor α (TNF-α) production by peripheral blood leukocytes in response to bacterial lipoprotein stimulation.

Results

Eight SNPs (rs28362491, rs3774932, rs4648068, rs7119750, rs4803789, rs12609547, rs1560725 and rs842647) were selected from the NF-κB family genes. All of them were shown to be high-frequency SNPs in this study cohort. Four SNPs (rs28362491, rs4648068, rs7119750 and rs842647) within the canonical NF-κB pathway were genotyped, and rs842647 was associated with sepsis morbidity rate and MOD scores. An association was also observed between the rs842647 A allele and lower TNF-α production.

Conclusions

rs842647 polymorphism might be used as relevant risk estimate for the development of sepsis and MOD syndrome in patients with major trauma.

Electronic supplementary material

The online version of this article (doi:10.1186/s13054-015-0836-6) contains supplementary material, which is available to authorized users.

Alterations of dendritic cells in sepsis: featured role in immunoparalysis

Sepsis, the leading cause of mortality in intensive care unit, is characterized by hyperinflammatory response in the early stage and followed by a period of immunosuppression. This immune disorder is believed to be the potent factor that is tightly associated with high mortality in sepsis. Dendritic cells (DCs) serve as professional antigen-presenting cells that play a vital role in immune response by activating T lymphocytes. During the progression of sepsis, DCs have been reported to take part in the aberrant immune response and be necessary for survival. Therefore, a better understanding of the DCs pathology will be undoubtedly beneficial for resolving the problems occurring in sepsis. This review discusses effects of sepsis on DCs number and function, including surface molecules expression, cytokines secretion, and T cell activation, and the underlying mechanism as well as some potential therapeutic strategies.

Inhibition of IKKβ in enterocytes exacerbates sepsis-induced intestinal injury and worsens mortality

OBJECTIVES

Nuclear factor-κB is a critical regulator of cell-survival genes and the host inflammatory response. The purpose of this study was to investigate the role of enterocyte-specific NF-kB in sepsis through selective ablation of IkB kinase.

DESIGN

Prospective, randomized controlled study.

SETTING

Animal laboratories in university medical centers.

SUBJECTS AND INTERVENTIONS

Mice lacking functional NF-kB in their intestinal epithelium (Vil-Cre/Ikkβ) and wild-type mice were subjected to sham laparotomy or cecal ligation and puncture. Animals were killed at 24 hours or followed 7 days for survival.

MEASUREMENTS AND MAIN RESULTS

Septic wild-type mice had decreased villus length compared with sham mice, whereas villus atrophy was further exacerbated in septic Vil-Cre/Ikkβ mice. Sepsis induced an increase in intestinal epithelial apoptosis compared with sham mice, which was further exacerbated in Vil-Cre/Ikkβ mice. Sepsis induced intestinal hyperpermeability in wild-type mice compared with sham mice, which was further exacerbated in septic Vil-Cre/Ikkβ mice. This was associated with increased intestinal expression of claudin-2 in septic wild-type mice, which was further increased in septic Vil-Cre/Ikkβ mice. Both, pro-inflammatory and anti-inflammatory cytokines were increased in serum following cecal ligation and puncture, and interleukin 10 and monocyte chemoattractant protein-1 levels were higher in septic Vil-Cre/Ikkβ mice than in septic wild-type mice. All septic mice were bacteremic, but no differences in bacterial load were identified between wild-type and Vil-Cre/Ikkβ mice. To determine the functional significance of these results, animals were followed for survival. Septic wild-type mice had lower mortality than septic Vil-Cre/Ikkβ mice (47% vs 80%, p<0.05). Antitumor necrosis factor administration decreased intestinal apoptosis, permeability, and mortality in wild-type septic mice, and a similar improvement in intestinal integrity and survival were seen when antitumor necrosis factor was given to Vil-Cre/Ikkβ mice.

CONCLUSIONS

Enterocyte-specific NF-kB has a beneficial role in sepsis by partially preventing sepsis-induced increases in apoptosis and permeability, which are associated with worsening mortality.

NF-κB inhibition after cecal ligation and puncture reduces sepsis-associated lung injury without altering bacterial host defense

Introduction. Since the NF-κB pathway regulates both inflammation and host defense, it is uncertain whether interventions targeting NF-κB would be beneficial in sepsis. Based on the kinetics of the innate immune response, we postulated that selective NF-κB inhibition during a defined time period after the onset of sepsis would reduce acute lung injury without compromising bacterial host defense. Methods. Mice underwent cecal ligation and puncture (CLP). An NF-κB inhibitor, BMS-345541 (50 µg/g mice), was administered by peroral gavage beginning 2 hours after CLP and repeated at 6 hour intervals for 2 additional doses. Results. Mice treated with BMS-345541 after CLP showed reduced neutrophilic alveolitis and lower levels of KC in bronchoalveolar lavage fluid compared to mice treated with CLP+vehicle. In addition, mice treated with CLP+BMS had minimal histological evidence of lung injury and normal wet-dry ratios, indicating protection from acute lung injury. Treatment with the NF-κB inhibitor did not affect the ability of cultured macrophages to phagocytose bacteria and did not alter bacterial colony counts in blood, lung tissue, or peritoneal fluid at 24 hours after CLP. While BMS-345541 treatment did not alter mortality after CLP, our results showed a trend towards improved survival. Conclusion. Transiently blocking NF-κB activity after the onset of CLP-induced sepsis can effectively reduce acute lung injury in mice without compromising bacterial host defense or survival after CLP.

Immune-pineal axis: nuclear factor κB (NF-kB) mediates the shift in the melatonin source from pinealocytes to immune competent cells

Pineal gland melatonin is the darkness hormone, while extra-pineal melatonin produced by the gonads, gut, retina, and immune competent cells acts as a paracrine or autocrine mediator. The well-known immunomodulatory effect of melatonin is observed either as an endocrine, a paracrine or an autocrine response. In mammals, nuclear translocation of nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) blocks noradrenaline-induced melatonin synthesis in pinealocytes, which induces melatonin synthesis in macrophages. In addition, melatonin reduces NF-κB activation in pinealocytes and immune competent cells. Therefore, pathogen- or danger-associated molecular patterns transiently switch the synthesis of melatonin from pinealocytes to immune competent cells, and as the response progresses melatonin inhibition of NF-κB activity leads these cells to a more quiescent state. The opposite effect of NF-κB in pinealocytes and immune competent cells is due to different NF-κB dimers recruited in each phase of the defense response. This coordinated shift of the source of melatonin driven by NF-κB is called the immune-pineal axis. Finally, we discuss how this concept might be relevant to a better understanding of pathological conditions with impaired melatonin rhythms and hope it opens new horizons for the research of side effects of melatonin-based therapies.

Extracorporeal therapy in sepsis: are we there yet?

The role of extracorporeal therapies (ECTs) in sepsis is unclear and is a strongly debated topic in critical-care medicine. Unfortunately, much of this debate arises because we lack a clear understanding of what defines the stage and severity of the disease, and the pivotal pathophysiological events dictating outcomes. In the absence of this knowledge, ECTs remain among a large group of therapies with high promise but unproven efficacy.

Functional imaging of Rel expression in inflammatory processes using bioluminescence imaging system in transgenic mice

c-Rel plays important roles in many inflammatory diseases. Revealing the dynamic expression of c-Rel in disease processes in vivo is critical for understanding c-Rel functions and for developing anti-inflammatory drugs. In this paper, a transgenic mouse line, B6-Tg(c-Rel-luc)(Mlit), which incorporated the transgene firefly luciferase driven by a 14.5-kb fragment containing mouse c-Rel gene Rel promoter, was generated to monitor Rel expression in vivo. Luciferase expression could be tracked in living mice by the method of bioluminescence imaging in a variety of inflammatory processes, including LPS induced sepsis and EAE disease model. The luciferase expression in transgenic mice was comparable to the endogenous Rel expression and could be suppressed by administration of anti-inflammatory drug dexamethasone or aspirin. These results indicate that the B6-Tg(c-Rel-luc)(Mlit) mouse is a valuable animal model to study Rel expression in physiological and pathological processes, and the effects of various drug treatments in vivo.

The c-Rel Transcription Factor in Development and Disease

c-Rel is a member of the nuclear factor κB (NF-κB) transcription factor family. Unlike other NF-κB proteins that are expressed in a variety of cell types, high levels of c-Rel expression are found primarily in B and T cells, with many c-Rel target genes involved in lymphoid cell growth and survival. In addition to c-Rel playing a major role in mammalian B and T cell function, the human c-rel gene (REL) is a susceptibility locus for certain autoimmune diseases such as arthritis, psoriasis, and celiac disease. The REL locus is also frequently altered (amplified, mutated, rearranged), and expression of REL is increased in a variety of B and T cell malignancies and, to a lesser extent, in other cancer types. Thus, agents that modulate REL activity may have therapeutic benefits for certain human cancers and chronic inflammatory diseases.

Trauma patients' elevated tumor necrosis related apoptosis inducing ligand (TRAIL) contributes to increased T cell apoptosis

Immunosuppression resulting from excessive post-trauma apoptosis of hyperactivated T cells is controversial. TRAIL mediated T cell apoptosis decreases highly activated T cells' responses. Caspase-10, a particular TRAIL target, was increased in trauma patients' T cells with concomitantly elevated plasma TRAIL levels. These patients' T cells developed anergy, implicating increased TRAIL-mediated T cell apoptosis in post-trauma T cell anergy. Control T cells cultured with patients' sera containing high TRAIL levels increased their caspase-10 activity and apoptosis. Stimulated primary T cells are TRAIL apoptosis resistant. Increased plasma thrombospondin-1 and T cell expression of CD47, a thrombospondin-1 receptor, preceded patients' T cell anergy. CD47 triggering of T cells increased their sensitivity to TRAIL-induced apoptosis. Augmentation of T cell TRAIL-induced apoptosis was secondary to CD47 triggered activation of the Src homology-containing phosphatase-1 (SHP-1) and was partially blocked by a SHP-1 inhibitor. We suggest that combined post-trauma CD47 triggering, SHP-1 mediated NFκB suppression, and elevated TRAIL levels increase patients' CD47 expressing T cell apoptosis, thus contributing to subsequent T cell anergy.