Innate Lymphocyte Subsets and Their Immunoregulatory Roles in Burn Injury and Sepsis

The Changes in the Quantity of Lymphocyte Subpopulations during the Process of Sepsis

Sepsis remains a global challenge, especially in low- and middle-income countries, where there is an urgent need for easily accessible and cost-effective biomarkers to predict the occurrence and prognosis of sepsis. Lymphocyte counts are easy to measure clinically, and a large body of animal and clinical research has shown that lymphocyte counts are closely related to the incidence and prognosis of sepsis. This review extensively collected experimental articles related to lymphocyte counts since the unification of the definition of sepsis. The article categorizes and discusses the relationship between absolute lymphocyte counts, intrinsic lymphocyte subsets, effector T-lymphocytes, B-lymphocytes, dendritic cells, and the incidence and prognosis of sepsis. The results indicate that comparisons of absolute lymphocyte counts alone are meaningless. However, in addition to absolute lymphocyte counts, innate lymphocyte subsets, effector T-cells, B-lymphocytes, and dendritic cells have shown certain research value in related studies.

Host and Pathogen-Directed Therapies against Microbial Infections Using Exosome- and Antimicrobial Peptide-derived Stem Cells with a Special look at Pulmonary Infections and Sepsis

Microbial diseases are a great threat to global health and cause considerable mortality and extensive economic losses each year. The medications for treating this group of diseases (antibiotics, antiviral, antifungal drugs, etc.) directly attack the pathogenic agents by recognizing the target molecules. However, it is necessary to note that excessive use of any of these drugs can lead to an increase in microbial resistance and infectious diseases. New therapeutic methods have been studied recently using emerging drugs such as mesenchymal stem cell-derived exosomes (MSC-Exos) and antimicrobial peptides (AMPs), which act based on two completely different strategies against pathogens including Host-Directed Therapy (HDT) and Pathogen-Directed Therapy (PDT), respectively. In the PDT approach, AMPs interact directly with pathogens to interrupt their intrusion, survival, and proliferation. These drugs interact directly with the cell membrane or intracellular components of pathogens and cause the death of pathogens or inhibit their replication. The mechanism of action of MSC-Exos in HDT is based on immunomodulation and regulation, promotion of tissue regeneration, and reduced host toxicity. This review studies the potential of mesenchymal stem cell-derived exosomes/ATPs therapeutic properties against microbial infectious diseases especially pulmonary infections and sepsis.

Advances in Immunomodulatory Mechanisms of Mesenchymal Stem Cells-Derived Exosome on Immune Cells in Scar Formation

Pathological scars are the result of over-repair and excessive tissue proliferation of the skin injury. It may cause serious dysfunction, resulting in psychological and physiological burdens on the patients. Currently, mesenchymal stem cells-derived exosomes (MSC-Exo) displayed a promising therapeutic effect on wound repair and scar attenuation. But the regulatory mechanisms are opinions vary. In view of inflammation has long been proven as the initial factor of wound healing and scarring, and the unique immunomodulation mechanism of MSC-Exo, the utilization of MSC-Exo may be promising therapeutic for pathological scars. However, different immune cells function differently during wound repair and scar formation. The immunoregulatory mechanism of MSC-Exo would differ among different immune cells and molecules. Herein, this review gave a comprehensive summary of MSC-Exo immunomodulating different immune cells in wound healing and scar formation to provide basic theoretical references and therapeutic exploration of inflammatory wound healing and pathological scars.

Gharbi W. Determination of IFN-y in Patients with Pseudomonas aeruginosa-Inflicted Burn and Wound

The sample collection was carried out from 1/12/2021 to 1/4/2022 at the burns hospital, Baghdad teaching hospital in Baghdad city, and Alhussain teaching hospital in Almuthana city. Samples were collected from patients' sera collection samples from (69) patients, from burn patients 53 and 16 samples from wound patients infected with pseudomonas aeruginosa; 41 patients were males, and 28 were females. This group used the other 69 patients that were not infected by bacteria as a control group. The level of IFN-y was investigated by ELISA assay in the teaching Laboratories in al Sawawah city. The results showed a decrease in IFN-y levels were 35.2±2.6 for burn patients and 35.4±2.3 for wound patients compared to the control group of 46±2.5. The current study reported a highly significant difference in IFN-y levels between the burn and wound patients and the control group (P<0.0001 ). Keywords: Pseudomonas aeruginosa; Burn; wound; Interferon – Gamma.

Predictive value of CD3+ cells and interleukin 2 receptor in systemic inflammatory response syndrome after percutaneous nephrolithotomy

Objective

The aim of the current study was to evaluate the risk factors that influence the development of postoperative systemic inflammatory response syndrome (SIRS) after percutaneous nephrolithotomy (PCNL), including cytokines and lymphocyte subsets.

Methods

A total of 154 patients who underwent PCNL at our hospital between October 2019 and January 2022 were retrospectively reviewed. The development of post-PCNL SIRS was the primary endpoint of the study. Univariable analysis and multivariable logistic regression analysis were performed to identify independent risk factors of post-PCNL SIRS. A nomogram was constructed using the independent risk factors, and receiver operating characteristic (ROC) curves were drawn.

Results

There were 50 patients (32.5%) who developed SIRS after PCNL. In multivariate analysis, positive urine culture (odds ratio [OR], 3.556; p = 0.048), long operation time (OR, 1.011; p = 0.027), high IL-2R (OR, 1.002; p = 0.018), low percentage of CD3⁺ cells (OR 0.931; p = 0.006), and high white blood cell (WBC) count (OR, 1.282; p = 0.044) were independent risk factors for post-PCNL SIRS. These five significant variables were used to generate a nomogram that exhibited favorable fitting. The discrimination area under the ROC curves was 0.795.

Conclusions

Patients with long operation times, positive urine cultures, high interleukin 2 receptor, high white blood cell counts, and low percentages of CD3⁺ cells may be at a higher risk of developing SIRS after PCNL. In these patients, cautious and comprehensive preoperative evaluations and appropriate treatment strategies should be considered.

Level of Decoy Receptor 3 for Monitoring Clinical Progression of Severe Burn Patients

The clinical value of Decoy receptor 3 (DcR3) in severe burn is investigated. Ten patients with severe burns were monitored for DcR3, PCT, CRP, IL6, SOFA score, white blood cell (WBC), and platelet. The correlations were analyzed. DcR3 increased on day 1. The nonsurvivors had a steady high level of DcR3 while the survivors had a relatively low level of DcR3. The peak magnitude of DcR3 was high in five nonsurvivors and low in five survivors without overlap. Three patients had a continuously increasing DcR3 level and then died. In the other two nonsurvivors, DcR3 reached the peak and then decreased before death. DcR3 correlated well with PCT (ρ = 0.4469, P < .0001), less with CRP, platelet, IL6, SOFA score and WBC (ρ = 0.4369, 0.4078, 0.3995, 0.2631, 0.1504, respectively, all P < .001). To explore the mechanisms, the HaCaT or THP-1 cells were stimulated by the plasma of burn patients, 45°C, LPS or stimulators of TLRs or NOD2 (PGN, CL264, MDP, iE-DAP, Gardiquimod), and their DcR3 was increased, which could be reduced by GDC-0941 or BEZ235 (inhibitors of PI3K and mTOR). The levels of DcR3 appeared to be a useful biomarker for monitoring the clinical severity and a predictor of mortality of severe burns.

Lymphocyte Immunosuppression and Dysfunction Contributing to Persistent Inflammation, Immunosuppression, and Catabolism Syndrome (PICS)

ABSTRACT

Persistent Inflammation, Immune Suppression, and Catabolism Syndrome (PICS) is a disease state affecting patients who have a prolonged recovery after the acute phase of a large inflammatory insult. Trauma and sepsis are two pathologies after which such an insult evolves. In this review, we will focus on the key clinical determinants of PICS: Immunosuppression and cellular dysfunction. Currently, relevant immunosuppressive functions have been attributed to both innate and adaptive immune cells. However, there are significant gaps in our knowledge, as for trauma and sepsis the immunosuppressive functions of these cells have mostly been described in acute phase of inflammation so far, and their clinical relevance for the development of prolonged immunosuppression is mostly unknown. It is suggested that the initial immune imbalance determines the development of PCIS. Additionally, it remains unclear what distinguishes the onset of immune dysfunction in trauma and sepsis and how this drives immunosuppression in these cells. In this review, we will discuss how regulatory T cells (Tregs), innate lymphoid cells, natural killer T cells (NKT cells), TCR-a CD4- CD8- double-negative T cells (DN T cells), and B cells can contribute to the development of post-traumatic and septic immunosuppression. Altogether, we seek to fill a gap in the understanding of the contribution of lymphocyte immunosuppression and dysfunction to the development of chronic immune disbalance. Further, we will provide an overview of promising diagnostic and therapeutic interventions, whose potential to overcome the detrimental immunosuppression after trauma and sepsis is currently being tested.

H2S, a Bacterial Defense Mechanism against the Host Immune Response

The biological mediator hydrogen sulfide (H₂S) is produced by bacteria and has been shown to be cytoprotective against oxidative stress and to increase the sensitivity of various bacteria to a range of antibiotic drugs. Here we evaluated whether bacterial H₂S provides resistance against the immune response, using two bacterial species that are common sources of nosocomial infections, Escherichia coli and Staphylococcus aureus Elevations in H₂S levels increased the resistance of both species to immune-mediated killing. Clearances of infections with wild-type and genetically H₂S-deficient E. coli and S. aureus were compared in vitro and in mouse models of abdominal sepsis and burn wound infection. Also, inhibitors of H₂S-producing enzymes were used to assess bacterial killing by leukocytes. We found that inhibition of bacterial H₂S production can increase the susceptibility of both bacterial species to rapid killing by immune cells and can improve bacterial clearance after severe burn, an injury that increases susceptibility to opportunistic infections. These findings support the role of H₂S as a bacterial defense mechanism against the host response and implicate bacterial H₂S inhibition as a potential therapeutic intervention in the prevention or treatment of infections.

Erythropoietin regulates immune/inflammatory reaction and improves neurological function outcomes in traumatic brain injury

INTRODUCTION

Traumatic brain injury (TBI) remains a leading cause of disability and death among young people in China. Unfortunately, no specific pharmacological agents to block the progression of secondary brain injury have been approved for clinical treatment. Recently, neuroprotective effects of erythropoietin (EPO) have been demonstrated in addition to its principal function in erythropoiesis, and hence it is viewed as a potential drug for TBI. In this study, we have investigated the neuroprotective effects of EPO associated with immune/inflammatory modulation in a mouse experimental TBI model.

METHODS

EPO (5000 U/kg body weight, i.p.) was injected at 1 hr, 1, 2, and 3 days after TBI, and its effect on cognitive function, brain edema, immune/inflammatory cells including regulatory T cells (Tregs), neutrophils, CD3⁺ T cells, and microglia, cytokines including interleukin-10 (IL-10), transforming growth factor-β (TGF-β), interleukin-1β (IL-1β), and tumor necrosis factor-α (TNF-α) were evaluated at different time points after treatment.

RESULTS

EPO treatment significantly decreased brain edema and improved cognitive function when compared to Saline-treated mice (p < .05). EPO treatment also significantly increased Tregs level in spleen and injured brain tissue as well as significantly reduced the infiltration and activation of immune/inflammatory cells (neutrophils, CD3⁺T cells, and microglia) in the injured hemisphere compared to Saline-treated control animals (p < .05). In addition, ELISA analysis demonstrated that EPO treatment increased the expression of anti-inflammatory cytokine IL-10, but decreased the expression of proinflammatory cytokine IL-1β and TNF-α in the injured brain tissue (p < .05).

CONCLUSIONS

These findings suggest that EPO could improve neurological and cognitive functional outcomes as well as regulate immune/inflammatory reaction in TBI.

Determination of lymphocytes surface markers in patients with thermal burns and the influence of burn size on mononuclear cell subsets

Background: Thermal burn injuries impair the host defence system. Hence, in the present study, we aimed at investigating the changes in the number and phenotype of peripheral blood lymphocyte populations (T, B, and natural killer cells) and their subpopulations in patients with thermal burns and determining the relationships with different sizes of total body surface area (TBSA). Methods: Blood samples from 67 patients, admitted to Motahary Burn Center in Tehran, with burns from 30% to more than 70% TBSA were collected on Days 3 and 7 postburn. Lymphocytes and their subpopulations were identified by monoclonal antibodies. The cells were analyzed using flow cytometry. The results were compared with healthy controls. Results: In this study, 3 and 7 days after burn injury, the percentages of CD3+, CD4+ and CD8+ lymphocyte significantly decreased, CD4+/CD8+ ratios were below the normal range, and CD19+ (B cells) significantly increased. No significant difference was obtained in the mean percentage of CD16+ (NK cells) between Days 3 and 7 postburn. Patients with burns of 30% TBSA or greater (>70%) had a significant reduction in CD3+, CD4+ and CD8+ ( T cells) numbers up to 7 days compared with 3 days after burn injury. Patients with 30% to >70 % TBSA burn failed to show any significant changes in CD4+/CD8+ ratio as well as CD16+ (NK cells) 3 to 7 days after burn. In patients with burns more than 30% to>70% TBSA, CD19+ (B cells) number changes were found to be complicated after 3 and 7 days. Conclusion: The results of this study suggest that alterations of immune cell surface markers and TBSA% can reflect postburn lymphocyte activation.

Signatures of inflammation and impending multiple organ dysfunction in the hyperacute phase of trauma: A prospective cohort study

BACKGROUND

Severe trauma induces a widespread response of the immune system. This "genomic storm" can lead to poor outcomes, including Multiple Organ Dysfunction Syndrome (MODS). MODS carries a high mortality and morbidity rate and adversely affects long-term health outcomes. Contemporary management of MODS is entirely supportive, and no specific therapeutics have been shown to be effective in reducing incidence or severity. The pathogenesis of MODS remains unclear, and several models are proposed, such as excessive inflammation, a second-hit insult, or an imbalance between pro- and anti-inflammatory pathways. We postulated that the hyperacute window after trauma may hold the key to understanding how the genomic storm is initiated and may lead to a new understanding of the pathogenesis of MODS.

METHODS AND FINDINGS

We performed whole blood transcriptome and flow cytometry analyses on a total of 70 critically injured patients (Injury Severity Score [ISS] ≥ 25) at The Royal London Hospital in the hyperacute time period within 2 hours of injury. We compared transcriptome findings in 36 critically injured patients with those of 6 patients with minor injuries (ISS ≤ 4). We then performed flow cytometry analyses in 34 critically injured patients and compared findings with those of 9 healthy volunteers. Immediately after injury, only 1,239 gene transcripts (4%) were differentially expressed in critically injured patients. By 24 hours after injury, 6,294 transcripts (21%) were differentially expressed compared to the hyperacute window. Only 202 (16%) genes differentially expressed in the hyperacute window were still expressed in the same direction at 24 hours postinjury. Pathway analysis showed principally up-regulation of pattern recognition and innate inflammatory pathways, with down-regulation of adaptive responses. Immune deconvolution, flow cytometry, and modular analysis suggested a central role for neutrophils and Natural Killer (NK) cells, with underexpression of T- and B cell responses. In the transcriptome cohort, 20 critically injured patients later developed MODS. Compared with the 16 patients who did not develop MODS (NoMODS), maximal differential expression was seen within the hyperacute window. In MODS versus NoMODS, 363 genes were differentially expressed on admission, compared to only 33 at 24 hours postinjury. MODS transcripts differentially expressed in the hyperacute window showed enrichment among diseases and biological functions associated with cell survival and organismal death rather than inflammatory pathways. There was differential up-regulation of NK cell signalling pathways and markers in patients who would later develop MODS, with down-regulation of neutrophil deconvolution markers. This study is limited by its sample size, precluding more detailed analyses of drivers of the hyperacute response and different MODS phenotypes, and requires validation in other critically injured cohorts.

CONCLUSIONS

In this study, we showed how the hyperacute postinjury time window contained a focused, specific signature of the response to critical injury that led to widespread genomic activation. A transcriptomic signature for later development of MODS was present in this hyperacute window; it showed a strong signal for cell death and survival pathways and implicated NK cells and neutrophil populations in this differential response.

An Optimized Protocol to Analyze Glycolysis and Mitochondrial Respiration in Lymphocytes

Lymphocytes respond to a variety of stimuli by activating intracellular signaling pathways, which in turn leads to rapid cellular proliferation, migration and differentiation, and cytokine production. All of these events are tightly linked to the energy status of the cell, and therefore studying the energy-producing pathways may give clues about the overall functionality of these cells. The extracellular flux analyzer is a commonly used device for evaluating the performance of glycolysis and mitochondrial respiration in many cell types. This system has been used to study immune cells in a few published reports, yet a comprehensive protocol optimized particularly for lymphocytes is lacking. Lymphocytes are fragile cells that survive poorly in ex vivo conditions. Oftentimes lymphocyte subsets are rare, and working with low cell numbers is inevitable. Thus, an experimental strategy that addresses these difficulties is required. Here, we provide a protocol that allows for rapid isolation of viable lymphocytes from lymphoid tissues, and for the analysis of their metabolic states in the extracellular flux analyzer. Furthermore, we provide results of experiments in which the metabolic activities of several lymphocyte subtypes at different cell densities were compared. These observations suggest that our protocol can be used to achieve consistent, well-standardized results even at low cell concentrations, and thus it may have broad applications in future studies focusing on the characterization of metabolic events in immune cells.

Functional aspects of fish lymphocytes

After almost 40 years of studies in comparative immunology, some light has been shed on the evolutive immunobiology of vertebrates, and experimental evidences have shown that acquired immunity, defined by somatic recombination of antigen-binding molecules and memory, is an achievement as ancient as jawless vertebrates. However, the molecular processes generating antigen receptors evolved independently between jawless and jawed fishes, and produced lymphocytic cells with similar functions but employing different sets of genes. In recent years, data have been provided describing some in vitro and in vivo functional responses of fish lymphocytes. After a long gap, the number of specific markers for fish lymphocytes is increasing, thus allowing a first characterisation of lymphocyte subsets. Overall, in the near future it will be possible to open a new chapter in fish immunology and investigate functional immunity of lymphocyte responses by combining the extensive knowledge on immune gene products with markers for molecules and cells. The present review summarizes current knowledge on functional features of fish lymphocytes.

Injury-elicited stressors alter endogenous retrovirus expression in lymphocytes depending on cell type and source lymphoid organ

Background

Murine leukemia virus-type endogenous retroviruses (MuLV-ERVs) constitute ~10% of the mouse genome and are associated with various pathophysiologic processes. In this study, we examined whether MuLV-ERVs’ response to burn-elicited stressors is specific for certain lymphocyte populations and/or locations of lymphoid organ.

Results

B- and T-cells, which were sorted from nine lymphoid organs of C57BL/6J mice after burn, were subjected to MuLV-ERV expression analyses. Overall, the post-burn MuLV-ERV expression pattern was dependent on lymphocyte type, time after injury, location of lymphoid organ, and MuLV-ERV type. For instance, the MuLV-ERV expression in T-cells from the thymus and three cervical lymph nodes decreased at 3 hours post-burn while the expression of some MuLV-ERVs was augmented in B-cells derived from the mesenteric lymph node. The MuLV-ERV U3 sequences population of the burn-24 hours group was less diverse in comparison to the no burn and burn-3 hours groups. In addition, it was apparent that at the 24 hours time point, the U3 populations of B-cells from both no burn and burn groups were less heterogeneous than the T-cells’ U3 populations. Using the U3 sequences, some of which were isolated only from specific experimental groups (B- vs. T-cells; no burn vs. burn), as probes, 51 putative MuLV-ERVs, including 16 full-length proviruses, were mapped followed by characterization of their biologic properties.

Conclusion

MuLV-ERVs’ response to burn-elicited stressors may be differentially controlled depending on lymphocyte type, location of lymphoid organ, MuLV-ERV type, and stress duration.

Viral cross-class serpin inhibits vascular inflammation and T lymphocyte fratricide; a study in rodent models in vivo and human cell lines in vitro

Poxviruses express highly active inhibitors, including serine proteinase inhibitors (serpins), designed to target host immune defense pathways. Recent work has demonstrated clinical efficacy for a secreted, myxomaviral serpin, Serp-1, which targets the thrombotic and thrombolytic proteases, suggesting that other viral serpins may have therapeutic application. Serp-2 and CrmA are intracellular cross-class poxviral serpins, with entirely distinct functions from the Serp-1 protein. Serp-2 and CrmA block the serine protease granzyme B (GzmB) and cysteine proteases, caspases 1 and 8, in apoptotic pathways, but have not been examined for extracellular anti-inflammatory activity. We examined the ability of these cross-class serpins to inhibit plaque growth after arterial damage or transplant and to reduce leukocyte apoptosis. We observed that purified Serp-2, but not CrmA, given as a systemic infusion after angioplasty, transplant, or cuff-compression injury markedly reduced plaque growth in mouse and rat models in vivo. Plaque growth was inhibited both locally at sites of surgical trauma, angioplasty or transplant, and systemically at non-injured sites in ApoE-deficient hyperlipidemic mice. With analysis in vitro of human cells in culture, Serp-2 selectively inhibited T cell caspase activity and blocked cytotoxic T cell (CTL) mediated killing of T lymphocytes (termed fratricide). Conversely, both Serp-2 and CrmA inhibited monocyte apoptosis. Serp-2 inhibitory activity was significantly compromised either in vitro with GzmB antibody or in vivo in ApoE/GzmB double knockout mice. Conclusions The viral cross-class serpin, Serp-2, that targets both apoptotic and inflammatory pathways, reduces vascular inflammation in a GzmB-dependent fashion in vivo, and inhibits human T cell apoptosis in vitro. These findings indicate that therapies targeting Granzyme B and/or T cell apoptosis may be used to inhibit T lymphocyte apoptosis and inflammation in response to arterial injury.

The nature of innate and adaptive interleukin-17A responses in sham or bacterial inoculation

Streptococcus pyogenes is the causative agent of numerous diseases ranging from benign infections (pharyngitis and impetigo) to severe infections associated with high mortality (necrotizing fasciitis and bacterial sepsis). As with other bacterial infections, there is considerable interest in characterizing the contribution of interleukin-17A (IL-17A) responses to protective immunity. We here show significant il17a up-regulation by quantitative real-time PCR in secondary lymphoid organs, correlating with increased protein levels in the serum within a short time of S. pyogenes infection. However, our data offer an important caveat to studies of IL-17A responsiveness following antigen inoculation, because enhanced levels of IL-17A were also detected in the serum of sham-infected mice, indicating that inoculation trauma alone can stimulate the production of this cytokine. This highlights the potency and speed of innate IL-17A immune responses after inoculation and the importance of proper and appropriate controls in comparative analysis of immune responses observed during microbial infection.

Gamma delta (γδ) T-cells are critical in the up-regulation of inducible nitric oxide synthase at the burn wound site

BACKGROUND

The high incidence of morbidity and mortality following major burn can in part be attributed to immune derangements and wound healing complications. Inflammation plays an important role in wound healing, of which inducible nitric oxide synthase (iNOS) derived nitric oxide is a central mediator. T-cells of the γδ TCR lineage have also been shown to be important in healing of the burn wound site. Nonetheless, the role of γδ T-cells in the regulation of the burn wound iNOS expression is unknown.

METHODS

Wildtype (WT) and δ TCR(-/-) male C57BL/6 mice were subjected to burn (3rd degree, 12.5% TBSA) or sham treatment. Three days after injury, skin samples from non-injured and the burn wound were collected and analyzed for the expression of iNOS and cytokines and chemokine levels. In a second series of experiments, WT mice were subjected to burn and left untreated or treated with the iNOS inhibitor, L-Nil. Skin cytokine and chemokine levels were assessed 3days thereafter.

RESULTS

Burn induced an 18-fold increase in iNOS expression at the wound site as compared to the uninjured skin of WT sham mice. In δ TCR(-/-) mice iNOS expression at the wound site was significantly lower than that of the WT group. Burn also induced increased levels of IL-1β, IL-6, G-CSF, TNF-α, KC, MCP-1, MIP-1α and MIP-1β at the wound site in WT and δ TCR(-/-) mice, but G-CSF, TNF-α, and MIP-1β levels were greater in δ TCR(-/-) mice. Inhibition of iNOS activity in WT mice with L-Nil suppressed burn wound levels of IL-1β, G-CSF, and MIP-1α, whereas IL-6, TNF-α, KC, MCP-1 and MIP-1β were unaffected.

CONCLUSIONS

T-cells of the γδ TCR lineage significantly contribute to the up-regulation of iNOS expression which contributes to wound inflammation.

Prevention of NKT cell activation accelerates cutaneous wound closure and alters local inflammatory signals

We previously reported that in the absence of NKT cells, wound closure was accelerated in a murine excisional punch wound model. Here, we explored whether purposefully inhibiting NKT cell activation had similar effects on wound closure and the dermal inflammatory response to injury. We found that prevention of NKT cell activation accelerated wound closure in a dose-responsive manner. If anti-CD1d was administered before wounding, NKT cell infiltration into cutaneous wounds was diminished without quantitative changes in cellular infiltrates. Furthermore, prevention of NKT cell activation transiently enhanced the local production of a subset of chemokines, including MIP-2, MCP-1, MIP-1α, and MIP-1β, and altered the relative expression of CD69 and CXCR2 on the surface of both circulating and wound NKT cells. Taken together, these findings suggest that wounding activates NKT cells via CD1d presentation of glycolipid antigen and help further define a role for NKT cells in the regulation of wound inflammation and closure. Many soluble factors have been targeted as potential wound healing therapies, but their clinical success has been limited. Given our findings, the NKT cell may be an attractive target for wound healing therapies.

Naturally existing CD11c(low)CD45RB(high) dendritic cells protect mice from acute severe inflammatory response induced by thermal injury

Despite a good understanding of the process that initiates and promotes host inflammation induced by acute injury, little is known about the host immune cells responsible for the inhibition of inflammatory response to thermal injury. The aim of this study was to investigate the potential effect of naturally existing CD11c(low)CD45RB(high) dendritic cells (CD11c(low)CD45RB(high) DCs) on acute severe inflammatory response and mortality rate in burned mice. Changes in the percentage of distinct subsets of splenic DCs and production of cytokines (IL-6, TNF-α, CCL-2) as well as CC chemokine (CCL)-2 were measured by FACS at various time points. The influence of CD11c(low)CD45RB(high) DCs on IL-6, TNF-α, CCL-2 as well as IL-10 levels and mortality rate was observed following a single intraperitoneal injection of DCs to scald mice. Levels of IL-6, CCL-2 and TNF-α were peaked at postburn hours (PBHs) 12, and percentages of CD11c(low)CD45RB(high) DCs were elevated at PBH 12-24. A single intraperitoneal injection of CD11c(low)CD45RB(high) DCs to 15% total body surface area in scald mice led to significant decrease in IL-6, TNF-α and CCL-2, and lethality, but up-regulation of IL-10 compared with untreated mice from PBH 0 to 48. CD11c(low)CD45RB(high) DCs can effectively down-regulate the production of inflammatory cytokines and reduce the mortality rate in 15% TBSA scald injury mice.

Stat 6-dependent induction of myeloid derived suppressor cells after physical injury regulates nitric oxide response to endotoxin

OBJECTIVE

To delineate the role of T-helper 2 (Th2) cytokines in the induction of trauma induced myeloid suppressor cells (TIMSC) and the regulation of nitric oxide production.

BACKGROUND

Trauma induces myeloid cells that express CD11b+/Gr1+ and arginase 1 and exhibit an immune suppressing activity. This article explores the mechanisms that induce TIMSC and the effects on nitric oxide production in response to endotoxin.

METHODS

TIMSC were studied in response to Th2 cytokines and a subsequent challenge to endotoxin. The role of Th2 cytokines was studied in STAT6-/- mice. Accumulation of TIMSC in spleens was studied using flow cytometry and immunhistochemistry. Plasma was recovered to measure accumulation of nitric oxide metabolites.

RESULTS

TIMSC accumulated in the spleen of injured mice and were particularly sensitive to IL-4 and IL-13 with large inductions of arginase activity. Significant blunting in both the accumulation of TIMSC in the spleen and induction of arginase 1 was observed in STAT6-/- mice after physical injury. Accumulation of nitric oxide metabolites to endotoxin was observed in STAT6-/- mice.

CONCLUSION

This study shows that induction of CD11b+/Gr1+ cells after physical injury play an essential role in the regulation of nitric oxide production after a septic challenge. The accumulation and induction of arginase 1 in TIMSC is Th2 cytokine dependent. To our knowledge, the role of TIMSC in the regulation of nitric oxide is a novel finding. This observation adds to the possibility that TIMSC could play an important role in immunosuppression observed after physical injury.

Association between regulatory T cell activity and sepsis and outcome of severely burned patients: a prospective, observational study

Introduction

To investigate the significance of changes in regulatory T cells (Tregs) activity and its relationship with sepsis, as well as outcome of patients with major burns.

Methods

The periphery blood samples of 106 patients were collected on post-burn days 1, 3, 7, 14, and 21. Tregs were isolated and their phenotypes (cytotoxic T-lymphocyte-associated antigen 4 and forkhead/winged helix transcription factor p3) were analyzed by flow cytometry, and the contents of cytokines (interleukin-10 and transforming growth factor-β1) released into supernatants by Tregs were also determined by enzyme-linked immunosorbent assay kits. Gene expressions of cytokines were assessed by real-time quantitative polymerase chain reaction.

Results

Expressions of Tregs phenotypes and gene/protein expression of cytokines were all elevated after burn, and there were obvious differences among patients with various burn sizes. They were also higher in septic patients than those without sepsis. Among septic patients, the expressions of Tregs phenotypes and the levels of cytokines were markedly lower in the survival group than those in patients with fatal outcome.

Conclusions

Severe burn injury per se could lead to the changes in Tregs activities. Elevated levels of cytokines produced by Tregs and activation markers on Tregs surface might play an important role in the pathogenesis of sepsis and mortality in burned patients.

[Immunology and sepsis syndrome in burn trauma]

Despite significant advances in burn surgery and critical care, severe burn trauma defined as injuries covering more than 25% of the total body surface area, is still associated with high mortality and morbidity. Burn trauma is a whole body injury where peripheral dermal injury rapidly results in systemic inflammation and inflammatory core organ damage. The severe disturbance of internal homeostasis involves all vital organ systems and obligates early referral to specialized burn centers. Treatment of severely burned patients is a multifaceted challenge directed by pathophysiologic events which progress from local skin destruction, disruption of physicochemical and microvascular barriers to breakdown of peripheral and central circulation, organ failure and ultimately death. While early intensive care focuses on maintenance of tissue oxygenation and perfusion, surgical treatment deals with management of the burn wounds as a source of inflammation and infection. Here wound debridement and coverage is essential to abrogate systemic effects of inflammation and limit pathogen invasion. While control of early burn stages minimizes mortality due to burn shock, subsequent burn sepsis continues to be a formidable challenge for physicians and the main cause of burn mortality.

The serpin saga; development of a new class of virus derived anti-inflammatory protein immunotherapeutics

Serine proteinase inhibitors, also called serpins, are an ancient grouping of proteins found in primitive organisms from bacteria, protozoa and horseshoe crabs and thus likely present at the time of the dinosaurs, up to all mammals living today. The innate or inflammatory immune system is also an ancient metazoan regulatory system, providing the first line of defense against infection or injury. The innate inflammatory defense response evolved long before acquired, antibody dependent immunity. Viruses have developed highly effective stratagems that undermine and block a wide variety of host inflammatory and immune responses. Some of the most potent of these immune modifying strategies utilize serpins that have also been developed over millions of years, including the hijacking by some viruses for defense against host immune attacks. Serpins represent up to 2-10 percent of circulating plasma proteins, regulating actions as wide ranging as thrombosis, inflammation, blood pressure control and even hormone transport. Targeting serpin-regulated immune or inflammatory pathways makes evolutionary sense for viral defense and many of these virus-derived inhibitory proteins have proven to be highly effective, working at very low concentrations--even down to the femptomolar to picomolar range. We are studying these viral anti-inflammatory proteins as a new class of immunomodulatory therapeutic agents derived from their native viral source. One such viral serpin, Serp-1 is now in clinical trial (conducted by VIRON Therapeutics, Inc.) for acute unstable coronary syndromes (unstable angina and small heart attacks), representing a 'first in class' therapeutic study. Several other viral serpins are also currently under investigation as anti-inflammatory or anti-immune therapeutics. This chapter describes these original studies and the ongoing analysis of viral serpins as a new class of virus-derived immunotherapeutic.

Up-regulation of cell surface Toll-like receptors on circulating gammadelta T-cells following burn injury

Burn injury is associated with profound inflammation and activation of the innate immune system involving gammadelta T-cells. Similarly, Toll-like receptors (TLR) are associated with activation of the innate immune response; however, it is unclear whether TLR expression is altered in gammadelta T-cells after major burn injury. To study this, male C57BL/6 mice were subjected to burn injury (25% TBSA) and 1 or 7 days thereafter, blood and spleen cells were isolated and subjected to FACs analysis for TLRs and other phenotypic markers (gammadelta TCR, alphabeta TCR, CD69, CD120b). A marked increase in the number of circulating gammadelta T-cells was observed at 24h post-burn (14% vs. 4%) and a higher percentage of these cells expressed TLR-2. TLR-4 expression was also increased post-burn, but to a lesser degree. These changes in TLR expression were not associated with altered CD69 or CD120b expression in gammadelta T-cells. The mobilization of, and increased TLR expression in, gammadelta T-cells was transient, as phenotypic changes were not evident at 7 days post-burn or in gammadelta T-cells from the circulation or spleen. The increases in TLR expression were not observed in alphabeta T-cells after burn injury. In conclusion, 24h after burn injury mobilization of gammadelta T-cells with increased TLR expression was observed. This finding suggests that this unique T-cell population is critical in the innate immune response to injury, possibly through the recognition of danger signals by TLRs.

Gammadelta T-cells: potential regulators of the post-burn inflammatory response

Severe burn induces an immunopathological response that contributes to the development of a systemic inflammatory response (SIRS) and subsequent multiple organ failure. While, multiple immune cells type (T-cells, macrophages, neutrophils) are involved in this response, recent evidence suggests that a unique T-cell subset, gammadelta T-cells are central in the response to injury. While gammadelta T-cells represent only a small percentage of the total T-cell population, they display specific functional characteristics that uniquely position them in the immune/inflammatory axis to influence a number of important aspects of the body's response to burn. This review will focus on the potential regulator role of gammadelta T-cells in immunopathological response following burn and thereby their potential as therapeutic targets for affecting inflammation and healing.

Medical countermeasures for radiation combined injury: radiation with burn, blast, trauma and/or sepsis. report of an NIAID Workshop, March 26-27, 2007

Non-clinical human radiation exposure events such as the Hiroshima and Nagasaki bombings or the Chernobyl accident are often coupled with other forms of injury, such as wounds, burns, blunt trauma, and infection. Radiation combined injury would also be expected after a radiological or nuclear attack. Few animal models of radiation combined injury exist, and mechanisms underlying the high mortality associated with complex radiation injuries are poorly understood. Medical countermeasures are currently available for management of the non-radiation components of radiation combined injury, but it is not known whether treatments for other insults will be effective when the injury is combined with radiation exposure. Further research is needed to elucidate mechanisms behind the synergistic lethality of radiation combined injury and to identify targets for medical countermeasures. To address these issues, the National Institute of Allergy and Infectious Diseases convened a workshop to make recommendations on the development of animal models of radiation combined injury, possible mechanisms of radiation combined injury, and future directions for countermeasure research, including target identification and end points to evaluate treatment efficacy.

Roles of heat shock proteins and gamma delta T cells in inflammation

Elimination of activated inflammatory cells that infiltrate and damage host organs can reduce morbidity and mortality. A better understanding of the mechanisms by which these processes occur may lead to new approaches to prevent tissue damage. The lungs, gastrointestinal tract, and skin are particularly prone to infection and collateral damage by inflammatory cells. Specialized lymphocytes protect these organs from collateral tissue damage by eliminating neutrophils and macrophages from inflamed tissues. These lymphocytes recognize signals produced by inflammatory cells. One such signal is heat shock protein (Hsp) expressed on the cell surface of inflamed phagocytes. Mammalian Hsp molecules closely resemble their microbial equivalents, and therefore phagocytes decorated with these molecules are recognized as target cells. T lymphocytes bearing the gammadelta T cell receptor (TCR) elicit cytotoxic activity toward macrophages and neutrophils that express Hsp60 and Hsp70, respectively, protecting host organs from collateral tissue damage by phagocytes.

Novel biphasic role for lymphocytes revealed during resolving inflammation

Acute inflammation is traditionally described as the influx of polymorphonuclear leukocytes (PMNs) followed by monocyte-derived macrophages, leading to resolution. This is a classic view, and despite subpopulations of lymphocytes possessing innate immune-regulatory properties, seldom is their role in acute inflammation and its resolution discussed. To redress this we show, using lymphocyte-deficient RAG1(-/-) mice, that peritoneal T/B lymphocytes control PMN trafficking by regulating cytokine synthesis. Once inflammation ensues in normal mice, lymphocytes disappear in response to DP1 receptor activation by prostaglandin D(2). However, upon resolution, lymphocytes repopulate the cavity comprising B1, natural killer (NK), gamma/delta T, CD4(+)/CD25(+), and B2 cells. Repopulating lymphocytes are dispensable for resolution, as inflammation in RAG1(-/-) and wild-type mice resolve uniformly. However, repopulating lymphocytes are critical for modulating responses to superinfection. Thus, in chronic granulomatous disease using gp91phox(-/-) mice, not only is resolution delayed compared with wild-type, but there is a failure of lymphocyte re-appearance predisposing to exaggerated immune responses upon secondary challenge that is rescued by resolution-phase lymphocytes. In conclusion, as lymphocyte repopulation is also evident in human peritonitis, we hereby describe a transition in T/B cells from acute inflammation to resolution, with a central role in modulating the severity of early onset and orchestrating responses to secondary infection.

Monitoring immune dysfunctions in the septic patient: a new skin for the old ceremony

Septic syndromes represent a major although largely underrecognized healthcare problem worldwide, accounting for thousands of deaths every year. It is now agreed that sepsis deeply perturbs immune homeostasis by inducing an initial tremendous systemic inflammatory response which is accompanied by an antiinflammatory process, acting as negative feedback. This compensatory inhibitory response secondly becomes deleterious as nearly all immune functions are compromised. These alterations might be directly responsible for worsening outcome, as they may play a major role in the decreased resistance to nosocomial infections in patients who survived initial resuscitation. Consequently, immunostimulatory therapies may now be assessed for the treatment of sepsis. This review focuses on immune dysfunctions described in septic patients and on their potential use as markers on a routine standardized basis for prediction of adverse outcome or of occurrence of secondary nosocomial infections. This constitutes a prerequisite to a staging system for individualized treatment for these hitherto deadly syndromes.

Regulatory T cell populations in sepsis and trauma

Sepsis syndrome remains the leading cause of mortality in intensive care units. It is now believed that along with the body's hyperinflammatory response designated to eliminate the underlying pathogen, mechanisms are initiated to control this initial response, which can become deleterious and result in immune dysfunctions and death. A similar state of immune suppression has been described after numerous forms of severe trauma/injury. Although the evidence for immune dysfunctions after sepsis has grown, much remains to be understood about mechanisms underpinning its development and how it acts to increase the morbid state of the critically ill patient. In this context, although the majority of clinical and basic science conducted so far has focused on the roles of myeloid cell populations, the contribution of T lymphocytes and in particular, of regulatory T cells has been somewhat ignored. The studies presented here support the concept that regulatory T lymphocytes (CD4+CD25+ regulatory, gammadelta, and NK T cells) play a role in the control of immune responses and are affected by injury and sepsis. This may be related to their capacity to interact with components of the innate and adaptive immune responses and to their ability to be activated nonspecifically by bacterial products and/or cytokines and to regulate through direct cell-cell and/or soluble mediators. It is our hope that a better understanding of the mechanism through which those rare lymphocyte subsets exert such a profound effect on the immune response may help in improving our ability not only to diagnose but also to treat the critically ill individual.