Early decreased neutrophil responsiveness is related to late onset sepsis in multitrauma patients: An international cohort study

Limited impact of traumatic brain injury on the post-traumatic inflammatory cellular response

PURPOSE

Trauma triggers a systemic inflammatory cellular response due to tissue damage, potentially leading to a secondary immune deficiency. Trauma severity is quantified by the Injury Severity Score (ISS). Severe Traumatic Brain Injury (TBI) is associated with high ISSs due to high lethality, despite limited tissue damage. Therefore, ISS might overestimate the post-traumatic inflammatory cellular response. This study investigated the effect of TBI on the occurrence of different systemic neutrophil phenotypes as alternative read-out for systemic inflammation.

METHODS

A single-center retrospective cohort study was conducted at a level-1 trauma center. Patients aged ≥ 18 years, admitted between 01-03-2021-01-11-2022 and providing a diagnostic blood sample were included. Four groups were created: isolated TBI, isolated non-TBI, multitrauma TBI and multitrauma non-TBI. Primary outcome was occurrence of different neutrophil phenotypes determined by automated flow cytometry. Secondary outcome was infectious complications.

RESULTS

In total, 404 patients were included. TBI and non-TBI patients demonstrated similar occurrences of different neutrophil phenotypes. However, isolated TBI patients had higher ISSs than their isolated non-TBI controls who suffered similar post-traumatic inflammatory cellular responses. Regardless of the type of injury, patients exhibiting higher systemic inflammation had a high infection risk.

CONCLUSION

When TBI is involved, ISS tends to be higher compared to similar patients in the absence of TBI. However, TBI patients did not demonstrate an increased inflammatory cellular response compared to non-TBI patients. Therefore, TBI does not add much to the inflammatory cellular response in trauma patients. The degree of the inflammatory response was related to the incidence of infectious complications.

Identification of neutrophil phenotype categories in geriatric hip fracture patients aids in personalized medicine

Objectives

The number of geriatric hip fracture patients is high and expected to rise in the coming years, and many are frail and at risk for adverse outcomes. Early identification of high-risk patients is crucial to balance treatment and optimize outcome, but remains challenging. Previous research in patients with multitrauma suggested that neutrophil phenotype analysis could aid in early identification of high-risk patients. This pilot study investigated the feasibility and clinical value of neutrophil phenotype analysis in geriatric patients with a hip fracture.

Methods

A prospective study was conducted in a regional teaching hospital in the Netherlands. At the emergency department, blood samples were collected from geriatric patients with a hip fracture and analyzed using automated flow cytometry. Flow cytometry data were processed using an automated clustering algorithm. Neutrophil activation data were compared with a healthy control cohort. Neutrophil phenotype categories were assessed based on two-dimensional visual assessment of CD16/CD62L expression.

Results

Blood samples from 45 geriatric patients with a hip fracture were included. Neutrophils showed an increased activation profile and decreased responsiveness to formyl peptides when compared to healthy controls. The neutrophil phenotype of all patients was categorized. The incidence of severe adverse outcome was significantly different between the different categories (P = 0.0331). Moreover, patients with neutrophil phenotype category 0 developed no severe adverse outcomes.

Conclusions

Using point-of-care fully automated flow cytometry to analyze the neutrophil compartment in geriatric hip fracture patients is feasible and holds clinical value in determining patients at risk for adverse outcome. This study is a first step toward immuno-based precision medicine for identifying geriatric hip fracture patients that are deemed fit for surgery.

Advances in trauma care to save lives from traumatic injury: A narrative review

ABSTRACT

Recent advances on trauma management from the prehospital setting to in hospital care led to a better surviving severe trauma rate. Mortality from exsanguination remains the first preventable mortality. Damage-control resuscitation and surgery are evolving and thus some promising concepts are developing. Transfusion toolkit is brought on the prehospital scene while temporary bridge to hemostasis may be helpful. Panel transfusion products allow an individualized ratio assumed by fresh frozen or lyophilized plasma, fresh or cold-stored whole blood, fibrinogen, four-factor prothrombin complex concentrates. Growing interest is raising in whole blood transfusion, resuscitative endovascular balloon occlusion of the aorta use, hybrid emergency room, viscoelastic hemostatic assays to improve patient outcomes. Microcirculation, traumatic endotheliopathy, organ failures and secondary immunosuppression are point out since late deaths are increasing and may deserve specific treatment.As each trauma patient follows his own course over the following days after trauma, trauma management may be seen through successive, temporal, and individualized aims.

Distinct subsets of neutrophils crosstalk with cytokines and metabolites in patients with sepsis

Sepsis is a life-threatening condition caused by a dysregulated host response to infection. Despite continued efforts to understand the pathophysiology of sepsis, no effective therapies are currently available. While singular components of the aberrant immune response have been investigated, comprehensive studies linking different data layers are lacking. Using an integrated systems immunology approach, we evaluated neutrophil phenotypes and concomitant changes in cytokines and metabolites in patients with sepsis. Our findings identify differentially expressed mature and immature neutrophil subsets in patients with sepsis. These subsets correlate with various proteins, metabolites, and lipids, including pentraxin-3, angiopoietin-2, and lysophosphatidylcholines, in patients with sepsis. These results enabled the construction of a statistical model based on weighted multi-omics linear regression analysis for sepsis biomarker identification. These findings could help inform early patient stratification and treatment options, and facilitate further mechanistic studies targeting the trifecta of surface marker expression, cytokines, and metabolites.

Emergency Medicine with Advanced Surgery Protocols: A Review

One of the most burning issues in health system is the concern of handling patients that requires emergency surgery. Emergency general surgery is done on both traumatic and nontraumatic acute disorders. Severe traumatic injury and bleeding is one of the causing agents for high mortality rate globally. Another group of patients that are in need of emergency surgery are those with heart failure, and in this particular paper, we analyzed emergency medicine with advanced surgery protocols focusing on gastric cancer, cardiac surgery, and bleeding as well as coagulopathy following traumatic injury.

Longitudinal assessment of the inflammatory response: The next step in personalized medicine after severe trauma

Infections in trauma patients are an increasing and substantial cause of morbidity, contributing to a mortality rate of 5-8% after trauma. With increased early survival rates, up to 30-50% of multitrauma patients develop an infectious complication. Trauma leads to a complex inflammatory cascade, in which neutrophils play a key role. Understanding the functions and characteristics of these cells is important for the understanding of their involvement in the development of infectious complications. Recently, analysis of neutrophil phenotype and function as complex biomarkers, has become accessible for point-of-care decision making after trauma. There is an intriguing relation between the neutrophil functional phenotype on admission, and the clinical course (e.g., infectious complications) of trauma patients. Potential neutrophil based cellular diagnostics include subsets based on neutrophil receptor expression, responsiveness of neutrophils to formyl-peptides and FcγRI (CD64) expression representing the infectious state of a patient. It is now possible to recognize patients at risk for infectious complications when presented at the trauma bay. These patients display increased numbers of neutrophil subsets, decreased responsiveness to fMLF and/or increased CD64 expression. The next step is to measure these biomarkers over time in trauma patients at risk for infectious complications, to guide decision making regarding timing and extent of surgery and administration of (preventive) antibiotics.

Kynurenine Pathway-An Underestimated Factor Modulating Innate Immunity in Sepsis-Induced Acute Kidney Injury?

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection, and it accounts for about half of the cases of acute kidney injury (AKI). Although sepsis is the most frequent cause of AKI in critically ill patients, its pathophysiological mechanisms are not well understood. Sepsis has the ability to modulate the function of cells belonging to the innate immune system. Increased activity of indoleamine 2,3-dioxygenase 1 (IDO1) and production of kynurenines are the major metabolic pathways utilized by innate immunity cells to maintain immunological tolerance. The activation of the kynurenine pathway (KP) plays a dual role in sepsis—in the early stage, the induction of IDO1 elicits strong proinflammatory effects that may lead to tissue damage and septic shock. Afterwards, depletion of tryptophan and production of kynurenines contribute to the development of immunosuppression that may cause the inability to overpower opportunistic infections. The presented review provides available data on the various interdependencies between elements of innate immunity and sepsis-induced AKI (SAKI) with particular emphasis on the immunomodulatory significance of KP in the above processes. We believe that KP activation may be one of the crucial, though underestimated, components of a deregulated host response to infection during SAKI.

Pathophysiology in patients with polytrauma

The pathophysiology after polytrauma represents a complex network of interactions. While it was thought for a long time that the direct and indirect effects of hypoperfusion are most relevant due to the endothelial permeability changes, it was discovered that the innate immune response to trauma is equally important in modifying the organ response. Recent multi center studies provided a "genetic storm" theory, according to which certain neutrophil changes are activated at the time of injury. However, a second hit phenomenon can be induced by activation of certain molecules by direct organ injury, or pathogens (damage associated molecular patterns, DAMPS - pathogen associated molecular patterns, PAMPS). The interactions between the four pathogenetic cycles (of shock, coagulopathy, temperature loss and soft tissue injuries) and cross-talk between coagulation and inflammation have also been identified as important modifiers of the clinical status. In a similar fashion, overzealous surgeries and their associated soft tissue injury and blood loss can induce secondary worsening of the patient condition. Therefore, staged surgeries in certain indications represent an important alternative, to allow for performing a "safe definitive surgery" strategy for major fractures. The current review summarizes all these situations in a detailed fashion.

Standardized porcine unilateral femoral nailing is associated with changes in PMN activation status, rather than aberrant systemic PMN prevalence

PURPOSE

Intramedullary nailing (IMN) of fractures is associated with increased rates of inflammatory complications. The pathological mechanism underlying this phenomenon is unclear. However, polymorphonuclear granulocytes (PMNs) seem to play an important role. We hypothesized that a femur fracture and standardized IMN in pigs is associated with altered appearance of PMNs in circulation and enhanced activation status of these cells.

METHODS

A porcine model including a femur fracture and IMN was utilized. Animals were randomized for control [anesthesia + mechanical ventilation only (A/MV)] and intervention [A/MV and unilateral femur fracture (FF) + IMN] conditions. PMN numbers and responsiveness, integrin (CD11b), L-selectin (CD62L) and Fcγ-receptor (CD16 and CD32)-expression levels were measured by flowcytometry of blood samples. Animals were observed for 72 h.

RESULTS

Circulatory PMN numbers did not differ between groups. Early PMN-responsiveness was retained after insult. PMN-CD11b expression increased significantly upon insult and peaked after 24 h, whereas CD11b in control animals remained unaltered (P = 0.016). PMN-CD16 expression levels in the FF + IMN-group rose gradually over time and were significantly higher compared with control animals, after 48 h (P = 0.016) and 72 h (P = 0.032). PMN-CD62L and CD32 expression did not differ significantly between conditions.

CONCLUSION

This study reveals that a femur fracture and subsequent IMN in a controlled setting in pigs is associated with enhanced activation status of circulatory PMNs, preserved PMN-responsiveness and unaltered circulatory PMN-presence. Indicating that monotrauma plus IMN is a specific and substantial stimulus for the cellular immune system. Early alterations of circulatory PMN receptor expression dynamics may be predictive for the intensity of the post traumatic response.

Damage Control Surgery after Burn Injury: A Narrative Review

Burn injuries with cutaneous loss result in a severe systemic response when profound injuries exceed 20% of the total body surface area. The management of severely burned patients is a complex and dynamic process. Timely and safe operative interventions are critical components of multidisciplinary care. Effective management of severely burned patients, their cutaneous injuries, and the associated systemic disease requires a comprehensive understanding of the pathophysiologic response to trauma, objective indicators of patient status, and an appreciation for the dynamic nature of these parameters. Progress in both clinical and basic science research has advanced our understanding of these concepts and our approach to the management of burn patients. Incorporating concepts such as early total care, damage control surgery (DCS), and safe definitive surgery (SDS) in the polytraumatized patient may further aid in optimizing outcomes and quality of care for burn patients. This article connects current knowledge of the lethal triad, inflammation, immunosuppression, and eschar-derived toxins, with surgical burn care, especially burn wound debridement. The concepts of DCS and SDS for the care and management of burn patients are strongly advocated. Experimental and clinical studies are encouraged to validate these concepts in an effort to optimize patient outcomes.

Immunomonitoring of Monocyte and Neutrophil Function in Critically Ill Patients: From Sepsis and/or Trauma to COVID-19

Immune cells and mediators play a crucial role in the critical care setting but are understudied. This review explores the concept of sepsis and/or injury-induced immunosuppression and immuno-inflammatory response in COVID-19 and reiterates the need for more accurate functional immunomonitoring of monocyte and neutrophil function in these critically ill patients. in addition, the feasibility of circulating and cell-surface immune biomarkers as predictors of infection and/or outcome in critically ill patients is explored. It is clear that, for critically ill, one size does not fit all and that immune phenotyping of critically ill patients may allow the development of a more personalized approach with tailored immunotherapy for the specific patient. In addition, at this point in time, caution is advised regarding the quality of evidence of some COVID-19 studies in the literature.

Effects of immune cells on mesenchymal stem cells during fracture healing

In vertebrates, bone is considered an osteoimmune system which encompasses functions of a locomotive organ, a mineral reservoir, a hormonal organ, a stem cell pool and a cradle for immune cells. This osteoimmune system is based on cooperatively acting bone and immune cells, cohabitating within the bone marrow. They are highly interdependent, a fact that is confounded by shared progenitors, mediators, and signaling pathways. Successful fracture healing requires the participation of all the precursors, immune and bone cells found in the osteoimmune system. Recent evidence demonstrated that changes of the immune cell composition and function may negatively influence bone healing. In this review, first the interplay between different immune cell types and osteoprogenitor cells will be elaborated more closely. The separate paragraphs focus on the specific cell types, starting with the cells of the innate immune response followed by cells of the adaptive immune response, and the complement system as mediator between them. Finally, a brief overview on the challenges of preclinical testing of immune-based therapeutic strategies to support fracture healing will be given.

Neutrophil kinetics and function after major trauma: A systematic review

BACKGROUND

Immune dysfunction following major traumatic injury is complex and strongly associated with significant morbidity and mortality through the development of multiple organ dysfunction syndrome (MODS), persistent inflammation, immunosuppression, and catabolism syndrome and sepsis. Neutrophils are thought to be a pivotal mediator in the development of immune dysfunction.

AIM

To provide a review with a systematic approach of the recent literature describing neutrophil kinetics and functional changes after major trauma in humans and discuss hypotheses as to the mechanisms of the observed neutrophil dysfunction in this setting.

METHODS

Medline, Embase and PubMed were searched on January 15, 2021. Papers were screened by two reviewers and those included had their reference list hand searched for additional papers of interest. Inclusion criteria were adults > 18 years old, with an injury severity score > 12 requiring admission to an intensive care unit. Papers that analysed major trauma patients as a subgroup were included.

RESULTS

Of 107 papers screened, 48 were included in the review. Data were heterogeneous and most studies had a moderate to significant risk of bias owing to their observational nature and small sample sizes. Key findings included a persistently elevated neutrophil count, stereotyped alterations in cell-surface markers of activation, and the elaboration of heterogeneous and immunosuppressive populations of cells in the circulation. Some of these changes correlate with clinical outcomes such as MODS and secondary infection. Neutrophil phenotype remains a promising avenue for the development of predictive markers for immune dysfunction.

CONCLUSION

Understanding of neutrophil phenotypes after traumatic injury is expanding. A greater emphasis on incorporating functional and clinically significant markers, greater uniformity in study design and assessment of extravasated neutrophils may facilitate risk stratification in patients affected by major trauma.

Innate Neutrophil Memory Dynamics in Disease Pathogenesis

Neutrophils, the most abundant leukocytes in circulation and the first responders to infection and inflammation, closely modulate both acute and chronic inflammatory processes. Resting neutrophils constantly patrol vasculature and migrate to tissues when challenges occur. When infection and/or inflammation recede, tissue neutrophils will be subsequently cleaned up by macrophages which collectively contribute to the resolution of inflammation. While most studies focus on the anti-microbial function of neutrophils including phagocytosis, degranulation, and neutrophil extracellular traps (NETs) formation, recent research highlighted additional contributions of neutrophils beyond simply controlling infectious agents. Neutrophils with resolving characteristics may alter the activities of neighboring cells and facilitate inflammation resolution, modulate long-term macrophage and adaptive immune responses, therefore having important impacts on host pathophysiology. The focus of this chapter is to provide an updated assessment of recent progress in the emerging field of neutrophil programming and memory in the context of both acute and chronic diseases.

Kinetics of Neutrophil Subsets in Acute, Subacute, and Chronic Inflammation

At homeostasis the vast majority of neutrophils in the circulation expresses CD16 and CD62L within a narrow expression range, but this quickly changes in disease. Little is known regarding the changes in kinetics of neutrophils phenotypes in inflammatory conditions. During acute inflammation more heterogeneity was found, characterized by an increase in CD16^dim banded neutrophils. These cells were probably released from the bone marrow (left shift). Acute inflammation induced by human experimental endotoxemia (LPS model) was additionally accompanied by an immediate increase in a CD62L^low neutrophil population, which was not as explicit after injury/trauma induced acute inflammation. The situation in sub-acute inflammation was more complex. CD62L^low neutrophils appeared in the peripheral blood several days (>3 days) after trauma with a peak after 10 days. A similar situation was found in the blood of COVID-19 patients returning from the ICU. Sorted CD16^low and CD62L^low subsets from trauma and COVID-19 patients displayed the same nuclear characteristics as found after experimental endotoxemia. In diseases associated with chronic inflammation (stable COPD and treatment naive HIV) no increases in CD16^low or CD62L^low neutrophils were found in the peripheral blood. All neutrophil subsets were present in the bone marrow during homeostasis. After LPS rechallenge, these subsets failed to appear in the circulation, but continued to be present in the bone marrow, suggesting the absence of recruitment signals. Because the subsets were reported to have different functionalities, these results on the kinetics of neutrophil subsets in a range of inflammatory conditions contribute to our understanding on the role of neutrophils in health and disease.

Activation of Neutrophil Granulocytes by Platelet-Activating Factor Is Impaired During Experimental Sepsis

Platelet-activating factor (PAF) is an important mediator of the systemic inflammatory response. In the case of sepsis, proper activation and function of neutrophils as the first line of cellular defense are based on a well-balanced physiological response. However, little is known about the role of PAF in cellular changes of neutrophils during sepsis. Therefore, this study investigates the reaction patterns of neutrophils induced by PAF with a focus on membrane potential (MP), intracellular pH, and cellular swelling under physiological and pathophysiological conditions and hypothesizes that the PAF-mediated response of granulocytes is altered during sepsis. The cellular response of granulocytes including MP, intracellular pH, cellular swelling, and other activation markers were analyzed by multiparametric flow cytometry. In addition, the chemotactic activity and the formation of platelet-neutrophil complexes after exposure to PAF were investigated. The changes of the (electro-)physiological response features were translationally verified in a human ex vivo whole blood model of endotoxemia as well as during polymicrobial porcine sepsis. In neutrophils from healthy human donors, PAF elicited a rapid depolarization, an intracellular alkalization, and an increase in cell size in a time- and dose-dependent manner. Mechanistically, the alkalization was dependent on sodium-proton exchanger 1 (NHE1) activity, while the change in cellular shape was sodium flux- but only partially NHE1-dependent. In a pathophysiological altered environment, the PAF-induced response of neutrophils was modulated. Acidifying the extracellular pH in vitro enhanced PAF-mediated depolarization, whereas the increases in cell size and intracellular pH were largely unaffected. Ex vivo exposure of human whole blood to lipopolysaccharide diminished the PAF-induced intracellular alkalization and the change in neutrophil size. During experimental porcine sepsis, depolarization of the MP was significantly impaired. Additionally, there was a trend for increased cellular swelling, whereas intracellular alkalization remained stable. Overall, an impaired (electro-)physiological response of neutrophils to PAF stimulation represents a cellular hallmark of those cells challenged during systemic inflammation. Furthermore, this altered response may be indicative of and causative for the development of neutrophil dysfunction during sepsis.

Refractory neutrophils and monocytes in patients with inflammatory bowel disease after repeated bouts of prolonged exercise

Background

Neutrophils and monocytes are key immune effector cells in inflammatory bowel disease (IBD) that is associated with chronic inflammation in the gut. Patients with stable IBD who perform exercise have significantly fewer flare‐ups of the disease, but no underlying mechanism has been identified. Therefore, the aim of this study was to compare the responsiveness/refractoriness of these innate immune cells after repeated bouts of prolonged exercise in IBD patients and controls.

Methods

Patients with IBD and age‐ and gender‐matched healthy controls were recruited from a cohort of walkers participating in a 4‐day walking event. Blood analysis was performed at baseline and after 3 days of walking. Responsiveness to the bacterial/mitochondrial‐stimulus N‐Formylmethionine‐leucyl‐phenylalanine (fMLF) was tested in granulocytes and monocytes by measuring the expression of activation markers after adding this stimulus to whole blood.

Results

In total 38 participants (54 ± 12 years) were included in this study: 19 walkers with and 19 walkers without IBD. After 3 days of prolonged exercise, a significant increase in responsiveness to fMLF was observed in all participants irrespective of disease. However, IBD patients showed significantly less responsiveness in neutrophils and monocytes, compared with non‐IBD walkers.

Conclusions

Increased responsiveness of neutrophils and monocyte to fMLF was demonstrated after repetitive bouts of prolonged exercise. Interestingly, this exercise was associated with relative refractoriness of both neutrophils and monocytes in IBD patients. These refractory cells might create a lower inflammatory state in the intestine providing a putative mechanism for the decrease in flare‐ups in IBD patients after repeated exercise.

Flow cytometric evaluation of the neutrophil compartment in COVID-19 at hospital presentation: A normal response to an abnormal situation

Coronavirus disease 2019 (COVID-19) is a rapidly emerging pandemic disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Critical COVID-19 is thought to be associated with a hyper-inflammatory process that can develop into acute respiratory distress syndrome, a critical disease normally mediated by dysfunctional neutrophils. This study tested the hypothesis whether the neutrophil compartment displays characteristics of hyperinflammation in COVID-19 patients. Therefore, a prospective study was performed on all patients with suspected COVID-19 presenting at the emergency room of a large academic hospital. Blood drawn within 2 d after hospital presentation was analyzed by point-of-care automated flow cytometry and compared with blood samples collected at later time points. COVID-19 patients did not exhibit neutrophilia or eosinopenia. Unexpectedly neutrophil activation markers (CD11b, CD16, CD10, and CD62L) did not differ between COVID-19-positive patients and COVID-19-negative patients diagnosed with other bacterial/viral infections, or between COVID-19 severity groups. In all patients, a decrease was found in the neutrophil maturation markers indicating an inflammation-induced left shift of the neutrophil compartment. In COVID-19 this was associated with disease severity.

Polytrauma: update on basic science and clinical evidence

The management of multiply injured or severely injured patients is a complex and dynamic process. Timely and safe fracture fixation is a critical component of the multidisciplinary care that these patients require. Effective management of these patients, and their orthopaedic injuries, requires a strong understanding of the pathophysiology of the response to trauma and indicators of patient status, as well as an appreciation for the dynamic nature of these parameters. Substantial progress in both clinical and basic science research in this area has advanced our understanding of these concepts and our approach to management of the polytraumatized patient. This article summarizes a symposium on this topic that was presented by an international panel of experts at the 2020 Virtual Annual Meeting of the Orthopaedic Trauma Association.

Polytrauma management - What is new and what is true in 2020 ?

This is a review of changes in the practice of treating polytrauma managemtent within the years prior to 2020. It focuses on five different topics, 1. The development of an evidence based definition of Polytrauma, 2. Resuscitation Associated Coagulopathy (RAC), 3. neutrophil guided initial resuscitation, 4. perioperative Scoring to evaluate patients at risk, and 5. evolution of fracture fixation strategies according to protocols^1,2 (Early total care, ETC, damage control orthopedics, DCO, early appropriate care, EAC, safe definitive surgery, SDS).

Distinguishing Sepsis From Infection by Neutrophil Dysfunction: A Promising Role of CXCR2 Surface Level

Sepsis is one of the well-established diseases with specific patterns of neutrophil dysfunctions. Previous studies demonstrated sepsis-related neutrophil dysfunctions in comparison with subjects without infection. Since sepsis and infection are recently recognized as distinctive processes, whether these neutrophil dysfunctions are associated with sepsis or infection are not known. Therefore, we longitudinally compared neutrophil functions, widely-cited as exhibiting sepsis-related changes, between patients with septic shock and infection. The surface level of cluster of differentiation 64 (CD64), C-C motif chemokine receptor 2 (CCR2), C-X-C motif chemokine receptor 2 (CXCR2); apoptosis; and NETosis were measured from peripheral blood neutrophils for seven consecutive days using flow cytometry. The between-group comparisons of neutrophil functions were made both on a day-by-day basis and as linear regression between time and measured neutrophil functions (sepsis status included as model predictors). Our study found that, among neutrophil functions studied, only CXCR2 surface level is associated with sepsis. At disease onset, CXCR2 level decrease, with a dose-response relationship with clinical severity. Its level reverts to resemble infected patients by the end of the week. The relationship between CD64 surface level, CCR2 surface level, NETosis, and sepsis are mediated through the effect of infection. Apoptosis activity between these groups are similar, hence, not sepsis-related.

Animal-Free Human Whole Blood Sepsis Model to Study Changes in Innate Immunity

Studying innate immunity in humans is crucial for understanding its role in the pathophysiology of systemic inflammation, particularly in the complex setting of sepsis. Therefore, we standardized a step-by-step process from the venipuncture to the transfer in a human model system, while closely monitoring the inflammatory response for up to three hours. We designed an animal-free, human whole blood sepsis model using a commercially available, simple to use, tubing system. First, we analyzed routine clinical parameters, including cell count and blood gas analysis. Second, we demonstrated that extracellular activation markers (e.g., CD11b and CD62l) as well as intracellular metabolic (intracellular pH) and functional (generation of radical oxygen species) features remained stable after incubation in the whole blood model. Third, we mimicked systemic inflammation during early sepsis by exposure of whole blood to pathogen-associated molecular patterns. Stimulation with lipopolysaccharide revealed the capability of the model system to evoke a sepsis-like inflammatory phenotype of innate immunity. In summary, the presented model serves as a convenient, economic, and reliable platform to study innate immunity in human whole blood, which may yield clinically important insights.

Analysis of human neutrophil phenotypes as biomarker to monitor exercise-induced immune changes

The amplitude of the innate immune response reflects the degree of physiological stress imposed by exercise load. An optimal balance of exercise intensity and duration is essential for a balanced immune system and reduces the risk of dysfunction of the immune system. Therefore, it is hypothesized that neutrophils, as key players in the innate immune system, can be used as biomarker in detecting overtraining. The aim was to monitor the state of the innate immune system by phenotyping neutrophils during consecutive bouts of prolonged exercise. Study subjects were recruited from a cohort of walkers participating in a walking event on 3 consecutive days. Participants with immune deficiencies were excluded. Questionnaires to determine the physiological status of the participants were completed. Analysis of neutrophil receptor expression was done by a point-of-care fully automated flow cytometer. A total of 45 participants were recruited, of whom 39 participants were included for data analysis. Study participants had a median age of 64 (58-70) years. The absolute numbers CD16^dim /CD62L^bright and CD16^bright /CD62L^dim neutrophils were increased after the first 2 days of exercise followed by an adaptation/normalization after the third day. Participants with activated neutrophils (high CD11b expression) had an impaired physical feeling indicated by the participant on a lower visual analog scale compared to participants who did not have activated neutrophils (P = 0.017, P = 0.022). Consecutive days of prolonged exercise results in an initial systemic innate immune response, followed by normalization/adaptation. Increased neutrophil activation was associated with impaired physical feeling measured by a validated VAS score indicated by the participant. Fully automated point-of-care flow cytometry analysis of neutrophil phenotypes in a field laboratory might be a useful tool to monitor relevant differences in the systemic innate immune response in response to exercise.

Point-of-Care Analysis of Neutrophil Phenotypes: A First Step Toward Immuno-Based Precision Medicine in the Trauma ICU

Supplemental Digital Content is available in the text.

Objectives:

The amount of tissue damage and the amplitude of the immune response after trauma are related to the development of infectious complications later on. Changes in the neutrophil compartment can be used as read out of the amplitude of the immune response after trauma. The study aim was to test whether 24/7 point-of-care analysis of neutrophil marker expression by automated flow cytometry can be achieved after trauma.

Design:

A prospective cohort study was performed. Polytrauma patients who developed infectious complications were compared with polytrauma patients who did not develop infectious complications.

Setting:

The study was performed in a level 1 trauma center.

Patients:

All trauma patients presented in the trauma bay were included.

Interventions:

An extra blood tube was drawn from all patients. Thereafter, a member of the trauma team placed the blood tube in the fully automated flow cytometer, which was located in the corner of the trauma room. Next, a modified and tailored protocol for this study was automatically performed.

Main Results:

The trauma team was able to successfully start the point-of-care automated flow cytometry analysis in 156 of 164 patients, resulting in a 95% success rate. Polytrauma patients who developed infectious complications had a significantly higher %CD16^dim/CD62L^bright neutrophils compared with polytrauma patients who did not develop infectious complications (p = 0.002). Area under the curve value for %CD16^dim/CD62L^bright neutrophils is 0.90 (0.83–0.97).

Conclusions:

This study showed the feasibility of the implementation of a fully automated point-of-care flow cytometry system for the characterization of the cellular innate immune response in trauma patients. This study supports the concept that the assessment of CD16^dim/CD62L^bright neutrophils can be used for early detection of patients at risk for infectious complications. Furthermore, this can be used as first step toward immuno-based precision medicine of polytrauma patients at the ICU.

A Rise in Neutrophil Cell Size Precedes Organ Dysfunction After Trauma

INTRODUCTION

Organ dysfunction remains a major cause of morbidity after trauma. The development of organ dysfunction is determined by the inflammatory response, in which neutrophils are important effector cells. A femoral fracture particularly predisposes for the development of organ dysfunction. This study investigated the chronologic relation between neutrophil characteristics and organ dysfunction in trauma patients with a femoral fracture.

METHODS

Patients with a femoral fracture presenting at the University Medical Center Utrecht between 2007 and 2013 were included. Data of neutrophil characteristics from standard hematological analyzers were recorded on a daily basis until the 28th day of hospital stay or until discharge. Generalized Estimating Equations were used to compare outcome groups.

RESULTS

In total 157 patients were analyzed, of whom 81 had polytrauma and 76 monotrauma. Overall mortality within 90 days was 6.4% (n = 10). Eleven patients (7.0%) developed organ dysfunction. In patients who developed organ dysfunction a significant increase in neutrophil count (P = 0.024), a significant increase in neutrophil cell size (P = 0.026), a significant increase in neutrophil complexity (P < 0.004), and a significant decrease in neutrophil lobularity (P < 0.001) were seen after trauma. The rise in neutrophil cell size preceded the clinical manifestation of organ dysfunction in every patient.

CONCLUSION

Patients who develop organ dysfunction postinjury show changes in neutrophil characteristics before organ dysfunction becomes clinically evident. These findings regarding post-traumatic organ dysfunction may contribute to the development of new prognostic tools for immune-mediated complications in trauma patients.

LEVEL OF EVIDENCE

Level II, etiologic study.

New automated analysis to monitor neutrophil function point-of-care in the intensive care unit after trauma

BACKGROUND

Patients often develop infectious complications after severe trauma. No biomarkers exist that enable early identification of patients who are at risk. Neutrophils are important immune cells that combat these infections by phagocytosis and killing of pathogens. Analysis of neutrophil function used to be laborious and was therefore not applicable in routine diagnostics. Hence, we developed a quick and point-of-care method to assess a critical part of neutrophil function, neutrophil phagosomal acidification. The aim of this study was to investigate whether this method was able to analyze neutrophil functionality in severely injured patients and whether a relation with the development of infectious complications was present.

RESULTS

Fifteen severely injured patients (median ISS of 33) were included, of whom 6 developed an infection between day 4 and day 9 after trauma. The injury severity score did not significantly differ between patients who developed an infection and patients who did not (p = 0.529). Patients who developed an infection showed increased acidification immediately after trauma (p = 0.006) and after 3 days (p = 0.026) and a decrease in the days thereafter to levels in the lower normal range. In contrast, patients who did not develop infectious complications showed high-normal acidification within the first days and increased tasset to identify patients at risk for infections after trauma and to monitor the inflammatory state of these trauma patients.

CONCLUSION

Neutrophil function can be measured in the ICU setting by rapid point-of-care analysis of phagosomal acidification. This analysis differed between trauma patients who developed infectious complications and trauma patients who did not. Therefore, this assay might prove a valuable asset to identify patients at risk for infections after trauma and to monitor the inflammatory state of these trauma patients.

TRIAL REGISTRATION

Central Committee on Research Involving Human Subjects, NL43279.041.13. Registered 14 February 2014. https://www.toetsingonline.nl/to/ccmo_search.nsf/Searchform?OpenForm.

Does Neutrophil Phenotype Predict the Survival of Trauma Patients?

According to the World Health Organization (WHO), trauma is responsible for 10% of deaths and 16% of disabilities worldwide. This is considerably higher than those for malaria, tuberculosis, and HIV/AIDS combined. While the human suffering and death caused by injury is well-recognized, injury has a significant medical care cost. Better prediction of the state of trauma patients in the days immediately after trauma may reduce costs. Traumatic injuries to multiple organs can cause dysfunction in all systems of the body especially the immune system placing patients at high risk of infections and inflammatory complications which are often fatal. Neutrophils are the most abundant leukocyte in the human circulation and are crucial for the prevention of microbial disease. Significant changes in neutrophil functions such as enhanced chemotaxis, Neutrophil extracellular trap (NET)-induced cell death (NETosis), and phagocytosis occur early after injury followed by prolonged functional defects such as phagocytosis, killing mechanisms, and receptor expression. Analysis of these changes may improve the prediction of the patient's condition over time. We provide a comprehensive and up-to-date review of the literature investigating the effect of trauma on neutrophil phenotype with an underlying goal of using this knowledge to examine the predictive potential of neutrophil alterations on secondary complications in patients with traumatic injuries. We conclude that alterations in neutrophil surface markers and functions may be potential biomarkers that predict the outcome of trauma patients.

Neutrophil heterogeneity and its role in infectious complications after severe trauma

Background

Trauma leads to a complex inflammatory cascade that induces both immune activation and a refractory immune state in parallel. Although both components are deemed necessary for recovery, the balance is tight and easily lost. Losing the balance can lead to life-threatening infectious complications as well as long-term immunosuppression with recurrent infections. Neutrophils are known to play a key role in these processes. Therefore, this review focuses on neutrophil characteristics and function after trauma and how these features can be used to identify trauma patients at risk for infectious complications.

Results

Distinct neutrophil subtypes exist that play their own role in the recovery and/or development of infectious complications after trauma. Furthermore, the refractory immune state is related to the risk of infectious complications. These findings change the initial concepts of the immune response after trauma and give rise to new biomarkers for monitoring and predicting inflammatory complications in severely injured patients.

Conclusion

For early recognition of patients at risk, the immune system should be monitored. Several neutrophil biomarkers show promising results and analysis of these markers has become accessible to such extent that they can be used for point-of-care decision making after trauma.

Intracellular Penetration and Effects of Antibiotics on Staphylococcus aureus Inside Human Neutrophils: A Comprehensive Review

Neutrophils are important assets in defense against invading bacteria like staphylococci. However, (dysfunctioning) neutrophils can also serve as reservoir for pathogens that are able to survive inside the cellular environment. Staphylococcus aureus is a notorious facultative intracellular pathogen. Most vulnerable for neutrophil dysfunction and intracellular infection are immune-deficient patients or, as has recently been described, severely injured patients. These dysfunctional neutrophils can become hide-out spots or “Trojan horses” for S. aureus. This location offers protection to bacteria from most antibiotics and allows transportation of bacteria throughout the body inside moving neutrophils. When neutrophils die, these bacteria are released at different locations. In this review, we therefore focus on the capacity of several groups of antibiotics to enter human neutrophils, kill intracellular S. aureus and affect neutrophil function. We provide an overview of intracellular capacity of available antibiotics to aid in clinical decision making. In conclusion, quinolones, rifamycins and sulfamethoxazole-trimethoprim seem very effective against intracellular S. aureus in human neutrophils. Oxazolidinones, macrolides and lincosamides also exert intracellular antibiotic activity. Despite that the reviewed data are predominantly of in vitro origin, these findings should be taken into account when intracellular infection is suspected, as can be the case in severely injured patients.

Monotrauma is associated with enhanced remote inflammatory response and organ damage, while polytrauma intensifies both in porcine trauma model

AIM

Severely injured patients experience substantial immunological stress upon traumatic insult. Next to the direct local tissue injury also other organs, which are not directly injured such as liver and lung, are frequently affected by a so-called remote organ damage (ROD) after trauma. Thus, we studied the inflammatory response of lung and liver either after isolated femur fracture as example for ROD, or after multiple trauma in a porcine polytrauma model.

METHODS

Twenty-four male pigs (Sus scrofa) underwent either isolated standardized femoral fracture (monotrauma, MT, n = 12) or polytrauma (PT, n = 12). PT consisted of a femur fracture, lung contusion, liver laceration, hemorrhagic shock, subsequent resuscitation and surgical fracture fixation. Six animals served as controls (sham). After 72 h inflammatory changes were determined by analyses of the interleukin (IL)-6 gene expression and tissue infiltration of polymorphonuclear leukocyte (PMN, myeloperoxidase staining). ROD in MT, and lung as well as liver damage in PT were assessed histologically by hematoxylin-eosin staining. Expression of phosphorylated p65 NF-κB was evaluated by immunohistology.

RESULTS

IL-6 increased in lungs and liver in both groups MT and PT, respectively, compared to sham. Similarly, PMN infiltration of the lungs and liver increased significantly after both MT and PT compared to sham. Histological evaluation demonstrated tissue damage notably in lungs after MT, while tissue damage after PT was found in both lung and liver after PT. p65 NF-κB tended to an increase upon MT, and was significantly enhanced after PT in both tissues.

CONCLUSION

Our data indicate that remote organ damage after MT notably in lungs was associated with an enhanced inflammatory response. Severe polytrauma substantially intensifies this response and organ damage in the underlying model.

Exhaustion of the immune system by Group A Streptococcus necrotizing fasciitis: the occurrence of late secondary infections in a retrospective study

BACKGROUND

Necrotizing fasciitis is a potentially lethal condition for which early and adequate treatment with surgical debridement and broad-spectrum intravenous antibiotics are essential for survival. It is hypothesized that Group A Streptococcus (GAS) necrotizing fasciitis causes exhaustion of the immune system, making these patients more susceptible for late secondary infections.

METHODS

A retrospective study was conducted of all patients with necrotizing fasciitis between 2002 and 2016. Patients with necrotizing fasciitis based on macroscopic findings, positive Gram staining, culture or fresh frozen section of fascia biopsies were included. Patients with necrotizing fasciitis were divided into two groups based on the presence of GAS. Of both groups, clinical course, outcome and occurrence of late secondary infections were analyzed. For the occurrence of secondary infections, pneumonia was chosen as reference for late secondary infections.

RESULTS

Eighty-one patients with necrotizing fasciitis were included of which 38 (47%) had GAS necrotizing fasciitis and 43 (53%) had non-GAS necrotizing fasciitis. Patients with GAS necrotizing fasciitis were younger (50 vs. 61 years, p=0.023) and more often classified as ASA I (45% vs. 14%, p=0.002) compared with patients with non-GAS necrotizing fasciitis. In-hospital mortality rate for necrotizing fasciitis was 32%. Patients with comorbidities were more likely to die of necrotizing fasciitis compared with patients without comorbidities (OR 7.41, 95% CI 1.58 to 34.63). Twelve patients (39%) with GAS necrotizing fasciitis developed pneumonia compared with four patients (13%) with non-GAS necrotizing fasciitis (p=0.017; OR 4.42, 95% CI 1.124 to 15.79). Median time from diagnosis to development of pneumonia in patients with GAS necrotizing fasciitis was 10 days (IQR 9).

CONCLUSION

Patients with GAS necrotizing fasciitis have an increased risk to develop late secondary infections during initial treatment for necrotizing fasciitis compared with patients with necrotizing fasciitis without involvement of GAS. This suggests exhaustion of the immune system after severe GAS infection.

LEVEL OF EVIDENCE

III.

Neutrophil phenotypes in health and disease

Neutrophils are one of the most important effector cells of the innate immune response (1). They are traditionally seen as a homogenous population of short-lived cells mainly involved in the defence against extracellular microorganisms by phagocytosis and intracellular killing (1,2). The cells contain a large armamentarium that aids in this function and ranges from the production of reactive oxygen species by a membrane-bound NADPH oxidase to cytotoxic proteins and peptides residing in the different granules present in the cytoplasm (3). Recently, the view of neutrophils belonging to a homogenous population of cells has been challenged, and several neutrophil phenotypes have been described that exhibit specialized functions, such as involvement in tissue repair, tumour killing and immune regulation (4). It is not clear whether these cells belong to separate parallel lineages originating from the bone marrow or that neutrophils become instructed in the distant tissues, thus changing their phenotypes. In addition, functional heterogeneity in a phenotypically homogenous population of neutrophils adds to the complexity of neutrophil phenotypes(5). This article will review the current literature describing the heterogeneity within the neutrophil compartment with respect to both phenotype and function in health and disease.

The impact of septic stimuli on the systemic inflammatory response and physiologic insult in a preclinical non-human primate model of polytraumatic injury

BACKGROUND

Established animal trauma models are limited in recapitulating the pathophysiology of human traumatic injury. Herein, we characterize the physiologic insult and inflammatory response in two clinically relevant non-human primate (NHP) trauma models.

METHODS

Mauritian Cynomolgus Macaques underwent either a laparoscopic closed abdomen liver injury (laparoscopic 60% left-lobe hepatectomy) in an established uncontrolled severe hemorrhage model (THM), or a polytrauma hemorrhage model (PHM) involving combined liver and bowel injury, uncontrolled severe hemorrhage as well as an open full-thickness cutaneous flank wound. Fixed volume resuscitation strategies were employed in the THM and goal directed resuscitation was used in the PHM. Complete peripheral blood and critical clinical chemistry parameters, serum biomarkers of systemic inflammation, tissue perfusion parameters, as well as survival, were compared between the models throughout the 2-week study period.

RESULTS

NHPs in both the THM (n = 7) and the PHM (n = 21) demonstrated tissue hypoperfusion (peak lactate 6.3 ± 0.71 mmol/L) with end organ injury (peak creatinine 3.08 ± 0.69 mg/dL) from a similar liver injury (60% left hemi-hepatectomy), though the PHM NHPs had a significantly higher blood loss (68.1% ± 12.7% vs. 34.3% ± 2.3%, p = 0.02), lower platelet counts (59 ± 25 vs. 205 ± 46 K/uL, p = 0.03) and a trend towards higher mortality (90.5% vs. 33.3%, p = 0.09). The inflammatory response was robust in both models with peak cytokine (IL-6 > 6000-fold above baseline) and peak leukocyte values (WBC 27 K/uL) typically occurring around t = 240 min from the time of hepatic injury. A more robust systemic inflammatory response was appreciated in the PHM resulting in marked elevations in peak serum IL-6 (7887 ± 2521 pg/mL vs.1076 ± 4833 pg/mL, p = 0.02), IL-1ra (34,499 ± 5987 pg/mL vs. 2511 ± 1228 pg/mL, p < 0.00), and IL-10 (13,411 pg/mL ± 5598 pg/mL vs. 617 pg/mL ± 252 pg/mL, p = 0.03).

CONCLUSION

This comparative analysis provides a unique longitudinal perspective on the post-injury inflammatory response in two clinically relevant models, and demonstrates that the addition of septic stimuli to solid organ injury increases both the hemorrhagic insult and inflammatory response.

Advances in the understanding and treatment of sepsis-induced immunosuppression

Sepsis is defined as a life-threatening organ dysfunction that is caused by a dysregulated host response to infection. Sepsis can induce acute kidney injury and multiple organ failures and represents the most common cause of death in the intensive care unit. Sepsis initiates a complex immune response that varies over time, with the concomitant occurrence of both pro-inflammatory and anti-inflammatory mechanisms. As a result, most patients with sepsis rapidly display signs of profound immunosuppression, which is associated with deleterious consequences. Scientific advances have highlighted the role of metabolic failure, epigenetic reprogramming, myeloid-derived suppressor cells, immature suppressive neutrophils and immune alterations in primary lymphoid organs (the thymus and bone marrow) in sepsis. An improved understanding of the mechanisms underlying this immunosuppression as well as of the similarities between sepsis-induced immunosuppression and immune defects in cancer or immunosenescence has led to novel therapeutic strategies aimed at stimulating immune function in patients with sepsis. Trials assessing the therapeutic benefit of IL-7, granulocyte-macrophage colony-stimulating factor (GM-CSF) and antibodies against programmed cell death protein 1 (PD1) and programmed cell death 1 ligand 1 (PDL1) for the treatment of sepsis are in progress. The reappraisal of sepsis pathophysiology has also resulted in a novel approach to the design of clinical trials evaluating sepsis treatments, based on an evaluation of the immune status and biomarker-based stratification of patients.