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Surgical shunts are commonly used to manage complications resulting from extrahepatic portal vein thrombosis (EHPVT) in children. We describe a single-center experience utilizing a functional Side-to-Side Splenorenal Shunt (fSRS), created using either an enlarged inferior mesenteric vein (IMV) or left adrenal vein (LAV).Pediatric patients with isolated EHPVT who were poor candidates for a Rex shunt and who underwent a fSRS procedure at our institution between 2003 and 2020 were reviewed. The pre/post shunt portosystemic gradient change, rates of early and late complications, postoperative shunt patency, and mortality were evaluated.Twelve EHPVT patients (mean age of 6.1 years) underwent a fSRS procedure. The mean portosystemic gradient change for the cohort was -11.7 mmHg (±4.9). There were no cases of recurrent variceal bleeding or episodes of shunt thrombosis reported after fSRS procedures.Surgical shunts continue to be an important adjunct in the treatment of complications related to EHPVT. The functional Side-to-Side Splenorenal Shunt is a safe alternative that is easy to perform, involves minimal dissection and requires only a single anastomosis.

Alagille syndrome (AGS) is a disorder that leads to increased serum cholesterol and bile acids, which can result in debilitating xanthomas and pruritus. External biliary drainage and transplantation are effective treatments for AGS. Internal biliary diversion with Roux-en-Y cholecystocolostomy has been described for other biliary conditions, but not AGS. Three patients with severe pruritus due to AGS underwent Roux-en-Y cholecystocolostomy for internal biliary drainage. Retrospective analysis compared preoperative and post-operative lab values and symptom scores (0, none–4, severe). Three patients underwent cholecystocolostomy. All patients had at least three diagnostic criteria for AGS. Mean preoperative pruritus score was 3.33 (range, 2–4) and mean post-operative score was 1. Mean preoperative xanthoma score was 1.33 (range, 0–4) and post-operative score was 1 at 2-month follow-up. Roux-en-Y cholecystocolostomy can be considered for AGS, which is refractory to medical management. This procedure accomplishes internal biliary diversion without significant physiologic derangements.

The practice of transplanting hepatitis C (HCV)-infected livers into HCV-uninfected recipients has not previously been recommended in transplant guidelines, in part because of concerns over uncontrolled HCV infection of the allograft. Direct-acting antivirals (DAAs) provide an opportunity to treat donor derived HCV-infection, and should be administered early in the post-transplant period. However, evidence on the safety and efficacy of an immediate DAA treatment approach, including how to manage logistical barriers surrounding timely DAA procurement, are required prior to broader use of HCV-positive donor organs. We report the results of a trial in which fourteen HCV-negative patients underwent successful liver transplantation from HCV-positive donors. Nine patients received viremic (nucleic acid testing (NAT)-positive) livers, and started a 12-week course of oral glecaprevir-pibrentasvir (GP) within 5 days of transplant. Five patients received livers from HCV antibody-positive non-viremic donors and were followed using a reactive approach. Survival in NAT-positive recipients is 100% at a median follow-up of 46 weeks. An immediate treatment approach for HCV NAT-positive liver transplantation into uninfected recipients is safe and efficacious. Securing payer approval for DAAs early in the post-transplant course could enable need-based allocation of HCV-positive donor organs irrespective of candidate HCV status, while averting chronic HCV allograft infection.

Midaortic syndrome (MAS) is a rare condition characterized by stenosis of the abdominal aorta with or without the involvement of branch vessels. The majority of cases are thought to be idiopathic though MAS has been associated with a number of conditions including granulomatous vasculitis, neurofibromatosis-1 (NF-1), Alagille Syndrome, fibromuscular dysplasia (FMD), and Williams syndrome. Patients typically present with hypertension due to decreased renal perfusion. Less common presentations include renal insufficiency, heart failure, claudication, stroke, and abdominal pain. Imaging modalities help establish the diagnosis of MAS including duplex ultrasound, computed tomography angiography (CTA), magnetic resonance angiography (MRA), and angiography. Initial therapy focuses on medical management with antihypertensives prior to intervention. Invasive interventions are indicated when there is evidence of end organ damage or dysfunction such as decreased renal function, poorly growing kidneys, cerebrovascular accident, left ventricular hypertrophy or frank cardiac failure. Endovascular interventions may assist in diagnosis and may treat some lesions although reintervention rates are high. Most patients require some type of surgical intervention, and a variety of surgical options are available based on anatomic findings. Renal revascularization may be accomplished by renal artery bypass, autotransplantation, or renal artery reconstruction. Aortic lesions may be repaired using patch angioplasty or aortoaortic bypass. Mesenteric arteries do not typically require reconstruction as they are rarely symptomatic. More novel options include the use of tissue expanders to lengthen the aorta to allow for primary aortic reconstruction (TESLA) or the use of the meandering mesenteric artery as an autologous aortic bypass graft (MAGIC).

Choledochal cysts are congenital malformations of the biliary tract that involve aberrant configurations of the pancreaticobiliary ductal system. The pathology exists on a spectrum from fusiform dilation of the common bile duct to multiple dilations involving the intra- and extrahepatic bile ducts with potential risks of malignant transformation and hepatic fibrosis. Advancements in ultrasound technology have increased the incidence of prenatal diagnosis of choledochal cysts. Here, we present the case of a prenatally diagnosed initially asymptomatic Type I choledochal cyst with rapid progression in the neonatal period to a complete gastric outlet obstruction within the first month of life. We demonstrate the feasibility of cyst resection and reconstruction with Roux-en-Y hepaticojejunostomy in the neonatal age group. Finally, we discuss management of the case based on evolving imaging findings and laboratory evidence of impending liver dysfunction.

Pediatric patients constitute an important group within the general transplant population, given the opportunity to significantly extend their lives with successful transplantation. Children have historically received special consideration under the various abdominal solid organ allocation algorithms, but matching patients with size and weight restrictions with appropriate donors remains an ongoing issue. Here, we describe the historical trends in pediatric organ allocation policies for liver, kidney, intestine, and pancreas transplantation. We also review recent changes to these allocation policies, with particular attention to recent amendments to geographical prioritization, with the dissolution of donor service areas and United Network for Organ Sharing (UNOS) regions and the subsequent creation of acuity circles.

Background BK viral infection in the posttransplant setting continues to cause serious morbidity with effects ranging from allograft nephropathy and dysfunction to urothelial malignancy. Results In this report, we present a patient that developed BK-associated nephropathy and, 6 years later, locally advanced urothelial malignancy in the renal allograft with nodal, muscle, and extremity involvement. Following radical allograft nephroureterectomy, he was treated with palliative radiation and the immune checkpoint inhibitor atezolizumab. Follow-up imaging at 1 year demonstrated radiographic complete response. Conclusions This report supports the growing body of evidence supporting the association of urothelial malignancy and BK virus infection in renal transplant recipients. Further, it highlights the novel application of immune checkpoint inhibitors in the treatment of advanced posttransplant malignancy, in particular when the allograft is removed and the tumor is possibly of donor origin.

Considerable strides have been made over the last several decades toward improving outcomes in pediatric liver transplantation. Refinements in surgical technique has allowed for the use of living donor and deceased donor split-liver grafts, thus expanding the pool of available organs and reducing waitlist mortality. The use of a multidisciplinary team continues to be paramount in the care of the transplant recipient. With improvements in overall graft and survival, indications for liver transplantation have also broadened. Currently, pediatric transplant patients have a 5-year survival of over 85%. Long-term morbidity is mainly associated with complications from immunosuppression and chronic rejection. Here we review indications for liver transplantation in children, surgical considerations, post-operative complications, and long-term outcomes.

Evaluation for liver transplant candidacy is a multidisciplinary effort that involves all aspects of clinical care including social work, nutrition, and a multitude of medical specialties. The prognosis of a pretransplant clinical condition is integrated into the decision to list a patient. Herein, we report a successful liver transplant and recovery of a 3-month-old male following a large right hemispheric subdural hematoma related to acute coagulopathy secondary to undiagnosed end-stage liver disease. On presentation with jaundice, lethargy, and unequal pupils, a CT scan was obtained which demonstrated a large right subdural hematoma with herniation. Once his coagulopathy was corrected, he went for decompressive craniectomy. He survived with medically controlled seizures and improving L-sided neglect and extremity weakness. Six weeks later, given his continued neurologic recovery and worsening liver function, the decision was made to list him for liver transplantation. One month later, he underwent orthotopic liver transplant. His post-operative hospital course was complicated by DVTs and heparin-induced thrombocytopenia, but no neurologic decline, and he was eventually discharged from the hospital on post-op day 26. Three years later, he has a well-functioning allograft and no clinically evident neurologic deficits. The prognosis following pediatric neurologic trauma remains somewhat unclear as recovery and neurologic examinations can be influenced by numerous extrinsic factors. This is one of the first reports of near full neurologic recovery of a pediatric liver transplant recipient following a large subdural hematoma with herniation.

Introduction. There are no reported survivors of gastroschisis with complete liver herniation. We describe a case report of two patients, one of whom survived. Case #1. The patient was born with gastroschisis and herniation of the entire liver. Along with silo placement, the abdominal fascia was attached to an external traction system for growth. Complete closure was achieved at 5 months. Due to pulmonary hypoplasia, high-frequency ventilation was required. The patient is doing well, on a home ventilator wean, at 20 months. Case #2. The patient was born prematurely with gastroschisis, total liver herniation, and a defect extending to the pericardium. A silo was attached to the fascia to provide growth of the abdominal cavity. The patient developed respiratory failure, diffuse anasarca, and renal failure. She died at 38 days of life. Discussion. We report the first survivor of gastroschisis with complete liver herniation, contrasting it with a death of a similar case. The associated pulmonary hypoplasia may require long-term ventilation, the inflammatory response can lead to anasarca, and renal injury can occur from acute-on-chronic compartment syndrome. Conclusion. External fascial traction systems can help induce growth of the abdominal wall, allowing closure of the challenging abdomen. While critical care management is complex, survival is possible.

Current evidence suggests that neonatal immunity is functionally distinct from adults. Although TLR signaling through the adaptor protein, MyD88, has been shown to be critical for survival to sepsis in adults, little is known about the role of MyD88 or TRIF in neonatal sepsis. We demonstrate that TRIF−/− but not MyD88−/− neonates are highly susceptible to Escherichia coli peritonitis and bacteremia. This was associated with decreased innate immune recruitment and function. Importantly, we found that the reverse was true in adults that MyD88−/− but not TRIF−/− or wild-type adults are susceptible to E. coli peritonitis and bacteremia. In addition, we demonstrate that TRIF but not MyD88 signaling is critical for the TLR4 protective adjuvant effect we have previously demonstrated. These data suggest a differential requirement for the survival of neonates versus adults to Gram-negative infection, and that modulation of TRIF in neonates can be used to augment survival to neonatal sepsis.

Cancer progression is associated with inflammation, increased metabolic demand, infection, cachexia, and eventually death. Myeloid-derived suppressor cells (MDSCs) commonly expand during cancer and are associated with adaptive immune suppression and inflammatory metabolite production. We propose that cancer-induced cachexia is driven at least in part by the expansion of MDSCs. MDSC expansion in 4T1 mammary carcinoma-bearing hosts is associated with induction of a hepatic acute-phase protein response and altered host energy and fat metabolism, and eventually reduced survival to polymicrobial sepsis and endotoxemia. Similar results are also seen in mice bearing a Lewis lung carcinoma and a C26 colon adenocarcinoma. However, a similar cachexia response is not seen with equivalent growth of the 66C4 subclone of 4T1, in which MDSC expansion does not occur. Importantly, reducing MDSC numbers in 4T1-bearing animals can ameliorate some of these late responses and reduce susceptibility to inflammation-induced organ injury and death. In addition, administering MDSCs from both tumor- and nontumor-bearing mice can produce an acute-phase response. Thus, we propose a previously undescribed mechanism for the development of cancer cachexia, whereby progressive MDSC expansion contributes to changes in host protein and energy metabolism and reduced resistance to infection.

Genomic analyses from blood leukocytes have concluded that mouse injury poorly reflects human trauma at the leukocyte transcriptome. Concerns have focused on the modest severity of murine injury models, differences in murine compared with human age, dissimilar circulating leukocyte populations between species, and whether similar signaling pathways are involved. We sought to examine whether the transcriptomic response to severe trauma in mice could be explained by these extrinsic factors, by utilizing an increasing severity of murine trauma and shock in young and aged mice over time, and by examining the response in isolated neutrophil populations.Preclinical controlled in vivo laboratory study and retrospective cohort study.Laboratory of Inflammation Biology and Surgical Science and multi-institution level 1 trauma centers.Six- to 10-week-old and 20- to 24-month-old C57BL/6 (B6) mice and two cohorts of 167 and 244 severely traumatized (Injury Severity Score15) adult (18 yr) patients.Mice underwent one of two severity polytrauma models of injury. Total blood leukocyte and neutrophil samples were collected.Fold expression changes in leukocyte and neutrophil genome-wide expression analyses between healthy and injured mice (p0.001) were compared with human total and enriched blood leukocyte expression analyses of severe trauma patients at 0.5, 1, 4, 7, 14, and 28 days after injury (Glue Grant trauma-related database). We found that increasing the severity of the murine trauma model only modestly improved the correlation in the transcriptomic response with humans, whereas the age of the mice did not. In addition, the genome-wide response to blood neutrophils (rather than total WBC) was also not well correlated between humans and mice. However, the expression of many individual gene families was much more strongly correlated after injury in mice and humans.Although overall transcriptomic association remained weak even after adjusting for the severity of injury, age of the animals, timing, and individual leukocyte populations, there were individual signaling pathways and ontogenies that were strongly correlated between mice and humans. These genes are involved in early inflammation and innate/adaptive immunity.

Populations encompassing extremes of age, including neonates and elderly, have greater mortality from sepsis. We propose that the increased mortality observed in the neonatal and elderly populations after sepsis is due to fundamental differences in host-protective immunity and is manifested at the level of the leukocyte transcriptome. Neonatal (5–7 d), young adult (6–12 wk), or elderly (20–24 mo) mice underwent a cecal slurry model of intra-abdominal sepsis. Both neonatal and elderly mice exhibited significantly greater mortality to sepsis (p < 0.05). Neonates in particular exhibited significant attenuation of their inflammatory response (p < 0.05), as well as reductions in cell recruitment and reactive oxygen species production (both p < 0.05), all of which could be confirmed at the level of the leukocyte transcriptome. In contrast, elderly mice were also more susceptible to abdominal peritonitis, but this was associated with no significant differences in the magnitude of the inflammatory response, reduced bacterial killing (p < 0.05), reduced early myeloid cell activation (p < 0.05), and a persistent inflammatory response that failed to resolve. Interestingly, elderly mice expressed a persistent inflammatory and immunosuppressive response at the level of the leukocyte transcriptome, with failure to return to baseline by 3 d. This study reveals that neonatal and elderly mice have profoundly different responses to sepsis that are manifested at the level of their circulating leukocyte transcriptome, although the net result of increased mortality is similar. Considering these differences are fundamental aspects of the genomic response to sepsis, interventional therapies will require individualization based on the age of the population.

The elderly have increased morbidity and mortality following sepsis; however, the cause(s) remains unclear. We hypothesized that these poor outcomes are due in part to defects in innate immunity, rather than to an exaggerated early inflammatory response. Young (6–12 wk) or aged (20–24 mo) mice underwent polymicrobial sepsis, and subsequently, the aged mice had increased mortality and defective peritoneal bacterial clearance compared with young mice. No differences were found in the magnitude of the plasma cytokine responses. Although septic aged mice displayed equivalent or increased numbers of circulating, splenic, and bone marrow myeloid cells, some of these cells exhibited decreased phagocytosis, reactive oxygen species production, and chemotaxis. Blood leukocyte gene expression was less altered in aged versus young mice 1 d after sepsis. Aged mice had a relative inability to upregulate gene expression of pathways related to neutrophil-mediated protective immunity, chemokine/chemokine receptor binding, and responses to exogenous molecules. Expression of most MHC genes remained more downregulated in aged mice at day 3. Despite their increased myeloid response to sepsis, the increased susceptibility of aged mice to sepsis appears not to be due to an exaggerated inflammatory response, but rather, a failure to mount an effective innate immune response.

For the past thirty years, since IL-1β and TNFα were first cloned, there have been efforts to measure plasma cytokine concentrations in patients with severe sepsis and trauma, and to use these measurements to predict clinical outcome and response to therapies. The numbers of cytokines and chemokines that have been measured in the plasma have literally exploded with the development of multiplex immune approaches. Dozens of relatively small cohort studies have shown plasma cytokine concentrations correlating with outcome in sepsis and trauma. Despite what appears to be a consensus that plasma cytokine concentrations should be useful in the clinical setting, only two cytokines, IL-6 and procalcitonin, have approached routine clinical use. IL-6 has been used as a research tool for entry into sepsis-intervention trials, while procalcitonin is being used clinically at a large number of institutions to distinguish sepsis from other inflammatory processes. For most cytokines, the relative lack of sensitivity and specificity of individual or multiplex cytokine measurements has hindered their utility to predict clinical trajectory in individual patients. The problem rests with a general misunderstanding of cytokine biology, failing to appreciate the general paracrine nature of these mediators, the presence of binding proteins, chaperones and inhibitors in the plasma, and the rapid clearance of these proteins by binding to cell receptors and clearance predominantly by the kidney. The future of using plasma cytokine measurements as an indicator of sepsis/trauma severity or predicting outcome is generally behind us, although there is optimism that procalcitonin measurements may ultimately prove to have utility in the diagnosis of severe sepsis.

OBJECTIVE To develop a novel polytrauma model that better recapitulates the immunologic response of the severely injured patient by combining long-bone fracture, muscle tissue damage, and cecectomy with hemorrhagic shock, resulting in an equivalent Injury Severity Score of greater than 15. We compared this new polytrauma/shock model to historically used murine trauma-hemorrhage models. DESIGN Pre-clinical controlled in vivo laboratory study. SETTING Laboratory of Inflammation Biology and Surgical Science. SUBJECTS Six- to 10-week-old C57BL/6 (B6) mice. INTERVENTIONS Mice underwent 90 minutes of shock (mean arterial pressure 30 mm Hg) and resuscitation via femoral artery cannulation followed by laparotomy (trauma-hemorrhage), hemorrhage with laparotomy and femur fracture, or laparotomy with cecetomy and femur fracture with muscle tissue damage (polytrauma). Mice were euthanized at 2 hours, 1 day, and 3 days postinjury. MEASUREMENTS AND MAIN RESULTS The spleen, bone marrow, blood, and serum were collected from mice for analysis at the above time points. None of the models were lethal. Mice undergoing polytrauma exhibited a more robust inflammatory response with significant elevations in cytokine/chemokine concentrations when compared with traditional models. Polytrauma was the only model to induce neutrophilia (Ly6G (+)CD11b(+) cells) on days 1 and 3 (p

Newborns are at increased risk of infection due to genetic, epigenetic, and environmental factors. Herein we examine the roles of the neonatal innate immune system in host defense against bacterial and viral infections. Full-term newborns express a distinct innate immune system biased toward T(H)2-/T(H)17-polarizing and anti-inflammatory cytokine production with relative impairment in T(H)1-polarizing cytokine production that leaves them particularly vulnerable to infection with intracellular pathogens. In addition to these distinct features, preterm newborns also have fragile skin, impaired T(H)17-polarizing cytokine production, and deficient expression of complement and of antimicrobial proteins and peptides (APPs) that likely contribute to susceptibility to pyogenic bacteria. Ongoing research is identifying APPs, including bacterial/permeability-increasing protein and lactoferrin, as well as pattern recognition receptor agonists that may serve to enhance protective newborn and infant immune responses as stand-alone immune response modifiers or vaccine adjuvants.

Background: Given that micelles of lipids are colloids, the hypothesis was generated that the rapid administration of large volumes of soybean oil micelles would be an effective perfusion fluid. We also hypothesized that oxygen loading would be enhanced due to the greater solubility of oxygen in lipids compared to water. Methods: A 100% lethal mouse model of blood loss was used to compare the ability of soybean oil micelles to that of Ringer’s lactate, blood and other fluids, with respect to raising and maintaining the blood pressure for one hour. Oxygen on- and off-loading of various concentrations of soybean oil micelles was determined using mass spectroscopy. Nitric oxide uptake by micelles was also determined in a similar fashion. Results: A 20% soybean oil emulsion was superior to Ringer’s lactate in raising and maintaining blood pressure. A 20% soybean oil emulsion with 5% albumin added was superior to shed blood as well as solutions comprised of 5% albumin added to either normal saline or Ringer’s lactate. There was a linear relationship between oxygen content and micelle concentration between 10% and 30%. Off-loading of oxygen from the micelles was nearly as fast as off-loading from water. Nitric oxide also loaded preferentially onto soybean oil micelles. Conclusions: (1) Soybean oil emulsions were superior to other fluids in restoring and maintaining the blood pressure; (2) oxygen-carrying ability of soybean oil micelles exceeds that of water and follows Henry’s law between 10% and 30% w/v oil content; (3) nitric oxide was carried by the micelles; (4) animals receiving soybean oil micelles did not exhibit fat embolization; (5) colloids comprised of soybean oil-containing micelles may be used to replace blood loss and may be used to deliver oxygen and other potentially therapeutic gases such as nitric oxide to tissues.

Pancreatic trauma is rare in children and optimal care has not been defined. We undertook this study to review the cumulative experience from three centers. After obtaining Institutional Review Board approval at each site, the trauma registries of three institutions were searched for pancreatic injuries. The charts were reviewed and data pertaining to demographics, hospital course, and outcome were obtained and analyzed. During the study period, a total of 79 pancreatic injuries were noted. The most common mechanism of injury was motor vehicle crash (44%) followed by child abuse (11%) and bicycle crashes (11%). Computed tomographic (CT) scans were obtained in 95 per cent with peripancreatic fluid the most common finding. Median Injury Severity Score (ISS) was 9, whereas median organ injury score was 2, and a higher grade correlated with need for operation ( P = 0.001). Pancreatic operations were performed in 32 patients, whereas non-operative management was noted in 47 cases. We noted no differences in length of stay, age, ISS, or initial blood pressure in operative versus nonoperatively managed cases. Pancreatic injuries were rare in children with trauma. CT scans were the most common method of diagnosis. Nonoperative management appeared to be safe and was more common, especially for the lower grade injuries.

The significance of meconium plug syndrome (MPS) is unclear but has been associated with Hirschsprung's disease and magnesium tocolysis. We reviewed our experience to attempt to identify any potential association with these conditions and to review our outcomes.Using the International Classification of Diseases, Ninth revision, code for meconium obstruction, patient charts were identified during the 1998-2008 period. A total of 61 cases of MPS were found, after excluding 7 of meconium ileus. Data regarding the hospital course and outcomes were collected and analyzed.Approximately 30% of patients had spontaneous resolution of the meconium plug without any treatment. Of those patients requiring treatment, contrast barium enema was used, with 97% success. Only 2 patients required surgical intervention owing to worsening distension and subsequent peritonitis. When we stratified the patients according to gestational age of36 and36 wk, contrast barium enemas were performed 2.2 ± 1.8 versus 8.6 ± 7.8 d after birth (P = 0.003), respectively, and the lower gestational age patients had a longer length of stay. Contrast barium enema was still successful in 94% of patients with a gestational age of36 wk. Magnesium tocolysis was noted in 16% of the cases, and Hirschsprung's disease was only found in 3.2% of patients.Patients with MPS have excellent outcomes, independent of gestational age. Contrast barium enema remains the initial diagnostic and treatment of choice for patients with MPS. Also, although previous reports have shown a link between magnesium tocolysis and Hirschsprung's disease with MPS, our experience suggests otherwise.

Surgical intensive care unit (ICU) stay of greater than ten days is often described by the experienced intensivist as a ‘complicated clinical course’, and is frequently attributed to persistent immune dysfunction. ‘Systemic inflammatory response syndrome’ (SIRS) followed by ‘compensatory anti-inflammatory response syndrome’ (CARS) is a conceptual framework to explain the immunological trajectory that ICU patients with severe sepsis, trauma or emergency surgery for abdominal infection often traverse, but the causes, mechanisms and reasons for persistent immune dysfunction remain unexplained. Often involving multiple organ failure (MOF) and death, improvements in surgical intensive care have altered its incidence, phenotype and frequency, and have increased the number of patients who survive initial sepsis or surgical events and progress to a persistent inflammation, immunosuppression, and catabolism syndrome (PICS). Often observed, but rarely reversible, these patients may survive to transfer to a long-term care facility only to return to the ICU, but rarely to self sufficiency. We propose that PICS is the dominant pathophysiology and phenotype that has replaced late MOF, and prolongs surgical ICU stay, usually with poor outcome. This review details the evolving epidemiology of MOF, the clinical presentation of PICS, and our understanding of how persistent inflammation and immunosuppression defines the pathobiology of prolonged intensive care. Therapy for PICS will require efficacy for multiple immune system defects and protein catabolism, and will involve innovative interventions for immune system rebalance and nutritional support to regain physical function and well being.

Critical injury in humans induces a genomic storm with simultaneous changes in expression of innate and adaptive immunity genes., Human survival from injury requires an appropriate inflammatory and immune response. We describe the circulating leukocyte transcriptome after severe trauma and burn injury, as well as in healthy subjects receiving low-dose bacterial endotoxin, and show that these severe stresses produce a global reprioritization affecting >80% of the cellular functions and pathways, a truly unexpected “genomic storm.” In severe blunt trauma, the early leukocyte genomic response is consistent with simultaneously increased expression of genes involved in the systemic inflammatory, innate immune, and compensatory antiinflammatory responses, as well as in the suppression of genes involved in adaptive immunity. Furthermore, complications like nosocomial infections and organ failure are not associated with any genomic evidence of a second hit and differ only in the magnitude and duration of this genomic reprioritization. The similarities in gene expression patterns between different injuries reveal an apparently fundamental human response to severe inflammatory stress, with genomic signatures that are surprisingly far more common than different. Based on these transcriptional data, we propose a new paradigm for the human immunological response to severe injury.

Objective Most children undergo an upper gastrointestinal study (UGI) before an anti-reflux (AR) procedure or gastrostomy tube placement (GT). Anatomic abnormalities detected by UGI are uncommon and we hypothesize that the value of routine preoperative use of this test is limited. Methods Five hundred and seventy-two patients who underwent either an AR or GT over a 10-y period at our institution were reviewed. Data including patient demographics, indications for surgery, preoperative testing, and type of operation were collected. Results Of the 572 cases, an UGI was performed in approximately 71%. The results were interpreted as normal in 63%, and abnormal in 37%. The most common abnormality noted was gastroesophageal reflux in approximately 80%, followed by an anatomic abnormality in 6%, most of which were expected. Of 36 anatomic abnormalities noted, only four were unexpected in the total cohort. In addition to an UGI, half of the subjects received additional evaluations that included pH probes and gastric emptying studies (GES). In these studies, 56% of pH probes and 45% of GES had findings in which reflux was noted. Compared with UGIs, these tests were significantly more likely to identify reflux in patients. Conclusion These results suggest that the utility of an UGI before AR or GT procedures is low. Anatomic abnormalities were rare and changed clinical management in a total of four cases. A prospective trial would help to further validate these findings and help identify patients who would benefit from an UGI.

Despite ongoing improvements in resuscitation, care, and outcomes, traumatic injury remains a significant health care and economic burden. The causes are multifactorial, but our approach to the clinical management of these patients remains limited by our current understanding of the pathobiology of the disease. A multicenter, multidisciplinary program known as the "Inflammation and the Host Response to Injury" Large Scale Collaborative Research Program was created by the National Institute of General Medical Sciences (NIGMS, U54 GM062119-10) in 2001 in a 10-year effort to address some of these issues. Its primary goal is to describe the human genomic response to severe trauma and burns, and to examine changes in gene expression in the context of different clinical outcomes. The Program has not only successfully implemented clinical care guidelines for managing the severe trauma patient based on the best available evidence to minimize iatrogenic variability, but it has also examined the genome-wide, immune-inflammatory response in total and isolated blood leukocyte populations. This review will address current milestones as well as future directions for the Program.

Gene expression analysis can be a powerful tool in predicting patient outcomes and identifying patients who may benefit from targeted therapies. However, isolating human blood polymorphonuclear cells (PMNs) for genomic analysis has been challenging. We used a novel microfluidic technique that isolates PMNs by capturing CD66b(+) cells and compared it with dextran-Ficoll gradient isolation. We also used microfluidic isolation techniques for blood and bronchoalveolar lavage (BAL) samples of patients with acute respiratory distress syndrome (ARDS) to evaluate PMN genomic alterations secondary to pulmonary sequestration. PMNs obtained from ex vivo lipopolysaccharide (LPS)-stimulated or -unstimulated whole blood from five healthy volunteers were isolated by either dextran-Ficoll gradient, microfluidics capture, or a combination of the two techniques. Blood and BAL fluid PMNs were also isolated using microfluidics from seven hospitalized patients with ARDS. Gene expression was inferred from extracted RNA using Affymetrix U133 Plus 2.0 GeneChips. All methods of PMN isolation produced similar quantities of high-quality RNA, when adjusted for recovered cell number. Unsupervised analysis and hierarchical clustering indicated that LPS stimulation was the primary factor affecting gene expression patterns among all ex vivo samples. Patterns of gene expression from blood and BAL PMNs differed significantly from each other in the patients with ARDS. Isolation of PMNs by microfluidics can be applied to both blood and BAL specimens from critically ill, hospitalized patients. Unique genomic expression patterns are obtained from the blood and BAL fluid of critically ill patients with ARDS, and these differ significantly from genomic patterns seen after ex vivo LPS stimulation.

Bone marrow (BM) hematopoietic stem and progenitor cells (HSPCs) can be activated by type I IFNs, TLR agonists, viruses, and bacteria to increase hematopoiesis. In this study, we report that endotoxin treatment in vivo induces TLR4, MyD88, and Toll/IL-1 resistance domain-containing adaptor-inducing IFN-β (TRIF)-dependent expansion of BM HSPCs. Bacterial infection by Staphylococcus aureus or cecal ligation and puncture also induces HSPC expansion, but MyD88, TRIF, type I IFN, cytokine, PG, or oxidative stress pathways are not required for their expansion. S. aureus-induced HSPC expansion in MyD88−/−TRIF−/− mice is also normal, but is associated with BM remodeling as granulocyte stores are released peripherally. Importantly, reduction in BM cellularity alone can reproduce HSPC expansion. These data show in vivo HSPC responses to bacterial infection are complex and not absolutely dependent upon key inflammatory signaling pathways.

Type I interferon (IFN) alpha/beta is critical for host defense. During endotoxicosis or highly lethal bacterial infections where systemic inflammation predominates, mice deficient in IFN-alpha/beta receptor (IFNAR) display decreased systemic inflammation and improved outcome. However, human sepsis mortality often occurs during a prolonged period of immunosuppression and not from exaggerated inflammation. We used a low lethality cecal ligation and puncture (CLP) model of sepsis to determine the role of type I IFNs in host defense during sepsis. Despite increased endotoxin resistance, IFNAR(-/-) and chimeric mice lacking IFNAR in hematopoietic cells display increased mortality to CLP. This was not associated with an altered early systemic inflammatory response, except for decreased CXCL10 production. IFNAR(-/-) mice display persistently elevated peritoneal bacterial counts compared with wild-type mice, reduced peritoneal neutrophil recruitment, and recruitment of neutrophils with poor phagocytic function despite normal to enhanced adaptive immune function during sepsis. Importantly, CXCL10 treatment of IFNAR(-/-) mice improves survival and decreases peritoneal bacterial loads, and CXCL10 increases mouse and human neutrophil phagocytosis. Using a low lethality sepsis model, we identify a critical role of type I IFN-dependent CXCL10 in host defense during polymicrobial sepsis by increasing neutrophil recruitment and function.

Background The epidemiology of Clostridium difficile-associated infection (CDI) has changed, and it is evident that susceptibility is related not only to exposures and bacterial potency, but host factors as well. Several small studies have suggested that CDI after trauma is associated with a different patient phenotype. The purpose of this study was to examine and describe the epidemiologic factors associated with C. difficile in blunt trauma patients without traumatic brain injury using the Trauma-Related Database as a part of the "Inflammation and Host Response to Injury" (Glue Grant) and the University of Florida Integrated Data Repository. Methods Previously recorded baseline characteristics, clinical data, and outcomes were compared between groups (67 C. difficile and 384 uncomplicated, 813 intermediate, and 761 complicated non-C. difficile patients) as defined by the Glue Grant on admission and at days seven and 14. Results The majority of CDI patients experienced complicated or intermediate clinical courses. The mean ages of all cohorts were less than 65 y and CDI patients were significantly older than uncomplicated patients without CDI. The CDI patients had increased days in the hospital and on the ventilator, as well as significantly higher new injury severity scores (NISS), and a greater percentage of patients with NISS >34 points compared with non-CDI patients. They also had greater Marshall and Denver multiple organ dysfunction scores than non-CDI uncomplicated patients, and greater creatinine, alkaline phosphatase, neutrophil count, lactic acid, and PiO2:FiO2 compared with all non-CDI cohorts on admission. In addition, the CDI patients had higher glucose concentrations and base deficit from uncomplicated patients and greater leukocytosis than complicated patients on admission. Several of these changes persisted to days seven and 14. Conclusion Analysis of severe blunt trauma patients with C. difficile, as compared with non-CDI patients, reveals evidence of increased inflammation, immunosuppression, worse acute kidney injury, higher NISS, greater days in the hospital and on the ventilator, higher organ injury scores, and prolonged clinical courses. This supports reports of an increased prevalence of CDI in a younger population not believed previously to be at risk. This unique population may have specific genomic or inflammation-related risk factors that may play more important roles in disease susceptibility. Prospective analysis may allow early identification of at-risk patients, creation of novel therapeutics, and improved understanding of how and why C. difficile colonization transforms into infection after severe blunt trauma.

Bone marrow-derived antigen-presenting cells (APCs) play a central role in the induction of tolerance to tumor antigens expressed by B-cell lymphomas. Here we show that in vivo disruption of this APC-mediated tolerogenic mechanism unveils an intrinsic ability of malignant B cells to efficiently present tumor antigens to antigen-specific CD4+ T cells, resulting in a strong antitumor effect. This intrinsic antigen-presenting ability of malignant B cells is, however, overridden by tolerogenic bone marrow-derived APCs, leading instead to T-cell unresponsiveness and lack of antitumor effect. These results highlight the concept that therapeutic strategies aimed at enhancing the antigen-presenting function of B-cell lymphomas might not succeed unless the tolerogenic mechanisms mediated by bone marrow-derived APCs are disrupted in the first place.

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Antigen-presenting cells (APCs) can induce T cell activation as well as T cell tolerance. The molecular mechanisms by which APCs regulate this critical decision of the immune system are not well understood. Here we show that Stat3 signaling plays a critical role in the induction of antigen-specific T cell tolerance. Targeted disruption of Stat3 signaling in APCs resulted in priming of antigen-specific CD4+ T cells in response to an otherwise tolerogenic stimulus in vivo. Furthermore, APCs devoid of Stat3 effectively break antigen-specific T cell anergy in vitro. Conversely, increased Stat3 activity in APCs led to impaired antigen-specific T cell responses. Stat3 signaling provides, therefore, a novel molecular target for manipulation of immune activation/tolerance, a central decision with profound implications in autoimmunity, transplantation, and cancer immunotherapy.

Over one million newborns die annually from sepsis with the highest mortality in premature and low-birthweight infants. The inflammasome plays a central role in the regulation of innate immunity and inflammation, and is presumed to be involved in protective immunity, in large part through the caspase-1-dependent activation of interleukin-1β (IL-1β) and IL-18. Studies in endotoxic shock, however, suggest that endogenous caspase-1 activity and the inflammasome contribute to mortality primarily by promoting excessive systemic inflammatory responses. We examined whether caspase-1 and the inflammasome also regulate neonatal inflammation, host protective immunity and myelopoiesis during polymicrobial sepsis. Neonatal (5-7 days) C57BL/6 and caspase-1/11(-/-) mice underwent a low-lethality caecal slurry model of intra-abdominal sepsis (LD25-45 ). Ablation of caspase-1/11, but not apoptosis-associated speck-like protein containing a CARD domain or nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3), improved neonatal survival following septic challenge compared with wild-type mice (P < 0·001), with decreased concentrations of inflammatory cytokines in the serum and peritoneum. Surprisingly, caspase-1/11(-/-) neonates also exhibited increased bone marrow and splenic haematopoietic stem cell expansion (P < 0·001), and increased concentrations of granulocyte and macrophage colony-stimulating factors in the peritoneum (P < 0·001) after sepsis. Ablation of caspase-1/11 signalling was also associated with increased recruitment of peritoneal macrophages and neutrophils (P < 0·001), increased phagocytosis by neutrophils (P = 0·003), and decreased bacterial colonization (P = 0·02) in the peritoneum. These findings suggest that endogenous caspase-1/11 activity, independent of the NLRP3 inflammasome, not only promotes the magnitude of the inflammatory response, but also suppresses protective immunity in the neonate, so contributing to innate immune dysfunction and poor survival in neonatal sepsis.

Neonates have increased susceptibility to infection, which leads to increased mortality. Whether or not this as a result of implicit deficits in neonatal innate immune function or recapitulation of innate immune effector cell populations following infection is unknown. Here, we examine the process of emergency myelopoiesis whereby the host repopulates peripheral myeloid cells lost following the initial infectious insult. As early inflammatory responses are often dependent upon NF-κB and type I IFN signaling, we also examined whether the absence of MyD88, TRIF or MyD88 and TRIF signaling altered the myelopoietic response in neonates to polymicrobial sepsis. Following neonatal polymicrobial septic challenge, hematopoietic stem cell (HSC) expansion in bone marrow and the spleen were both attenuated and delayed in neonates compared with adults. Similar reductions in other precursors were observed in neonates. Similar to adult studies, the expansion of progenitor stem cell populations was also seen in the absence of MyD88 and/or TRIF signaling. Overall, neonates have impaired emergency myelopoiesis in response to sepsis compared with young adults. Despite reports that this expansion may be related to TLR signaling, our data suggest that other factors may be important, as TRIF–/– and MyD88–/– neonatal HSCs are still able to expand in response to polymicrobial neonatal sepsis.

Tumor antigen-specific T-cell tolerance may limit the efficacy of therapeutic cancer vaccines. Direct presentation of antigens by tumor cells incapable of providing adequate costimulation to tumor-specific T cells has been suggested as the basis for this unresponsiveness. Using parent-into-F1 bone marrow (BM) chimeras, this study unambiguously demonstrates that the induction of this tolerant state requires T-cell recognition of tumor antigen presented by BM-derived antigen-presenting cells (APCs), not tumor cells themselves. In the absence of host APC presentation, tumor-specific T cells remained functional, even in the setting of antigen expressed by B-cell lymphomas residing in secondary lymphoid tissues. The intrinsic APC capacity of tumor cells has therefore little influence over T-cell priming versus tolerance, a decision that is regulated at the level of host APCs. (Blood. 2001;98:1070-1077)

We recently proffered that a new syndrome persistent inflammation, immunosuppression, and catabolism syndrome (PICS) has replaced late multiple-organ failure as a predominant phenotype of chronic critical illness. Our goal was to validate this by determining whether severely injured trauma patients with complicated outcomes have evidence of PICS at the genomic level.We performed a secondary analysis of the Inflammation and Host Response to Injury database of adults with severe blunt trauma. Patients were classified into complicated, intermediate, and uncomplicated clinical trajectories. Existing genomic microarray data were compared between cohorts using Ingenuity Pathways Analysis. Epidemiologic data and outcomes were also analyzed between cohorts on admission, Day 7, and Day 14.Complicated patients were older, were sicker, and required increased ventilator days compared with the intermediate/uncomplicated patients. They also had persistent leukocytosis as well as low lymphocyte and albumin levels compared with uncomplicated patients. Total white blood cell leukocyte analysis in complicated patients showed that overall genome-wide expression patterns and those patterns on Days 7 and 14 were more aberrant from control subjects than were patterns from uncomplicated patients. Complicated patients also had significant down-regulation of adaptive immunity and up-regulation of inflammatory genes on Days 7 and 14 (vs. magnitude in fold change compared with control and in magnitude compared with uncomplicated patients). On Day 7, complicated patients had significant changes in functional pathways involved in the suppression of myeloid cell differentiation, increased inflammation, decreased chemotaxis, and defective innate immunity compared with uncomplicated patients and controls. Subset analysis of monocyte, neutrophil, and T-cells supported these findings.Genomic analysis of patients with complicated clinical outcomes exhibit persistent genomic expression changes consistent with defects in the adaptive immune response and increased inflammation. Clinical data showed persistent inflammation, immunosuppression, and protein depletion. Overall, the data support the hypothesis that patients with complicated clinical outcomes are exhibiting PICS.Epidemiologic study, level III.

Blood transfusion is a well-established risk factor for adverse outcomes during sepsis. The specific mechanisms responsible for this effect remain elusive, and few studies have investigated this phenomenon in a model that reflects not only the clinical circumstances in which blood is transfused, but also how packed red blood cells (PRBCs) are created and stored. Using a cecal ligation and puncture model of polymicrobial sepsis as well as creating murine allogeneic and stored PRBCs in a manner that replicates the clinical process, we have demonstrated that transfusion of PRBCs induces numerous effects on leukocyte subpopulations. In polymicrobial sepsis, these responses are profoundly dissimilar to the proinflammatory effects of PRBC transfusion observed in the healthy mouse. Transfused septic mice, as opposed to mice receiving crystalloid resuscitation, had a significant loss of blood, spleen, and bone marrow lymphocytes, especially those with an activated phenotype. Myeloid cells behaved similarly, although they were able to produce more reactive oxygen species. Overall, transfusion in the septic mouse may contribute to the persistent immune dysfunction known to be associated with this process, rather than simply promote proinflammatory or anti-inflammatory effects on the host. Thus, it is possible that blood transfusion contributes to the multiple known effects of sepsis on leukocyte populations that have been shown to result in increased morbidity and mortality.

Through improvements in supportive care measures over the last few decades, such as those guidelines based on the `Surviving Sepsis Campaign' and early goal directed therapy trials, we have been able to survive most of our patients through the initial systemic inflammatory response period [1, 2]. Unfortunately, a significant portion of patients still have protracted hospital courses and eventually succumb to late nosocomial infections [3]. These late sepsis associated morbidities are thought to be related to global host immunosuppression. Though this is not a newly described phenomenon, there is still considerable controversy as to how this immunosuppression occurs [4, 5]. Many investigators, including ourselves, have demonstrated extensive lymphocyte and antigen presenting cell apoptosis in secondary lymphoid organs [6–8]. In addition, the presence of T cell exhaustion, as well as the expansion of regulatory T cell populations, has been described in both septic humans and mice [9–11]. Also, we and others have demonstrated the expansion of an immature myeloid population, known as myeloid derived suppressor cells (MDSCs), occurs following sepsis [12, 13]. However the question remains, which of these phenomena, if any, contribute to or are critical for persistent inflammation and the late global immunosuppression that leads to protein wasting and the increased prevalence of nosocomial infections in our septic patients? Despite the large body of data that exists looking at each one of these cell populations, there is no consensus, and the answer is more than likely multifactorial. In addition, though the presence of these cell populations may be associated with late mortality and morbidity in sepsis, the role they play in the early response to sepsis may be critical to mitigate the deleterious effects of the systemic inflammatory response syndrome. This is more than likely true of the MDSC, which despite its well publicized deleterious effects on tumor immune surveillance, may actually be a critically important component of the innate immune response following septic insult. Originally described in the cancer literature, it is now clear that MDSCs, roughly characterized as CD11b+Gr-1+ cells, arise in many pathologic processes including autoimmunity and burn/trauma injury [12]. MDSCs are purported to suppress immunosurveillance during tumorigenesis, through the production of arginase, reactive oxygen species, and/or inducible nitric oxide, though their role in sepsis is less clear. Delano et al. originally described a dramatic expansion of MDSCs following murine polymicrobial sepsis and demonstrated that these cells may indeed suppress adaptive immune responses [12]. However since then, several groups including ourselves, have demonstrated that this expansion of MDSCs during sepsis may actually be protective [14, 15]. The current report in Intensive Care Medicine by Derive et al. explores this subject further. Though many investigators have ascribed one standard phenotype to MDSCs, Derive and colleagues demonstrate a phenotypic change in the CD11b+Gr-1+ cells isolated at day 3 following sepsis compared to the CD11b+Gr-1+ isolated 10 days after polymicrobial sepsis. We have also shown such a phenotypic change in neutrophils (CD11b+Gr-1+ cells) from the bronchiolar lavages of septic mice and shown that neutrophils isolated day 3 following sepsis produced significantly less ROS compared to neutrophils isolated 7 days following sepsis and were less mature [15]. Derive et al. demonstrates a similar decrease in ROS in response to IL-6 at day 3 but an increase in ROS production in MDSCs isolated from mice 10 days post sepsis. They also show that day 3 MDSCs produce significantly less cytokines in response to LPS stimulation than MDSCs isolated from mice day 10 post sepsis. These data together with gene expression array data from MDSCs isolated from mice either at day 3 vs day 10 following sepsis suggest that CD11b+Gr-1+ cells isolated 3 days following sepsis expand but are not capable of being activated until days 7–10. In addition, the authors also demonstrate that MDSCs isolated from mice day 10 following sepsis are able to attenuate inflammatory cytokines locally, facilitate bacterial clearance, and overall improves survival to polymicrobial sepsis. This data is similar to the findings of Sander et al., who showed that the MDSCs that expand following septic insult suppress inflammatory responses and may indeed be protective [14]. However, taken together with the data that demonstrate that MDSCs suppress T cell responses, it's easy to see how the robust expansion of these cells that occur following sepsis may also contribute to adaptive immunosuppression. Unfortunately, these data also exemplify the difficulty in defining a discreet novel population in the MDSC from traditional innate immune effector cells, such as the neutrophil, using only the cell surface markers, CD11b+Gr-1+. In the adult, CD11b+Gr-1+ can encompass neutrophil, monocyte, and MDSC populations, which are clearly heterogenous, comprised of both granulocytic and monocytic subsets [17]. The authors do demonstrate that these MDSCs can suppress adaptive immune responses, which is one of the defining characteristics of the MDSC but again, are the authors looking at the MDSC or the more mature neutrophil? Is there a difference between these two cell populations or are the neutrophils that expand following the initial `left' shift that typically follows severe infection represent a compartment of these MDSCs? More than likely, as the data the authors and other investigators have suggested, the MDSC and the phenotypic changes that occur following sepsis are part of the primary myeloid compartment reconstitution that occurs following infection, otherwise known as emergency myelopoiesis[18]. As `MDSCs' emerge from the bone marrow in an attempt to localize and clear the infectious insult, they represent a continuum from immature to mature activated innate immune effector cells that are, at least in the mouse, protective to the initial septic hit. However, is it the absence of activated MDSCs in some patients following sepsis the reason why our patients subsequently succumb to nosocomial infection? Is it the expansion of MDSCs in the host following sepsis that leads to global adaptive immune suppression and secondary infection in the sepsis patient? The answer is unknown, as the corollary for the MDSC in human sepsis has yet to be identified. Once this has been established, more work will be needed to understand clearly what their role is in our critically ill patient populations and whether or not the MDSC is truly the friend or the foe. More than likely, it will be both.

To determine and compare outcomes with accepted benchmarks in trauma care at 7 academic level I trauma centers in which patients were treated on the basis of a series of standard operating procedures (SOPs).Injury remains the leading cause of death for those younger than 45 years. This study describes the baseline patient characteristics and well-defined outcomes of persons hospitalized in the United States for severe blunt trauma.We followed 1637 trauma patients from 2003 to 2009 up to 28 hospital days using SOPs developed at the onset of the study. An extensive database on patient and injury characteristics, clinical treatment, and outcomes was created. These data were compared with existing trauma benchmarks.The study patients were critically injured and were in shock. SOP compliance improved 10% to 40% during the study period. Multiple organ failure and mortality rates were 34.8% and 16.7%, respectively. Time to recovery, defined as the time until the patient was free of organ failure for at least 2 consecutive days, was developed as a new outcome measure. There was a reduction in mortality rate in the cohort during the study that cannot be explained by changes in the patient population.This study provides the current benchmark and the overall positive effect of implementing SOPs for severely injured patients. Over the course of the study, there were improvements in morbidity and mortality rates and increasing compliance with SOPs. Mortality was surprisingly low, given the degree of injury, and improved over the duration of the study, which correlated with improved SOP compliance.

Previous studies have suggested that neonates rely heavily on innate immunity for their antimicrobial response to bacterial infections. However, the innate immune response by neonates to bacterial infection remains poorly characterized. Here, we show that in a murine model of neonatal polymicrobial sepsis, CXC ligand 10 (CXCL10) concentrations increase in the blood and peritoneum concordant with the peritoneal recruitment of granulocytes and macrophages. Additionally, CXC receptor 3 (CXCR3) expression on elicited peritoneal macrophages and granulocytes increases following sepsis. Blockade of CXCL10 worsens not only recruitment and phagocytic function of peritoneal granulocytes and macrophages but also survival. Deletion of CXCR3 also significantly increases mortality to a septic challenge. Finally, we demonstrate that the protective adjuvant effect of pretreatment with a Toll-like receptor 4 agonist to neonatal sepsis is dependent on an endogenous CXCL10 response and that pretreatment of neonates with CXCL10 can also significantly improve macrophage and granulocyte function and modestly improve outcome to polymicrobial sepsis. Together, these data suggest a critical role for CXCL10 signaling during neonatal sepsis.

Neutrophils are essential for successful host eradication of bacterial pathogens and for survival to polymicrobial sepsis. During inflammation, the bone marrow provides a large reserve of neutrophils that are released into the peripheral circulation where they traverse to sites of infection. Although neutrophils are essential for survival, few studies have investigated the mechanisms responsible for neutrophil mobilization from the bone marrow during polymicrobial sepsis. Using a cecal ligation and puncture model of polymicrobial sepsis, we demonstrated that neutrophil mobilization from the bone marrow is not dependent on TLR4, MyD88, TRIF, IFNARα/β, or CXCR2 pathway signaling during sepsis. In contrast, we observed that bone marrow CXCL12 mRNA abundance and specific CXCL12 levels are sharply reduced, whereas splenic CXCR4 mRNA and cell surface expression are increased during sepsis. Blocking CXCL12 activity significantly reduced blood neutrophilia by inhibiting bone marrow release of granulocytes during sepsis. However, CXCL12 inhibition had no impact on the expansion of bone marrow neutrophil precursors and hematopoietic progenitors. Bone marrow neutrophil retention by CXCL12 blockade prevented blood neutrophilia, inhibited peritoneal neutrophil accumulation, allowed significant peritoneal bacterial invasion, and increased polymicrobial sepsis mortality. We concluded that changes in the pattern of CXCL12 signaling during sepsis are essential for neutrophil bone marrow mobilization and host survival but have little impact on bone marrow granulopoiesis.