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Preterm infants often show pathologies of the cerebellum, which are associated with impaired motor performance, lower IQ and poor language skills at school ages. Using a mouse model of inflammation-induced encephalopathy of prematurity driven by systemic administration of pro-inflammatory IL-1β, we sought to uncover causes of cerebellar damage. In this model, IL-1β is administered between postnatal day (P) 1 to day 5, a timing equivalent to the last trimester for brain development in humans. Structural MRI analysis revealed that systemic IL-1β treatment induced specific reductions in gray and white matter volumes of the mouse cerebellar lobules I and II (5% false discovery rate [FDR]) from P15 onwards. Preceding these MRI-detectable cerebellar volume changes, we observed damage to oligodendroglia, with reduced proliferation of OLIG2+ cells at P10 and reduced levels of the myelin proteins myelin basic protein (MBP) and myelin-associated glycoprotein (MAG) at P10 and P15. Increased density of IBA1+ cerebellar microglia were observed both at P5 and P45, with evidence for increased microglial proliferation at P5 and P10. Comparison of the transcriptome of microglia isolated from P5 cerebellums and cerebrums revealed significant enrichment of pro-inflammatory markers in microglia from both regions, but cerebellar microglia displayed a unique type I interferon signaling dysregulation. Collectively, these data suggest that perinatal inflammation driven by systemic IL-1β leads to specific cerebellar volume deficits, which likely reflect oligodendrocyte pathology downstream of microglial activation. Further studies are now required to confirm the potential of protective strategies aimed at preventing sustained type I interferon signaling driven by cerebellar microglia as an important therapeutic target., (© 2022 The Authors. GLIA published by Wiley Periodicals LLC.)

Background: Necrotising enterocolitis (NEC) is a devastating bowel disease, primarily affecting premature infants, with a poorly understood aetiology. Prior studies have found associations in different cases with an overabundance of particular elements of the faecal microbiota (in particular Enterobacteriaceae or Clostridium perfringens), but there has been no explanation for the different results found in different cohorts. Immunological studies have indicated that stimulation of the TLR4 receptor is involved in development of NEC, with TLR4 signalling being antagonised by the activated TLR9 receptor. We speculated that differential stimulation of these two components of the signalling pathway by different microbiota might explain the dichotomous findings of microbiota-centered NEC studies. Here we used shotgun metagenomic sequencing and qPCR to characterise the faecal microbiota community of infants prior to NEC onset and in a set of matched controls. Bayesian regression was used to segregate cases from control samples using both microbial and clinical data., Results: We found that the infants suffering from NEC fell into two groups based on their microbiota; one with low levels of CpG DNA in bacterial genomes and the other with high abundances of organisms expressing LPS. The identification of these characteristic communities was reproduced using an external metagenomic validation dataset. We propose that these two patterns represent the stimulation of a common pathway at extremes; the LPS-enriched microbiome suggesting overstimulation of TLR4, whilst a microbial community with low levels of CpG DNA suggests reduction of the counterbalance to TLR4 overstimulation., Conclusions: The identified microbial community patterns support the concept of NEC resulting from TLR-mediated pathways. Identification of these signals suggests characteristics of the gastrointestinal microbial community to be avoided to prevent NEC. Potential pre- or pro-biotic treatments may be designed to optimise TLR signalling., (© 2021. The Author(s).)

Background: Very preterm infants are at high risk of developing chronic lung disease, which requires respiratory support and might have long-term sequelae. As lung inflammation plays an important role in pathogenesis, antileukotrienes have been explored in both clinical and animal studies. We aimed to assess the benefits and harms of antileukotrienes for the prevention and treatment of respiratory morbidity and mortality in very preterm newborns., Methods: In this systematic review, we included randomized trials and non-randomized studies in humans and animals reporting the effects of antileukotrienes in very preterm infants or other mammals within 10 days of birth. Our pre-specified primary outcomes were all-cause mortality and any harm, and, for the clinical studies, incidence of chronic lung disease. Included studies underwent risk of bias-assessment and data extraction performed by two authors independently. There were no language restrictions., Results: Fifteen studies totally met our inclusion criteria: one randomized trial and four non-randomized studies in humans and 10 animal studies (five in rodents, two in lambs and one in either guinea pigs, rabbits or caprinae). All five clinical studies used montelukast and had a small sample size, ranging from 4 to 77 infants. The randomized trial (n = 60) found no difference in the incidence of chronic lung disease between the groups. Only one clinical study, which enrolled four very preterm infants and had a critical overall risk of bias, reported long-term outcomes. All other studies had unclear or greater overall risk of bias and meta-analyses were therefore deemed unfeasible. Eight of ten animal studies used leukotriene receptor antagonists as antileukotriene (montelukast in three of ten studies) and seven had an experimental study design (i.e. some animals were not exposed to antileukotrienes but no randomization). Three of the ten animal studies assessed different doses. Animal studies found no effect on the outcomes mortality, growth, or lung function related surrogate outcomes., Conclusions: Use of antileukotrienes in very preterm infants to prevent or treat chronic lung disease is not supported by the available evidence. Large randomized trials focusing on outcomes relevant to patients, including long-term outcomes, are needed. Studies should also minimize risk of bias., (© 2021. The Author(s).)

The fetus can deploy a local or systemic inflammatory response when exposed to microorganisms or, alternatively, to non-infection-related stimuli (e.g., danger signals or alarmins). The term "Fetal Inflammatory Response Syndrome" (FIRS) was coined to describe a condition characterized by evidence of a systemic inflammatory response, frequently a result of the activation of the innate limb of the immune response. FIRS can be diagnosed by an increased concentration of umbilical cord plasma or serum acute phase reactants such as C-reactive protein or cytokines (e.g., interleukin-6). Pathologic evidence of a systemic fetal inflammatory response indicates the presence of funisitis or chorionic vasculitis. FIRS was first described in patients at risk for intraamniotic infection who presented preterm labor with intact membranes or preterm prelabor rupture of the membranes. However, FIRS can also be observed in patients with sterile intra-amniotic inflammation, alloimmunization (e.g., Rh disease), and active autoimmune disorders. Neonates born with FIRS have a higher rate of complications, such as early-onset neonatal sepsis, intraventricular hemorrhage, periventricular leukomalacia, and death, than those born without FIRS. Survivors are at risk for long-term sequelae that may include bronchopulmonary dysplasia, neurodevelopmental disorders, such as cerebral palsy, retinopathy of prematurity, and sensorineuronal hearing loss. Experimental FIRS can be induced by intra-amniotic administration of bacteria, microbial products (such as endotoxin), or inflammatory cytokines (such as interleukin-1), and animal models have provided important insights about the mechanisms responsible for multiple organ involvement and dysfunction. A systemic fetal inflammatory response is thought to be adaptive, but, on occasion, may become dysregulated whereby a fetal cytokine storm ensues and can lead to multiple organ dysfunction and even fetal death if delivery does not occur ("rescued by birth"). Thus, the onset of preterm labor in this context can be considered to have survival value. The evidence so far suggests that FIRS may compound the effects of immaturity and neonatal inflammation, thus increasing the risk of neonatal complications and long-term morbidity. Modulation of a dysregulated fetal inflammatory response by the administration of antimicrobial agents, anti-inflammatory agents, or cell-based therapy holds promise to reduce infant morbidity and mortality., (Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).)

The fetal inflammatory response syndrome (FIRS) is characterized by umbilical cord inflammation and elevated fetal pro-inflammatory cytokines. Surviving neonates, especially very preterm infants, have increased rates of neonatal morbidity including neurodevelopmental impairment. The mechanism of brain injury in FIRS is complex and may involve "multiple hits." Exposure to in utero inflammation initiates a cascade of the fetal immune response, where pro-inflammatory cytokines can cause direct injury to oligodendrocytes and neurons. Activation of microglia results in further injury to vulnerable pre-myelinating oligodendrocytes and influences the integrity of the fetal and newborn's blood-brain barrier, resulting in further exposure of the brain to developmental insults. Newborns exposed to FIRS are frequently exposed to additional perinatal and postnatal insults that can result in further brain injury. Future directions should include evaluations for new therapeutic interventions aimed at reducing brain injury by dampening FIRS, inhibition of microglial activation, and regeneration of immature oligodendrocytes., (© 2020 Published by Elsevier Ltd.)

Introduction: Deficiencies in innate immune responses may contribute to the increased susceptibility to infection in preterm infants. In vivo cytokine profiles in response to sepsis in very preterm infants are not fully understood., Aims: To characterise plasma pro- and anti-inflammatory cytokine concentrations and pre-defined ratios in very preterm infants with late-onset sepsis (LOS)., Methods: In this observational study, peripheral blood samples were collected at the time of evaluation for suspected LOS from 31 preterm infants (<30 weeks gestational age). Plasma cytokine concentrations were determined by 12-plex immunoassay., Results: IL-10, IFN-γ, IL-12p70, IP-10, IL-6 and CCL2 were elevated in the majority infants with LOS (n = 12) compared to those without LOS (n = 19). There was no difference in TNF-α, IL-1β, IL-17AF, IL-8 and IL-15 concentrations between groups. IL-10/TNF-α ratios were increased, while CCL2/IL-10 and IL-12p70/IL-10 ratios were decreased in infants with LOS compared to those without., Conclusion: Very preterm infants have a marked innate inflammatory response at the time of LOS. The increase in IL-10/TNF-α ratio may indicate early immune hypo-responsiveness. Longitudinal studies with a larger number of participants are required to understand immune responses and clinical outcomes following LOS in preterm infants., Competing Interests: The authors have declared that no competing interests exist.

Introduction : Mortality due to sepsis is still prevalent, peaking at extreme ages of life including infancy. Despite many efforts, the peculiarity of the infant immune system has limited further advances in its treatment. Indeed, neonates experience a dramatic physiological transition from immune tolerance to the maternal antigens to functional maturity. Such a transition is extremely dynamic, as is the pathophysiology of infant sepsis, which is dependent on many infant, maternal, and environmental factors. Areas covered : In this review, the authors critically update and summarize the current paradigm of immunomodulation in infant sepsis. They confirm how exogenous stimulation of the immune system through intravenous immunoglobulin, colony stimulating factors, and granulocyte transfusion have failed to impact on the prognosis of infant sepsis. They also strongly support the beneficial effects of supplementation/replacement therapies with products naturally contained within maternal milk as well as antioxidant compounds. Expert opinion : Breastfeeding is beneficial against sepsis. Knowledge of the neonatal immune system is indeed too limited to effectively strengthen immune response by exogenous interventions, especially in preterm and low-birth-weight infants. Awareness of this limitation should pave the way for future studies (e.g. gender- and omics -based) aimed at better characterizing the infant immune system and promoting a more tailored approach.

Necrotizing enterocolitis (NEC) is a poorly defined disease that primarily affects preterm infants. There has not been much progress in the prevention or treatment of NEC since it became recognized as a common problem in preterm infants. Reasons for this lack of progress include the likelihood that different diseases are being put under the same moniker of "NEC," similar to using "diabetes" for the different diseases it represents. In order to make progress, better delineation of the phenotypes that present as NEC will be necessary to clearly establish their pathophysiology, find specific and sensitive biomarkers, and establish preventative regimens. In this review, we summarize some of the entities that are being called NEC, discuss the pathophysiology of the most classic form of NEC, and provide an overview of how we might proceed in the future to make progress in this field.

Background: Neonatal infections are a leading cause of morbi-mortality despite advances in antimicrobials and neonatal care. Preterm infants have greater susceptibility to sepsis due to an immature immune system and lower immunoglobulin levels. Intravenous immunoglobulins (IVIG) have been used in several studies as an adjuvant treatment to improve this physiological immune deficiency, with different outcomes., Methods: Very low birth weight (VLBW) infants who developed sepsis in the neonatal ICU were studied. They were randomly divided in 2 groups: one group was treated with antibiotics (Group I), and the other received antibiotics plus a 500 mg/kg/day of IVIG during 7 days (Group II). Serum IgG concentration was determined at initiation, during and after treatment Group I, and daily during the 7 days of therapy in Group II., Results: The baseline IgG concentration in group II was 486 g/dL, and increased to 852 mg/dL after the first dose of IVIG (p < 0.01). After the seventh day of infusion a mean IgG level of 1898 mg/dL was achieved. A direct correlation (r = 0.94) between IgG concentration and days of treatment was observed. Blood cultures were positive in 70% of the infants in group I and 75.5% in group II. Staphylococcus epidermidis was the most frequent isolated bacteria in blood cultures. The lethality rate was 25.0% in group I and 5.0% in Group II (p < 0.03). We did not observe collateral effects with the administration of IVIG., Conclusions: Prolonged therapy with IVIG seems to be safe and effective as an adjuvant treatment in VLBW infants with sepsis.

Infants born prematurely (before completion of 37 weeks of gestation) are at increased risk of morbidity and mortality due to vaccine preventable diseases, mostly because of their immunological immaturity and failure of transfer of maternal protective antibodies. Despite their great need of being vaccinated, concerns on vaccine safety and efficacy, constitute the main reasons for which vaccinations are often delayed in this group. In this review we summarize the latest evidence on vaccine safety, efficacy and immunogenicity in preterm infants which is similar to full-term infants. Therefore there is no reason for delaying vaccination in this population., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: Differences in the susceptibility of preterm infants to develop necrotizing enterocolitis (NEC) implicate potential genetic differences in response to the inflammatory stimuli leading to NEC. Dual specificity phosphatases (DUSPs) are a key suppressor pathway of the mitogen-activated protein kinase (MAPK) pro-inflammatory signaling pathway. We hypothesized that inherited single nucleotide polymorphisms (SNPs) in DUSP genes contribute to NEC susceptibility in premature infants., Methods: Patients admitted between 2010 and 2015 born at <  32 weeks GA and≤1,500 g BW with stage II+NEC (cases; n = 50) and age, weight-matched controls (n = 38) were included. Blood samples were collected for DNA isolation. Agena Mass Array assay was used to examine 31 SNPs in 9 different DUSP genes. Calculated minor allele frequencies (MAF) for cases and controls were compared using χ2 and logistic regression., Results: The presence of the rs704074 SNP was associated with a 48% decreased risk of developing NEC (OR 0.52; 95% CI 0.27- 1.01, p = 0.04). The odds of surgical NEC decreased by 78% (OR 0.22; 95% CI 0.06- 0.84, p = 0.027) for each copy of rs704074/G allele in patients with NEC., Conclusion: In this small single-center pilot study, DUSP-6 SNP (rs704074) was associated with a lower risk of developing NEC and surgical NEC, the most severe form of NEC, in preterm infants.

Objectives: Immunizations provide important protection from serious childhood illnesses. Infant chronic lung disease (CLD) is a serious complication of prematurity and predisposes premature infants to respiratory morbidity, rehospitalization, and mortality. This high-risk group is especially vulnerable to infections, such as invasive pneumococcal disease, influenza, and bronchiolitis. Our purpose for this project was to increase 2-, 4-, and 6-month immunization rates in eligible infants with CLD in the NICU by 30% through December 2016., Methods: A multidisciplinary team developed weekly targeted rounds to identify eligible patients with outstanding immunizations. Exclusion criteria included the following: (1) a fraction of inspired oxygen requirement of >80%, (2) pulmonary hypertensive crisis, (3) positive blood culture results or if within 48 hours of a sepsis evaluation, (4) if within 5 days of a surgical or interventional procedure, (5) receiving steroid treatment (not including a physiologic hydrocortisone dose for adrenal insufficiency), (6) a CLD team consensus of contraindication, and (7) parental refusal., Results: The project managed 60 patients from March 2016 to December 2016. Immunization of eligible patients increased from 44% to 75% and was sustained for the next 6 months. The average number of days from admission to immunization record review decreased from 71 days at baseline to 27 days., Conclusions: The implementation of (1) an in-hospital immunization record review, (2) an e-mail reminder, (3) a weekly multidisciplinary eligibility discussion, and (4) an updated rounding tool was successful in increasing and sustaining immunization rates in this population of infants with CLD. The multidisciplinary CLD meeting was a novel opportunity to discuss immunization eligibility and safety monitoring., Competing Interests: POTENTIAL CONFLICT OF INTEREST: The authors have indicated they have no potential conflicts of interest to disclose., (Copyright © 2018 by the American Academy of Pediatrics.)

One in 10 newborns will be born before completion of 36 weeks' gestation (premature birth). Infection and sepsis in preterm infants remain a significant clinical problem that represents a substantial financial burden on the healthcare system. Many factors predispose premature infants for having the greatest risk of developing and succumbing to infection as compared with all other age groups across the age spectrum. It is clear that the immune system of preterm infants exhibits distinct, rather than simply deficient, function as compared with more mature and older humans and that the immune function in preterm infants contributes to infection risk. While no single review can cover all aspects of immune function in this population, we will discuss key aspects of preterm neonatal innate and adaptive immune function that place them at high risk for developing infections and sepsis, as well as sepsis-associated morbidity and mortality., Competing Interests: Competing interests: None declared., (© Article author(s) (or their employer(s) unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

Objectives: The aim of this study was to determine the effect of digested whole human milk (HM; first sample available after birth from mothers of premature infants) on inflammation, oxidative stress, and cytotoxicity in Caco-2 human intestinal epithelial cells stimulated with lipopolysaccharides or tumor necrosis factor (TNF) to mimic the potential in vivo insults facing the premature infant's gastrointestinal tract., Methods: Fully differentiated Caco-2 cells were exposed to digested HM (n = 10; samples from 10 different individuals) before stimulation with lipopolysaccharides, TNF, or no stimulation overnight. Inflammation was determined by production of interleukin-8, oxidative stress by levels of F2-isoprostane, and cytotoxicity by released lactate dehydrogenase., Results: HM significantly suppressed interleukin-8 production and cytotoxicity in TNF-stimulated cells, while also suppressing cell death under baseline conditions. Individual HM samples differed widely in their ability to modulate cellular responses., Conclusions: Results from this study provide evidence that digested HM can reduce both an exaggerated inflammatory response and intestinal damage that contribute to the pathogenesis of necrotizing enterocolitis.

Preterm birth accounts for nearly one million deaths among children under five years of age, and although its etiopathogenesis is not fully elucidated, ascending intrauterine infection and fetal inflammatory response seem to be the main triggers. The intense inflammatory response mediated by IL-1β, TNF-α, PAF, IFN-γ and IL-6, PGE 2 and MMP-1 and MMP-9 causes fetal membrane damage and rupture, increased uterine contractions and biochemical and structural changes in the cervix. Furthermore, preterm neonates have deficient innate and adaptive immune responses characterized by reduced levels of IgG, opsonization and phagocytosis, as well as increased activation of Th1 cells in relation to Th2 cells. Therefore, this triad is favors the occurrence of neonatal complications, such as respiratory distress syndrome, necrotizing enterocolitis, retinopathy of prematurity and bronchopulmonary dysplasia. Due to serious maternal and child health complications of intrauterine infection, several studies have tried to identify biomarkers for the early diagnosis of this entity. This literature review aims to discuss the main scientific findings regarding the association between ascending intrauterine infection, immune system and preterm birth.

The aim of the study was to determine whether routine probiotic supplementation (RPS) with Lactobacillus rhamnosus GG (LGG) or Lactobacillus acidophilus +Lactobacillus bifidum is associated with reduced risk of necrotising enterocolitis (NEC)≥Stage II in preterm neonates born at ≤32 weeks' gestation. We conducted a retrospective cohort study on the effect of probiotic supplementation in very low birth weight infants in our neonatal unit by comparing two periods: before and after supplementation. The incidence of NEC≥Stage II, late-onset sepsis and all-cause mortality was compared for an equal period 'before' (Period I) and 'after' (Period II) RPS with LGG or L. acidophillus+L. bifidum. Multivariate logistic regression analysis was conducted to adjust for relevant confounders. The study population was composed of 261 neonates (Period I v. II: 134 v. 127) with comparable gestation duration and birth weights. In <32 weeks, we observed a significant reduction in NEC≥Stage II (11·3 v. 4·8 %), late-onset sepsis (16 v. 10·5 %) and mortality (19·4 v. 2·3 %). The benefits in neonates aged ≤27 weeks did not reach statistical significance. RPS with LGG or L. acidophillus+L. bifidum is associated with a reduced risk of NEC≥Stage II, late-onset sepsis and mortality in preterm neonates born at ≤32 weeks' gestation.

Necrotizing enterocolitis (NEC), a disease most commonly seen in preterm infants, often presents without warning and is associated with very high mortality and morbidity. Progress in the prevention and treatment of NEC has been slow. In this article, we will discuss some of the reasons as to why this progress has been slow. We will describe some of the factors that appear to be highly associated and important components in the pathophysiology of NEC. We will discuss the intestinal microbial environment of the fetus as well as the preterm infant and how interaction of dysbiosis with an immature gastrointestinal tract combined with dietary factors play a role in the pathogenesis of NEC. Testable hypotheses are discussed as well as how these may lead to not only a better understanding of the pathophysiology of the disease but also the preventative strategies., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Necrotizing enterocolitis (NEC) is a devastating disease in premature infants with high case fatality and significant morbidity among survivors. Immaturity of intestinal host defenses predisposes the premature infant gut to injury. An abnormal bacterial colonization pattern with a deficiency of commensal bacteria may lead to a further breakdown of these host defense mechanisms, predisposing the infant to NEC. Here, we review the role of the innate and adaptive immune system in the pathophysiology of NEC., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Cytokines and growth factors play diverse roles in the uninflamed fetal/neonatal intestinal mucosa and in the development of inflammatory bowel injury during necrotizing enterocolitis (NEC). During gestational development and the early neonatal period, the fetal/premature intestine is exposed to high levels of many "inflammatory" cytokines and growth factors, first via swallowed amniotic fluid in utero and then, after birth, in colostrum and mother's milk. This article reviews the dual, seemingly counter-intuitive roles of cytokines, where these agents play a "trophic" role and promote maturation of the uninflamed mucosa, but can also cause inflammation and promote intestinal injury during NEC., (Copyright © 2016 Elsevier Inc. All rights reserved.)

An underlying genetic predisposition to necrotizing enterocolitis (NEC) is increasingly being recognized. Candidate gene or pathway approaches as well as genome-wide approaches are beginning to identify potential pathogenic variants for NEC in premature infants. However, a majority of these studies have not yielded definitive results because of limited sample size and lack of validation. Despite these challenges, understanding the contribution of genetic variation to NEC is important for providing new insights into the pathogenesis of NEC as well as allowing for targeted care of infants with inherent susceptibility. In this review we provide a summary of published genetic association studies in NEC along with defining the challenges and possible future approaches., (Copyright © 2016 Elsevier Inc. All rights reserved.)

Preterm neonates are highly sensitive to systemic infections in early life but little is known about systemic immune development following preterm birth. We hypothesized that preterm neonates have immature systemic immunity with distinct developmental trajectory for the first several weeks of life, relative to those born at near-term or term. Using pigs as a model, we characterized blood leukocyte subsets, antimicrobial activities and TLR-mediated cytokine production during the first weeks after preterm birth. Relative to near-term and term pigs, newborn preterm pigs had low blood leukocyte counts, poor neutrophil phagocytic rate, and limited cytokine responses to TLR1/2/5/7/9 and NOD1/2 agonists. The preterm systemic responses remained immature during the first postnatal week, but thereafter showed increased blood leukocyte numbers, NK cell proportion, neutrophil phagocytic rate and TLR2-mediated IL-6 and TNF-α production. These immune parameters remained different between preterm and near-term pigs at 2-3 weeks, even when adjusted for post-conceptional age. Our data suggest that systemic immunity follows a distinct developmental trajectory following preterm birth that may be influenced by postnatal age, complications of prematurity and environmental factors. Consequently, the immediate postnatal period may represent a window of opportunity to improve innate immunity in preterm neonates by medical, antimicrobial or dietary interventions.

The predisposition of preterm neonates to invasive infection is, as yet, incompletely understood. Regulatory T cells (Tregs ) are potential candidates for the ontogenetic control of immune activation and tissue damage in preterm infants. It was the aim of our study to characterize lymphocyte subsets and in particular CD4(+) CD25(+) forkhead box protein 3 (FoxP3)(+) Tregs in peripheral blood of well-phenotyped preterm infants (n = 117; 23 + 0 - 36 + 6 weeks of gestational age) in the first 3 days of life in comparison to term infants and adults. We demonstrated a negative correlation of Treg frequencies and gestational age. Tregs were increased in blood samples of preterm infants compared to term infants and adults. Notably, we found an increased Treg frequency in preterm infants with clinical early-onset sepsis while cause of preterm delivery, e.g. chorioamnionitis, did not affect Treg frequencies. Our data suggest that Tregs apparently play an important role in maintaining maternal-fetal tolerance, which turns into an increased sepsis risk after preterm delivery. Functional analyses are needed in order to elucidate whether Tregs have potential as future target for diagnostics and therapeutics., (© 2016 British Society for Immunology.)

Objectives: Fetal brain maturation is disrupted by preterm birth. Inflammation during the neonatal period may further harm neurodevelopmental outcomes. The present study aimed to determine the effect of short-chain galacto-oligosaccharides/long-chain fructo-oligosaccharides/pectin-derived acidic oligosaccharides (scGOS/lcFOS/pAOS) on neurodevelopmental outcomes measured by Bayley Scales of Infant and Toddler Development in preterm infants at 24 months., Methods: In this randomized controlled trial, scGOS/lcFOS/pAOS or placebo was supplemented between days 3 and 30 of life. Serum samples at day 1, 7, and 14 were analyzed for cytokine levels. Stool samples at day 1, 7, 14, and 30 were measured for bacterial count and bifidobacteria percentage. At 24 months corrected age infants were followed up by a blinded pediatric psychologist for the Bayley Scales of Infant and Toddler Development II or III., Results: Seventy-seven of one hundred one (76%) eligible infants participated in the follow-up study. Neurodevelopmental outcomes were not different in the scGOS/lcFOS/pAOS and placebo group. Infections during the neonatal period, lower percentages of bifidobacteria at day 7 (F = 3.8, P = 0.05) and day 14 (F = 5.0, P = 0.02) and higher levels of Interleukine (IL)-1β (F = 4.0, P = 0.04) and IL-8 (F = 8.0, P = 0.01) at day 7 are associated with lower mental developmental index. Lower psychomotor outcomes are associated with IL-2 (F = 4.0, P = 0.05), IL-4 (F = 6.0, P = 0.02) at birth, and interferon gamma at day 7 (F = 4.4, P = 0.04)., Conclusions: scGOS/lcFOS/pAOS showed no significant improvement of neurodevelopmental outcomes at 24 months in preterm infants. Infections, lower bifidobacteria counts, and higher serum cytokine levels during the neonatal period were associated with lower neurodevelopmental outcomes at 24 months of age indicating the relevance of microbiome and immune responses in neurodevelopmental processes.

Sepsis is a major cause of neonatal morbidity and mortality, especially in vulnerable preterm populations. Immature immune defenses, and environmental and maternal factors contribute to this risk, with as many as a third of very preterm infants experiencing sepsis during their stay in the neonatal intensive care unit (NICU). Epidemiologic and twin studies have suggested that there is a genetic contribution to sepsis predilection. Several investigators have conducted candidate gene association studies on variants of specific interest and potential functional significance in neonatal sepsis. In this review, we describe details of studies that have evaluated genetic susceptibility in neonatal sepsis, and summarize findings from a review of candidate gene association studies., (Copyright © 2015 Elsevier Inc. All rights reserved.)

Aim: This study evaluated the impact of an exclusive human milk diet to nourish extremely low birth weight infants in the neonatal intensive care unit., Materials and Methods: This multicenter pre-post retrospective study included all inborn infants <1,000 g admitted to four Level IV neonatal intensive care units either before or after implementing a donor human milk policy. The feeding protocol was unchanged in both periods. Collected data included maternal/infant demographics, infant clinical data, and enteral intake as mother's own milk, donor milk, and formula., Results: Two hundred one infants were enrolled. Infant growth and other clinical outcomes were similar in both groups. Exposure to mother's own milk at discharge was not different. Median time in oxygen and duration of mechanical ventilation were significantly higher among formula-fed infants (63 versus 192 hours [p=0.046] and 24 versus 60 hours [p=0.016], respectively)., Conclusions: Our results add evidence supporting the safety of donor milk. This study also found an association between exposure to formula in preterm infants and the requirement for respiratory support, a finding that warrants further investigation.

Objectives: This study evaluated the immune response and safety profile of 13-valent pneumococcal conjugate vaccine (PCV13) in preterm infants compared with term infants., Methods: This Phase IV, open-label, 2-arm, multicenter, parallel-group study enrolled 200 healthy infants (preterm, n = 100; term, n = 100) aged 42 to 98 days. All subjects received PCV13 at ages 2, 3, 4 (infant series), and 12 (toddler dose [TD]) months, together with routine vaccines (diphtheria-tetanus-acellular pertussis, hepatitis B, inactivated poliovirus, and Haemophilus influenzae type b vaccine and meningococcal group C conjugate vaccine)., Results: Most subjects achieved an anticapsular immunoglobulin G (IgG) antibody concentration ≥ 0.35 μg/mL for all serotypes: >85% after the infant series (except preterm infants for serotypes 5, 6A, and 6B) and >97% after TD (except for serotype 3). Preterm infants had overall lower IgG geometric mean concentrations compared with term infants; however, geometric mean fold increases after TD were similar for all serotypes. Opsonophagocytic activity results were consistent with IgG results and titers increased after TD in both groups for all serotypes, including serotype 3. PCV13 was generally well tolerated, with similar safety profiles in all preterm subgroups., Conclusions: Immune responses were lower in preterm infants than in term infants. However, the majority of subjects in both groups achieved both pneumococcal serotype-specific IgG antibody levels after the infant series that exceeded the World Health Organization-established threshold of protection and functional antibody responses. Responses were uniformly higher after TD, reinforcing the importance of a timely booster dose. PCV13 was well tolerated regardless of gestational age., (Copyright © 2015 by the American Academy of Pediatrics.)

Objectives: Gastroesophageal reflux and aspiration can occur in premature infants who are supported with mechanical ventilation. The relation between physical positioning and gastric aspiration in ventilated infants has not been studied. Pepsin measured in tracheal aspirate (TA) emerged as a specific marker for aspiration. The objective of our study was to assess pepsin in TA of ventilated infants at 2 different positions: supine and right lateral., Methods: We conducted a randomized controlled trial on premature infants who were enterally fed and supported with mechanical ventilation. Patients were randomized into intervention and control groups. In the intervention group, infants were placed supine for 6 hours before a sample of TA was obtained. A second sample was collected 6 hours later while lying in the right lateral position. In the control group, the 2 samples of TA were obtained while infants remained in the supine position during the entire study time. Pepsin in TA was measured while blinded to the group assignment., Results: A total of 34 patients were enrolled and randomized to intervention (n = 17) and control (n = 17) groups. Gestational age was 32.7 ± 2.7 weeks, and birth weight was 1617 ± 526 g; both groups had similar demographic and clinical characteristics. Pepsin concentration did not differ between groups at baseline. In the intervention group, pepsin concentration significantly declined from 13 ng/mL (interquartile range [IQR] 11.9-38.7) to 10 ng/mL (IQR 7-12; P < 0.001), whereas it did not change in the control group (P = 0.42)., Conclusions: The right lateral positioning is associated with decreased TA pepsin. The implications of the present study on hospital practice and clinical outcomes need further investigations.

Sepsis and necrotizing enterocolitis (NEC) cause significant morbidity and mortality in the newborn. Their ill effects persist in spite of appropriate and effective antibiotic therapy. Lactoferrin as an adjunct to antibiotics in the treatment of sepsis or NEC in the newborn may improve the clinical outcomes by enhancing the host defense and modulating the inflammatory response. This review focuses on the various aspects of lactoferrin use in the newborn.

Unlabelled: Bordetella pertussis or whooping cough is a vaccine-preventable disease that still remains a serious infection in neonates and young infants. We describe two young infants, monozygotic twins, with a severe B. pertussis pneumonia of whom one needed extracorporeal membrane oxygenation. Diagnostic work-up of unexplained hematuria and proteinuria during the illness revealed low serum complement component 3 (C3) levels. During follow-up, C3 levels remained low (400-600 mg/L). Extensive analysis of the persistent low C3 levels revealed an unknown heterozygous mutation in the C3 gene in both siblings and their mother. This C3 mutation in combination with the specific virulence mechanisms of B. pertussis probably contributed to the severe disease course in these cases., Conclusion: We propose that genetically caused complement disorders should be considered when confronted with severe cases of B. pertussis infection.

Human milk and breastfeeding represent the nutritional normative standards for term and preterm newborns. With the term "surgical infants" we refer to all newborns who undergo surgery during the first days of life and who are assisted in the neonatal intensive care unit during the postoperative period and then in the neonatal surgery unit. There are many obstacles to breastfeeding these newborns. The "barriers" include the unstable clinical conditions before and after surgery, the period of separation between the mother and child, and often the lack of attention to breastfeeding. Few studies have assessed if newborns with surgical diseases are breastfeed and if human milk is beneficial for their outcome. We believe that the best option is to offer them their own mother's milk through the promotion and support of breastfeeding. A specific program focused on the needs of these vulnerable children should be created. Furthermore the surgical and pediatric staff of the neonatal surgery unit should be informed and trained to increase such a program's feasibility.

The immunization of infants against infectious diseases still raises many controversies, not only with parents, but also among physicians. This refers particularly to preterm infants. Due to the increasing popularity of polyvalent vaccines, a number of studies has recently been conducted to verify their immunogenicity and safety in preterm infants. The aim of the present paper was to review the current literature dealing with the problem in question. The following recommendations regarding the use of polyvalent vaccines in preterm infants and neonates with low birth weight can be formulated on the basis of current evidence (1). Due to sufficient immunogenicity, polyvalent vaccines can be administered to preterm infants in accordance with their calendar age (2). Booster vaccination of preterm infants after completing 12 months of age is vital for achieving complete and persistent immunity against all vaccine antigens (3). In order to reduce the risk of adverse events after the administration of a polyvalent vaccine, it is essential to carefully consider the cardiorespiratory status of preterm infants during preimmunization examination, as well as their history of any cardiorespiratory dysfunctions. In such cases administering the first dose of the vaccine in a hospital setting is strongly advised.

Objective: This study tested the hypothesis that feeding an exclusively human milk (EHM) diet to premature infants reduces the incidence of necrotizing enterocolitis (NEC) associated with enteral feeding., Study Design: An observational study for infants born at less than 33 weeks of gestational age was performed in a single neonatal intensive care unit. An EHM diet prospectively eliminated bovine-based artificial milk, including bovine-based fortifier, through 33 weeks postmenstrual age (PMA). The clinical data from a 2.5-year interval of the EHM diet were compared with data from the previous 6.5 years for similar infants who received bovine-based milk products before 33 weeks PMA., Results: In the EHM diet cohort, 148 of 162 infants (91%) received EHM through 33 weeks PMA. In order to achieve an EHM diet, 140 of 162 infants (86%) received their own mother's milk, and 98 of 162 infants (60%) received donor human milk. The EHM cohort was also fed a human milk-based fortifier to truly eliminate bovine products. The distribution of NEC onset in the EHM cohort was significantly different from that in the control cohort for the day of onset (p=0.042) and the PMA at onset (p=0.011). In the control cohort, NEC onset after Day 7 of life occurred in 15 of 443 infants (3.4%), significantly more than in the EHM cohort where NEC occurred in two of 199 infants (1%) (p=0.009)., Conclusions: Changing to an EHM milk diet through 33 weeks PMA reduced the incidence of NEC associated with enteral feeding.

Newborn infants, including those born at term without congenital disorders, are at high risk of severe disease from respiratory syncytial virus (RSV) infection. Indeed, our current local surveillance data demonstrate that approximately half of children hospitalized with RSV were ≤3 mo old, and 74% were born at term. Informed by this clinical epidemiology, we investigated antiviral innate immune responses in early life, with the goal of identifying immunological factors underlying the susceptibility of infants and young children to severe viral lower respiratory tract infections. We compared RSV-induced innate cytokine production in blood mononuclear cells from neonates, young children aged 12-59 mo, and healthy adults. RSV-induced IFN-α production was primarily mediated by plasmacytoid dendritic cells (pDCs), and was significantly lower in term infants and young children < 5 y of age than in adults (p < 0.01). RSV-induced IFN-α production in human pDCs proceeded independently of endosomal TLRs, and human pDCs from healthy adult donors produced IFN-α in a retinoic acid-inducible gene I protein (RIG-I)-dependent manner. Of interest, young age and premature birth were independently associated with attenuated RIG-I-dependent IFN-α responses (p < 0.01). In contrast to IFN-α production, proinflammatory IL-6 responses to RSV were mediated by monocytes, appeared less dependent on RIG-I, and were significantly impaired only among preterm infants, not in term infants and young children. Our results suggest that human pDCs are less functional in early life, which may contribute to the increased susceptibility of infants and young children to severe RSV disease.

This article highlights some of the important developmental characteristics that underpin common problems seen in moderate and late preterm infants. Preterm birth is associated with an increased prevalence of clinical problems caused by functional immaturities in a wide variety of organ systems, acquired problems, and problems associated with inadequate monitoring and/or follow-up plans. There are variations in the degree of maturation among infants of similar gestational ages because the developmental process is nonlinear. Therefore, different organ systems mature at rates and trajectories that are specific to their functions. A better understanding of these principles can help guide optimal treatment strategies., (Copyright © 2013 Elsevier Inc. All rights reserved.)

This study aimed to evaluate the levels of pro- and anti-inflammatory cytokines in umbilical cord blood of preterm neonates who developed focal early-onset infection (EOI) after preterm premature rupture of membranes (PPROM). This is a prospective study conducted on 46 preterm infants from mothers with PPROM. The cytokines were measure by flow cytometry. Newborns were classified into two groups as focal EOI (n=19) and non-infected (n=27). Interleukin (IL)-6 and IL-8 levels were higher, whereas IL-10 and IL-12 p70 levels were lower in the EOI when compared to the non-infected group. The best combination of cytokines was IL-6+IL-8, with a diagnostic accuracy of 0.97. Focal EOI after PPROM is associated with increased levels of IL-6 and IL-8 and diminished IL-10 and IL-12 in the cord blood of preterm infants. Combined assessment of IL-6 and IL-8 in cord blood may provide an additional tool for identifying preterm infants who develop EOI after PPROM.

Objective: Sepsis in older children and adults modifies immune system function. We compared serotype-specific antibody responses to heptavalent pneumococcal conjugate vaccine (PCV7) in very low birth weight infants (<1500 g,VLBWs) with and without blood stream infection (BSI) during their birth hospitalization., Study Design: Retrospective analysis of prospectively collected data for the Neonatal Research Network study of PCV7 responses among VLBWs. Infants received PCV7 at 2, 4 and 6 months after birth with blood drawn 4 to 6 weeks after third dose. Serotype antibodies were compared between infants with or without a history of BSI. Regression models were constructed with BW groups and other confounding factors identified in the primary study., Result: In all, 244 infants completed the vaccine series and had serum antibody available; 82 had BSI. After adjustment, BSI was not associated with reduced odds of serum antibody 0.35 μg ml(-1)., Conclusion: BSI was not associated with reduced odds of World Health Organization-defined protective PCV7 responses in VLBWs.

Necrotizing enterocolitis (NEC) is a severe intestinal inflammatory disorder in newborns. Although the pathogenesis of NEC is not completely understood, we reviewed the literature and our previous studies to explore the mechanism of NEC and to evaluate the role for probiotics in this disease. NEC may be associated with an inappropriate innate immune and excessive inflammatory response of the immature intestine. Probiotics are widely used in promoting human health and adjunctive therapy of human disease. There are growing clinical trials and research studies that support a beneficial role for probiotics for NEC. We have reviewed the literature associated with the use of probiotics in NEC., (Copyright © 2013 Elsevier Inc. All rights reserved.)

Due to their high risk of developing severe Bordetella pertussis (Bp) infections, it is recommended to immunize preterm infants at their chronological age. However, little is known about the persistence of their specific immune responses, especially of the cellular responses recognized to play a role in protection. We compared here the cellular immune responses to two major antigens of Bp between three groups of one year-old children born prematurely, who received for their primary vaccination respectively the whole cell vaccine Tetracoq(®) (TC), the acellular vaccine Tetravac(®) (TV), or the acellular vaccine Infanrix-hexa(®) (IR). Whereas most children had still detectable IFN-γ responses at one year of age, they were lower in the IR-vaccinated children compared to the two other groups. In contrast, both the TV- and the IR-vaccinated children displayed higher Th2-type immune responses, resulting in higher antigen-specific IFN-γ/IL-5 ratios in TC- than in TV- or IR-vaccinated children. The IFN-γ/IL-5 ratio of mitogen-induced cytokines was also lower in IR- compared to TC- or TV-vaccinated children. No major differences in the immune responses were noted after the booster compared to the pre-booster responses for each vaccine. The IR-vaccinated children had a persistently low specific Th1-type immune response associated with high specific Th2-type immune responses, resulting in lower antigen-specific IFN-γ/IL-5 ratios compared to the two other groups. We conclude that antigen-specific cellular immune responses persisted in one year-old children born prematurely and vaccinated during infancy at their chronological age, that a booster dose did not significantly boost the cellular immune responses, and that the Th1/Th2 balance of the immune responses is modulated by the different vaccines., (Copyright © 2013 Elsevier Ltd. All rights reserved.)

Background: The level of maternal antibodies decreases more quickly in preterm than term infants, leaving them unprotected against measles. To protect premature infants from measles, an early vaccination trial was investigated., Methods: Changes in the serum measles neutralization test (NT) antibody titer were examined in 152 infants (average gestational period, 29 weeks; average birthweight, 1203 g)., Results: The average antibody titer (2(n)) was 2(3.5) at birth and 2(2.2) at 1-3 months of age, and in all cases, NT antibody titer decreased to <1:4 (150 IU/mL). The AIK-C measles vaccine was given to 17 preterm infants at the age of 6 months, and induced sufficient serological responses without any serious adverse events. NT antibody level did not decay during 12 months after vaccination., Conclusion: Early immunization at 6 months of age is effective to protect preterm infants in the outbreak setting., (© 2013 The Authors. Pediatrics International © 2013 Japan Pediatric Society.)

Current evidence highlights the importance of developing a healthy intestinal microbiota in the neonate. Many aspects that promote health or disease are related to the homeostasis of these intestinal microbiota. Their delicate equilibrium could be strongly influenced by the intervention that physicians perform as part of the medical care of the neonate, especially preterm infants. As awareness of the importance of the development and maintenance of these intestinal flora increase and newer molecular techniques are developed, it will be possible to provide better care of infants with interventions that will have long-lasting effects., (Copyright © 2013 Elsevier Inc. All rights reserved.)

When microbial communities colonize in the developing intestinal tract after birth, microorganisms interact with specific apical surface receptors on the enterocytes. This interaction triggers a response that prevents overexpression of inflammatory cytokines, thus providing protection from pathogen-induced mucosal damage. Multiple immune modulatory factors in human milk and innate humoral factors also control inflammatory responses, providing additional protective effects. Our understanding of the role of the luminal microbial communities or microbiota is growing rapidly as novel technologies provide new insights into their taxonomy, function during early development, and impact on life-long health. Multiple studies have evaluated the effects of the specific nutrients, glutamine, arginine, nucleotides, polyunsaturated fatty acids, and lactoferrin, on disease outcomes in premature infants. These studies support a role for nutrients to modulate host defense mechanisms in premature infants, to develop normal digestive function, to protect from bacterial translocation, and to preserve mucosal barrier integrity. These effects are clearly important. However, not enough is yet known to design specific clinical care practices that support a healthy microbiota., (Copyright © 2013 Mosby, Inc. All rights reserved.)

Introduction: Being born small for gestational age (SGA) can be a reference to intrauterine growth retardation (IUGR) and is associated with increased neonatal morbidity and mortality. In pregnancies complicated by IUGR placental insufficiency is thought to be one of the leading underlying pathogenetic mechanisms. As cytokines appear to be implicated in implantation and -placental development, imbalances in cytokine levels may contribute to pregnancy disorders i. e., IUGR., Objective: Cord blood cytokine profiles were analyzed in order to characterize differences in cytokine profiles between SGA and appropriate for gestational age (AGA) preterm infants., Methods: Cytokine concentrations were measured in venous cord blood of preterm infants delivered by caesarean section without previous labour activity and without signs of maternal or fetal infection., Results: 93 preterm infants were enrolled, 29 SGA preterm infants (GA 31.0 (24.6-36.7) weeks; BW 1080 (315-2010) grams) and 63 AGA preterm infants (GA 33.3 (26.0-36.9) weeks; BW 1790 (760-3570) grams). In both groups multiple cytokines could be detected. Significant differences in cytokine levels between the groups were found for G-CSF, IL-12p40 and IL-8, while levels of IL-1a, IL-6, IL-10, IP-10, MCP-1, MCP-3, MIP-1a and TNF-a were not different., Conclusions: Alteration of cytokine levels in SGA preterm infants may be involved in the pathogenesis of reduced intrauterine growth as well as in the higher morbidity in these infants. Further studies are needed to get more comprehension of the complex function of cytokines in pregnancies complicated by IUGR., (© Georg Thieme Verlag KG Stuttgart · New York.)

The interplay between microorganisms and the intestine of newborn infants is associated with diverse functional and clinical outcomes that result from the specific interactions among microbial communities, their products, and the unique characteristics of the gastrointestinal tract. Multiple mechanisms of action for infant formula ingredients with probiotic activity appear to exist. These mechanisms are thought to protect the host not only from intestinal diseases but also from systemic infection. However, questions about the safety of probiotics for preterm infants remain unanswered, particularly with regard to sepsis, immunomodulatory effects, and microbial resistance. Few well-designed studies have been conducted to evaluate the effects of probiotic, prebiotic, and synbiotic ingredients on relevant clinical outcomes in preterm infants. Although existing data are encouraging, there is insufficient evidence to recommend the routine use of these ingredients in all preterm infants., (Copyright © 2013 Mosby, Inc. All rights reserved.)

Background: Necrotising enterocolitis (NEC) is the most common gastrointestinal emergency in premature infants. Immaturity of gastrointestinal immune regulation may predispose preterm infants to NEC as FOXP3 T regulatory cells (Treg) are critical for intestinal immune homoeostasis., Objective: To investigate the hypothesis that abnormal developmental regulation of lamina propria Treg would define premature infants with NEC., Design: Lamina propria mononuclear cell populations from surgically resected ileum from 18 patients with NEC and 30 gestational age-matched non-NEC surgical controls were prospectively isolated. Polychromatic flow cytometry was performed to phenotype and analyse lamina propria T cell populations. The cytokine gene expression profile in NEC tissue was compared with that of non-NEC controls., Results: The total number of Treg, CD4, or CD8 T cells in each ileum section was independent of gestational age, age or postmenstrual age and similar between patients with NEC and controls. In contrast, the ratio of Treg to CD4 T cells or Treg to CD8 T cells was significantly lower in NEC ileum than in infants without NEC (medians 2.9% vs 6.6%, p=0.001 and medians 6.6% vs 25.9%, p<0.001, respectively). For any given number of CD4 or CD8 T cells, Treg were, on average, 60% lower in NEC ileum than in controls. NEC tissue cytokine gene expression profiles were characteristic of inhibited Treg development or function. Treg/CD4 and Treg/CD8 ratios recovered between initial resection for NEC and reanastomosis., Conclusion: The proportion of lamina propria Treg is significantly reduced in the ileum of premature infants with NEC and may contribute to the excessive inflammatory state of this disease.

Early breast milk, known as colostrum ("liquid gold") provides immune benefits to infants, offering potential risk reduction for nosocomial infection (NI) and necrotizing enterocolitis (NEC), a serious gastrointestinal emergency. Provision of colostrum is recognized as oral immune therapy (OIT) and is valuable to all NICU infants unable to feed orally. A quality improvement project was initiated by the multidisciplinary NICU Quality Care Council at London Health Sciences Centres-Victoria (LHSC-VH) to obtain mothers' colostrum for early OIT. The initiative was driven by the Canadian EPIQ (Evidence-based Practice for Improving Quality) group as a means of reducing the rates of NEC and NI, two major morbidities in the NICU. The overall aim was to facilitate the availability of OIT to preterm and critically ill neonates as soon as possible after birth.

Monoclonal antibodies are widely used both in infants and in adults for several indications. Humanized monoclonal antibodies (palivizumab) have been used for many years for the prevention of respiratory syncytial virus infection in pediatric populations (preterm infants, infants with chronic lung disease or congenital heart disease) at high risk of severe and potentially lethal course of the infection. This drug was reported to be safe, well tolerated and effective to decrease the hospitalization rate and mortality in these groups of infants by several clinical trials. In the present paper we report the development and the current use of monoclonal antibodies for prophylaxis against respiratory syncytial virus.

Necrotizing enterocolitis (NEC) is a challenging disease to treat, and caring for patients afflicted by it remains both frustrating and difficult. While NEC may develop quickly and without warning, it may also develop slowly, insidiously, and appear to take the caregiver by surprise. In seeking to understand the molecular and cellular processes that lead to NEC development, we have identified a critical role for the receptor for bacterial lipopolysaccharide (LPS) toll like receptor 4 (TLR4) in the pathogenesis of NEC, as its activation within the intestinal epithelium of the premature infant leads to mucosal injury and reduced epithelial repair. The expression and function of TLR4 were found to be particularly elevated within the intestinal mucosa of the premature as compared with the full-term infant, predisposing to NEC development. Importantly, factors within both the enterocyte itself, such as heat shock protein 70 (Hsp70), and in the extracellular environment, such as amniotic fluid, can curtail the extent of TLR4 signaling and reduce the propensity for NEC development. This review will highlight the critical TLR4-mediated steps that lead to NEC development, with a focus on the proinflammatory responses of TLR4 signaling that have such devastating consequences in the premature host.