Comparison of L-selectin and CD11b on neutrophils of adults and neonates during the first month of life

Neonatal Sepsis: Aetiology, Pathophysiology, Diagnostic Advances and Management Strategies

Neonatal sepsis, a bloodstream infection in the first 28 days of life, is a leading cause of morbidity and mortality among infants in both developing and developed countries. Additionally, sepsis is distinguished in neonates by unique pathophysiological and presentational factors relating to its development in immature neonatal immune systems. This review focuses on the current understanding of the mechanics and implications of neonatal sepsis, providing a comprehensive overview of the epidemiology, aetiology, pathophysiology, major risk factors, signs and symptoms and recent consensus on the diagnosis and management of both early-onset and late-onset neonatal sepsis. It also includes a discussion on novel biomarkers and upcoming treatment strategies for the condition as well as the potential of COVID-19 infection to progress to sepsis in infants.

Targeting lipid nanoparticles to the blood-brain barrier to ameliorate acute ischemic stroke

Effective delivery of mRNA or small molecule drugs to the brain is a significant challenge in developing treatment for acute ischemic stroke (AIS). To address the problem, we have developed targeted nanomedicine to increase drug concentrations in endothelial cells of the blood-brain barrier (BBB) of the injured brain. Inflammation during ischemic stroke causes continuous neuronal death and an increase in the infarct volume. To enable targeted delivery to the inflamed BBB, we conjugated lipid nanocarriers (NCs) with antibodies that bind cell adhesion molecules expressed at the BBB. In the transient middle cerebral artery occlusion mouse model, NCs targeted to vascular cellular adhesion molecule-1 (VCAM) achieved the highest level of brain delivery, nearly two orders of magnitude higher than untargeted ones. VCAM-targeted lipid nanoparticles with luciferase-encoding mRNA and Cre-recombinase showed selective expression in the ischemic brain. Anti-inflammatory drugs administered intravenously after ischemic stroke reduced cerebral infarct volume by 62% (interleukin-10 mRNA) or 35% (dexamethasone) only when they were encapsulated in VCAM-targeted NCs. Thus, VCAM-targeted lipid NCs represent a new platform for strongly concentrating drugs within the compromised BBB of penumbra, thereby ameliorating AIS.

Interleukin-27-dependent transcriptome signatures during neonatal sepsis

Human newborns exhibit increased vulnerability and risk of mortality from infection that is consistent with key differences in the innate and adaptive immune responses relative to those in adult cells. We have previously shown an increase in the immune suppressive cytokine, IL-27, in neonatal cells and tissues from mice and humans. In a murine model of neonatal sepsis, mice deficient in IL-27 signaling exhibit reduced mortality, increased weight gain, and better control of bacteria with reduced systemic inflammation. To explore a reprogramming of the host response in the absence of IL-27 signaling, we profiled the transcriptome of the neonatal spleen during Escherichia coli-induced sepsis in wild-type (WT) and IL-27Rα-deficient (KO) mice. We identified 634 genes that were differentially expressed, and those most upregulated in WT mice were associated with inflammation, cytokine signaling, and G protein coupled receptor ligand binding and signaling. These genes failed to increase in the IL-27Rα KO mice. We further isolated an innate myeloid population enriched in macrophages from the spleens of control and infected WT neonates and observed similar changes in gene expression aligned with changes in chromatin accessibility. This supports macrophages as an innate myeloid population contributing to the inflammatory profile in septic WT pups. Collectively, our findings highlight the first report of improved pathogen clearance amidst a less inflammatory environment in IL-27Rα KO. This suggests a direct relationship between IL-27 signaling and bacterial killing. An improved response to infection that is not reliant upon heightened levels of inflammation offers new promise to the potential of antagonizing IL-27 as a host-directed therapy for neonates.

The Association between Maternal Oral Inflammation and Neutrophil Phenotypes and Poly-Unsaturated Fatty Acids Composition in Human Milk: A Prospective Cohort Study

This prospective cohort study aimed to investigate the impact of maternal oral inflammation on human milk composition including neutrophil counts, activation state (based on cluster of differentiation (CD) markers expression), and fatty acid levels. Fifty mothers were recruited from St. Michael's hospital, Toronto, and followed up from 2-4 weeks until 4 months postpartum. Oral rinse and human milk samples were collected at both timepoints. Oral polymorphonuclear neutrophils (oPMNs) within the rinses were quantified using flow cytometry and the participants' oral health state was categorized into three groups (i.e., healthy, moderate, and severe) based on the oPMNs counts. Fatty acids were identified and quantified using a gas chromatography-flame ionization detector (GC-FID). Compared to mothers with a healthy oral health state, mothers with moderate to severe oral inflammation had a statistically significant decrease in the expression of CD64 biomarker, an increase in the expression of CD14 biomarker on human milk neutrophils and a decrease in the levels of eicosapentaenoic acid (C20:5n-3) in their human milk at follow-up compared to baseline. This study demonstrates for the first time that maternal oral inflammation can affect human milk composition. The mechanism by which these alterations can affect infant health outcomes in the long term critically needs to be considered.

The extracellular sialidase NEU3 primes neutrophils

Some extracellular glycoconjugates have sialic acid as the terminal sugar, and sialidases are enzymes that remove this sugar. Mammals have 4 sialidases and can be elevated in inflammation and fibrosis. In this report, we show that incubation of human neutrophils with the extracellular human sialidase NEU3, but not NEU1, NEU2 or NEU4, induces human male and female neutrophils to change from a round to a more amoeboid morphology, causes the primed human neutrophil markers CD11b, CD18, and CD66a to localize to the cell cortex, and decreases the localization of the unprimed human neutrophil markers CD43 and CD62-L at the cell cortex. NEU3, but not the other 3 sialidases, also causes human male and female neutrophils to increase their F-actin content. Human neutrophils treated with NEU3 show a decrease in cortical levels of Sambucus nigra lectin staining and an increase in cortical levels of peanut agglutinin staining, indicating a NEU3-induced desialylation. The inhibition of NEU3 by the NEU3 inhibitor 2-acetylpyridine attenuated the NEU3 effect on neutrophil morphology, indicating that the effect of NEU3 is dependent on its enzymatic activity. Together, these results indicate that NEU3 can prime human male and female neutrophils, and that NEU3 is a potential regulator of inflammation.

The impact of opioid exposure during pregnancy on the human neonatal immune profile

BACKGROUND

The increasing magnitude of the opioid crisis and rising rates of neonatal abstinence syndrome (NAS) diagnoses highlight the need for increased research into how maternal substance use during pregnancy can impact the neonatal immune profile and its functionality. We hypothesized that neonates with opioid exposure would have reduced proportions of some immune cells, an anti-inflammatory cytokine profile, reduced T cell proliferation, and monocyte bacterial killing activity compared to the control population.

METHODS

The present study compares immune cell populations, inflammatory and anti-inflammatory cytokine and chemokine levels in the serum, and monocyte and T cell functional activity using umbilical cord samples from neonates with known opioid exposure during gestation and from control neonates without known exposure.

RESULTS

Our findings demonstrated a significant reduction in neutrophils, decreased levels of inflammatory cytokines in the serum, and reduced IL-2 production during in vitro CD4+ T cell proliferation in neonates exposed to opioids compared to controls. The neutrophil findings were supported by retrospective analysis of an extended network of deidentified patient records.

CONCLUSIONS

This study is the first of its kind to evaluate differences in neonatal immunity as a result of opioid exposure in the human population that will inform continued mechanistic studies.

IMPACT

The opioid epidemic has become a public health crisis in the United States, and the corresponding incidence of neonatal abstinence syndrome (NAS) have risen accordingly. New research is required to understand the short and long-term health impacts of opioid exposure to the neonate. This is the first human study to investigate the immunologic profile and functionality in neonates with known opioid exposure in utero. The abundance of neutrophils and the ratio of neutrophils to lymphocytes is significantly reduced along with inflammatory cytokines and chemokines following opioid exposure during pregnancy. The immune profile in opioid-exposed neonates may promote susceptibility to infection.

The Neonatal Innate Immune Response to Sepsis: Checkpoint Proteins as Novel Mediators of This Response and as Possible Therapeutic/Diagnostic Levers

Sepsis, a dysfunctional immune response to infection leading to life-threatening organ injury, represents a significant global health issue. Neonatal sepsis is disproportionately prevalent and has a cost burden of 2-3 times that of adult patients. Despite this, no widely accepted definition for neonatal sepsis or recommendations for management exist and those created for pediatric patients are significantly limited in their applicability to this unique population. This is in part due to neonates' reliance on an innate immune response (which is developmentally more prominent in the neonate than the immature adaptive immune response) carried out by dysfunctional immune cells, including neutrophils, antigen-presenting cells such as macrophages/monocytes, dendritic cells, etc., natural killer cells, and innate lymphoid regulatory cell sub-sets like iNKT cells, γδ T-cells, etc. Immune checkpoint inhibitors are a family of proteins with primarily suppressive/inhibitory effects on immune and tumor cells and allow for the maintenance of self-tolerance. During sepsis, these proteins are often upregulated and are thought to contribute to the long-term immunosuppression seen in adult patients. Several drugs targeting checkpoint inhibitors, including PD-1 and PD-L1, have been developed and approved for the treatment of various cancers, but no such therapeutics have been approved for the management of sepsis. In this review, we will comparatively discuss the role of several checkpoint inhibitor proteins, including PD-1, PD-L1, VISTA, and HVEM, in the immune response to sepsis in both adults and neonates, as well as posit how they may uniquely propagate their actions through the neonatal innate immune response. We will also consider the possibility of leveraging these proteins in the clinical setting as potential therapeutics/diagnostics that might aid in mitigating neonatal septic morbidity/mortality.

A role for metabolism in determining neonatal immune function

Immune responses of neonates differ markedly to those of adults, with skewed cytokine phenotypes, reduced inflammatory properties and drastically diminished memory function. Recent research efforts have started to unravel the role of cellular metabolism in determining immune cell fate and function. For studies in humans, much of the work on metabolic mechanisms underpinning innate and adaptive immune responses by different haematopoietic cell types is in adults. Studies investigating the contribution of metabolic adaptation in the unique setting of early life are just emerging, and much more work is needed to elucidate the contribution of metabolism to neonatal immune responses. Here, we discuss our current understanding of neonatal immune responses, examine some of the latest developments in neonatal immunometabolism and consider the possible role of altered metabolism to the distinctive immune phenotype of the neonate. Understanding the role of metabolism in regulating immune function at this critical stage in life has direct benefit for the child by affording opportunities to maximize immediate and long-term health. Additionally, gaining insight into the diversity of human immune function and naturally evolved immunometabolic strategies that modulate immune function could be harnessed for a wide range of opportunities including new therapeutic approaches.

Perinatal Inflammation: Could Partial Blocking of Cell Adhesion Molecule Function Be a Solution?

In spite of the great advances made in recent years in prenatal and perinatal medicine, inflammation can still frequently result in injury to vital organs and often constitutes a major cause of morbidity. It is today well established that in neonates—though vulnerability to infection among neonates is triggered by functional impairments in leukocyte adhesion—the decreased expression of cell adhesion molecules also decreases the inflammatory response. It is also clear that the cell adhesion molecules, namely, the integrins, selectins, and the immunoglobulin (Ig) gene super family, all play a crucial role in the inflammatory cascade. Thus, by consolidating our knowledge concerning the actions of these vital cell adhesion molecules during the prenatal period as well as regarding the genetic deficiencies of these molecules, notably leukocyte adhesion deficiency (LAD) I, II, and III, which can provoke severe clinical symptoms throughout the first year of life, it is anticipated that intervention involving blocking the function of cell adhesion molecules in neonatal leukocytes has the potential to constitute an effective therapeutic approach for inflammation. A promising perspective is the potential use of antibody therapy in preterm and term infants with perinatal inflammation and infection focusing on cases in which LAD is involved, while a further important scientific advance related to this issue could be the combination of small peptides aimed at the inhibition of cellular adhesion.

Neuroimmune responses in the developing brain following traumatic brain injury

Traumatic brain injury (TBI) is one of the leading causes of both acute and long-term morbidity in the pediatric population, leading to a substantial, long-term socioeconomic burden. Despite the increase in the amount of pre-clinical and clinical research, treatment options for TBI rely heavily on supportive care with very limited targeted interventions that improve the acute and chronic sequelae of TBI. Other than injury prevention, not much can be done to limit the primary injury, which consists of tissue damage and cellular destruction. Secondary injury is the result of the ongoing complex inflammatory pathways that further exacerbate tissue damage, resulting in the devastating chronic outcomes of TBI. On the other hand, some level of inflammation is essential for neuronal regeneration and tissue repair. In this review article we discuss the various stages of the neuroimmune response in the immature, pediatric brain in the context of normal maturation and development of the immune system. The developing brain has unique features that distinguish it from the adult brain, and the immune system plays an integral role in CNS development. Those features could potentially make the developing brain more susceptible to worse outcomes, both acutely and in the long-term. The neuroinflammatory reaction which is triggered by TBI can be described as a highly intricate interaction between the cells of the innate and the adaptive immune systems. The innate immune system is triggered by non-specific danger signals that are released from damaged cells and tissues, which in turn leads to neutrophil infiltration, activation of microglia and astrocytes, complement release, as well as histamine release by mast cells. The adaptive immune response is subsequently activated leading to the more chronic effects of neuroinflammation. We will also discuss current attempts at modulating the TBI-induced neuroinflammatory response. A better understanding of the role of the immune system in normal brain development and how immune function changes with age is crucial for designing therapies to appropriately target the immune responses following TBI in order to enhance repair and plasticity.

Development of allergic immunity in early life

The growth and maturity of the peripheral immune system and subsequent development of pulmonary immunity in early life is dictated by host, environmental and microbial factors. Dysregulation during the critical window of immune development in the postnatal years results in disease which impacts on lifelong lung health. Asthma is a common disease in childhood and is often preceded by wheezing illnesses during the preschool years. However, the mechanisms underlying development of wheeze and how and why only some children progress to asthma is unknown. Human studies to date have generally focused on peripheral immune development, with little assessment of local tissue pathology in young children. Moreover, mechanisms underlying the interactions between inflammation and tissue repair at mucosal surfaces in early life remain unknown. Disappointingly, mechanistic studies in mice have predominantly used adult models. This review will consider the aspects of the neonatal immune system which might contribute to the development of early life wheezing disorders and asthma, and discuss the external environmental factors which may influence this process.

Postnatal Innate Immune Development: From Birth to Adulthood

It is well established that adaptive immune responses are deficient in early life, contributing to increased mortality and morbidity. The developmental trajectories of different components of innate immunity are only recently being explored. Individual molecules, cells, or pathways of innate recognition and signaling, within different compartments/anatomical sites, demonstrate variable maturation patterns. Despite some discrepancies among published data, valuable information is emerging, showing that the developmental pattern of cytokine responses during early life is age and toll-like receptor specific, and may be modified by genetic and environmental factors. Interestingly, specific environmental exposures have been linked both to innate function modifications and the occurrence of chronic inflammatory disorders, such as respiratory allergies. As these conditions are on the rise, our knowledge on innate immune development and its modulating factors needs to be expanded. Improved understanding of the sequence of events associated with disease onset and persistence will lead toward meaningful interventions. This review describes the state-of-the-art on normal postnatal innate immune ontogeny and highlights research areas that are currently explored or should be further addressed.

Neutrophil Receptor Response to Bacterial N-formyl Peptides is Similar in Term Newborn Infants and Adults in Contrast to IL-8

We have previously observed that neutrophils from neonates exhibit different migratory responses to intermediate and end-target chemoattractants compared to adults. The aim of this study was to investigate the effect of the chemoattractants IL-8 (intermediate) and formyl-methionyl-leucyl-phenylalanine (fMLP; end-target) on cell surface receptor expression involved in adhesion, migration and granule release of neutrophils from term newborn infants and adults. Heparinized cord blood from 16 healthy term newborn infants delivered by caesarean section and peripheral blood from 17 healthy adults were incubated with 1 μm IL-8 or 0.1 μm fMLP, previously defined as optimal inducers of neutrophil migration. The leukocytes were labelled with antibodies to cell surface receptors (CD11b, CD15S, CD18, CD35, CD44, CD64, CD65, CD88, CD162, CD181 and CD182). Receptor expression was quantified by flow cytometry analysis. Upregulation of CD11b and downregulation of CD88 and CD182 after stimulation with IL-8 were more pronounced in adults than in neonates (P < 0.05, P < 0.05 and P ≤ 0.001, respectively), whereas fMLP induced changes in receptor expression that were of the same magnitude in neutrophils from neonates as from adults. We observed similar expression of receptors that mediate adhesion, migration, granule activation and phagocytosis induced by fMLP in neutrophils from neonates and adults. In contrast, differences between neonates and adults, induced by IL-8, suggest that the neutrophil response to intermediate chemoattractants might lead to a compromised infectious response in newborn infants.

Alterations in neonatal neutrophil function attributable to increased immature forms

At birth neonatal neutrophil composition differs from that of adults due to a higher number of circulating immature forms. To date only a single study has evaluated neutrophil performance based on cell maturity. For this study, we examined functional differences in chemotaxis and phagocytosis between neonatal and adult neutrophils based on cell development and labor exposure.

METHODS

Neutrophils were obtained by venipuncture from adults and cord blood from healthy term neonates delivered vaginally or by cesarean section. Transwells and the chemoattractant fMLP were used to evaluate chemotaxis. Phagocytosis assays were performed using GFP-labeled E.coli (RS218) and whole blood. Neutrophil maturation was measured by an accurate and verified flow cytometry technique using the markers CD45, CD11b, and CD16. QuantiGene Plex and Procarta immunoassays were used to determine cytokine and chemokine gene expression and protein concentration, respectively.

RESULTS

Labor exposure did not alter neonatal neutrophil function in this study. Neonatal and adult mature neutrophils performed chemotaxis and phagocytosis equally well, while immature forms showed marked impairments. Neonatal immature granulocytes, though, completed chemotaxis more proficiently than those of adults. Although cytokine and chemokine levels varied between neonatal and adult groups, no differences were detected in neonates based upon labor exposure.

CONCLUSION

Historically documented functional impairments of neonatal neutrophils may be due to the increased number of developmentally immature forms at birth rather than absolute global deficiencies.

Immune responses in neonates

Neonates have little immunological memory and a developing immune system, which increases their vulnerability to infectious agents. Recent advances in the understanding of neonatal immunity indicate that both innate and adaptive responses are dependent on precursor frequency of lymphocytes, antigenic dose and mode of exposure. Studies in neonatal mouse models and human umbilical cord blood cells demonstrate the capability of neonatal immune cells to produce immune responses similar to adults in some aspects but not others. This review focuses mainly on the developmental and functional mechanisms of the human neonatal immune system. In particular, the mechanism of innate and adaptive immunity and the role of neutrophils, antigen presenting cells, differences in subclasses of T lymphocytes (Th1, Th2, Tregs) and B cells are discussed. In addition, we have included the recent developments in the neonatal mouse immune system. Understanding neonatal immunity is essential to development of therapeutic vaccines to combat newly emerging infectious agents.

Physiologic underpinnings for clinical problems in moderately preterm and late preterm infants

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.

Inflammatory responses in hypoxic ischemic encephalopathy

Inflammation plays a critical role in mediating brain injury induced by neonatal hypoxic ischemic encephalopathy (HIE). The mechanisms underlying inflammatory responses to ischemia may be shared by neonatal and adult brains; however, HIE exhibits a unique inflammation phenotype that results from the immaturity of the neonatal immune system. This review will discuss the current knowledge concerning systemic and local inflammatory responses in the acute and subacute stages of HIE. The key components of inflammation, including immune cells, adhesion molecules, cytokines, chemokines and oxidative stress, will be reviewed, and the differences between neonatal and adult inflammatory responses to cerebral ischemic injury will also be discussed.

Colostrum-derived B and T cells as an extra-lymphoid compartment of effector cell populations in humans

Colostrum contains cellular components that convey immunological protection to offspring. In the present study the main subsets of lymphocytes present in colostrum and in peripheral blood of healthy screened mothers were compared through the evaluation of >15 different flow cytometry markers. Colostrum and peripheral blood samples were collected within 3 days after full-term delivery. Flow cytometry assays and laboratory tests were performed soon after collection. Among B cells, percentages of CD19(+)CD5(+) cells, pertaining to natural immunity system, were significantly higher in colostrum than in peripheral blood (33 vs. 5%, p = 0.047). CD4(+) T cells, effector cells (CD45RA(+)/CD27(-)) and effector memory cells (CD45RA(-)/CD27(-)) were significantly higher in colostrum (p < 0.001) than in peripheral blood, as well as activated CD4(+) T cells (HLA(-)DR(+)) (36% vs. 6% p = 0.0022) and CD4(+) terminally differentiated effector T cells (CD57(+)) (p < 0.001). With regards to CD8(+) T cells, a comparable significant increase in effector (p < 0.02) and effector memory cells (p < 0.001) was also observed. Moreover, an increased surface expression of HLA-DR and CD57 (p < 0.001) on CD8(+) T cells in colostrum was detected. Colostrum contains a different distribution of lymphocyte subsets with respect to peripheral blood from mothers, confirming the observation that lymphocytes probably migrate in milk in a selective way. Colostrum T and B lymphocytes appear to be enriched with subsets possessing effector functions or belonging to the innate immune system, what could transfer a prompt line of defence to offspring.

Different modulating effects of adenosine on neonatal and adult polymorphonuclear leukocytes

Polymorphonuclear leukocytes (PMNs) are the major leukocytes in the circulation and play an important role in host defense. Intact PMN functions include adhesion, migration, phagocytosis, and reactive oxygen species (ROS) release. It has been known for a long time that adenosine can function as a modulator of adult PMN functions. Neonatal plasma has a higher adenosine level than that of adults; however, little is known about the modulating effects of adenosine on neonatal PMNs. The aim of this study was to investigate the effects of adenosine on neonatal PMN functions. We found that neonatal PMNs had impaired adhesion, chemotaxis, and ROS production abilities, but not phagocytosis compared to adult PMNs. As with adult PMNs, adenosine could suppress the CD11b expressions of neonatal PMNs, but had no significant suppressive effect on phagocytosis. In contrast to adult PMNs, adenosine did not significantly suppress chemotaxis and ROS production of neonatal PMNs. This may be due to impaired phagocyte reactions and a poor neonatal PMN response to adenosine. Adenosine may not be a good strategy for the treatment of neonatal sepsis because of impaired phagocyte reactions and poor response.

Neonatal sepsis and neutrophil insufficiencies

Sepsis has continuously been a leading cause of neonatal morbidity and mortality despite current advances in chemotherapy and patient intensive care facilities. Neonates are at high risk for developing bacterial infections due to quantitative and qualitative insufficiencies of innate immunity, particularly granulocyte lineage development and response to infection. Although antibiotics remain the mainstay of treatment, adjuvant therapies enhancing immune function have shown promise in treating sepsis in neonates. This article reviews current strategies for the clinical management of neonatal sepsis and analyzes mechanisms underlying insufficiencies of neutrophil defense in neonates with emphasis on new directions for adjuvant therapy development.

Role of innate host defenses in susceptibility to early-onset neonatal sepsis

Neonatal sepsis continues to take a devastating toll globally. Although adequate to protect against invasive infection in most newborns, the distinct function of neonatal innate host defense coupled with impairments in adaptive immune responses increases the likelihood of acquiring infection early in life, with subsequent rapid dissemination and death. Unique differences exist between neonates and older populations with respect to the capacity, quantity, and quality of innate host responses to pathogens. Recent characterization of the age-dependent maturation of neonatal innate immune function has identified novel translational approaches that may lead to improved diagnostic, prophylactic, and therapeutic modalities.

Dysfunction of innate immunity and associated pathology in neonates

The neutrophils and complement system are the critical elements of innate immunity mainly due to participation in the first line of defense against microorganisms by means of phagocytosis, lysis of bacteria and activation of naive B-lymphocytes. In this report we provide an overview of the up to date information regarding the neutrophil and complement system's functional ability in newborn infants in association with the maternal conditions that exist during the intrauterine stage, gestational age and post-neonatal pathology. The neonates' capacity to control the neutrophil and complement protein activation process has also been discussed because of the evidence that uncontrolled activation of these immune elements provides a significant contribution to the tissue damage and subsequent pathology. The authors are confident that despite the many unanswered questions this review updates their knowledge and points the need for further research to clarify the role of the age-associated dysfunction of neutrophils and complement system in the infection and inflammation related pathology of newborn infants.

Generation of reactive oxygen species by umbilical blood cells and immune status of newborns at risk of infectious inflammatory diseases

We carried out a comparative clinical and immunological examination of newborns whose mothers were at risk of infectious inflammatory diseases. Umbilical blood cell phenotype was evaluated by flow cytofluorometry. ROS level was evaluated by chemiluminescence intensity. Spontaneous production of ROS and phagocytic activity of cells in the whole umbilical blood was reduced in newborns born after complicated pregnancy. Low immunoregulatory index indicating changed CD4+/CD8+ ratio and low percentage of natural killer cells were observed in children with manifestations of bacterial infection. ROS production by isolated granulocytes and the effects of PI3K and p38 MAPK (kinases involved in the regulation of activity of NADPH oxidase responsible for the production of ROS) in the risk group infants differed from the corresponding parameters in the control group. The results indicate shifts in the phagocytosis system, immune status, and the receptor-conjugated regulatory systems of ROS generation by granulocytes in newborns at risk of infectious inflammatory diseases.

Oxidase activity in cord blood neutrophils: a balance between increased membrane associated cytochrome b558 and deficient cytosolic components

INTRODUCTION

Newborn infants are prone to develop life-threatening pyogenic infections. Alterations in the function of neonatal phagocytes, including the activity of the neutrophil NADPH oxidase, have been suggested as one cause of increased susceptibility to such infections.

METHODS

In the present study, comprehensive analysis of NADPH oxidase enzyme system was performed in cord blood neutrophils from vaginally and cesarean section (CS) delivered, healthy, full-term infants.

RESULTS

Superoxide anion (O(2) (-)) production by intact neutrophils from cord blood in response to soluble stimuli was equal to or increased compared to levels generated by cells from adult controls. In the sodium dodecyl sulfate (SDS) cell-free system, cytosol and plasma membrane from cord blood neutrophils generated O(2) (-) at comparable rates to subcellular fractions from healthy adults. However, mixing experiments demonstrated higher O(2) (-) generation with combination of cytosol from adult controls and membrane from cord blood neutrophils and lower O(2) (-) production with combination of cytosol from cord blood neutrophils and membrane from adult controls. Kinetic parameters for cord blood specimens were no different from those obtained for fractions from adult controls. Quantitative analysis of cytosolic components showed moderately reduced amount of p40-phox, p47-phox, and p67-phox in neutrophils from cord blood. In contrast, cytochrome b(558) content of plasma membrane of cord blood neutrophils was approximately 2-fold higher compared to adult controls.

CONCLUSION

The normal to increased respiratory burst of intact cord blood neutrophils is the result of alterations to oxidase components: increased content of cytochrome b(558) in the plasma membrane and decreased levels of cytosolic components p47-phox, p67-phox, and p40-phox.

The immunological components of human milk and their effect on immune development in infants

There have been considerable advances in our understanding of the diverse mixture of bioactive components in human milk that influence the immune status of infants by not only providing protection but also facilitating development, tolerance, and an appropriate inflammatory response. It could be suggested that milk is the communication vehicle between the maternal immune system and the infant, a system actively directing and educating the immune, metabolic, and microflora systems within the infant, while conferring multiple means of protection from pathogens. The physiological and protective functions of many of the immune components in human milk have been deduced not from studies in infants but from what is known in other species and in vitro models. This update briefly reviews immune development in infants and focuses on current knowledge of how both the "classical" immune and the nonimmune ingredients found in mature human milk promote immune development, facilitate the development of tolerance, and regulate the inflammatory response of infants.

Differential maturation of the innate immune response in human fetuses

Newborns and especially preterm infants show a unique susceptibility to severe bacterial infections that cause significant morbidity and mortality. As very few data are available on innate immune functions in human fetuses, we conducted a comprehensive study to investigate the expression of several adhesion molecules essentially involved in migration (CD11a, CD11b, CD11c, CD18, and CD62L). Furthermore, phagocytic activity, generation of respiratory burst products, and production of several proinflammatory cytokines were assessed. Various functions of the fetal innate immune system were demonstrated to be essentially different from those observed in term neonates or adults. Expression of several surface markers was significantly diminished on fetal granulocytes. Furthermore, a significantly reduced phagocytic activity of fetal granulocytes and monocytes was found, contrasted by an enhanced generation of reactive oxygen products. In addition, we demonstrate that significant numbers of fetal monocytes are capable of the production of proinflammatory cytokines in response to stimulation. However, the pattern of cytokine production is different from the more mature individuals: the number of IL-6- and tumor necrosis factor-alpha-positive monocytes were significantly diminished, whereas more IL-8-producing monocytes were found compared with adults. The results of our study add significantly to our understanding of the maturation and impairment of the innate immune response.

Labor promotes neonatal neutrophil survival and lipopolysaccharide responsiveness

Labor is a mild proinflammatory state that is associated with fetal leukocytosis. Elective cesarean section has been linked with increased neonatal morbidity, which may be partially immune mediated. We hypothesized that labor may alter neutrophil phenotype and thereby decrease neonatal complications. We characterized neutrophil function and survival in normal neonates after either uncomplicated vaginal delivery (VD) or elective cesarean section (CS) without labor. Spontaneous neutrophil apoptosis is delayed in cord blood neutrophils of neonates after normal labor (VD) compared with CS, as assessed by propidium iodide DNA incorporation using flow cytometry. This demonstrates their ability to maintain an inflammatory response. CD11b expression on neonatal neutrophils after CS is decreased, providing further evidence of altered activation or priming. Lipopolysaccharide responsiveness, characterized by CD11b and apoptosis, is similar in VD and adults, but CS-derived neutrophils are unresponsive. Baseline TLR-4 levels are elevated in CS in contrast to the other groups, although expression is not up-regulated by lipopolysaccharide co-incubation. Neonatal neutrophil survival and function are altered by labor and may increase antibacterial function and neutrophilia. This suggests that labor of any duration may be immunologically beneficial to the normal term neonate.

Neonatal neutrophils: the good, the bad, and the ugly

Neonates are at considerable risk for bacterial and fungal infections,due in great part to a variety of age-related impairments in neutrophil function. In addition, evidence suggests that the tendency of the most immature neonates to develop chronic inflammatory disorders is also related to neutrophil dysfunction. This article provides an overview of specific functional deficiencies of neutrophils that have been reported in neonates.

Neutrophil adhesion molecule expression in the developing neonatal rat exposed to hyperoxia

Neonatal rats have an increased tolerance to hyperoxia, which is associated with a diminished pulmonary inflammatory response compared with adults. To investigate this differing response, expression of the neutrophil adhesion molecules, L-selectin and CD18, and levels of soluble L-selectin, were examined using flow cytometry and sandwich enzyme-linked immunosorbent assay on air-exposed neonatal rat neutrophils at 0-24 and 72 h and 7, 10, 14, and 21 d of age compared with the adult and after exposure to hyperoxia (>/= 98% O2) for 56 h in adults and for 72 h and 7 d in neonates. Expression of L-selectin in 0-24-h neonates was similar to adults, but was significantly lower than adults at 72 h and 7 d (P = 0.011). Soluble L-selectin levels were significantly higher than those in adults in the 0-24- and 72-h neonates (P < 0.001). CD18 expression in unstimulated and activated neutrophils of neonatal rats was higher at 0-24 h than in the adult (P < 0.001), but thereafter did not differ from adults. After hyperoxic exposure, L-selectin did not differ between the exposure groups but soluble L-selectin tended to increase in neonates after 7 d of O2 exposure Finally, CD18 was significantly higher after hyperoxic exposure of the adult (P = 0.008), but did not change with oxygen exposure in the neonate. Based on these findings, we speculate that differences between neonatal and adult rats in expression of L-selectin may contribute to delayed oxygen toxicity in neonatal rats.