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Objectives: To enumerate the cellular composition of the airways in infants with acute bronchiolitis. Methodology: Cells were obtained by airway lavage from the upper and lower airway and the peripheral blood of infants with respiratory syncytial virus (RSV)+ bronchiolitis, RSV– bronchiolitis and age-matched controls. Results: Neutrophils are the predominant cells present in the upper and lower airway. Neutrophils are present at a higher number/unit volume in the airway than in the peripheral blood. Conclusions: Neutrophils, being the dominant cellular infiltrate into the airway, are likely to contribute to the pathophysiology of bronchiolitis. Therapies targeted at limiting neutrophil influx or neutrophil-mediated damage in the airway may have a therapeutic role. [ABSTRACT FROM AUTHOR]

Changes in plasma fibronectin concentrations were determined during bacterial septicaemia in extremely preterm infants. The study was a prospective study of fibronectin concentrations in infants of less than 30 weeks' gestation. Concentrations were determined at birth, before sepsis, and throughout the episode of sepsis. Fibronectin concentrations at birth or immediately before sepsis were not significantly different between those infants who developed septicaemia and those who did not (98 (15) v 97 (10) micrograms/ml). In the infants with septicaemia, fibronectin concentrations decreased significantly on day 1 (106 (13) v 173 (18) micrograms/ml for the controls) and remained significantly lower on day 2 (123 (26) v 201 (17) micrograms/ml). By day 5 fibronectin concentrations had increased and were no longer statistically different from controls. Fibronectin is a key modulator of the immune response, with important functions in neutrophil adhesion, bacterial opsonisation, T cell activation, and vascular integrity. Acute depletion of plasma fibronectin during sepsis in preterm neonates may further abrogate their ability to control sepsis. [ABSTRACT FROM AUTHOR]

Objective: A comprehensive, well-trained pediatric workforce is needed to ensure high-quality child health interventions around the globe. Further understanding of pediatric workforce training capacity would assist planning at the global and country level. The purpose of this study was to better understand the availability and process of training programs for pediatricians and pediatric subspecialists worldwide, as well as in-country presence of subspecialists., Methods: A survey was developed and distributed by e-mail to national pediatric leaders across the globe. The survey asked about the number of pediatric training programs, duration and logistics of training, and whether practicing pediatric subspecialists and subspecialty training programs were available in their country., Results: We received responses from 121 of the 166 countries contacted (73%). Of these, 108 countries reported the presence of one or more general pediatric postgraduate training programs, ranging from 1 to 500 programs per country. The number of training programs did not vary significantly by gross domestic product but did vary by region, with the fewest in Africa (P < .001). Most countries identified national guidelines for training (82% of countries) and accreditation (84% of countries). Availability of pediatric subspecialists varied significantly by income and region, from no subspecialties available in 4 countries to all 26 queried subspecialties available in 17 countries. Neonatology was most common, available in 88% of countries. Subspecialty training programs were less available overall, significantly correlating with country income., Conclusion: Education for general pediatrics and pediatric subspecialties is quite limited in many of the countries surveyed, particularly in Africa. The creation of additional educational capacity is a critical issue challenging the adequate provision of pediatrics and pediatric subspecialty services., (Copyright © 2019 Academic Pediatric Association. Published by Elsevier Inc. All rights reserved.)

Bronchiolitis is one of the leading causes of hospitalisation in infancy, with highly variable clinical presentations ranging from mild disease safely managed at home to severe disease requiring invasive respiratory support. Identifying immune biomarkers that can predict and stratify this variable disease severity has important implications for clinical prognostication/disposition. A systematic literature search of the databases Embase, PubMed, ScienceDirect, Web of Science, and Wiley Online Library was performed. English language studies that assessed the association between an immune biomarker and bronchiolitis disease severity among children aged less than 24 months were included. 252 distinct biomarkers were identified across 90 studies. A substantial degree of heterogeneity was observed in the bronchiolitis definitions, measures of disease severity, and study designs. 99 biomarkers showed some significant association with disease severity, but only 18 were significant in multiple studies. However, all of these candidate biomarkers had comparable studies that reported conflicting results. Conclusion: The heterogeneity among included studies and the lack of a consistently significant biomarker highlight the need for consensus on bronchiolitis definitions and severity measures, as well as further studies assessing their clinical utility both in isolation and in combination., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Objective: Our primary objective was to examine the global paediatric workforce and to better understand geographic differences in the number of paediatricians globally. Secondary objectives were to describe paediatric workforce expectations, who provides children with preventative care and when children transition out of paediatric care., Design: Survey of identified paediatric leaders in each country., Setting: Paediatric association leaders worldwide., Main Outcome Measures: Paediatrician numbers, provision of primary care for children, age of transition to adult care., Results: Responses were obtained from 121 countries (73% of countries approached). The number of paediatricians per 100 000 children ranged from a median of 0.5 (IQR 0.3-1.4) in low-income countries to 72 (IQR 4-118) in high-income countries. Africa and South-East Asia reported the lowest paediatrician density (median of 0.8 paediatricians per 100 000 children, IQR 0.4-2.6 and median of 4, IQR 3-9, respectively) and fewest paediatricians entering the workforce. 82% of countries reported transition to adult care by age 18% and 39% by age 15. Most countries (91%) but only 64% of low-income countries reported provision of paediatric preventative care (p<0.001, Cochran-Armitage trend test). Systems of primary care provision varied widely. A majority of countries (63%) anticipated increases in their paediatric workforce in the next decade., Conclusions: Paediatrician density mirrors known inequities in health provider distribution. Fewer paediatricians are entering the workforce in areas with already low paediatrician density, which may exacerbate disparities in child health outcomes. In some regions, children transition to adult care during adolescence, with implications for healthcare training and delivery. Paediatrician roles are heterogeneous worldwide, and country-specific strategies should be used to address inequity in child health provision., Competing Interests: Competing interests: None declared.

Pertussis is a vaccine-preventable disease that causes morbidity and mortality, particularly in infants and children <5 years of age. The Global Pertussis Initiative (GPI) recommendations represent a systematic evaluation and prioritization of strategies to prevent pertussis-related infant and child deaths, reduce global disease burden and prevent resurgence through vaccination strategies and public health policies at national, regional and local levels. The GPI recommendations are based on clinical trials and observational and surveillance data, which are essential in the planning, implementation and evaluation of vaccination practices and best use of available resources. Many low- and middle-income countries (LMIC) continue to use whole-cell pertussis (wP) vaccines for primary vaccination, while most high-income countries have replaced wP with the less-reactogenic acellular pertussis (aP) vaccines. This present manuscript pertains to discussions held during the GPI's meeting on November 11-13, 2016, in Cape Town, Republic of South Africa. The GPI recommends that LMIC aim for high coverage of infant series pertussis vaccines as a priority. In LMIC and countries with constrained vaccine funding, if wP vaccines are currently used, wP should continue to be used. Furthermore, given that protection against disease and death due to pertussis in neonates is a key priority of the GPI, it recommends that ap immunization in pregnancy should be implemented as a priority in all countries if resources allow. Given that surveillance and epidemiology data on which to base vaccine decisions are important, the GPI also suggests that, in areas where wP vaccines are implemented, standardization and calibration of wP vaccines are checked, considering the many different manufacturers and variable standards of production and quality control. In addition, as immunity to pertussis wanes following the primary infant series of vaccination, the GPI further recommends that toddlers, adolescents, healthcare and childcare workers receive booster vaccine doses, where resources allow., (Copyright © 2018 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pertussis remains a major cause of morbidity and mortality, particularly in infants and young children, and despite the availability of vaccines and pertinent national and international guidelines. The disease burden is more severe in low- and middle-income countries (LMICs), especially in the African continent. Pertussis is more prevalent among young infants in Africa. Poor or no pertussis surveillance, lack of disease awareness, diagnostic limitations, and competing health priorities are considered key contributory factors for this high pertussis burden in Africa. Most African countries use whole-cell pertussis (wP) vaccines, but coverage with three primary doses of diphtheria-tetanus-pertussis vaccines falls short of the World Health Organization's recommended goal of >90%. The Global Pertussis Initiative (GPI) works toward developing recommendations through systematic evaluation and prioritization of strategies to prevent pertussis-related infant and child deaths, as well as reducing global disease burden to acceptable national, regional, and local levels. For countries using wP vaccines, the GPI recommends continuing to use wP to improve primary and toddler booster vaccination coverage. Vaccination during pregnancy is the next priority when acellular pertussis (aP) vaccines and other resources are available that directly protect newborns too young to be vaccinated, followed by, in order of priority, booster doses in older children, adolescents, healthcare workers and finally, all adults. Improved surveillance should be a high priority for African LMICs assessing true disease burden and vaccine effectiveness to inform policy. More research is warranted to evaluate the safety and efficacy of wP and aP vaccines and strategies, and to determine their optimal use., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Viral bronchiolitis is one of the most common hospital presentations in infancy and as such represents a major healthcare burden worldwide. However despite this, there are currently no effective targeted therapies nor can those infants at highest risk for developing severe disease or subsequent respiratory morbidity be predicted on initial hospital presentation. Current definitions of bronchiolitis in the published literature vary significantly in terms of the age range at presentation, specific clinical symptoms, causative virus, and the inclusion or exclusion of infants with previous presentations and/or various comorbidities. In this review, we highlight how this heterogeneity among definitions contributes to a lack of clarity on this condition and its likely multiple endotypes. We argue that without a new universal consensus definition or sets of definitions, progress into bronchiolitis will continue to be stalled., (© 2017 Wiley Periodicals, Inc.)

Objective: Infants are born immunologically immature. However, breastfeeding mothers retain an immunological link to their infants. While it is generally accepted that infants are at an immunological advantage when compared with formula-fed infants, the benefit of long-term exclusive breastfeeding by atopic mothers remains controversial. Inconsistency in the conferral of benefit may be due to differences in the immunological constituents passed to the recipient infant. The aim of this investigation was to examine the profile of human milk cells and cytokines from asthmatic compared to non-asthmatic mothers., Methods: Twenty-five exclusively breastfeeding mothers with a clinical diagnosis of asthma were postpartum age matched in a double-control 2:1 design with 50 non-asthmatic controls. Each mother provided a single milk sample which was assayed for cell differential by flow cytometry, for ex vivo cytokine production in culture and for aqueous phase cytokines., Results: Milks from asthmatic mothers differed from non-asthmatics in that they contained a higher proportion of polymorphonuclear (PMN) cells and lower proportion of lymphocytes, predominantly CD3 + /CD4 + T helper cells, reflected by a decrease in the chemokine CCL5 in the milk aqueous phase. More PMN and lymphocytes from asthmatic mothers expressed the adhesion molecule CD11b and lymphocytes the IgE receptor CD23, than those from non-asthmatic mothers., Conclusions: Changes to human milk leucocyte prevalence, activation state and cytokines due to maternal asthma may result in changes to immunological priming in the infant. Consequently, the protective effect of long-term breastfeeding may be altered in these mother-infant pairs., (Copyright © 2016 SEICAP. Published by Elsevier España, S.L.U. All rights reserved.)

Competing Interests: Competing interests: None declared.

Background: Hospitalization with bronchiolitis is linked to the development of early childhood chronic wheeze and asthma. Viral etiology and severity of inflammation are potential contributing factors. Previously we observed reduced airway neutrophil infiltration in breastfed bronchiolitic infants, with a corresponding reduction in disease severity. This study aimed to examine whether respiratory viral etiology and co-infection alters the pattern of neutrophil influx, and the inflammatory mediator profile, resulting in epithelial damage in bronchiolitis., Methods: Nasopharyngeal aspirates (NPAs) collected from hospitalized infants were assessed for viruses, soluble protein, cellular infiltrate, interleukin (IL)-6, -8, and myeloperoxidase (MPO)., Results: NPAs were collected from 228 bronchiolitic and 14 non-bronchiolitic infants. In the bronchiolitic cohort, human rhinovirus was most prevalent (38%), followed by respiratory syncytial virus (36%), adenovirus (10%), and human metapneumovirus (6%), with 25% positive for viral co-infections and 25% negative for all screened viruses. Viral-induced bronchiolitis was associated with increased cellular infiltrate and protein, above control, and virus-negative infants (P < 0.05). Cellular infiltrate correlated to IL-6, -8, and MPO (r = 0.331, 0.669, and 0.661; P < 0.01). Protein, IL-6, -8, and MPO differed significantly between viral groups; however, the majority of marker values for all groups fall within an overlapping, indistinguishable range, precluding their use as biomarkers of viral etiology. No significant difference was found between single and viral co-infections for any parameter., Conclusion: Bronchiolitic infants presenting with a detectable respiratory virus during hospitalization demonstrated elevated markers of airway tissue inflammation and injury. In this cohort, viral etiology did not discernibly modulate chemokine-mediated neutrophil infiltration and activation. Pediatr Pulmonol. 2017;52:238-246. © 2016 Wiley Periodicals, Inc., (© 2016 Wiley Periodicals, Inc.)

The mechanism by which severe bronchiolitis can result in the development of recurrent childhood wheeze is unclear. However, mucosal inflammation and immune activation may play a major role. Prostaglandin (PG) E(2) has been highlighted as a possible therapeutic target for both the treatment of bronchiolitis and the prevention of subsequent airway hyperresponsiveness. The aim of this pilot study was to examine PGE(2) in the airways of infants hospitalised with bronchiolitis. Nasopharyngeal aspirates (NPA) were collected from 18 infants within 12 hours of admission and assayed by enzyme immunoassays for PGE(2), interleukin (IL)-10, and IL-12, as well as cyclooxygenase (COX) 1 and 2 activity. NPA PGE(2) concentration correlated with length of illness preadmission, but was not related to disease severity, causal virus, or IL-10. NPA COX 1 and 2 activity and IL-12 were all below the level of detection. Neither NPA PGE(2) nor disease severity was related to development of recurrent wheeze over 3 years following bronchiolitis. These data suggest that nasopharygeal PGE(2) at hospital admission may be neither directly causal or diagnostic of severity of infant bronchiolitis, or prognostic of development of recurrent wheeze. However, large-cohort temporal examinations are required to adequately define this mediator as a therapeutic target for bronchiolitis.

Breastfeeding during the first 12 months of life confers demonstrable immunologic benefit against infective pathogens, including those of the respiratory tract. However, the mechanism by which the ingestion of human milk modifies immunologic defense against such pathogens remains elusive. Bronchiolitis, caused predominantly by respiratory syncytial virus, is the most common clinical presentation of severe upper respiratory illness requiring hospitalization in infants and remains one of the developed world's leading causes of infant mortality and morbidity over both the short and long term. The mechanism by which an early, severe case of bronchiolitis can result in the development of recurrent childhood wheeze or asthma is unclear; however, mucosal inflammation and pulmonary neutrophilia are believed to play a significant role. The aim of this study was to examine the immune response of breastfed infants hospitalized with severe bronchiolitis, compared with formula-fed controls. Nasopharyngeal aspirates (NPA) were collected from 18 infants (aged

Although epidemiological evidence is generally supportive of a causal association between respiratory syncytial virus (RSV) bronchiolitis during infancy and the development of persistent wheeze/asthma, if not allergy, the mechanism by which this occurs and an explanation for why all children do not succumb remains to be elucidated. Breast feeding has been found to confer a protective effect against respiratory infections such as RSV bronchiolitis and allergy; however, again there is little direct evidence and no clear mechanism. In this study, we examined whether human milk immunomodulatory factors (cells, cytokines) change in response to clinically diagnosed, severe bronchiolitis in the recipient breast-fed infant. We examined milk from 36 breast feeding mothers of infants hospitalized with bronchiolitis and compared them with milk from 63 mothers of postpartum age-matched healthy controls. Milks from mothers of infants hospitalized with bronchiolitis had significantly greater numbers of viable cells when compared with the milks obtained from mothers of healthy infants (1.3 +/- 0.4 vs. 0.3 +/- 0.03 x 10(6) cells/ml, mean +/- s.e.m.; p < or = 0.001). Further, the cells obtained from the mothers of infants hospitalized with bronchiolitis were found to produce a skewed cytokine profile ex vivo in response to stimulation by live RSV but not when cultured with a non-specific mitogen (concanavalin A). This study provides preliminary evidence for an immunological link between mothers and their breast-fed infants during severe respiratory infections as well as a possible contributing factor to the development of persistent wheeze in these infants.

The Global Pertussis Initiative (GPI) was established in 2001 to assess the global extent of the ongoing problem of pertussis and to evaluate and prioritize pertussis control strategies. Exchange of data, knowledge, and experience, facilitated by discussion and debate, resulted in the formulation, in 2002, of the following recommendation: all countries should consider expanding existing vaccination strategies to include adding pertussis booster doses to pre-school children (4-6 years old), to adolescents, and to those specific adults that have the highest risk of transmitting Bordetella pertussis infection to vulnerable infants. The GPI met again in 2005, where it reinforced its previous recommendation for universal adolescent immunization. Additionally, the GPI recommended implementation of the cocoon strategy (immunization of family members and close contacts of the newborn) in countries where it is economically feasible, and encouraged efforts toward global standardization of pertussis disease clinical definitions and diagnostics. Universal adult vaccination is a logical goal for the ultimate elimination of pertussis disease, but feasibility issues remain obstacles to implementation.

A protective association between breastfeeding and the development of bronchial asthma has been demonstrated. However, a mechanism remains unclear. FA present in human milk but rare in infant formula have been associated with marked immunological modulation as well as some indications of protection from asthma development. We examined the effect of in vitro manipulation of membrane phospholipid on the production of cytokines and prostaglandin (PG)E2 by respiratory epithelial cells (A549) in response to stimulation by mast cell mediators of allergic disease [histamine, tumor necrosis factor (TNF)-alpha, interleukin (IL)-4 and IL-5]. DHA and CLA significantly decreased the production of IL-8 in response to stimulation by TNF-alpha [2907 +/- 970 (DHA) and 6471 +/- 1203 (CLA) vs. 12,287 +/- 2309 (control) pg/mL; P < or = 0.05, mean +/- SEM], whereas both EPA and DHA reduced histamine-stimulated RANTES (regulation on activation, T cell-expressed and -secreted) production [2314 +/- 861 (EPA) and 877 +/- 326 (DHA) vs. 8526 +/- 1118 (control) pg/mL; P < or = 0.03]. PGE2 released in response to histamine was decreased by n-3 [1305 +/- 399 (alpha-linolenic acid), 406 +/- 73 (EPA), and 265 +/- 32 (DHA) vs. 9324 +/- 3672 (control) pg/mL; P < or = 0.05] and increased by n-6 [18,843 +/- 4439 (arachidonic acid) vs. 9324 +/- 3672 (control) pg/mL; P = 0.02], with CLA producing a decrease of the same magnitude as DHA [553 +/- 126 (CLA) vs. 9324 +/- 3672 (control) pg/mL; P = 0.03]. This study demonstrates the potential for immunological manipulation of the respiratory epithelium by FA in situ during allergic responses and suggests that further investigation into FA intervention in infants via human milk or supplemented infant formula, to prevent the development of allergic disease, may be worthwhile.

Development of lymphocyte subpopulations and response to antigen exposure will be influenced by the limited ability of neonates to produce cytokines. In the case of cytokines such as interleukin (IL)-2 which are potent T lymphocyte regulators but poorly produced by newborn infants, the supply of cytokines through human milk could alleviate an immunological deficit and potentially aid the maturation of the immune system. We analysed human milk from 52 mothers (15-357 days postpartum) by ELISA to determine levels of aqueous IL-2, as well as production by human milk cells. IL-2 was detectable (>8 pg/mL) in the aqueous phase of 81% of all day 1 samples with no significant difference found in the mean concentration over 3 consecutive days. IL-2 was produced constitutively at detectable levels by 57% of milk cell samples and production was significantly increased by stimulation with Con A (380%). No correlation was found between aqueous and cellular IL-2, however there was a significant correlation between milk aqueous IL-2 and serum IL-2. This is the first report of IL-2 in the aqueous phase of human milk. A supply of exogenous IL-2 in human milk may provide the suckling infant with important immunological signals during a significant stage of T cell development.

Background: The Global Pertussis Initiative, an expert scientific forum, was established to address the ongoing problems associated with pertussis disease worldwide., Methods: The group analyzed pertussis disease trends, developed recommendations to improve disease control through expanded vaccination strategies, and proposed solutions to barriers to implementation and support of research activities., Results: Bordetella pertussis infection is endemic and continues to be a serious problem among unvaccinated or incompletely vaccinated infants. In addition, the reported incidence of pertussis disease is increasing in adolescents and adults, who not only experience a considerable health burden themselves but also infect vulnerable infants., Conclusions: Current vaccination strategies need to be reinforced. Expanded vaccination should include adding booster doses to existing childhood schedules (preschool or adolescent) and booster doses for those specific adult subgroups that have the highest risk of transmitting B. pertussis infection to infants (i.e., new parents, other contacts of newborns, and health care workers). More epidemiological studies and studies of disease transmission and the cost-effectiveness of vaccination would be valuable, and surveillance, diagnostic improvements, and educational campaigns are needed for implementation. However, as a prelude to universal adult vaccination, immediate universal adolescent vaccination should be instituted in countries in which it is economically feasible.

Viral respiratory infection is very common. Respiratory syncytial virus (RSV) infects almost all children during the first 2 years of life. Respiratory syncytial virus is the most frequent cause of bronchiolitis, which is strongly linked with asthma. However, the pathophysiology of RSV bronchiolitis is unclear. Neutrophils are the predominant airway leucocytes in RSV bronchiolitis and other viral infections. Neutrophils and their products are likely to play an important role in viral infection. Current evidence indicates that: (i) viral infection of epithelial cells increases the production of neutrophil chemoattractants or chemokines, which induce neutrophil migration into the inflammatory sites; (ii) the expression of adhesion molecules on neutrophils and epithelial cells is up-regulated in viral infection, and neutrophil-epithelial adhesion is increased; (iii) neutrophils augment epithelial damage and detachment induced by viral infection and contribute to the pathophysiology of viral disease; (iv) neutrophil apoptosis is up-regulated in RSV infection, which may be an in vivo mechanism to limit neutrophil-induced epithelial damage; (v) inhibitors of chemokines, adhesion molecules or neutrophil proteases may be useful in prevention of neutrophil-induced epithelial damage. In conclusion, neutrophils play an important role in viral infection, and intervention to prevent neutrophil-induced epithelial damage may be a potential clinical therapy.

Respiratory epithelium is both a target and an effector of airway inflammation. Adhesion molecules on epithelium play an important role in a variety of airway diseases. Respiratory syncytial virus (RSV) is the most important pathogen for airway diseases in infants. The expression of adhesion molecules on epithelium in RSV infection, however, is unclear. The expression of selected adhesion molecules and major histocompatibility complex (MHC) class I and II antigens on a human alveolar type II epithelial cell line (A549) infected with RSV was investigated by means of flow cytometry and immunocytochemistry. The results showed that intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) were expressed on A549 cells at a low level. E-cadherin and MHC class I antigen were constitutively expressed on the cells. RSV infection of A549 cells significantly upregulated the expression of ICAM-1, VCAM-1 and MHC class I and II antigens on these cells. RSV infection also altered the expression of E-cadherin on A549 cells. Immunostaining showed that E-cadherin was mainly upregulated around or in RSV-induced giant cells. These data suggest that respiratory syncytial virus infection of respiratory epithelial cells enhances the expression of adhesion molecules and major histocompatibility complex antigens. These changes may play an important role in the pathophysiology of respiratory syncytial virus disease.

Respiratory syncytial virus (RSV) is the most frequent cause of bronchiolitis. However the pathophysiology of bronchiolitis is unclear. Leukocytes, especially neutrophils, may play an important role in the pathogenesis of bronchiolitis. Whereas we have previously shown that neutrophils augment epithelial leakage and detachment in RSV infection in vitro, it is unknown whether epithelial damage occurs in vivo in infants with RSV bronchiolitis. We hypothesized that respiratory epithelial damage occurs in infants with RSV bronchiolitis and that surfactant proteins leak into the circulation. The plasma concentrations of surfactant protein-A and surfactant protein-B in infants with RSV bronchiolitis were measured by ELISA. Plasma immunoreactive surfactant protein-B in infants with RSV bronchiolitis was markedly higher than that in matching controls. Our study suggests that alveolocapillary permeability is increased in infants with RSV bronchiolitis in vivo and that surfactant protein-B may be a sensitive marker for lung injury in such infants.

Infancy is a time of unparalleled infection exposure. Coming from the privilege of the uterus, the newborn infant must make appropriate immune responses following infection that eliminates the infection but protects the host. There is evidence that in sudden infant death syndrome (SIDS) subjects there is a background of recent 'trivial' infection and immunological/inflammatory reactivity. This immunological/inflammatory reactivity is seen in enhanced pulmonary immunoglobulins and T-cell activation. It may be that in certain SIDS cases a trivial infection triggers an exaggerated inflammatory response, inducing cytokine cascades and eventual demise of the infant.

Bronchiolitis is characterized histologically by epithelial necrosis and peribronchial infiltration of leukocytes, with a high percentage of neutrophils in the airways. We investigated the expression of adhesion molecules (CD11a, CD11b, CD18, CD31, CD54, and CD62L) on neutrophils from nasopharyngeal aspirates (NPAs) and peripheral blood (PB) of infants with respiratory syncytial virus (RSV)-induced bronchiolitis. The expression of CD31 and CD62L on neutrophils from NPAs is decreased and the expression of CD11b, CD18, and CD54 on neutrophils from NPAs is increased compared with cells from PB of RSV-infected infants. The expression of CD18 and CD54 on neutrophils from PB of RSV-infected infants is also increased compared with cells from PB of control infants. Shedding of CD31 and CD62L on neutrophils in RSV infection may contribute to the neutrophil emigration from blood to airways; the upregulation of Mac-1 (CD11b/CD18) and CD54 on neutrophils may help explain the high percentage of neutrophils in the airways of RSV bronchiolitis; and the upregulation of Mac-1 may be involved in the increased neutrophil-airway epithelial adhesion in RSV infection.

Neutrophils are the predominant inflammatory cell in the lung tissues and airways in RSV infection, and can augment the epithelial cell damage induced by RSV. Neutrophil apoptosis has been suggested to be a mechanism to reduce the potential for tissue injury. The apoptosis of neutrophils from nasopharyngeal aspirates (NPA) (n = 19) and peripheral blood (PB) of infants with RSV bronchiolitis (n = 11) and PB from healthy controls (n = 9) was investigated. Monoclonal antibody against CD95 (Fas) and a binding protein Annexin V were used to determine the apoptosis of neutrophils. The expression of CD11b and CD18 on neutrophils was also detected with flow cytometry. The mean fluorescence intensity (MFI) of CD95 on neutrophils from RSV+ NPA was increased compared with cells from control PB (73.6 +/- 7.6 versus 31.5 +/- 4.3); the MFI of Annexin V, CD11b and CD18 on neutrophils from RSV+ NPA was up-regulated compared with cells from both control PB (105.3 +/- 18.1 versus 11.8 +/- 1.5; 1683 +/- 153.3 versus 841.1 +/- 72.3; 517 +/- 50.5 versus 147 +/- 8.7, respectively) and RSV+ PB (105.3 +/- 18.1 versus 35.8 +/- 4.1; 1683 +/- 153.3 versus 818 +/- 141.2; 517 +/- 50.5 versus 260 +/- 25.8, respectively). Furthermore, the percentage of neutrophils expressing Annexin V and the MFI of CD18 on neutrophils from RSV+ PB were increased compared with neutrophils from control PB. In addition, both CD11b (MFI) and CD18 (MFI) correlated with Annexin V (MFI) on neutrophils. We conclude that neutrophil apoptosis in RSV bronchiolitis is accelerated; and CD11b/CD18 may play an important role in RSV infection by influencing neutrophil apoptosis.

Vascular damage, initiated by host inflammatory cells, is a component of the pathophysiology of many acute and chronic inflammatory disorders. Neutrophil-mediated tissue damage is mediated primarily by proteinases, particularly elastase and cathepsin G. In this study we have identified endothelial binding of two key serine proteinase inhibitors (serpins), alpha 1-antitrypsin, the inhibitor of elastase, and alpha 1-antichymotrypsin, the inhibitor of cathepsin G. These serpins are shed from the endothelium into the supernatant when neutrophils adherent to the endothelium are activated. Endothelium activated by lipopolysaccharide (LPS) augments this process. Serpin-proteinase complexes activate neutrophils and induce further cytokine release, thereby amplifying inflammatory processes. Strategies aimed at preventing endothelial serpin depletion may help minimize vascular damage during inflammation.

Fibronectin has in the past been considered to function simply as a non-specific plasma opsonin. However, recent studies have demonstrated that this molecule plays an important role in fundamental components of the immune response, for example, neutrophil adhesion, T cell activation and endothelial function. Additionally, fibronectin is important in lung homeostasis where it contributes to alveolar epithelial integrity. In this study plasma fibronectin levels were measured longitudinally in a group of extremely preterm infants, mean gestational age 27 weeks. Plasma fibronectin levels at birth were significantly lower in the preterm study group than in term controls (mean 91 +/- 33 micrograms/mL compared with 214 +/- 62 micrograms/mL in the term controls, P < 0.0001). The preterm cohort demonstrated a more than two-fold rise in plasma fibronectin on days one and two; levels fell almost to baseline values by day three with a subsequent slow rise to a plateau by day 28. No further increase was seen by day 56. This sequence of early changes in fibronectin levels mirrored closely the time course of respiratory distress syndrome. Infants of mothers with pre-eclampsia had significantly lower peak fibronectin levels than in those without (P = 0.016), and those infants with bronchopulmonary dysplasia showed a trend towards lower basal fibronectin levels (P = 0.07) and a greater difference between peak and basal levels (P = 0.05). Neonates, particularly those born preterm, have blunted immunological responses to infection. Fibronectin plays a key role in immunological responsiveness. The significant changes in fibronectin levels after birth in the preterm neonate are likely to have important pathophysiological consequences.(ABSTRACT TRUNCATED AT 250 WORDS)

Wiskott Aldrich syndrome, a combined cellular and humoral X-linked immunodeficiency, is generally considered to be rare. The aim of this study was to ascertain the true prevalence in the paediatric population in Western Australia, describe the clinical features, and summarise the current literature on this unusual condition. All cases of Wiskott Aldrich syndrome presenting to Princess Margaret Hospital in Perth during the period from January 1960 to January 1990 were identified by a retrospective review of case records and by interviewing hospital immunology, haematology and general clinical staff. Nine cases of Wiskott Aldrich syndrome are described, demonstrating that the prevalence of Wiskott Aldrich syndrome in Western Australia is nine times that expected from previous reports. Death occurred in a number of patients before the correct diagnosis was recognised. The clinical features in this group are quite variable. Low isohaemagglutinins, elevated IgE, blunted DTH skin multitest, and very low CD8 numbers are however consistent features. Wiskott Aldrich syndrome may be more prevalent than previously recognised, and should be considered in males with thrombocytopenia and infection.

The CD45 family of Ag expressed by leukocytes play a key role in lymphocyte activation. In this study, we identify both a restricted pattern of expression of CD45 Ag by human endothelial cells and differences in m.w. of endothelial CD45 compared with lymphocyte CD45. Initially, immunoperoxidase staining of endothelial cells in culture revealed the presence of the CD45RO isoform provided the endothelial cells had been stimulated by IL-1 for several days. No other isoform of CD45 was detected by immunoperoxidase staining of endothelium. Leukocyte common antibodies, reputed to detect all isoforms of CD45, did not detect endothelial CD45RO. A polymerase chain reaction method was then used to demonstrate that the message for the CD45RO isoform was constitutively present, with increased levels after IL-1 stimulation. Western blot confirmed the presence of the RO isoform. No other CD45 isoform was detected, either by PCR amplification for message or by Western blot. There were clear differences between lymphocyte and endothelial CD45. The RO isoform expressed by endothelium has an estimated M(r) of 235,000 in contrast to lymphocyte RO that, on our gels, has an estimated M(r) of 190,000. Given the large surface area of endothelium (approximately 1 km2 in the human), the close apposition of lymphocytes and endothelium in immunologic tissues such as lymph nodes, and the pivotal role CD45 plays in activation, expression of CD45RO by endothelium may have important implications in lymphocyte-endothelial interactions. This is most likely to occur in endothelium after a few days of IL-1 stimulation, e.g., at sites of chronic inflammation, or in the draining lymph node of an inflammatory focus.

Glucocorticoids are very effective inhibitors of both the acute and chronic inflammatory response. In this study the hypothesis that glucocorticoids inhibit an early component of the inflammatory response, neutrophil adhesion to endothelium, by down-regulation of adhesion molecules on neutrophils or endothelium was examined. No effect of dexamethasone on neutrophil adhesion to endothelium or of antigen expression by neutrophils or endothelium was found. The mechanism of action of glucocorticoids in the inflammatory response is probably not mediated by alterations in adhesion molecules.

Flow cytometry is generally utilized to quantify antigen expression by cells in suspension. To detect antigens on endothelium, which grows as a monolayer, either the creation of a suspension of endothelial cells for flow cytometry, or the use of alternative techniques (such as immunoperoxidase staining) is required. We demonstrate here that creating suspensions of endothelial cells for flow cytometry underestimates the expression of certain antigens. In addition, morphological information regarding certain antigens (serpins and fibronectin) is only discernible by immune microscopy, a subjective procedure. We would recommend caution in using flow cytometry for the estimation of endothelial antigens. Using computerized estimates of microscopic immunostaining (e.g., with video image analysis) it may be possible to overcome some of the subjective limitations of immune microscopy.

Anti-CD9 antibodies which bind to the CD9 (p24) antigen are known to induce platelet and pre-B-cell aggregation. We show here that human endothelium expresses the CD9 antigen, and anti-CD9 antibodies incubated with endothelium induce a rapid increase in adhesion of neutrophils to endothelium by an action on the endothelial cell. This augmented adhesion is not mediated by glycoprotein IIb/IIIa or by the leucocyte integrins. Binding of anti-CD9 antibody to CD9 induces shedding of the CD9/anti-CD9 complex off the endothelial cell in a time-dependent manner. It is likely that CD9 binding to its ligand induces an activation event within the endothelial cell, resulting in surface expression of a pre-formed adhesive ligand for the neutrophil, or an activation change to a constitutively expressed ligand to render it functional.

We have observed that fibronectin has a characteristic fibrillar morphology within the extracellular matrix surrounding endothelial cells. This morphology, which is easily recognizable by conventional immunoperoxidase techniques, is disrupted if neutrophils are induced to degranulate on endothelial monolayers. Loss of the fibrillar morphology (degraded fibronectin) is characterized by fragmentation and diffuse spreading of fibronectin over the surface of the endothelial cells. Loss of the normal fibronectin architecture following neutrophil degranulation is more rapid and extensive in endothelium pretreated with Interleukin-1 (IL-1). In addition, there is loss from the fibronectin molecule of a chymotryptic protease-sensitive epitope recognized by a cellular fibronectin specific antibody. Degraded fibronectin is stimulatory for neutrophils, and is likely to induce further fibronectin breakdown. This sequence has the potential to set up an amplification inflammatory loop with neutrophil mediated loss of vascular homeostasis. Alteration of fibronectin architecture is a useful marker of endothelial injury, and has important pathophysiological consequences.

The majority of studies involving neutrophil integrin expression and function are performed at physiological temperatures subsequent to routine preparative procedures at 4 degrees C. We have shown that surface expression of the leukocyte integrin molecules on neutrophils is increased by cooling and subsequently re-warming of neutrophils to 37 degrees C when compared with cells held at room temperature or 37 degrees C. This increase in expression is secondary to prior cooling of the neutrophils. There is an associated increase in function of these newly expressed adhesion molecules, making the neutrophils more adherent to endothelium. Preparation of cells at 4 degrees C and subsequently warmed to 37 degrees C is stimulatory for neutrophils, probably causing translocation of intracellular stores of the leukocyte integrins to the cell surface in a manner analogous to the stimulant FMLP. Our results indicate that the cooling of neutrophils during isolation is an inappropriate method of neutrophil preparation.

The incidence of the sudden infant death syndrome parallels that of respiratory tract infections in the paediatric community. On the basis that the aetiology of the sudden infant death syndrome may lie in an unusual response to a trivial intercurrent respiratory infection a necropsy study was carried out investigating pulmonary immunoglobulins in 16 victims of the syndrome and a series of infants (controls) who had died of non-pulmonary causes. Compared with the controls victims of the sudden infant death syndrome had grossly raised concentrations of IgG, IgM, and to a less extent IgA in lung lavage samples. In addition, pulmonary interstitial and terminal airway cells expressing these immunoglobulins were identified far more often in victims than controls. The study failed to determine whether the increased immunoglobulin concentrations were a consequence of an unusual response to a trivial infection or an expression of otherwise altered immunological control in the respiratory tract. Epidemiological evidence and the findings of this study suggest that the respiratory tract is the prime target organ in the sudden infant death syndrome.

Neutrophil leucocytosis is associated with a poor outcome in the haemolytic uraemic syndrome (HUS). This study tested the hypothesis that neutrophils from HUS patients are activated and through release of their intracellular contents damage endothelium. The proportion of neutrophils adhering to endothelium in culture was twice as high for HUS patients' neutrophils as for control neutrophils (n = 12). In addition, these neutrophils induced endothelial injury, assessed morphologically by degradation of endothelial cell fibronectin. In an attempt to inhibit neutrophil adhesion and subsequent endothelial damage the hyperadhesive neutrophils from HUS patients were incubated with a CD18 antibody directed against the common beta chain of the leucocyte integrin molecules. The CD18 antibody was able to abrogate endothelial damage in four of the ten subjects studied. These observations suggest that the neutrophil is of prime pathophysiological importance in HUS, and that methods aimed at reducing neutrophil adhesion and neutrophil-mediated endothelial damage are likely to be beneficial.

Neutrophil adherence to endothelium is known to be mediated, at least in part, by adhesion molecules such as LFA-1. Deficiency of these adhesion molecules leads to recurrent infection and early death from infection. As screening for defects of these adhesion glycoproteins is often performed by the ability of neutrophils to adhere to plastic plates, in this study a comparison of neutrophil adherence by the CD18/CD11a (LFA-1) mechanism to endothelium and plastic surfaces was examined. Baseline neutrophil adherence was two-fold higher to plastic than to endothelium (17% +/- 9 for plastic, 8% +/- 5 for endothelium). Baseline adherence to endothelium was partially inhibitable by anti-LFA-1 antibodies, whereas no inhibition of adherence occurred on plastic. Neutrophil stimulants increased adherence to both surfaces, although only on endothelium was this increase attributable to the LFA-1 mechanism. IL-1 increased adherence to endothelium, but had no effect on plastic. We conclude that adherence of neutrophils to plastic surfaces probably represents overall activation status through undefined mechanisms, is not by LFA-1 receptor ligand interactions, and is therefore a non-physiological phenomenon. Endothelial receptors are pivotal in neutrophil adherence. It would be more appropriate to screen leucocytes for leucocyte adhesion deficiency by assaying for specific receptor occupancy with monoclonal antibodies, rather than an assay such as adhesion to plastic where the adhesion ligand is non specific.

The phenotype of cells obtained from pulmonary lavage in infants who have died from sudden infant death syndrome were examined and compared with cells from control subjects. The only striking difference between the groups was a lack of reactivity of lavage cells with antibody of the CD14A cluster in the sudden infant death syndrome subjects, while antibodies of the CD14B cluster reacted strongly with cells from both the sudden infant death syndrome group and controls. Major histocompatibility complex class II antigens were expressed on approximately 95% of lavage cells, with DQ expressed more frequently than DR or DP. The majority of the lavage cells was macrophages, yet they reacted with CD3 (OKT3) and CD8 (OKT8) antibodies. No interleukin 2 was found in the lavage fluid.

Anti-neutrophil antibodies (CD15) bind to a simple sugar (lactose-N-fucopentaose III, LNF III) known to be present on the chains of the adhesion molecules on neutrophils. We have demonstrated that pre-incubation of neutrophils with a CD15 antibody increases neutrophil adherence to endothelium by a neutrophil-dependent mechanism. This augmented adhesion can be inhibited by antibodies directed against the alpha and beta chain of the leukocyte function-associated antigen 1 (LFA-1) molecule. There is also some increase in surface LFA-1 expression on neutrophils after CD15 incubation, suggesting that CD15 antibodies increase neutrophil adhesion by an LFA-1-dependent mechanism. The increase in LFA-1 expression after CD15 incubation occurs in the presence of a protein synthesis inhibitor. As LFA-1 is not stored intracellularly, the increased adherence of the neutrophils, and increased LFA-1 expression on their surface, suggests the possibility that the CD15 antibodies are binding to the LNF III antigen present on the alpha and beta chains of LFA-1, producing their effect by activating the molecule, perhaps by exposing new antigen sites by a stearic effect.