An evaluation of transit procurement training

We evaluated a training course called "Orientation to Transit Procurement", designed and conducted by the National Transit Institute. This course is designed to provide Federal Transit Administration (FTA) grantees an overview of regulations and best practices related to the procurement process. Our objective in conducting the evaluation was to understand how transit agency staff made changes in procurement practices in response to the course training. The evaluation was mixed mode: an Internet survey followed by in-depth interviews with a small group of respondents. Survey respondents were also provided with an open-ended question providing us with additional context for our evaluation. Results show that the training is substantially successful at meeting the goal of improving procurement practices at transit agencies; indeed, most respondents report making changes at their agencies as the proximate result of the training. This was at odds with our exploration of knowledge of procurement topics, as most respondents gave inaccurate answers on multiple-choice "knowledge questions". This may have been due to question structure or, more likely, the nature of online surveys. Suitable training on the procurement of information technology was also a main concern. The lack of training in this area is indicative of the broader challenge facing public transit agencies in how to incorporate new forms of technology into their existing practices and bureaucratic structures.

A critical role for ATF2 transcription factor in the regulation of E-selectin expression in response to non-endotoxin components of Neisseria meningitidis

Vascular injury is a serious complication of sepsis due to the gram‐negative bacterium Neisseria meningitidis. One of the critical early steps in initiating this injury is via the interaction of leucocytes, particularly neutrophils, with adhesion molecules expressed on inflamed endothelium. We have previously demonstrated that both lipopolysaccharide (LPS) and non‐LPS components of meningococci can induce very high levels of expression of the vascular endothelial cell adhesion molecule E‐selectin, which is critical for early tethering and capture of neutrophils onto endothelium under flow. Using an LPS‐deficient strain of meningococcus, we showed that very high levels of expression can be induced in primary endothelial cells, even in the context of weak activation of the major host signal transduction factor [nuclear factor‐κB (NF‐κB)]. In this study, we show that the particular propensity for N. meningitidis to induce high levels of expression is regulated at a transcriptional level, and demonstrate a significant role for phosphorylation of the ATF2 transcription factor, likely via mitogen‐activated protein (MAP) kinases, on the activity of the E‐selectin promoter. Furthermore, inhibition of E‐selectin expression in response to the lpxA− strain by a p38 inhibitor indicates a significant role of a p38‐dependent MAPK signalling pathway in ATF2 activation. Collectively, these data highlight the role that LPS and other bacterial components have in modulating endothelial function and their involvement in the pathogenesis of meningococcal sepsis. Better understanding of these multiple mechanisms induced by complex stimuli such as bacteria, and the specific inflammatory pathways they activate, may lead to improved, focused interventions in both meningococcal and potentially bacterial sepsis more generally.

Immunohistochemical expression of inflammatory markers in sudden infant death; ancillary tests for identification of infection

Aims

Sudden unexpected death in infancy (SUDI) investigation requires extensive ancillary investigations, the results of which, such as postmortem microbiology, can be difficult to interpret. Markers of an inflammatory response, including interleukin 6 (IL-6), c-reactive protein (CRP) and cellular adhesion molecules are elevated in infections, yet little attention has been paid to their assessment after death. This study investigates the role of inflammatory markers in SUDI autopsies for determining cause of death.

Methods

Cases of SUDI over a 14 year period were identified from an autopsy database and 100 cases were selected for immunohistochemical staining of heart and liver for IL-6, CRP, P-selectin, VCAM-1 and ICAM-1 (CD54), with staining patterns compared between five groups, including infectious and unexplained SUDI.

Results

There were significant differences between groups. Cases of histological infection demonstrated strongly positive hepatocyte CRP and ICAM-1 expression and increased myocardial staining for CRP. Half of trauma-related deaths demonstrated diffuse hepatic CRP expression but without myocardial CRP staining. Staining of unexplained SUDI cases were predominantly negative, apart from a subgroup in whom Escherichia Coli was identified, who had increased expression of hepatic IL-6.

Conclusions

There were distinct patterns of organ-specific CRP and ICAM-1 expression in SUDI by cause of death. These markers of inflammation were rarely present in unexplained SUDI suggesting either a non-inflammatory cause of death or a failure to mount an effective acute phase response. Immunohistochemical staining offers potential to identify infection-related deaths and provides insight into SUDI mechanisms.

Management of Kawasaki disease

Kawasaki disease (KD) is an acute self-limiting inflammatory disorder, associated with vasculitis, affecting predominantly medium-sized arteries, particularly the coronary arteries. In developed countries KD is the commonest cause of acquired heart disease in childhood. The aetiology of KD remains unknown, and it is currently believed that one or more as yet unidentified infectious agents induce an intense inflammatory host response in genetically susceptible individuals. Genetic studies have identified several susceptibility genes for KD and its sequelae in different ethnic populations, including FCGR2A, CD40, ITPKC, FAM167A-BLK and CASP3, as well as genes influencing response to intravenous immunoglobulin (IVIG) and aneurysm formation such as FCGR3B, and transforming growth factor (TGF) β pathway genes. IVIG and aspirin are effective therapeutically, but recent clinical trials and meta-analyses have demonstrated that the addition of corticosteroids to IVIG is beneficial for the prevention of coronary artery aneurysms (CAA) in severe cases with highest risk of IVIG resistance. Outside of Japan, however, clinical scores to predict IVIG resistance perform suboptimally. Furthermore, the evidence base does not provide clear guidance on which corticosteroid regimen is most effective. Other therapies, including anti-TNFα, could also have a role for IVIG-resistant KD. Irrespective of these caveats, it is clear that therapy that reduces inflammation in acute KD, improves outcome. This paper summarises recent advances in the understanding of KD pathogenesis and therapeutics, and provides an approach for managing KD patients in the UK in the light of these advances.

Do lower income areas have more pedestrian casualties?

Pedestrian and motor vehicle casualties are analyzed for the State of New Jersey with the objective of determining how the income of an area may be associated with casualties. We develop a maximum-likelihood negative binomial model to examine how various spatially defined variables, including road, income, and vehicle ownership, may be associated with casualties using census block-group level data. Due to suspected spatial correlation in the data we also employ a conditional autoregressive Bayesian model using Markov Chain Monte Carlo simulation, implemented with Crimestat software. Results suggest that spatial correlation is an issue as some variables are not statistically significant in the spatial model. We find that both pedestrian and motor vehicle casualties are greater in lower income block groups. Both are also associated with less household vehicle ownership, which is not surprising for pedestrian casualties, but is a surprising result for motor vehicle casualties. Controls for various road categories provide expected relationships. Individual level data is further examined to determine relationships between the location of a crash victim and their residence zip code, and this largely confirms a residual effect associated with both lower income individuals and lower income areas.

Randomized clinical trial of glutamine-supplemented versus standard parenteral nutrition in infants with surgical gastrointestinal disease

BACKGROUND

Addition of glutamine to parenteral nutrition in surgical infants remains controversial. The aim of this trial was to determine whether glutamine supplementation of parenteral nutrition in infants requiring surgery would reduce the time to full enteral feeding and/or decrease the incidence of sepsis and septicaemia.

METHODS

A prospective double-blind multicentre randomized clinical trial was performed in surgical infants less than 3 months old who required parenteral nutrition. Patients were allocated to treatment or control groups by means of minimization. Infants received either 0·6 g per kg per day alanyl-glutamine (treatment group) or isonitrogenous isocaloric parenteral nutrition (control group) until full enteral feeding was achieved. Primary outcomes were time to full enteral feeding and incidence of sepsis. Cox regression analysis was used to compare time to full enteral feeding, and to calculate risk of sepsis/septicaemia.

RESULTS

A total of 174 patients were randomized, of whom 164 completed the trial and were analysed (82 in each group). There was no difference in time to full enteral feeding or time to first enteral feeding between groups, and supplementation with glutamine had no effect on the overall incidence of sepsis or septicaemia. However, during total parenteral nutrition (before the first enteral feed), glutamine administration was associated with a significantly decreased risk of developing sepsis (hazard ratio 0·33, 95 per cent confidence interval 0·15 to 0·72; P = 0·005).

CONCLUSION

Glutamine supplementation during parenteral nutrition did not reduce the incidence of sepsis in surgical infants with gastrointestinal disease.

REGISTRATION NUMBER

ISRCTN83168963 (http://www.controlled-trials.com).

Aberrant response to commensal Bacteroides thetaiotaomicron in Crohn's disease: an ex vivo human organ culture study

BACKGROUND

Human ex vivo evidence indicating that an inappropriate immune response(s) to nonpathogenic bacteria contributes to disease pathogenesis in pediatric Crohn's disease (CD) is limited. The aim of the present study was to compare and contrast the early innate immune response of pediatric "healthy" versus CD mucosa to pathogenic, probiotic, and commensal bacteria.

METHODS

"Healthy control" and CD pediatric mucosal biopsies (terminal ileum and transverse colon) were cocultured for 8 hours with E. coli O42, Lactobacillus GG (LGG), Bacteroidesthetaiotaomicron (B. theta), or stimulated with interleukin (IL)-1β (positive control). Matched nonstimulated biopsies served as experimental controls. IL-8 was the immune marker of choice. IL-8 mRNA and protein levels were quantified by quantitative polymerase chain reaction and sandwich enzyme-linked immunosorbent assay, respectively.

RESULTS

IL-8 secretion was observed when control, ileal biopsies were exposed to pathogenic O42 and probiotic LGG, with no response noted to commensal B. theta. In comparison, Crohn's ileal biopsies showed impaired ability to induce IL-8 in response to O42 and LGG. Control colonic tissue showed a limited response to O42 or B. theta and LGG significantly reduced IL-8 secretion. Unlike control tissue, however, Crohn's ileal and colonic tissue did respond to B. theta, with more enhanced expression in the colon.

CONCLUSIONS

We provide the first ex vivo data to support the notion that aberrant mucosal recognition of commensal bacteria may contribute to pediatric CD. While IL-8 responses to O42 and LGG varied with disease status and anatomical location, B. theta consistently induced significant IL-8 both in ileal and colonic CD tissue, which was not seen in control, healthy tissue.

Endothelial injury and repair in systemic vasculitis of the young

OBJECTIVE

Endothelial injury is central to the pathogenesis of vasculitis. The purpose of this study was to assess how indices of endothelial injury and repair change during different stages of disease activity in children with primary systemic vasculitis (PSV).

METHODS

Fifty children with PSV, 17 children with nonvasculitic inflammatory diseases (pediatric inflammatory disease controls), 35 healthy age- and sex-matched pediatric controls, and 27 healthy adult controls were included in the study. Biomarkers examined were endothelial microparticles (EMPs), circulating endothelial cells (CECs), angiogenic growth factors, and endothelial progenitor cells (EPCs). EMP binding to annexin V, EMPs expressing CD144 or E-selectin, and EPCs expressing vascular endothelial growth factor receptor 2 (VEGFR-2), CD133, and CD34 were examined by flow cytometry. CECs were enumerated using immunomagnetic bead extraction techniques, and VEGF and angiopoietin 2 (Ang-2) were measured by enzyme-linked immunosorbent assay.

RESULTS

Levels of CD144+ EMPs, CECs, VEGF, and EPCs were all significantly elevated in children with active vasculitis as compared with healthy children, and the levels declined with remission-inducing therapy in the individual patients. Treatment-naive patients with active disease had significantly higher levels of VEGF and Ang-2 than did those with active disease who were receiving treatment, although the levels of CECs and EMPs remained high in both of these groups.

CONCLUSION

Elevation of the levels of CECs, EMPS, EPCs, VEGF, and Ang-2 occurs during active vasculitis in children. EPC responses to active vasculitis are different in children as compared with that observed in adults with vasculitis, and both CECs and EMPs can be used to monitor disease activity in children with vasculitis.

Mannose-binding lectin is present in the infected airway: a possible pulmonary defence mechanism

BACKGROUND

Mannose-binding lectin (MBL) deficiency has been associated with infections of the respiratory tract and with increased disease severity in cystic fibrosis (CF). The mechanism is uncertain, and could relate either to systemic or local effects. The aim of this study was to determine, in a large cohort of children, whether MBL is present on the airway surface in health or disease.

METHODS

Bronchoalveolar lavage (BAL) fluid from children with and without respiratory infection (some with underlying disease) was analysed for MBL and neutrophil elastase (NE). Levels were compared between groups, and correlations were examined with local and systemic inflammatory markers, infective organisms and load.

RESULTS

85 children were recruited to the study. MBL was absent in the lavage of all 7 children without lung infection but present in 62% (8/13) of those with acute pneumonia/pneumonitis, 23% (5/22) with recurrent respiratory tract infections, 17% (1/6) with primary ciliary dyskinesia and 8% (3/37) with CF (p<0.01). Children with acute pneumonia/pneumonitis had significantly higher levels than those in the other groups. There was no relationship with organisms cultured or systemic markers of inflammation, although in the group with detectable MBL in the BAL fluid, the levels correlated positively with levels of NE.

CONCLUSIONS

MBL is undetectable in the non-infected airway but is present in a significant number of samples from children with lung infection. The levels found in the BAL fluid could be physiologically active and the protein may therefore be playing a role in host defence.

Infection and sudden unexpected death in infancy: a systematic retrospective case review

BACKGROUND

The cause and mechanism of most cases of sudden unexpected death in infancy (SUDI) remain unknown, despite specialist autopsy examination. We reviewed autopsy results to determine whether infection was a cause of SUDI.

METHODS

We did a systematic retrospective case review of autopsies, done at one specialist centre between 1996 and 2005, of 546 infants (aged 7-365 days) who died suddenly and unexpectedly. Cases of SUDI were categorised as unexplained, explained with histological evidence of bacterial infection, or explained by non-infective causes. Microbial isolates gathered at autopsy were classified as non-pathogens, group 1 pathogens (organisms usually associated with an identifiable focus of infection), or group 2 pathogens (organisms known to cause septicaemia without an obvious focus of infection).

FINDINGS

Of 546 SUDI cases, 39 autopsies were excluded because of viral or pneumocystis infection or secondary bacterial infection after initial collapse and resuscitation. Bacteriological sampling was done in 470 (93%) of the remaining 507 autopsies. 2079 bacteriological samples were taken, of which 571 (27%) were sterile. Positive cultures yielded 2871 separate isolates, 484 (32%) of which showed pure growth and 1024 (68%) mixed growth. Significantly more isolates from infants whose deaths were explained by bacterial infection (78/322, 24%) and from those whose death was unexplained (440/2306, 19%) contained group 2 pathogens than did those from infants whose death was explained by a non-infective cause (27/243, 11%; difference 13.1%, 95% CI 6.9-19.2, p<0.0001 vs bacterial infection; and 8.0%, 3.2-11.8, p=0.001 vs unexplained). Significantly more cultures from infants whose deaths were unexplained contained Staphylococcus aureus (262/1628, 16%) or Escherichia coli (93/1628; 6%) than did those from infants whose deaths were of non-infective cause (S aureus: 19/211, 9%; difference 7.1%, 95% CI 2.2-10.8, p=0.005; E coli: 3/211, 1%, difference 4.3%, 1.5-5.9, p=0.003).

INTERPRETATION

Although many post-mortem bacteriological cultures in SUDI yield organisms, most seem to be unrelated to the cause of death. The high rate of detection of group 2 pathogens, particularly S aureus and E coli, in otherwise unexplained cases of SUDI suggests that these bacteria could be associated with this condition.

Decreased monocyte class II MHC expression following major abdominal surgery in children is related to operative stress

Monocyte class II major histocompatibility complex (MHC) expression is necessary for antigen presentation and stimulation of T-cells. The aim of this study was to correlate monocyte class II MHC response to operative stress in children and the possible influence of cytokines in the postoperative period. We studied 21 children undergoing elective abdominal surgery. Operative stress score (OSS) was calculated. Monocyte class II MHC expression was measured preoperatively, immediately after surgery, 24 and 48 h postoperatively, using flow cytometry. Class II MHC is expressed as mean fluorescence intensity (MFI) of monocytes expressing MHC (mean +/- SD). Cytokine levels (interleukins 1ra, 6, and 10, and tumor necrosis factor-alpha) were also measured. Data between time points were compared using repeated measures ANOVA. There was an immediate postoperative decrease in class II MHC expression, with lowest levels 24 h postoperatively (preoperative 50 +/- 23.6, 24 h 18.2 +/- 9.4, P < 0.0001 vs. preoperative). At 48 h there was partial recovery in class II MHC, but levels were still significantly lower than preoperative (23.9 +/- 11.1, P < 0.001). The degree of monocyte depression was related to the magnitude of operative stress. Patients who had OSS <10 displayed some recovery in expression at 48 h 25.5 +/- 11.1), whereas in patients with OSS > or = 10 (severe surgical stress), expression further decreased at 48 h (MFI 14.0 +/- 0.1). There was an elevation of interleukin-1ra in the immediate postoperative period in both groups. There was no elevation in the other cytokines. Abdominal surgery in children decreases monocyte MHC expression. Class II MHC depression was related to magnitude of surgical trauma, implying that more severe immuneparesis follows surgery of greater magnitude. This may predispose to postoperative infection.

Endotoxin immunity and the development of the systemic inflammatory response syndrome in critically ill children

BACKGROUND

The systemic inflammatory response syndrome (SIRS) may be triggered by endotoxin. Humans have antibodies directed against the core of endotoxin (endotoxin core antibodies, EndoCAb) that appear to be protective following surgery and in sepsis. We hypothesised that children with elevated antibodies to endotoxin core would be less likely to develop SIRS in their initial period on intensive care. Because of the existing literature we defined two sub-groups according to the primary reason for ICU admission: infection and non-infection.

METHODS

We recruited 139 consecutive patients admitted to a paediatric intensive care unit (PICU) with more than one organ failure for longer than 12 h as part of another study. Patients were classified on admission to PICU as having an infectious or a non-infections diagnosis. The occurrence of SIRS within 48 h of admission was recorded along with detailed clinical and demographic data, EndoCAb concentration and the potential confounding variables C-reactive protein and mannose-binding lectin.

RESULTS

In the 71 patients admitted without infection (primarily post-operative and head injured) IgG EndoCAb was significantly lower in patients who developed SIRS than those who did not (72 vs. 131 MU/ml), independent of potential confounding variables. In patients with infection there was no significant difference in IgG EndoCAb between children developing SIRS and those who did not (111 vs. 80 MU/ml).

CONCLUSION

Head injured and post-operative patients admitted to PICU who develop early SIRS have significantly lower serum IgG EndoCAb levels than those who do not.

Susceptibility to infection in patients with neutropenia: the role of the innate immune system

Chemotherapy-induced neutropenia increases the risk of infection. There appears to be a wide variability in the severity and length of infective episodes. Susceptibility to infections is determined by the underlying malignant disease and its treatment, environmental factors (e.g. nutritional state of the patient and hygiene) and genetically determined variations of the immune system. The majority of primary immunodeficiencies are rare (c. frequency one in 10 000), whereas some genetic polymorphisms in the innate immune system, such as profound mannose-binding lectin deficiency, are much more common (c. frequency one in 10). Here, we review the potential role of the innate immune system in determining susceptibility to infections in patients with neutropenia.

Mannose-binding lectin: do we need it?

Mannose-binding lectin (MBL) deficiency has now been recognised for 15 years. Numerous studies have shown that MBL deficiency is associated with an increased susceptibility to a range of infections. However, the importance of MBL, in defence against infection, is still debated. This article discusses recent developments in MBL research and explores how MBL may be operating in the setting of modern medical practice.

Interleukin-4 increases the permeability of human endothelial cells in culture

BACKGROUND

IL-4 plays a key role in the induction of allergic inflammation, but its role as an effector molecule is less well-established. Although some observations suggest that IL-4 may mediate increased vascular permeability, which is a characteristic feature of allergic inflammation, evidence for a direct effect on endothelial cell permeability is lacking.

OBJECTIVE

To determine the effect of human IL-4 on the albumin permeability of cultured human endothelial cells.

METHODS

Human umbilical vein endothelial cells were cultured on permeable membranes and the albumin permeability of endothelial monolayers was measured with and without exposure to recombinant human IL-4. Endothelial cells were exposed to various concentrations of IL-4 (0.001-100 U/mL), for various durations (6-24 h), either in the presence or absence of anti-IL-4 antibody. Recovery of endothelial barrier function following exposure to IL-4 was also examined.

RESULTS

IL-4 induced a dose-dependent, reversible increase in endothelial permeability to albumin. Low concentrations of IL-4 (1 U/mL) induced a significant increase in endothelial permeability (P=0.004). IL-4-mediated endothelial leak occurred rapidly, within 6 h of exposure.

CONCLUSIONS

IL-4 has the capacity to induce vascular leak by a direct effect on cultured endothelial cells, suggesting a potential effector role for IL-4 in the pathogenesis of vascular leak in allergic diseases.

High-level endothelial E-selectin (CD62E) cell adhesion molecule expression by a lipopolysaccharide-deficient strain of Neisseria meningitidis despite poor activation of NF-kappaB transcription factor

Binding of host inflammatory cells to the endothelium is a critical contributor to the vascular damage characteristic of severe meningococcal disease and is regulated by endothelial cell adhesion molecules such as ICAM-1, VCAM-1 and CD62E. Intact meningococci induce far higher levels of CD62E than lipopolysaccharide (LPS) alone, whereas LPS is at least as potent as meningococci at inducing both VCAM-1 and ICAM-1 expression. This suggests that meningococci possess additional factors other than LPS present in whole bacteria that result in differential adhesion molecule expression. To investigate this possibility, we studied the capacity of an LPS-deficient isogenic strain of serogroup B Neisseria meningitidis H44/76 (lpxA-) to induce endothelial cell adhesion molecule expression and translocation of the transcription factor NF-kappaB, and compared it to both parent and unencapsulated strains of both B1940 and H44/76 and purified LPS. Although the LPS-deficient isogenic mutant of strain H44/76 was found to be a poor inducer of NF-kappaB, it induced higher levels of CD62E expression than LPS alone. These data provide evidence that intact meningococci induce a range of signals in the endothelium that are distinct from those seen with purified LPS alone and that they occur in a LPS-dependent and LPS-independent manner. These signals may explain the potent effects of N. meningitidis on CD62E expression on vascular endothelium and provide a basis for the complex endothelial dysregulation seen in meningococcal sepsis.

Severe meningococcal disease is characterized by early neutrophil but not platelet activation and increased formation and consumption of platelet-neutrophil complexes

Approximately 25% of polymorphonuclear leukocytes (PMNL) circulate in heterotypic complexes with one or more activated platelets. These platelet-neutrophil complexes (PNC) require platelet CD62P expression for their formation and represent activated subpopulations of both cell types. In this study, we have investigated the presence, time course, and mechanisms of PNC formation in 32 cases of severe pediatric meningococcal disease (MD) requiring intensive care. There were marked early increases in PMNL CD11b/CD18 expression and activation, and reduced CD62L expression compared with intensive care unit control cases. Minimal platelet expression of the active form of alphaIIbbeta3 (GpIIb/IIIa) was seen. PNC were reduced on presentation and fell to very low levels after 24 h. Immunostaining of skin biopsies demonstrated that PNC appear outside the circulation in MD. In vitro studies of anticoagulated whole blood inoculated with Neisseria meningitidis supported these clinical findings with marked increases in PMNL CD11b/CD18 expression and activation but no detectable changes in platelet-activated alphaIIbbeta3 or CD62P expression. In vitro PMNL activation with N. meningitidis (or other agonists) potentiated the formation of PNC in response to platelet activation with adenine diphosphate. Therefore, in severe MD, PMNL activation is likely to promote PNC formation, and we suggest that the reduced levels of PNC seen in established MD reflect rapid loss of PNC from the circulation rather than reduced formation.

Gut overgrowth with abnormal flora: the missing link in parenteral nutrition-related sepsis in surgical neonates

BACKGROUND AND AIMS

Patients receiving parenteral nutrition are at risk of septicaemia. Intestinal dysmotility and impaired gut immunity due to parenteral nutrition promote bacterial overgrowth. Gut overgrowth with aerobic Gram-negative bacilli (AGNB) impairs systemic immunity. The aim of this study was to determine the potential role of gut overgrowth with AGNB in the pathogenesis of septicaemia related to parenteral nutrition.

METHODS

A prospective 5 y study of surgical infants less than 6 months of age was undertaken. Surveillance samples of the oropharynx and gut were obtained at the start of parenteral nutrition and thereafter twice weekly, to detect AGNB carriage. Blood cultures were taken on clinical indication only.

RESULTS

Two-hundred and eight infants received parenteral nutrition for 6271 days (median 13 days, range 1-512 days). The incidence of AGNB carriage was 42%, whilst the septicaemia rate was 15%. Eighty-four percent of septicaemic infants carried AGNB, whilst 16% never carried AGNB (P<0.005). Carriage developed significantly earlier than septicaemia.

CONCLUSIONS

The incidence of septicaemia was significantly greater in the subset of abnormal carriers. Although gut overgrowth with abnormal flora reflects illness severity, the fact that it preceded septicaemia implicates AGNB overgrowth, per se, as a contributory factor in the development of septicaemia related to parenteral nutrition. Prevention is unlikely to be successful if it ignores the abnormal flora.

Mannose-binding lectin regulates the inflammatory response of human professional phagocytes to Neisseria meningitidis serogroup B

The influence of the innate immune protein mannose-binding lectin (MBL) on the response of human phagocytes to Neisseria meningitidis was investigated. MBL increased the association of killed meningococci with neutrophils, monocytes, and macrophages by increasing the proportion of cells that recognized bacteria. MBL down-regulated the normal change in expression of the leukocyte adhesion molecules CD11b and CD62L. In an ex vivo model, the addition of MBL to the blood of MBL-deficient donors influenced the production of monocyte-derived inflammatory cytokines. The addition of high concentrations of MBL (>6 microg/mL) profoundly decreased the production of interleukin (IL)-6, IL-1beta, and tumor necrosis factor-alpha by monocytes in response to meningococci, whereas lower concentrations enhanced the production of IL-6 and IL-1beta. These results suggest that MBL not only is involved in complement activation but also is a potent regulator of inflammatory pathways and, as such, may affect the severity of meningococcal disease.

Poststreptococcal acute disseminated encephalomyelitis with basal ganglia involvement and auto-reactive antibasal ganglia antibodies

Antibasal ganglia antibodies (ABGA) are associated with Sydenham's chorea and pediatric autoimmune neuropsychiatric disorders associated with streptococcal infections. We present 10 patients with acute disseminated encephalomyelitis (ADEM) associated with Group A beta hemolytic streptococcal infection. The clinical phenotype was novel, with 50% having a dystonic extrapyramidal movement disorder, and 70% a behavioral syndrome. None of the patients had rheumatic fever or Sydenham's chorea. Enzyme-linked immunosorbent assay, Western immunoblotting, and immunohistochemistry were used to detect ABGA. Neurological (n = 40) and streptococcal (n = 40) controls were used for comparison. Enzyme-linked immunosorbent assay results showed significantly elevated ABGA in the patients with poststreptococcal ADEM. Western immunoblotting demonstrated ABGA reactivity to three dominant protein bands of 60, 67, or 80 kDa; a finding not reproduced in controls. Fluorescent immunohistochemistry demonstrated specific binding to large striatal neurones, which was not seen in controls. Streptococcal serology was also significantly elevated in the poststreptococcal ADEM group compared with neurological controls. Magnetic resonance imaging studies showed hyperintense basal ganglia in 80% of patients with poststreptococcal ADEM, compared to 18% of patients with nonstreptococcal ADEM. These findings support a new subgroup of postinfectious autoimmune inflammatory disorders associated with Group A beta hemolytic streptococcus, abnormal basal ganglia imaging, and elevated ABGA.

Mannose-binding lectin accelerates complement activation and increases serum killing of Neisseria meningitidis serogroup C

The capacity for different lipo-oligosaccharide (LOS) sialylation patterns of Neisseria meningitidis serogroup C to influence the binding and function of the innate humoral component, mannose-binding lectin (MBL), was investigated. By use of flow cytometry and immunogold electron microscopy, a clinical isolate with reduced endogenous LOS sialylation was found to bind more MBL than did strains with higher endogenous sialylation. MBL binding was reduced but not ablated if the same strain was allowed to exogenously sialylate its LOS structures after incubation with cytidine-5'-monophospho-neuraminic acid. MBL binding led to an increased rate of complement activation, with enhanced deposition of the complement components C4 and C5b-9, and this correlated with an increase in bactericidal activity. LOS sialylation appears to be an important determinant of MBL binding to N. meningitidis and can modulate complement-dependent killing of the bacterium. These findings could explain the observed susceptibility to meningococcal disease of individuals genetically deficient in MBL.

Deficiency of mannose-binding lectin and burden of infection in children with malignancy: a prospective study

BACKGROUND

Infection is a major cause of morbidity and mortality in children with malignancy. Individuals with serum deficient in mannose-binding lectin (MBL)-an important component of the innate immune system-are more susceptible to infection than those with adequate concentrations. In this study, we investigated the capacity of this protein to influence infectious complications in children undergoing treatment for malignancy.

METHODS

We enrolled 100 children receiving chemotherapy for malignancy at a children's hospital in London, UK. The frequency, duration, and causes of febrile neutropenic episodes were recorded, and MBL genotype and phenotype were determined by heteroduplex analysis and ELISAs, respectively. Serial MBL concentrations were also measured in patients during febrile episodes, and the results correlated with the MBL genotype (A/A indicating wild type, O/O indicating homozygous for MBL structural-gene mutations, and A/O indicating heterozygous for such mutations).

FINDINGS

In the A/A patients, MBL concentrations almost doubled by day 7 of the febrile neutropenic episode before declining by day 14 (p=0.004). By contrast, in patients with MBL mutations, concentrations did not alter significantly during the neutropenic episode. In the 6 months after initial diagnosis, most patients had at least one febrile neutropenic episode, but the median duration in patients with MBL mutations was twice as long as that in children with the wildtype genotype (20.5 days vs 10.0 days; p=0.014). Individuals with the lowest serum MBL concentrations at the time of diagnosis (<1000 microg/L) had a higher median number of days of febrile neutropenia than did individuals with higher concentrations of MBL (p=0.012).

INTERPRETATION

MBL deficiency seems to have an important influence on the duration of febrile neutropenic episodes in children with malignancy. This finding suggests that MBL infusions could represent a new therapeutic approach which would aid the management of chemotherapy-induced complications in this population of children.

Differential recognition of obligate anaerobic bacteria by human mannose-binding lectin

Deficiency of the innate, humoral immune component mannose-binding lectin (MBL) predisposes individuals to a variety of infections, but the importance of MBL in infection by anaerobes has not been addressed. The attachment of MBL to a wide range of anaerobic bacteria associated with human disease and colonization was surveyed. The results suggest that for the species we examined, resistance to MBL binding may be associated with organisms that are more commonly pathogenic and that MBL binding to some bacteria may be phase variable.

Mannose-binding lectin: targeting the microbial world for complement attack and opsonophagocytosis

Mannose-binding lectin (MBL) is an important constituent of the innate immune system. This protein binds through multiple lectin domains to the repeating sugar arrays that decorate many microbial surfaces, and is then able to activate the complement system through a specific protease called MBL-associated protease-2. We have used flow cytometry to study both the binding of MBL to microorganisms and the subsequent activation of complement. For selected Gram-negative organisms, such as Salmonella and Neisseria, we have examined the relative roles of lipopolysaccharide (LPS) structure and capsule in determining binding and conclude that the LPS is of major importance. Our results from studies with several clinically relevant organisms also show that MBL binding detected by flow cytometry leads to measurable activation of purified C4, suggesting that the bound lectin is capable of initiating opsonophagocytosis and/or bacterial lysis. There is an increasing literature suggesting that MBL deficiency, which mainly results from three relatively common single point mutations in exon 1 of the gene, predisposes both to infection by extracellular pathogens and to autoimmune disease. In addition, the protein also modulates disease severity, at least in part through a complex, dose-dependent influence on cytokine production. The mechanisms and signalling pathways involved in such processes remain to be elucidated.

Management of primary nocturnal enuresis

Most parents believe that their child should not be wetting the bed by age 5. Statistics show that 10% to 20% of 5 year olds continue with a least one episode of nocturnal enuresis per month. There is evidence that successful treatment leads to improved self-concept in children (Moffatt, Kato, & Pless, 1987). Treatment consists of various behavior modifications or pharmacologic regimes. Nurses and nurse practitioners in family practice, pediatric practice, school health, and urologic practice are in ideal roles to seek out and manage children with primary nocturnal enuresis.

Platelet and leucocyte activation in childhood sickle cell disease: association with nocturnal hypoxaemia

We hypothesized that vaso-occlusive events in childhood sickle cell disease (SCD) may relate to inflammatory cell activation as well as interactions between sickle erythrocytes and vascular endothelium. Peripheral blood was examined from 24 children with SCD, of whom 12 had neurological sequelae and seven had frequent painful crises, and 10 control subjects. Platelet (CD62P and CD40L expression) and granulocyte (CD11b expression) activation and levels of platelet-erythrocyte and platelet-granulocyte complexes were determined by flow cytometry. Platelets (P = 0.019), neutrophils (P = 0.02) and monocytes (P = 0.001) were more activated and there were increased platelet-erythrocyte complexes (P = 0.026) in SCD patients compared with controls. Platelet-granulocyte complexes were not raised. There were no differences between the different groups of SCD. As hypoxia activates monocytes, platelets and endothelial cells and causes sickling of SCD erythrocytes, we also investigated 20 SCD patients with overnight pulse oximetry. Minimum overnight saturation correlated with the level of platelet-erythrocyte complexes (Spearman's rho -0.668, P < 0.02), neutrophil CD11b (Spearman's rho -0.466, P = 0.038) and monocyte CD11b (Spearman's rho -0.652, P = 0. 002). These findings provide important clues about the mechanism by which SCD patients may become predisposed to vaso-occlusive events.

Mannose-binding lectin is a component of innate mucosal defense against Cryptosporidium parvum in AIDS

BACKGROUND & AIMS

Nonimmune mechanisms of mucosal defense seem to be biologically important and might explain the observed variability in the course of enteric infection in immunodeficiency. Mannose-binding lectin (MBL) deficiency is associated with persistent diarrhea in children. We found that genetic determinants of MBL deficiency appear to predispose to cryptosporidiosis in patients with the acquired immunodeficiency syndrome (AIDS), and went on to study interactions of MBL and complement on Cryptosporidium parvum sporozoites.

METHODS

This study involved cross-sectional study of MBL genotype and enteric infection in 72 Zambian AIDS patients with diarrhea, immunofluorescence analysis of MBL and C4 binding to C. parvum, and immunoblotting for MBL and complement in small intestinal fluid.

RESULTS

Individuals homozygous for MBL structural gene mutations were at increased risk of cryptosporidiosis (odds ratio, 8.2; 95% confidence interval, 1. 5-42; P = 0.02). Lectin-mediated and concentration-dependent binding of purified MBL was detected on sporozoites but not oocysts, and MBL activated C4 on sporozoites. MBL, C3, C4, and albumin were detected in small intestinal fluid in half the patients tested, suggesting transudation of serum components into the enteropathic gut.

CONCLUSIONS

The increased risk of cryptosporidiosis in MBL deficiency appears to include patients with AIDS. It may operate through MBL-mediated complement activation on sporozoites.

Biological function of CD40 on human endothelial cells: costimulation with CD40 ligand and interleukin-4 selectively induces expression of vascular cell adhesion molecule-1 and P-selectin resulting in preferential adhesion of lymphocytes

The expression of adhesion molecules on vascular endothelial cells determines the pattern of migration and extravasation of leucocytes in inflammation and immunity. Here we show that costimulation with CD40 ligand (CD40L) and interleukin (IL)-4 (or IL-13) gives rise to a unique pattern of adhesion molecule expression by human umbilical vein endothelial cells (HUVEC). CD40 ligation alone enhanced expression of vascular cell adhesion molecule-1 (VCAM-1), intracellular adhesion molecule-1 (ICAM-1) and E-selectin whereas IL-4 and IL-13 increased expression of VCAM-1 and P-selectin but not ICAM-1 or E-selectin. When IL-4 and CD40L were combined there was an additional increase of both VCAM-1 and P-selectin, but ICAM-1 and E-selectin were both inhibited. The combined effects of IL-4 and CD40L signalling were not the result of altered response kinetics, enhanced sensitivity of the endothelium, or increased expression of CD40 or the IL-4 receptor. The rise in VCAM-1 expression induced by combined IL-4 and CD40L stimulation was slower and more sustained than with tumour necrosis factor-alpha (TNF-alpha) and occurred only on a subset (75-80%) of the endothelial cell population compared to 100% with TNF-alpha. Costimulation with IL-4 and CD40L increased adhesion of T cells and B cells above levels obtained with either signal alone, but decreased adhesion of neutrophils. Furthermore, CD40 and IL-4 synergistically increased IL-6 but decreased IL-8 production by HUVEC. These results show that interactions between IL-4 and CD40 on endothelial cells give rise to specific patterns of adhesion molecule expression and cytokine production that may have important implications for lymphocyte and neutrophil migration and function at sites of inflammation.

The lipopolysaccharide structures of Salmonella enterica serovar Typhimurium and Neisseria gonorrhoeae determine the attachment of human mannose-binding lectin to intact organisms

Mannose-binding lectin (MBL) is an important component of the innate immune system. It binds to the arrays of sugars commonly presented by microorganisms and activates the complement system independently of antibody. Despite detailed knowledge of the stereochemical basis of MBL binding, relatively little is known about how bacterial surface structures influence binding of the lectin. Using flow cytometry, we have measured the binding of MBL to a range of mutants of Salmonella enterica serovar Typhimurium and Neisseria gonorrhoeae which differ in the structure of expressed lipopolysaccharide (LPS). For both organisms, the possession of core LPS structures led to avid binding of MBL, which was abrogated by the addition of O antigen (Salmonella serovar Typhimurium) or sialic acid (N. gonorrhoeae). Truncation of the LPS within the core led to lower levels of MBL binding. It was not possible to predict the magnitude of MBL binding from the identity of the LPS terminal sugar alone, indicating that the three-dimensional disposition of LPS molecules is probably also of importance in determining MBL attachment. These results further support the hypothesis that LPS structure is a major determinant of MBL binding.

Absence of platelet CD40L identifies patients with X-linked hyper IgM syndrome

CD40 ligand (CD40L), a membrane protein expressed on activated T cells, plays a pivotal role in B cell proliferation and differentiation. Mutations in the CD40L gene are associated with a rare immunodeficiency state, X-linked hyper IgM syndrome (XLHIGM). Recently, platelets have been described as capable of expressing CD40L within minutes of stimulation. We have developed a rapid technique to determine expression of CD40L on activated platelets by flow cytometry in whole blood. We have demonstrated that this technique is useful in neonatal screening, in rapid diagnosis and in determining reconstitution by donor bone marrow post-transplantation.

Mannose-binding lectin binds to a range of clinically relevant microorganisms and promotes complement deposition

Mannose-binding lectin (MBL) is a collagenous serum lectin believed to be of importance in innate immunity. Genetically determined low levels of the protein are known to predispose to infections. In this study the binding of purified MBL to pathogens isolated from immunocompromised children was investigated by flow cytometry. Diverse Candida species, Aspergillus fumigatus, Staphylococcus aureus, and beta-hemolytic group A streptococci exhibited strong binding of MBL, whereas Escherichia coli, Klebsiella species, and Haemophilus influenzae type b were characterized by heterogeneous binding patterns. In contrast, beta-hemolytic group B streptococci, Streptococcus pneumoniae, and Staphylococcus epidermidis showed low levels of binding. Bound MBL was able to promote C4 deposition in a concentration-dependent manner. We conclude that MBL may be of importance in first-line immune defense against several important pathogens.

Inflammatory mediators in human renal dysplasia

BACKGROUND

Cytokines regulate many processes in the immune system and have recently been implicated in normal organogenesis. We previously demonstrated that the archetypal inflammatory cytokine tumour necrosis factor-alpha (TNF-alpha) is expressed in the murine metanephros, and exogenous TNF-alpha inhibits nephrogenesis and increases macrophage numbers in vitro (Cale et al., Int J Dev Biol 1998; 42: 663-674). The phenotype seen, with an arrest of ureteric bud branching and failure of mesenchymal to epithelial conversion, is similar to human renal dysplasia. Methods and results. In normal human fetal kidneys we demonstrated the presence of macrophages and T cells and also documented TNF receptor expression on ureteric bud derivatives. In contrast to normal tissues, TNF-alpha protein was detected in dysplastic kidneys. This factor was also detected in the urine of fetuses with obstructive uropathy and TNF receptors were expressed in dysplastic tubules. Furthermore, we noted a fetal distribution of macrophages and T cells in dysplastic tissues and persistent expression of the adhesion molecules neural cell adhesion molecule and intercellular adhesion molecule.

CONCLUSIONS

We suggest that abnormal expression of cytokines early in renal development dysregulates normal patterns of adhesion molecule expression and inflammatory cells, and may contribute to the pathogenesis of renal dysplasia.

Bactericidal activity against coagulase-negative staphylococci is impaired in infants receiving long-term parenteral nutrition

OBJECTIVE

To examine the role of total parenteral nutrition (TPN) in predisposing infants to infection caused by coagulase-negative staphylococci.

SUMMARY BACKGROUND DATA

Total parenteral nutrition is an important means of providing essential nutrients to newborn infants. However, its use has been associated with complications, particularly infection caused by coagulase-negative staphylococci. Recent data suggest that TPN may modulate immune function; however, reports directly indicating impaired immunity against coagulase-negative staphylococci during TPN are limited.

METHODS

Study 1 involved 31 infants younger than 4 months who had undergone surgery and were not receiving antibiotics; 20 were receiving TPN and 11 were receiving a normal enteral diet. An in vitro whole blood model was used to measure the host bactericidal activity against coagulase-negative staphylococci. Bacterial killing and phagocytosis were measured after a 45-minute challenge with viable coagulase-negative staphylococci. In study 2, whole blood killing and intracellular killing of coagulase-negative staphylococci were measured in five newborn infants (younger than 2 months) who were receiving long-term TPN (>10 days), five control infants receiving a normal enteral diet, and five healthy adults.

RESULTS

In study 1, infants receiving a normal enteral diet showed a high capacity to ingest and kill coagulase-negative staphylococci. In contrast, the blood of infants receiving long-term TPN showed a reduction in coagulase-negative staphylococci phagocytosis and killing. There were significant negative linear correlations between the duration of TPN and killing of coagulase-negative staphylococci and phagocytosis of coagulase-negative staphylococci. In study 2, infants receiving long-term TPN had lower whole blood killing and intracellular killing than infants receiving a normal enteral diet and healthy adult volunteers. These data seem to indicate a neutrophil dysfunction mediated by TPN in infancy.

CONCLUSIONS

Host defense mechanisms, including phagocytosis and killing of coagulase-negative staphylococci, are impaired during long-term TPN. The impaired bactericidal activity seems to be related to defective intracellular killing in neutrophils. These findings may explain the high rate of septicemia caused by coagulase-negative staphylococci in infants receiving TPN.

Assessment of immune response to meningococcal disease: comparison of a whole-blood assay and the serum bactericidal assay

A whole-blood assay (WBA), which assesses the complete bactericidal activity of blood, was compared with the serum bactericidal assay (SBA), which measures antibody and complement mediated cell lysis. Twenty children infected with serogroup B strains and 25 infected with serogroup C strains were studied 8-12 weeks after disease, and 29 healthy children were used as controls. The infecting strain (convalescent children only) and two reference strains, MC58 (B:15:P1.7, 16) and NCTC 8554 (C:NT:P1.5) were used. In children previously infected with a serogroup B strain, bactericidal activity was detected in 95% and 85% to their infecting strain by the WBA (>50% killing) and the SBA (s), respectively. Bactericidal activity to the reference serogroup B and C strain was detected by WBA in 70 and 75% of children, respectively, and the SBA in 45% and 20%. In contrast bactericidal activity was detected to both serogroup C strains in >80% of children previously infected with a serogroup C strain using either assay and in 48% (WBA) and 20% (SBA) to the reference serogroup B strain. Levels of bactericidal activity were detectable in fewer control children. Children convalescing from meningococcal disease develop an immune response to their infecting strain, detectable by both the WBA and SBA, which is independent of age. However, the WBA appears to be a more sensitive measure of bactericidal activity to heterologous strains than the SBA.

Circulating platelet-neutrophil complexes represent a subpopulation of activated neutrophils primed for adhesion, phagocytosis and intracellular killing

Platelets play a prominent role in linking the processes of inflammation, haemostasis and thrombosis. Recent studies have shown that platelets form heterotypic aggregates with leucocytes via platelet CD62P and leucocyte beta2 integrins. These interactions have been observed in vitro in blood taken from healthy volunteers and in clinical conditions in which thrombosis and inflammation are prominent. This study investigated the properties of platelet-neutrophil complexes (PNCs) in anticoagulated whole blood. At rest, neutrophils in PNCs exhibit a significantly more activated adhesion molecule profile than free neutrophils with increased CD11b expression and activation (increased binding of the CD11b/CD18 'activation reporter' monoclonal antibody 24) and decreased CD62L expression. In addition, neutrophils in PNCs phagocytosed significantly more Neisseria meningitidis and produced more toxic oxygen metabolites than free neutrophils. Stimulation with the platelet agonist adenosine diphosphate (ADP) led to further increases in CD11b expression and activation, loss of CD62L as well as increased phagocytosis and toxic oxygen metabolite production throughout the whole neutrophil population. When these experiments were repeated with the CD62P blocking antibody G1 the effects were inhibited to a variable extent, dependent upon the parameter under investigation. These results indicate that both soluble and contact-dependent factors contribute to platelet-mediated neutrophil activation. Platelet neutrophil complexes represent a large subpopulation of neutrophils with a more activated adhesion molecule profile, and a greater capacity for phagocytosis and toxic oxygen metabolite production. This study provides further support for a role for PNCs in both health and disease.

Upregulation of intercellular adhesion molecule-1 expression on human endothelial cells by tumour necrosis factor-alpha in an in vitro model of the blood-brain barrier

Adhesion molecules on the endothelial surface of the blood-brain barrier (BBB) play an important role in the pathogenesis of many encephalopathies, including multiple sclerosis (MS) and cerebral malaria (CM). The expression of four surface molecules of relevance to MS and CM on the immortalized human umbilical vein endothelial cell line, ECV304, was investigated using immunofluorescence flow cytometry. We found that ECV304 cells express intercellular adhesion molecule-1 (ICAM-1) and low levels of CD36, but not vascular cell adhesion molecule-1 (VCAM-1) or E-selectin. This expression pattern was unaltered on ECV304 cells which were co-cultured with C6 glioma cells; conditions under which the endothelial cells display enhanced barrier formation. Tumour necrosis factor-alpha (TNF-alpha), which is elevated in MS and CM, decreased the integrity of the barrier in co-cultured endothelial cells and upregulated the expression of ICAM-1 nine-fold. The significance of elevated ICAM-1 expression in relation to the binding of parasitised erythrocytes at the BBB in CM is discussed.

Neutrophil response to Neisseria meningitidis: inhibition of adhesion molecule expression and phagocytosis by recombinant bactericidal/permeability-increasing protein (rBPI21)

Polymorphonuclear neutrophil (PMNL) activation enhances microbial clearance but also contributes to the vascular damage and multiorgan failure associated with severe meningococcal sepsis. By use of a whole blood model of meningococcal bacteremia, loss of PMNL L-selectin and up-regulation of CD11b was observed in response to Neisseria meningitidis serogroups B and C, which is followed by opsonophagocytosis. PMNL priming with either Escherichia coli lipopolysaccharide (LPS) or FMLP prior to meningococcal challenge resulted in enhancement of both PMNL L-selectin shedding (1.5- to 4-fold) and phagocytosis (2- to 3-fold). Blockade of meningococcal LPS lipid A with recombinant bactericidal/permeability-increasing protein (rBPI21) resulted in partial inhibition of the PMNL activation and phagocytosis response to N. meningitidis. The effect of rBPI21 was reversed by excess E. coli LPS or FMLP. It is proposed that PMNL priming by N. meningitidis results in an exaggerated activation and phagocytosis response to the organism.

Autoimmune enteropathy with distinct mucosal features in T-cell activation deficiency: the contribution of T cells to the mucosal lesion

BACKGROUND

Autoimmune enteropathy is normally characterised by crypt hyperplastic villous atrophy with enterocyte autoantibodies, activation of mucosal lymphocytes and increased epithelial HLA-DR. This case involved a severely affected Portuguese infant who was found to have lymphocyte activation deficiency and demonstrated correspondingly distinct mucosal features.

METHODS

A female infant of nonconsanguineous parents was treated for vomiting and diarrhoea, first with milk exclusion and then with parenteral nutrition. Lymphocyte subsets and immunoglobulin concentrations were normal, but in vitro testing showed no activation in response to phytohaemagglutinin, Candida, or purified protein derivative, although the response to interleukin (IL)-2 was intact. Interleukin-2 deficiency was excluded. Analysis of jejunal biopsy specimens revealed only mild villous blunting with absent goblet cells, normal epithelial proliferation, and no crypt hyperplasia. The dense infiltrate of CD8+ and CD4+ T lymphocytes showed normal CD2 and CD3 expression but no activation or proliferation markers. HLA-DR was not increased on epithelium or lymphocytes. Thus, in addition to in vitro evidence for lymphocyte activation deficiency, the mucosal specimens showed no evidence of in situ T-cell activation.

RESULTS

After development of overwhelming septicaemia, the patient died at 18 months, just before a planned bone marrow transplant.

CONCLUSIONS

These findings confirm significant heterogeneity within autoimmune enteropathy. Formal immune function testing should be performed in all affected infants to identify T-cell activation deficiencies. The distinct mucosal findings suggest that activated T cells usually induce the crypt hyperplastic villous atrophy characteristic of classic autoimmune enteropathy.

Total parenteral nutrition directly impairs cytokine production after bacterial challenge

BACKGROUND/PURPOSE

Previous studies have shown that total parenteral nutrition (TPN) influences host immunity, but the mechanism is unclear. This study explored the effect of TPN solution on neutrophil phagocytosis and whole-blood cytokine production in response to coagulase-negative staphylococci in vitro challenge.

METHODS

Blood samples were taken from five enterally fed infants (age <6 months) and six healthy adults. Samples were incubated for 45 minutes with four isovolemic solutions: (A) control (saline), (B) TPN (0.1 microL/mL of blood), (C) TPN (1 microL/mL), (D) TPN (10 microL/mL). Solution C (1 microL/mL) corresponded to TPN-blood ratio used in clinical practice. After incubation, blood was challenged with coagulase-negative staphylococci. Neutrophil phagocytosis was measured by flow cytometry after 40 minutes of bacterial challenge, and tumour necrosis factor alpha (TNF-alpha) was measured by enzyme-linked immunosorbent assay (ELISA) after 2 hours of bacterial challenge.

RESULTS

In infant blood, TNF-alpha production after coagulase-negative staphylococci challenge was impaired after the addition of a "physiological" dose of TPN solution (1 microL/mL of blood) as well as "supranormal" doses (10 microL/mL of blood). In adult blood, a similar effect was observed only after the addition of a supranormal dose of TPN. In both the infant and adult blood, there was no direct effect of TPN solution on neutrophil phagocytosis.

CONCLUSIONS

These results suggest that infants are more susceptible than adults to TPN-related depression of cytokine production. The level of proinflammatory cytokines may be important in the host defence against bacterial infection.

Peter Paul Rickham Prize--1998. Neutrophil dysfunction the cellular mechanism of impaired immunity during total parenteral nutrition in infancy

BACKGROUND

Studies have shown that total parenteral nutrition (TPN) in infancy is associated with impaired immunity. The causes of this acquired immunodeficiency are poorly understood. Bacterial infection is a major complication of TPN suggesting neutrophils may be affected by this feeding modality.

PURPOSE

The aim of this study was to test the hypothesis that TPN-related impaired bactericidal activity is related to impairment of neutrophil function, particularly intracellular killing.

METHODS

Studies were performed in five infants (age <2 months) who received long-term TPN (>10 days), five control infants who received a normal enteral diet, and five healthy adults. Patients on long-term TPN were clinically stable with no evidence of sepsis. The experimental study used an in vitro whole-blood model of septicaemia. Coagulase-negative staphylococci were the bacterial challenge. Whole-blood killing of coagulase-negative staphylococci was measured after 45 minutes using the Miles-Misra technique. Neutrophils were separated from whole blood after 15, 30, 45, and 60 minutes of bacterial challenge. The survival rate of the bacteria within the neutrophils was analysed by flow cytometry and the percentage of the bacteria killed by neutrophil intracellular killing assessed at each time-point.

RESULTS

Whole-blood killing was significantly lower (P = .05) in infants who received long-term TPN (33.3%) compared with control infants (69.7%) and adults (67.7%). In all subjects studied, neutrophil intracellular killing increased with incubation time. At each time point the intracellular killing in infants on long-term TPN was significantly lower (P < .05) than in normal control infants and adults.

CONCLUSION

Future strategies to prevent TPN-related infection should aim to minimise this acquired neutrophil dysfunction.

Tumor necrosis factor-alpha inhibits epithelial differentiation and morphogenesis in the mouse metanephric kidney in vitro

Tumor necrosis factor-alpha (TNF-alpha), an inflammatory cytokine, has diverse actions both within and outside the immune system and has been implicated in the etiology of a wide range of pathological conditions. Evidence is accumulating that it may also have important roles in the normal development of the embryo. In this study we demonstrated that the addition of recombinant TNF-alpha to metanephric organ culture induced a dose dependent and reversible decrease in growth and development, with inhibition of ureteric bud branching and nephron formation beyond the condensate stage and despite appropriate expression of the transcription factor pax-2. TNF-alpha also increased the point prevalence of apoptosis after only 1 day of culture. We also noted that macrophages were present in renal rudiments at the inception of nephrogenesis and their numbers significantly increased during the culture period. This effect was enhanced by TNF-alpha. We have also demonstrated expression of mRNAs for TNF-alpha and its receptors in whole mouse metanephroi from the inception of renal development. TNF-alpha protein was also detected, predominantly at mesenchymal/epithelial interfaces. In addition, TNF-alpha mRNA and protein were expressed by clonal renal mesenchymal cells in vitro, suggesting that these cells are a source of TNF-alpha in vivo.

Activation of complement by mannose-binding lectin on isogenic mutants of Neisseria meningitidis serogroup B

Mannose-binding lectin (MBL) is a serum protein that has been demonstrated to activate the classical complement pathway and to function directly as an opsonin. Although MBL deficiency is associated with a common opsonic defect and a predisposition to infection, the role of the protein in bacterial infection remains unclear. We have investigated MBL binding to Neisseria meningitidis serogroup B1940 and three isogenic mutants, and the subsequent activation of the two major isoforms of C4 (C4A and C4B) by an associated serine protease, MASP. The mutants lacked expression of the capsular polysaccharide (siaD-), the lipo-oligosaccharide (LOS) outer core that prevented LOS sialylation (cpsD-), or both capsule and LOS outer core (cps-). Using flow cytometry, it was possible to detect strong MBL binding to the cps- and cpsD- mutants over a wide range of concentrations. In contrast, minimal or no MBL binding was detected on the parent organism, with binding to siaD- only at higher MBL concentrations. C4 was activated and bound by mutants that had previously bound MBL/MASP, but there was no significant difference in the amounts of C4A and C4B bound. When sialic acid residues were removed from the parent organism by neuraminidase treatment, the binding of both MBL and C4 increased significantly. Our results suggest that MBL may bind to and activate complement on these encapsulated organisms, and the major determinants of these effects are the LOS structure and sialylation.

Investigation of platelet-neutrophil interactions in whole blood by flow cytometry

Evidence is increasing that platelets can initiate and propagate inflammatory processes by interacting with leucocytes and the vascular endothelium. Platelets have been shown to bind to neutrophils, existing as platelet/neutrophil complexes (PNC) within the circulation. We describe a simple flow cytometric method for assessing and investigating platelet interactions with neutrophils in small volumes of whole blood. Twenty-five percent (sd 6%) of circulating neutrophils from healthy adults were associated with platelets. Formation of these platelet-neutrophil complexes was CD62P (P-selectin) and divalent cation dependent. Platelet activation (with ADP or thrombin) caused a rapid and sustained rise in %PNC which differed from the pattern of free platelet activation as assessed by CD62P expression. F-met-leu-phe induced neutrophil activation but did not increase the percentage PNC. Platelet activation also caused increased neutrophil CD11b/CD18 expression which was most marked on neutrophils complexed with platelets. This straightforward technique is simple, reproducible, and allows assessment of platelet-neutrophil interactions and activation of neutrophils. It may also provide a method for estimating platelet activation in whole blood.