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Neutrophil Chemotaxis and Respiratory Burst in Term and Preterm Newborn Infants
Uppsala University, Disciplinary Domain of Medicine and Pharmacy, Faculty of Medicine, Department of Women's and Children's Health. (Perinatal, neonatal och barnkardiologisk forskning/Westas)
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Neutrophil activation is the most important initial immune defense against invading microbes in newborn infants. The reduced neutrophil migration and uncontrolled regulation of reactive oxygen species (ROS) production observed in neonates, could result in a diminished infectious response or in tissue damage. The aims were to study neutrophil chemotactic response towards IL-8 and fMLP in term neonates; to examine neutrophil receptor expression involved in adhesion, migration, phagocytosis and complement after stimulation with IL-8 and fMLP in term neonates; and to investigate neutrophil production of ROS, induced by PMA and E.coli, after preincubation with IL-8 and fMLP in term and preterm newborn infants. Comparisons were made to neutrophils from healthy adults.

Chemotaxis was distinguished from randomly migrating neutrophils, and the neutrophil migration distance and the number of migrating neutrophils per distance was evaluated. Neutrophils were labeled with antibodies to cell surface antigens (CD11b, CD18, CD65, CD15S, CD162, CD44, CD35, CD88, CD181, CD182 and CD64) after stimulation with IL-8 and fMLP. After preincubation of neutrophils with fMLP or IL-8 and stimulation with PMA or E.coli, respiratory burst was detected. The same analyses were also made in preterm infants (median 25+3weeks GA; range 23+0–29+2) within 3 days postnatal age.

Neutrophils from neonates exhibited different migratory and receptor responses to IL-8 and fMLP, with a diminished response towards IL-8 in term newborn infants in terms of reduced chemotaxis and modulation of receptors involved in adhesion, chemotaxis, complement and phagocytosis as compared to adults. fMLP reduced PMA- and E.coli-induced respiratory burst in neutrophils from term neonates and adults. The reduced respiratory burst by fMLP may be a mechanism for reducing the detrimental effects of uncontrolled inflammation. Although a similar burst reduction was observed in preterm infants born >25 weeks GA with fMLP, a diminished neutrophil respiratory burst modulation in very preterm infants cannot be excluded and requires further studies at different gestational and postnatal ages.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2016. , 47 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Medicine, ISSN 1651-6206 ; 1265
Keyword [en]
innate immunity, neutrophil, term newborn infants, preterm newborn infants, chemotaxis, respiratory burst, reactive oxygen species, cell surface receptor, IL-8, bacterial N-formyl peptide
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:uu:diva-305009ISBN: 978-91-554-9722-4OAI: oai:DiVA.org:uu-305009DiVA: diva2:1034376
Public defence
2016-11-23, C8:305, BMC, Husargatan 3, Uppsala, 13:00 (Swedish)
Opponent
Supervisors
Available from: 2016-11-02 Created: 2016-10-11 Last updated: 2016-11-16
List of papers
1. Differential Neutrophil Chemotactic Response towards IL-8 and Bacterial N-formyl Peptides in Term Newborn Infants.
Open this publication in new window or tab >>Differential Neutrophil Chemotactic Response towards IL-8 and Bacterial N-formyl Peptides in Term Newborn Infants.
2016 (English)In: Upsala Journal of Medical Sciences, ISSN 0300-9734, E-ISSN 2000-1967Article in journal (Refereed) Epub ahead of print
Abstract [en]

BACKGROUND: A prerequisite for an effective innate immunity is the migrative ability of neutrophils to respond to inflammatory and infectious agents such as the intermediate interleukin (IL)-8 and the end-target formyl-methionyl-leucyl-phenylalanine (fMLP) chemoattractants. The aim was to study the chemotactic capacity of neutrophils from newborn infants and adults in response to IL-8 and the bacterial peptide fMLP.

METHODS: In the under-agarose cell migration assay, isolated leukocytes from healthy adults and from cord blood of healthy term newborn infants were studied with dose responses towards IL-8 and fMLP. The same number of leukocytes (1 × 10(5) cells), with the same distribution of neutrophils and monocytes, were analyzed in neonates and adults. Chemotaxis was distinguished from randomly migrating neutrophils, and the neutrophil pattern of migration, i.e. the migration distance and the number of migrating neutrophils per distance, was evaluated.

RESULTS: In comparison to adults, fewer neutrophils from newborn infants migrated towards IL-8 and for a shorter distance (P < .01, respectively). The number of neutrophils migrating to different gradients of fMLP, the distance they migrated, and the correlation between the number and the distance were the same for neonates and adults. Random migration did not differ in any instance.

CONCLUSION: Chemotaxis of neutrophils from newborn infants was as co-ordinated as neutrophils from adults in response to fMLP, whereas the response to IL-8 was reduced. The differential response of neutrophils from neonates to intermediate and end-target chemoattractants could indicate a reduced infectious response.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-304756 (URN)10.1080/03009734.2016.1228721 (DOI)27690722 (PubMedID)
Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2016-10-17
2. Neutrophil Receptor Response to Bacterial N-formyl Peptides is Similar in Term Newborn Infants and Adults in Contrast to IL-8.
Open this publication in new window or tab >>Neutrophil Receptor Response to Bacterial N-formyl Peptides is Similar in Term Newborn Infants and Adults in Contrast to IL-8.
2016 (English)In: Scandinavian Journal of Immunology, ISSN 0300-9475, E-ISSN 1365-3083Article in journal (Refereed) Epub ahead of print
Abstract [en]

We have previously observed that neutrophils from neonates exhibit different migratory responses to intermediate and end-target chemoattractants compared to adults. The aim of the present study was to investigate the effect of the chemoattractants IL-8 (intermediate) and formyl-methionine-leucyl-phenylalanine (fMLP; end-target) on cell surface receptor expression involved in adhesion, migration and granule release of neutrophils from term newborn infants and adults. Heparinized cord blood from 16 healthy term infants delivered by caesarean section and peripheral blood from 17 healthy adults were incubated with 1 μM IL-8 or 0.01 μM fMLP, previously defined as optimal inducers of neutrophil migration. The leukocytes were labelled with antibodies to cell surface receptors (CD11b, CD15S, CD18, CD35, CD44, CD64, CD65, CD88, CD162, CD181 and CD182). Receptor expression was quantified by flow cytometry analysis. Up regulation of CD11b and down regulation of CD88 and CD182 after stimulation with IL-8, was more pronounced in adults than in neonates (p<0.05, p<0.05 and p≤0.001 respectively), whereas fMLP induced changes in receptor expression that were of the same magnitude in neutrophils from neonates as from adults. We observed similar expression of receptors that mediate adhesion, migration, granule activation, and phagocytosis induced by fMLP in neutrophils from neonates and adults. In contrast, differences between neonates and adults, induced by IL-8, suggest that the neutrophil response to intermediate chemoattractants might lead to a compromised infectious response in newborn infants. This article is protected by copyright. All rights reserved.

Keyword
neutrophils, cell surface molecules, term newborn infants, IL-8, fMLP
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-304757 (URN)10.1111/sji.12477 (DOI)27606963 (PubMedID)
Available from: 2016-10-10 Created: 2016-10-10 Last updated: 2016-10-12
3. Bacterial N-formyl Peptides Reduce PMA and E.coli Induced Neutrophil Respiratory Burst in Term Neonates and Adults
Open this publication in new window or tab >>Bacterial N-formyl Peptides Reduce PMA and E.coli Induced Neutrophil Respiratory Burst in Term Neonates and Adults
(English)Article in journal (Other academic) Submitted
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:uu:diva-214732 (URN)
Available from: 2014-01-09 Created: 2014-01-09 Last updated: 2016-10-17
4. Compromised Ability to Modulate Neutrophil Respiratory Burst in Very Pretem Newborn Infants -A Pilot Study
Open this publication in new window or tab >>Compromised Ability to Modulate Neutrophil Respiratory Burst in Very Pretem Newborn Infants -A Pilot Study
2016 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Background: Chemotaxis and respiratory burst can be compromised in preterm newborn infants where sustained neutrophil accumulation, reduced scavenging, and uncontrolled burst might cause inadvertent tissue damage. Neutrophil respiratory burst induced by phorbol myristate acetate (PMA) and E.coli can be reduced by the chemoattractant formyl-methionyl-leucyl-phenylalanine (fMLP), but not IL-8, in full term newborn infants and adults. The aim of this study was to investigate whether a similar modulatory response on respiratory burst could be detected in neutrophils from very preterm newborn infants.

Methods: Whole blood from eight preterm infants (median 25+3weeks GA; range 23+0–29+2) was collected within three days of birth (median 1.4 days PNA; range 0.4 – 2.5 days) and preincubated with fMLP or IL-8 prior to stimulation with PMA or E.coli bacteria. Respiratory burst was registered by flow cytometry analysis of rhodamine fluorescence.

Results: All infants responded with an increased neutrophil respiratory burst to PMA and E.coli, but with a higher response to PMA than to E.coli (p<0.05). Although no significant modulation of neutrophil respiratory burst by preincubation with fMLP or IL-8 was observed in the whole group, there was a reduced PMA-induced burst with fMLP (p=0.09), and more specifically in infants born >25 GA (n=4/4) than in <25 GA (n=2/4). Two extremely preterm neonates had a neutrophil sub population with a marked reduction in ROS production than with fMLP induced by PMA.

Conclusions: The fMLP reduction in PMA- and E.coli-induced respiratory burst of neutrophils in full term newborn infants and adults could not be confirmed in this pilot study of preterm infants. Although respiratory reduction was observed in more mature infants with fMLP, a compromised neutrophil respiratory burst modulation in very preterm infants could not be excluded: this requires further studies at different gestational and postnatal ages.

National Category
Medical and Health Sciences
Research subject
Medical Science
Identifiers
urn:nbn:se:uu:diva-305008 (URN)
Available from: 2016-10-11 Created: 2016-10-11 Last updated: 2016-10-13

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