Phagocytosis and postphagocytic reaction of cord blood and adult blood monocyte after infection with green fluorescent protein-labeled Escherichia coli and group B Streptococci.
BACKGROUND
Neonatal sepsis is characterized by an excessive inflammatory response induced by immune cells (monocytes). We investigated the initial stage of monocyte-pathogen interaction, i.e. bacterial ingestion and degradation at the single-cell level, by comparing a new flow cytometric procedure with culture methods. We also examined the hypothesis that, in terms of phagocytosis-induced cell death (PICD), phenotype, or cytokine production, cord blood monocytes (CBMO) differ from monocytes derived from adults (peripheral blood monocytes, PBMO).


METHODS
Phagocytosis and intracellular degradation were assessed by means of flow cytometry and bacterial cultures of green fluorescent protein-labeled group B Streptococci (GBS) and Escherichia coli. The production of reactive oxygen species (ROS) was measured through luminol-enhanced chemiluminescence. Apoptosis, phenotype, and cytokine production were assessed through flow cytometry.


RESULTS
Flow cytometry and bacterial cultures showed no difference between phagocytosis and degradation of GBS and E. coli by PBMO and CBMO. A high correlation between both methods was observed. No difference in ROS production was evident. In comparison with PBMO, CBMO apoptosis was lower after exposure to GBS and E. coli. Similarities were found between nonapoptotic monocytes and pro-inflammatory monocytes.


CONCLUSIONS
PICD is lower in CBMO during the early stages of monocyte-pathogen interaction. Our results emphasize that monocyte apoptosis has a potential role in tailoring the immune response in neonatal sepsis.
Gille
Ch
Ch
Department of Neonatology, University Children's Hospital, 72076 Tübingen, Germany.
Leiber
A
A
Mundle
I
I
Spring
B
B
Abele
H
H
Spellerberg
B
B
Hartmann
H
H
Poets
Ch F
ChF
Orlikowsky
Th W
TW
D000328:Adult; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D004926:Escherichia coli / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D004927:Escherichia coli Infections / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D005312:Fetal Blood / Q000166:cytology / Q000276:immunology*; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007231:Infant, Newborn; D050296:Microbial Viability; D009000:Monocytes / Q000276:immunology* / Q000473:pathology; D010587:Phagocytosis / Q000276:immunology* / Q000502:physiology*; D017382:Reactive Oxygen Species / Q000378:metabolism; D013194:Staining and Labeling / Q000379:methods; D013290:Streptococcal Infections / Q000235:genetics / Q000276:immunology* / Q000473:pathology; D013292:Streptococcus agalactiae / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D017382:Reactive Oxygen Species; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins