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Phagocytosis of group B streptococcus by neutrophils from newborn infants
Insights
Neonatal neutrophils (PMN) show enhanced phagocytosis of Group B Streptococcus (GBS) compared to adults, regardless of infant stress levels. Severe stress did not significantly alter this increased phagocytic capacity in newborns.
Area of Science:
- Immunology
- Neonatal Medicine
Background:
- Neonatal immune responses are critical for combating infections.
- Neutrophil phagocytosis is a key component of innate immunity.
- The impact of severe stress on neonatal neutrophil function requires further investigation.
Purpose of the Study:
- To investigate the effect of severe stress on neonatal neutrophil (PMN) phagocytosis.
- To compare the phagocytic capacity of neonatal and adult PMNs against Group B Streptococcus (GBS).
Main Methods:
- Utilized radiolabeled type Ic GBS opsonized with adult serum.
- Incubated GBS with PMN monolayers from healthy/stressed neonates and healthy adults.
- Quantified bacterial uptake over time (0-80 min).
Main Results:
- Both healthy and stressed neonatal PMNs demonstrated increased GBS uptake over time.
- Neonatal PMNs (both groups) exhibited enhanced bacterial uptake compared to adult PMNs at 40, 60, and 80 min.
- No significant difference in GBS uptake was observed between stressed and healthy neonates.
Conclusions:
- Neonatal neutrophils possess a heightened phagocytic capacity for GBS compared to adult neutrophils.
- Severe stress, as defined in the study, did not significantly impair or enhance neonatal PMN phagocytosis of GBS.
- Findings suggest robust neonatal immune defense mechanisms against GBS, irrespective of significant stress exposure.
Abstract:
The purpose of this study was to investigate the effect of severe "stress" on neonatal neutrophil (PMN) phagocytosis, and to compare the ability of neonatal and adult PMNs to ingest [3H]-labeled type Ic group B streptococcus (GBS). Three patient populations were studied: healthy and "stressed" newborn infants and healthy adults. Severe "stress" was defined as an acute, noninfectious respiratory illness, sepsis or severe birth asphyxia; 94% of these infants required assisted ventilation. Radiolabeled GBS was opsonized with 5% adult serum, and incubated with PMN monolayers adherent to glass coverslips. Bacterial uptake was determined at 0, 40, 60, and 80 min and expressed as counts per min/10(6) PMNs. Neutrophils from healthy and "stressed" newborn infants demonstrated a significant increase in bacterial uptake with time. Adult controls also showed a significant increase in phagocytosis through 60 min, but not during the 60--80 min time period. PMNs from "stressed" and healthy infants demonstrated enhanced bacterial uptake when compared to adults at 40, 60, and 80 min. There were no significant differences in bacterial ingestion between "stressed" and healthy infants. Radiolabeled GBS uptake did not correlate with birth weight, study age, Apgar scores, or peripheral leukocyte count for the "stressed" newborn population. Neutrophils from healthy and "stressed" newborn infants thus demonstrate increased phagocytosis of GBS when compared to healthy adults.