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.