Plasma effects on phagocytic activity and hydrogen peroxide production by polymorphonuclear leukocytes in neonates

To elucidate the defense mechanism in neonates against bacterial infections, phagocytic activity and hydrogen peroxide (H2O2) production by polymorphonuclear leukocytes (PMNs) in the whole blood and the effects of plasma on these functions were investigated on 44 healthy mature neonates (term 37 to 41 weeks) and 15 premature neonates (term 30 to 36 weeks) using two color flow cytometric analysis. The results were compared to those of a healthy adult control group (n = 10). PMN phagocytic activity was low in both mature and premature neonates. H2O2 production of PMN with phorbol myristate acetate (PMA) stimulation and following phagocytosis was augmented in both mature and premature neonates. When plasma and PMNs of adults and neonates were separated and combined differently, phagocytic activity and H2O2 production of PMNs appeared to be principally regulated by the plasma employed. This finding indicates that plasma has major effects on both phagocytosis and H2O2 production by PMNs of newborn neonates.