METABOLIC AND FUNCTIONAL DEFECTS IN NEONATAL GRANULOCYTES (PMN)

Abstract

Newborns (N) have an increased susceptibility to infection. Because of conflicting previous data on the functional capabilities of their PMN metabolic, phagocytic and bactericidal activities of normal full term N were studied and compared to normal adult controls. Phagocytosis of ¹⁴C S. aureus 502A at 20 min. and myeloperoxidase mediated protein iodination at 60 min. were not depressed. Resting ¹⁴C-1-glucose oxidation was equivalent, however 60 min. after phagocytosis of yeast N-PMN exhibited significant depressions in activity when compared to the controls (783±132 cpm ¹⁴CO₂/1×10⁶ PMN v.s. 1545±179, P<0.01). This was paralleled by reduced rates of O₂ consumption by N-PMN after 10 min. of phagocytosis (10-15 min. 2.89±0.19 μmoles/15×10⁶ PMN/min. v.s. 3.66±0.20, P<0.02; 15-20 min.;1.76±0.11 v.s. 2.30±0.11, P<0.02), while initial rates were similar. These defects may reflect decreased H₂O₂ production. These observations were paralleled by a mild but significant reduction in the killing of S. aureus 502A by N-PMN evident only on prolonged incubation (60 min,;92.8% killed v.s. 95.7%, P<0.02, 120 min.;95.1% v.s. 97.2%, P<0.05). These studies suggest that N-PMN have diminished H₂O₂ production reflected in a mild impairment of bactericidal activity. When coupled with previously documented opsonic and chemotactic defects these findings may have pathogenetic significance in the increased susceptibility of the N to infection.

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