NEUTROPHIL RESPIRATORY BURST IN TERM AND PRETERM NEONATES WITHOUT SIGNS OF INFECTION AND IN THOSE WITH INCREASED LEVELS OF C-REACTIVE PROTEIN

Developmental immaturities in neonatal host defense predispose the neo nates to an increased mortality rate during bacterial infections. Earl y diagnosis is of great clinical importance, but, especially in neonat es, is sometimes very difficult. The ability to generate reactive oxyg en species, the so-called respiratory burst, is essential for neutroph ils to kill infectious microorganisms. Therefore, changes of respirato ry burst may reflect increased susceptibility of neonates to infection s and may be useful for the early detection of infections. Superoxide anion production was determined by a how cytometric method using dihyd rorhodamine 123 (DHR) as an oxidative probe after priming of neutrophi ls with PBS buffer (spontaneous burst), with N-formyl-methionyl-leucyl -phenylalanine (fMLP), or with Escherichia coli. During the study peri od, the spontaneous percentage of activated cells in whole blood as we ll as the percentage of activated cells after stimulation with fMLP wa s lower in adults (n = 100; PBS, 1.0 +/- 0.1%; fMLP, 8.3 +/- 0.9%) com pared with neonates without signs of infection (n = 143). Among the la tter, the percentage of activated cells (PBS and fMLP assay) varied wi th respect to gestational age and hours of life: lowest values were me asured in preterm newborns with gestational age less than 32 wk and be tween 25 and 120 h of life. The same correlation to gestational age wa s true for total neutrophil cell counts. In neonates with increased le vels of C-reactive protein during the first 5 d of life (n = 43), the percentages of activated cells after PBS and fMLP incubation were high er than those of neonates without signs of infection. The relationship of neutrophil respiratory burst and neutrophil cell counts to gestati onal age might reflect at least in part a reason for the increased sus ceptibility of neonates to infections. Furthermore, determination of r espiratory burst may prove to be a new laboratory parameter of neonata l infection.