THE EFFECTS OF RECOMBINANT HUMAN GRANULOCYTE-MACROPHAGE COLONY-STIMULATING FACTOR ON THE NEUTROPHIL RESPIRATORY BURST IN THE TERM AND PRETERM INFANT WHEN STUDIED IN WHOLE-BLOOD

To investigate further the susceptibility to infection of newborn infa nts, particularly those born prematurely, we have used a ''whole blood '' flew cytometric assay to compan the respiratory burst activity in r ecombinant human granulocyte-macrophage colony stimulating factor ''pr imed'' neutrophils obtained from healthy adults, term infants, and pre term newborn infants. The use of whole blood avoids prior cell separat ion procedures that may cause artifactual activation or priming. In he althy adults (n = 21), the bacterial cell wall peptide N-formyl-methio nyl-leucyl-phenylalanine induced little neutrophil respiratory burst a ctivity, suggesting that the circulating cell is relatively quiescent. Prior exposure to recombinant human granulocyte-macrophage colony sti mulating factor augmented the median N-formyl-methionyl-leucyl-phenyla lanine response by 425%. In cord blood from full-term neonates (n = 9) , recombinant human granulocyte-macrophage colony stimulating factor p roduced less enhancement of the N-formyl-methionyl-leucyl-phenylalanin e response (345%), but the absolute level of respiratory burst activit y was at least as great as in adults, suggesting that the neutrophils are fully functional and partially primed after delivery. In preterm i nfants receiving intensive care (n = 10), the degree of priming was si milar to that in neutrophils from term infants (344%), although the ab solute level of respiratory burst activity was reduced (p = 0.0003). I n response to stimulation with phorbol ester, 73.5% (18-99%) (median a nd range) of neutrophils obtained from adults and 77.6% (50-92%) from term babies exhibit respiratory burst activity detectable in the whole blood assay. However, in neutrophils obtained from preterm infants, t here was a significant reduction in the phorbol ester-induced respirat ory burst, with only 32.9% (21-61%) of cells responding (p = 0.0129).