Polymorphonuclear leukocyte function in term and preterm newborn infants.

Bacterial infections are a major problem in the care for newborn infants. In search for immunological deficits we investigated phagocytosis and killing of staphylococci using polymorphonuclear leukocytes (PMN) isolated from 2 ml of venous blood. Phagocytosis of PMN from preterm (n = 10) and newborn infants (n = 9; mean birth weights 1,949 and 3,523 g, respectively) was not different from that of adult PMN (n = 14). Killing capacity of PMN from preterm infants was markedly impaired compared to term newborn infants and to adult PMN. We found similar rates of superoxide anion production and similar times for activation in response to phorbolmyristate acetate stimulation. Our study gives further evidence that PMN from term newborn infants have normal phagocytotic and bactericidal capacity. In PMN from preterm newborn infants, however, the bactericidal capacity is diminished similar to newborn infants under stress as described earlier by others.