Abstract 1263 Poster Session IV, Tuesday, 5/4 (poster 334)

Background: Neutrophil activation is associated with tissue injury. Increased CD11b/CD18 expression on neutrophils is a sign of neutrophil activation. Subjects: We studied the CD11b/CD18 expression on neutrophils in cord blood from preterm infants (GA 27.7±2.2 wks) and term infants; and in blood samples during postnatal days 1-5. As controls we measured the expression in healthy adults. Results: In preterm infants (N=10) CD11b expression in cord blood was 109±25 RFU (relative fluorescence units), and in term infants (N=29) 119±11 RFU; in 29 adult controls it was 110±32 RFU. On d 1 in preterm infants with respiratory distress syndrome (RDS) (N=29) the expression was 161±44 RFU, and during d 2-5 165±51 RFU (N=47). In term infants during d 2-5 the expression was 119±11 RFU (N=10). In preterm infants the expression was higher on d 1 (P=0.0036) and d 2-5 (P=0.0005) than in cord blood; the expression during d 2-5 was higher than in term infants (P=0.0018) and in adults (P=0.0001).

Conclusion: In preterm infants with RDS expression of CD11b/CD18 on neutrophils is increased from the first postnatal day. In term infants this expression does not differ from adult controls. Increased neutrophil activation may play a role in the morbidity of the preterm infant.