Newborn, premature infants have greater susceptibility to infection compared to older newborn infants. Although the reason for greater susceptibility to bacterial infection in premature infants is unknown, there are many reports that focus on polymorphonuclear leukocytes (neutrophils) as the defective cell type in the immature neonatal system. However, we have recently reported that in an rat model of inflammation, neutrophils from adult rats failed to migrate efficiently in neonatal rats. Furthermore, we found that this defect was associated with decreased expression of P-selectin on the surface of neonatal endothelial cells in situ. P-selectin is an adherence molecule that is expressed by activated endothelial cells and serves as the counterligand for CD11/CD18, the β2- integrin that is expressed by activated neutrophils.

We hypothesized that endothelial cell P-selectin expression would be less in human umbilical cord veins from prematurely born (preterm) infants compared to normal term infants. To test this hypothesis, we collected umbilical cords from preterm infants (<27 weeks gestation) and term infants (>38 weeks gestation).