Is there an effect of immunoglobulins and G-CSF on neutrophil phagocytic activity in preterm infants?

The percentage of neutrophils phagocytosing group B streptococci (GBS) in vitro was determined in ten healthy preterm infants (< 32 weeks of gestation) and adult controls by using an acridine orange fluorescence whole blood assay. When GBS were opsonized with adult serum, no difference in phagocytic activity was found between both groups after 10 and 30 min (preterms: 40% and 68%, adults: 32% and 56%, respectively). Phagocytosis rates in preterm infants decreased significantly to 6% and 18% (at 10 and 30 min) when pool serum of preterm infants was used instead. Supplementation of the preterm serum with either intravenous immunoglobulin or IgM-enriched immunoglobulin did not change the results significantly. The addition of granulocyte colony-stimulating factor (G-CSF) accelerated phagocytosis significantly after 10 min, but did not increase the overall phagocytic activity after 30 min in either group. Hence the potential benefits of intravenous immunoglobulins and G-CSF in neonatal sepsis may not be attributable to an immediate increase in and direct effect on neutrophil phagocytic activity.