A longitudinal study of granulocyte colony-stimulating factor levels and neutrophil counts in newborn infants

The goal of this study was to longitudinally measure endogenous granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) levels in newborn infants and to attempt to correlate these levels with neutrophil counts.

Samples for complete blood count, G-CSF, and GM-CSF were obtained from groups of healthy full-term infants at 0 (cord blood or nursery admission), 12, 24, 48, and 72 h. Samples were also obtained from premature infants at the above times and at 1 week. G-CSF and GM-CSF levels were measured using bioassays.

Levels of G-CSF ranged from < 5 to 53,800 pg/ml. Levels were significantly higher (p < 0.001) in premature infants and decreased over time in all infants. White blood cell counts also decreased over the first week of life. All GM-CSF levels were below the detectable range.

Levels of G-CSF at birth are higher than those seen in adults. These increased levels may partially explain the leukocytosis seen in the first week of life. This, as has been shown in preliminary studies, suggests that infants are capable of an increase in neutrophil count after administration of exogenous G-CSF.