Purpose: An immaturity in humoral, cellular, and phagocytic immunity predisposes the newborn to overwhelming bacterial infection. The maturation and proliferation of early hemapoietic stem cells give rise to all three of these aspects of immunity. Defects in the regulation of early hematopoiesis may account in part for the immaturity of neonatal host defense. A new hematopoietic growth factor, Steel factor (SLF), has recently been demonstrated to induce the proliferation of early hematopoietic progenitor cells. Our purpose was to study SLF and its effect on hematopoiesis.
Patients and methods: We measured circulating serum SLF levels in preterm and term newborns and compared them to adults, matched third trimester pregnant mothers, and to circulating granulocyte colony-stimulating factor (G-CSF) levels.
Results: There was no significant difference in SLF levels between preterm and term newborns and adults (3000 +/- 200 vs. 2700 +/- 200 vs. 3100 +/- 300 pg/ml) (Pt vs. T vs. A) (p = NS). Also, there was no significant difference between matched third trimester maternal levels and their matched term newborn (2650 +/- 330 pg/ml vs. 3530 +/- 400 pg/ml) (p = NS). However, G-CSF levels were significantly higher in preterm newborns compared to term newborns and adults (p < or = 0.025). The preterm newborn G-CSF levels, however, were significantly lower compared to positive controls obtained from neutropenic patients post bone marrow transplantation (ANC < or = 200/mm3) (174 +/- 86 vs. 669 +/- 82.3 pg/ml) (p < 0.001). Additionally, there were no significant differences in G-CSF levels between matched third trimester maternal samples and matched term newborns.
Conclusion: These studies suggest that circulating levels of SLF in the preterm and term newborn are similar to adults and do not account for differences in hematopoiesis.