Plasma concentration of granulocyte-colony-stimulating factor in neonates

The role of granulocyte colony-stimulating factor in the neutrophilia observed in the fetal inflammatory response syndrome

OBJECTIVES

Fetal neutrophilia is present in two-thirds of cases with the fetal inflammatory response syndrome (FIRS). The mechanisms responsible for this finding have not been elucidated. Granulocyte colony-stimulating factor (G-CSF) is the primary physiologic regulator of neutrophil production and plays a key role in the rapid generation and release of neutrophils in stressful conditions (i.e., infection). The objective of this study was to determine: 1) whether FIRS was associated with changes in fetal plasma G-CSF concentrations; and 2) if fetal plasma G-CSF concentrations correlated with fetal neutrophil counts, chorioamnionitis, neonatal morbidity/mortality and cordocentesis-to-delivery interval.

STUDY DESIGN

Percutaneous umbilical cord blood sampling was performed in a population of patients with preterm labor (n=107). A fetal plasma interleukin-6 (IL-6) concentration >11 pg/mL was used to define FIRS. Cord blood G-CSF was measured by a sensitive and specific immunoassay. An absolute neutrophil count was determined and corrected for gestational age. Receiver operating characteristic (ROC) curve, survival analysis and Cox proportional hazard model were employed.

RESULTS

1) G-CSF was detected in all fetal blood samples; 2) fetuses with FIRS had a higher median fetal plasma G-CSF concentration than those without FIRS (P<0.001); 3) a fetal plasma G-CSF concentration ≥134 pg/mL (derived from an ROC curve) was associated with a shorter cordocentesis-to-delivery interval, a higher frequency of chorioamnionitis (clinical and histological), intra-amniotic infection, and composite neonatal morbidity/mortality than a fetal plasma concentration below this cut-off; and 4) a fetal plasma G-CSF concentration ≥134 pg/mL was associated with a shorter cordocentesis-to-delivery interval (hazard ratio 3.2; 95% confidence interval 1.8-5.8) after adjusting for confounders.

CONCLUSIONS

1) G-CSF concentrations are higher in the peripheral blood of fetuses with FIRS than in fetuses without FIRS; and 2) a subset of fetuses with FIRS with elevated fetal plasma G-CSF concentrations are associated with neutrophilia, a shorter procedure-to-delivery interval, chorio-amnionitis and increased perinatal morbidity and mortality.

Intravenous immunoglobulins and haematopoietic growth factors in the prevention and treatment of neonatal sepsis: ground reality or glorified myths?

Neonatal sepsis is a significant cause of morbidity and mortality in the neonatal intensive care unit. The epidemiology of neonatal infections is complex; however, they are in large part secondary to developmentally immature host defence mechanisms. These immunodeficiencies, which are exaggerated in premature and sick neonates, include quantitative and qualitative deficits in phagocytes, complement components, cytokines and immunoglobulins. Therapies that modulate or augment host defences may attenuate the virulence of neonatal infections. In this paper, we have reviewed immunotherapies that modulate the immune system of the neonate, including intravenous immunoglobulins and myeloid haematopoietic growth factors. Future studies should focus on investigating other abnormalities of neonatal host defence and/or combined immunotherapy approaches in an attempt to circumvent the immaturity of host defence and potentially reduce both the incidence and severity of neonatal sepsis.

Granulocyte colony-stimulating factor and granulocyte-macrophage colony-stimulating factor have differential effects on neonatal and adult neutrophil survival and function

Neutropenia is a common sequela of neonatal sepsis. Recent clinical trials have shown the beneficial effects of colony-stimulating factors (CSFs) on outcome in this group, but the exact mechanism remains unknown. Neonates and mothers who were at high-risk for infection were recruited for cord blood sampling in a university tertiary referral maternity hospital. Neonatal and adult neutrophils were evaluated for their ability to combat bacterial infection by examining their functional activity (CD11b and reactive oxygen intermediates) and their persistence at inflammatory sites (apoptosis). The mechanism for altered apoptotic responses was assessed by caspase activation assays, X chromosome-linked inhibitor of apoptosis protein expression, and cytosolic cytochrome c release. Although granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) significantly delayed neutrophil apoptosis in normal adults, only G-CSF had a similar effect in normal neonates. Neutrophils from neonates who are at high risk for infection are unresponsive to the antiapoptotic effects of G-CSF or GM-CSF, unlike maternal neutrophils, which have delayed apoptosis in response to GM-CSF. However, CD11b expression and reactive oxygen intermediate production were significantly increased in normal neonatal neutrophils that were incubated with GM-CSF versus controls but not G-CSF or lipopolysaccharide. Decreased cytosolic cytochrome c release and caspases 3 and 9 activity are associated with the CSF-mediated delay in apoptosis in adults but not in newborns. The antiapoptotic X chromosome-linked inhibitor of apoptosis protein is up-regulated in neonates compared with adults and may mediate their differential spontaneous apoptosis. These results have important implications for the use of CSFs in neonatal sepsis, as responses differ from those seen in adults. Further delineation of neonatal neutrophil responses to CSFs may improve their therapeutic potential.

Granulocyte colony-stimulating factor in the cord blood of premature neonates born to mothers with pregnancy-induced hypertension

OBJECTIVES

To estimate the cord blood levels of granulocyte colony-stimulating factor (G-CSF) and granulocyte-macrophage colony-stimulating factor (GM-CSF) in preterm infants and to study the relationship of these levels to pregnancy-induced hypertension (PIH) and absolute neutrophil counts.

STUDY DESIGN

G-CSF and GM-CSF levels in the cord blood of preterm neonates (n = 74) either with or without maternal PIH were estimated by enzyme-linked immunosorbent assay.

RESULTS

Infants in the PIH group had lower white blood cell, absolute neutrophil, absolute lymphocyte, and monocyte counts. The levels of G-CSF in cord blood were significantly lower in infants whose mothers had PIH (P =.04) and in infants with neutropenia (P =. 01). G-CSF levels were positively correlated with both absolute neutrophil count (P =.02) and total white blood cell count (P =.01). GM-CSF was undetectable in all subjects. According to logistic regression with neutropenia as the dependent variable, only maternal PIH (P <.001), gestational age (P <.001), and G-CSF (P =.01) were independently related.

CONCLUSION

In this study maternal PIH and low gestational age were significantly associated with neutropenia in premature infants. Low G-CSF levels may contribute to the neutropenia that is commonly seen in infants born to mothers with PIH.