CD64 (Fcgamma receptor I) cell surface expression on maturing neutrophils from preterm and term newborn infants.

BACKGROUND: The expression of CD64 (FcgammaRI) is increased from an almost negligible to a marked level on neutrophils in patients with bacterial infections. CD64 expression on neutrophils might therefore be a potential candidate for the diagnosis of bacterial infections in infants. AIM: This study was performed to monitor changes of neutrophil expression of CD64 during the postpartum period to further evaluate the usefulness of this analysis. The possible influence on the expression of this receptor by other factors was also investigated, including respiratory distress syndrome (RDS) and preterm rupture of the membranes (PROM). METHODS: Cell surface expression of CD64 on neutrophils from preterm and term newborn infants and healthy adults was analysed by flow cytometry. The expression of the other Fcgamma receptors, CD32 and CD16, and the complement receptors CD11b/CD18 and CD35 was also analysed for comparison. RESULTS: Neutrophils from preterm newborn infants showed a moderately increased level of CD64 expression that, during their first month of life, was reduced to the level observed on neutrophils from term newborn infants and adults. In contrast, the level of neutrophil expression of CD32 and CD16 was significantly lower in preterm than term newborn infants and adults. Neutrophils from all groups indicated similar levels of CD11b expression, but the expression on neutrophils from newborn infants increased after birth. CONCLUSION: Our results showed that neutrophil expression of CD64 is moderately increased in preterm newborn infants at birth. It seems not to be influenced by RDS, PROM or other factors related to preterm birth but by bacterial infection.

Human neutrophil lipocalin: normal levels and use as a marker for invasive infection in the newborn.

AIM: To evaluate human neutrophil lipocalin (HNL) as a marker of neonatal invasive infection and determine the normal serum levels of HNL in newborns. METHODS: HNL is released from neutrophil granulocytes and is regarded as a specific marker of neutrophil activity. In 81 newborns < or = 28 d of age with signs of infection on a total of 87 occasions, HNL and C-reactive protein (CRP) were measured at inclusion and on the three following days. As controls, term healthy newborns were recruited at birth (cord blood, n = 45) and at ages 3-5 d (n = 46). Serum HNL was measured by a radioimmunoassay. RESULTS: 25/87 episodes were classified as infection and 62 as non-proven infection. HNLmax was significantly higher in the infected group (mean 587.6 microg/l) than in the non-proven infected group (mean 217.7 microg/, p < 0.001). HNL peaked at inclusion, 1 d earlier than CRP. In the healthy controls. HNL was the same at 3-5 d of age as at birth (mean 82.4-81.7 microg/l) and similar to normal adult levels. CONCLUSIONS: The release of HNL is not increased in healthy newborns at birth, but neonatal neutrophils rapidly release HNL upon microbial stimulation in vivo. HNL might be useful as an early marker of neonatal infection.

Reactivation of human herpesvirus 6 during pregnancy.

Reactivation of human herpesvirus 6 (HHV-6) and cytomegalovirus (CMV) during pregnancy and transmission of the viruses to the fetus were investigated by polymerase chain reaction (PCR) and serology. In all, 104 blood samples were obtained 3 times during pregnancy and once at delivery. In another 107 women, samples were obtained only at delivery. Cord blood samples were obtained from both groups of women. HHV-6 DNA was detected in 41%-44% of the samples during months 3-8 of pregnancy, in 25% at delivery, and in 24% of age-matched controls. HHV-6 DNA was found in 1.0% of the cord blood samples. CMV DNA was detected in 1.7% of leukocytes from 104 pregnant women but in no cord blood sample. IgG antibodies to HHV-6 were found in 96% and CMV IgG in 62.5% of the women. HHV-6 IgG titers were significantly higher in HHV-6 PCR-positive women. Thus, HHV-6 reactivation seems common during pregnancy, and transfer of HHV-6 to the fetus may occur in approximately 1% of pregnancies.

Neutrophils from term and preterm newborn infants express the high affinity Fcgamma-receptor I (CD64) during bacterial infections.

The high affinity Fcgamma-receptor I (FcgammaRI, CD64) is normally expressed only to a very low extent by neutrophils. During bacterial infections, however, neutrophils from adult patients significantly increase their expression of FcgammaRI. Stimulation through FcgammaRI is a highly effective way to improve various aspects of neutrophil function, including phagocytosis. In our study the expression of FcgammaRI on neutrophils from preterm (n = 9) and term (n = 3) newborn infants, children (n = 14), and adults (n = 6) during the early phase of an acute bacterial infection was investigated. Our results showed that neutrophils from newborn infants with bacterial infection expressed FcgammaRI to a significantly higher extent than both noninfected preterm (p < 0.001) and term (p < 0.001) newborn infants and that neutrophils from preterm neonates expressed FcgammaRI to the same extent as neutrophils from term neonates and older infants, children, and adults. No difference in the neutrophil cell surface expression of FcgammaRI during bacterial infections was found among newborn infants, children, and adults. Expression of FcgammaRI probably represents an important mechanism to improve neutrophil phagocytosis as well as other aspects of neutrophil function during bacterial infections, especially in preterm infants. Our study indicates that measurement of cell surface expression of FcgammaRI on neutrophils could be a useful indicator of severe bacterial infections in preterm and term neonates, as well as in older children and adults.