Modulation of pro- and anti-inflammatory cytokine production in very preterm infants

In premature infants, outcome of infection-associated complications is heterogeneous despite advances in antibiotic treatment and diagnosis. Information on the immune response in preterm infants is limited. Immune modulatory strategies require detailed analysis of mediators and their kinetics.

To determine the kinetics of IL-1beta, TNFalpha, IL-6, IL-8, IL-10, gammaINF and G-CSF in preterm and term infants in an ex vivo cord blood culture (CBC) endotoxin model.

Cord blood of 25 infants was obtained immediately after birth from the fetal side of the placenta and incubated in culture medium (RPMI 1640) in the presence or absence of 500 pg/ml lipopolysaccharide (LPS) for 48h. TNFalpha, IL-1beta, IL-6 and IL-8 were measured by sequential immunometric assay (IMMULITE, DPC Biermann, Germany); IL-10 (Milenia Biotec, Bad Nauheim, Germany), gammaINF (Diaclone, Besancon, France) and G-CSF (R & D Systems, Wiesbaden, Germany) were determined by ELISA in supernatants at 0, 4, 8, 12, 24 and 48h. Infants were stratified into three gestational age groups (< or =32 weeks, 33-36 weeks, > or =37 weeks). Variations between the groups were first analyzed for significance by Kruskal-Wallis test and pairs were compared by Mann-Whitney-U test. Effects of gestational age, leucocyte count, hematocrit and frequency of antenatal steroid exposure were tested by linear regression analysis. To correct a possible impact of variable, WBC count, cytokine levels were adjusted according to individual leucocyte numbers.

LPS-stimulated maximum levels of IL-6, IL-1beta,TNFalpha and G-CSF in CBC were significantly lower in very preterm infants compared to more advanced gestational age groups. After adjusting the cytokine levels for 10(5) leucocytes, a significant effect of gestational age on IL-6 and G-CSF production (p<0.05) was detected. A non-significant trend towards reduced cytokine levels was observed following multiple antenatal steroid exposures. IL-10:TNFalpha ratio increased in very preterm neonates when compared with the advanced gestational age, although the increase was not significant.

Pro-inflammatory cytokine activity in CBC correlates with gestational age, whereas IL-10 does not. Although ex vivo synthesis of IL-1beta, TNFalpha, IL-6, G-CSF in CBC depends in part on leucocyte numbers, IL-6 and G-CSF synthesis appeared to be related to immaturity. Non-significant effects of multiple antenatal steroid exposure and increased IL-10:TNFalpha ratio in preterm neonates, observed in a small sample size, warrant further investigation.