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The effect of dexamethasone (DEX) on interleukin (IL)-10 and IL-12p40 production was examined in preterm newborns, term infants and was compared to that in adults. Mononuclear cells isolated from newborn cord blood (CBMC) and peripheral blood from adults (PBMC) were incubated with lipopolysaccharide in the absence or presence of DEX at concentrations between 10^–8 and 10^–5 M. Cytokine concentration in the supernatants was tested using ELISA kits. DEX induced a dose-dependent inhibition of IL-10 production by PBMC from adults whereas CBMC from newborns were mostly unaffected by the drug. DEX caused a dose-dependent inhibition of IL-12p40 secretion by cells of the three age groups, although to a different extent. Since IL-12 plays a critical role in the development of a protective immune response to fungal infection, it is conceivable that the inhibition of IL-12p40 secretion caused by DEX may contribute to the increased occurrence of fungal infections in preterms treated with this drug.

CD14 expression and the capacity of mononuclear cells (MC) from preterm and term neonates to secrete the proinflammatory cytokines interleukin (IL) 1β, tumor necrosis factor α and IL-6 in response to lipopolysaccharide (LPS) was investigated and compared to that of adults. MC were incubated with various doses of LPS, and the cytokine level in the supernatants was tested. CD14 receptors on MC and the intensity of their expression were analyzed. MC of preterm and term neonates and adults responded to LPS with low, medium and high proinflammatory cytokine production, respectively. CD14 expression was lowest in preterm infants, intermediate in term infants and highest in adults. The difference between term and preterm neonates for both parameters was significant. The results suggest a possible correlation between the lower expression of CD14 receptor on neonatal cells and the reduced secretion of proinflammatory cytokines by these cells. This decreased production may possibly contribute to the low ability of neonates to develop fever.