Circulating cytokine concentrations and cytokine production by monocytes from newborn babies and adults.

As a possible factor responsible for reduced fever responses in the newborn, we measured plasma cytokine concentrations and cytokine production by neonatal monocytes after lipopolysaccharide or IL (interleukin)-1 alpha stimulation in vitro and compared these data with those obtained from adult plasma and monocytes. Whole blood was collected from afebrile adults (n = 12) and the umbilical cord of normal term infants (n = 12). Plasma and peripheral blood monocytes were prepared by conventional techniques. Significantly lower concentrations of IL-1 alpha, IL-1 beta (P < 0.05, t-test) and IL-6 (P < 0.01, t-test) were found in the plasma of newborn babies compared with that of adults. There was no significant difference in plasma tumour necrosis factor (TNF) concentrations between the adults and newborn babies. Monocytes from newborn babies had the capacity to produce IL-1 alpha and IL-1 beta as readily as adult cells after stimulation with lipopolysaccharide or IL-1 alpha, and produced significantly lower concentrations of TNF and IL-6 than those produced by stimulated adult monocytes (P < 0.01, ANOVA). Our results suggest that the reduced production of IL-6 by monocytes of the newborn during infection could be partly responsible for attenuated fever responses observed in the neonate.