Imbalanced cytokine secretion in newborns

In adults, a balance between Th1 and Th2 cytokine networks has been proposed to be associated with a healthy status. Newborn babies are reported to express Th2-type immune reactions. Further, the impaired protection of newborn babies against infections has been attributed to a deficient secretion of interferon gamma (IFN-gamma) and interleukin-10 (IL-10). Using IFN-gamma and IL-10 as surrogate markers of Th1 and Th2 orientation, we compared the patterns of IFN-gamma and IL-10 secretion by peripheral blood mononuclear cells between 52 healthy newborns and 35 adults. The baseline secretion of IFN-gamma in adults was similar to that of newborns. The lipopolysaccharide-stimulated IFN-gamma secretion was higher in newborns than in adults, whereas the concanavalin-A-stimulated IFN-gamma secretion was higher in adults. The unstimulated and stimulated IL-10 secretion was significantly lower in newborns than in adults. Using a threshold level of 1,000 pg/ml, we classified neonates and adults on the basis of their stimulated IL-10 and IFN-gamma secretion. Four different groups were identified: IL-10-oriented secretion, IFN-gamma- oriented secretion, balanced high secretion, and balanced low secretion. Only 25% of the neonates had a high IL-10 and a high IFN-gamma secretion as compared with 77% of the adults. Eight percent of the newborns, but none of the adults, had a low secretion of both cytokines. Thirty-six percent of the neonates, but only 5% of the adults, had a high IL-10 and a low IFN-gamma secretion. Thirty-one percent of the neonates and 18% of the adults had a high IFN-gamma secretion, but a low IL-10 secretion. We conclude that neonates have an immature IL-10 and IFN-gamma response as compared with adults. However, individual neonates may have a mature cytokine secretion, whereas others may have a Th1- or a Th2-directed immune response.