Innate immunity in human newborn infants: prematurity means more than immaturity

Neonates, particularly those born prematurely, are exquisitely vulnerable to life-threatening infections. This increased susceptibility to infection is maintained into childhood. Despite the considerable human and economic cost of infection-related neonatal morbidity and mortality, the mechanisms underlying this heightened susceptibility are only partly understood. It is increasingly recognised that innate immune responses are key to the protection against infection early in life, and emerging data suggest that such responses are deficient in the newborn and especially in preterm infants. Here we review the current understanding of the maturation of the innate immune response in human neonates highlighting the clinical relevance and possible avenues for therapeutic intervention.