Naturally acquired regulatory mechanism of perioperative cytokine response in neonates

The inflammatory reaction is known to be controlled in neonates. We clarified the characteristics of cytokine profile in neonatal patients and assess its clinical significance. Serum levels of interleukin (IL)-6 and IL-1 receptor antagonist (ra) were determined in 152 pediatric patients and 33 each of maternal and cord bloods. Supernatant IL-1ra levels of cultured monocytes and granulocytes stimulated with IL-1β or LPS, and IL-1ra mRNA expression of granulocytes were assayed in 15 each of cord and healthy adult bloods. Although surgical stress in neonates was heavier than that in infants, there was no difference in the occurrence of postoperative morbidity and mortality. In neonates, the perioperative serum level of IL-1ra was significantly raised, and the postoperative IL-6 response was well controlled. The serum concentration of IL-1ra in cord blood was not different from that in maternal blood, whereas, the serum concentration of IL-6 in cord blood was significantly reduced than that in maternal blood. In granulocytes, significantly more IL-1ra was produced from cord than from adult blood. An IL-1ra predominant immune status in neonates may be a naturally acquired adaptation system and play a crucial role in attenuating acute inflammatory reaction in a vulnerable host defense.