Neonatal neutrophil host defense. Prospects for immunologic enhancement during neonatal sepsis
M. S. Cairo
Division of Neonatalogy and Hematology/Oncology, Childrens Hospital of Orange County, CA 92668.
Neonatal host defense simulates a clinical state of immunodeficiency that
predisposes the preterm and term newborn to overwhelming bacterial sepsis.
There are various immunologic components that are deficient in the newborn
and new methods to enhance their function. Defects in both the quantitative
and qualitative aspects of the neonatal phagocyte contribute substantially
to the immaturity of neonates' immune systems. The neonate lacks an
adequate number of granulocyte bone marrow progenitor cells, and has a
decreased neutrophil storage pool and an increased tendency to peripheral
neutropenia during neonatal sepsis. Additionally, the neonatal granulocyte
demonstrates altered physiologic function compared with that found in the
adult with respect to chemotaxis, phagocytosis, oxidative metabolism, and
bacterial killing. Some recent clinical studies have suggested the benefit
of using adult neutrophil transfusions as adjuvant treatment during
neonatal bacterial sepsis, yet other studies have found the use of
polymorphonuclear neutrophil leukocyte transfusions to be inconclusive.
Reduced circulating immunoglobulins and impaired production of specific
antibody have also led to recent trials in the use of prophylactic
intravenous immunoglobulin in preterm infants predisposed to sepsis.
Recently, hematopoietic colony-stimulating factors have been demonstrated
to improve in vitro neonatal neutrophil physiologic activity. Future
therapy of neonatal sepsis will depend on new nontoxic methods for
enhancing neonatal host defense.
