Improved immunodiagnosis of neutrophil dysfunction in the newborn and infant.

An improved assay for the simultaneous assessment of phagocytic uptake (via Immunobeads) and metabolic integrity (via nitroblue tetrazolium (NBT) dye reduction) was used to evaluate the neutrophil function in neonates, one year olds, and adults. The unique advantage of this assay is that it offers greater standardization since the beads are commercially available with a known quantity of immunoglobulin bound to their surface which allows for considerably less variation than particles opsonized in vivo. Blood samples were collected from 20 full term healthy neonates, 20 healthy one year olds, and 20 healthy adults. The neutrophils were isolated, and phagocytic and killing function compared among the three groups. It was found that the neonates had a small but significant neutrophil dysfunction with respect to phagocytic and intracellular killing ability when compared to the one year olds and adults. Additionally, blood was collected and evaluated from five premature infants with varying degrees of stress. Their neutrophil dysfunction was much more pronounced. Although it was previously thought that full term healthy neonates have no demonstrable neutrophil dysfunction unless stressed in some manner, a subtle dysfunction was identified even in unstressed neonates. It was, however, found to be more pronounced if the neonate was either premature or stressed in some manner. It is hoped that this assay, through its greater sensitivity and ease of standardization, will uncover subtle neutrophil dysfunctions in various disease states that as yet remain undiagnosed. The clinical significance of such subtle neutrophil dysfunctions is not yet known.