It has become evident that a number of developmental deficiencies exist in the function of neonatal phagocytes. Although the degree to which each contributes to the recognized impairment of host defenses in the normal human neonate is yet unclear, we have derived much valuable information from the study of neonatal polymorphonuclear leukocytes (PMNs) and monocytes (MNLs). In this discussion, we focus upon three functional components of PMN—phagocytosis, bactericidal activity, and movement. This is followed by a brief consideration of correlative studies between neonatal PMNs and MNLs. A more detailed discussion of monocyte functions is found elsewhere in this symposium.
As with many in vitro systems, phagocytic assays vary considerably in design. Included among the important variables are cell concentration, opsonic concentration, type of particle being ingested, and phagocyte:particle ratio. Despite these differences, results obtained by most investigators studying neonatal PMNs have been reasonably consistent. The data fall into two groups. In the first, PMN phagocytosis has been studied in the presence of normal, or approximately normal plasma (or serum) concentration.1-5 In general, such experiments have yielded data suggesting that the neonatal PMN is equal to the adult PMN in phagocytic ability. A number of particles have been utilized in these studies, including Staphylococcus aureus 502A, Serratia marcescens, Sta pyogenes, Diplococcus pneumoniae, and Pseudomonas aeruginosa. The second group of studies has been carried out under "stress" conditions in vitro or in vivo, and suggest that the neomatal PMN is deficient in phagocytic ability when compared with that of the adult PMN.
- Copyright © 1979 by the American Academy of Pediatrics