Bactericidal and Metabolic Function of Polymorphonuclear Leukocytes

The bactericidal and metabolic function of the phagocytic system requires integration of several complex humoral and cellular factors responding to different regulators. Polymorphonuclear leukocytes are highly mobile cells, capable of phagocytosis of bacteria or fungi with formation of a "cellular digestive system" containing reactive oxygen radicals, hydrogen ions, and digestive enzymes. The unique metabolism of oxygen in neutrophils results in release of energy as light (chemiluminescence), a response closely associated with microbial killing. Neonatal neutrophils cope with normal bacterial challenges in vitro as efficiently as adult neutrophils; however, these cells have decreased capacity for locomotion, decreased deformabiity, decreased phagocytosis in low serum concentrations, and decreased chemiluminescence. These subtle defects in function can be amplified by exaggerated challenge which may be related to a higher incidence of sepsis during the neonatal period.