OXIDATIVE METABOLISM IN HUMAN CORD BLOOD NEUTROPHILS

Abstract

Oxidative metabolism (OxM) was assessed in cord blood, neutrophils (CBN) in an attempt to explain the susceptibility of infants to infections. A variety of methods were employed in prior reports, and results have been contradictory. Isolated neutrophils were used in this study. Hexose monophosphate shunt (HMS) activity was determined by glucose-1-14C oxidation. The kinetics of OxM were measured as the rate of light emission by chemiluminescence (CL), an assay related to superoxide and singlet oxygen formation. HMS activity in both resting and phagocytic cells was greater (p < 0.05) in 17 CBN than in cells from 9 simultaneously studied adult controls, however, the absolute increase from resting to phagocytic values was significantly less in CBN. Mean values for peak CL during phagocytosis of zymosan from 14 CBN and 9 controls were similar (18.0 vs 20.7 CPM × 104, p > 0.05), but the kinetics of CL were quite different. During the first 8 min. of phagocytosis CL (light emission) increased sharply in both groups. At later times CL was sustained by control cells, but waned in CBN and within 15 min. was significantly less (p < 0.05). Thus, CBN initiated post-phagocytic OxM and reached normal peak values of HMS activity and CL. However, CBN were unable to maintain the increased rate of OxM after phagocytosis when compared to adult controls. This difference may indicate a functional defect.