Spontaneous and Fas-mediated apoptosis are diminished in umbilical cord blood neutrophils compared with adult neutrophils.

Apoptosis mediates neutrophil (PMN) phagocytosis and is influenced by cytokines and the Fas/Fas ligand pathway. To determine whether apoptosis of cord blood PMN differs from those of adults, cultured PMN were evaluated by morphological analysis, flow cytometry (TUNEL assay), and DNA gel electrophoresis. In addition, we studied the effect of anti-Fas IgM or cycloheximide on induction of PMN apoptosis. Spontaneous apoptosis (24 h) was less in cord blood PMN (mean +/- SD; 29 +/- 9 vs. adults, 56 +/- 14%, P < 0.001). Treatment (6 h) with anti-Fas IgM induced less apoptosis in cord blood PMN (24 +/- 6 vs. adults, 63 +/- 7%, P < 0.001), as did treatment with cycloheximide (13 +/- 10 vs. adults, 55 +/- 16%, P < 0.01). These data suggest the pre-existence of proteins that inhibit apoptosis or the absence of those that promote apoptosis in cord blood PMN.