The Higher CD34+ Cell Counts in Cord Blood Than Those in Neonatal Peripheral Blood Correlate with Increased Expression of Cytokine Receptors and Cell Adhesion Molecules on the CD34+ Cells in Cord Blood.

The hematologic values of neonatal peripheral blood show a characteristic series of changes during neonatal period. The hematopoietic stem cells in cord blood (CB) are more primitive and abundant than those in neonatal peripheral blood (NB). However, there have been no studies regarding the reasons for those differences. Thus, We investigated the kinetics of nucleated cells and CD34+ cells in CB and neonatal peripheral blood. We obtained the CB and NB samples from 14 normal full-term babies for this study, which were collected immediately after delivery as well as at 24 hours and 48 hours after delivery. We analysed the expressions of CD34, CD34/CXCR4, CD34/CD49d and CD34/CD44 as well as CD3, CD19 and CD16/56 on the isolated mononuclear cells by using FACSort. We also performed CFU-GM counts and apoptotic analysis with isolated mononuclear cells. The total white blood cell counts as well as absolute neutrophil counts of NB at delivery were higher than those of CB (p=0.04) and increased until 24 hours, when decreased until 48 hours after delivery. There were no differences of absolute lymphocyte counts, CD3+ cell and CD19+ cell counts among CB and NB at 0, 24 and 48 hours postnatally, however, the CD16/56+ cell counts were lower in CB than in NB and gradually decreased until 48 hours after delivery (p=0.011). The number of CFU-GM counts (p=0.02) and CD34+ cells (p=0.049) as well as CD34+CXCR4+ cells (p=0.002), CD34+CD49d+ (p=0.001) and CD34+CD44+ cells (p=0.001) in CB were more significantly higher than those of NB at delivery, when decreased gradually until 48 hours after delivery. The incidence of apoptosis were statistically not significant among CB and NB at 0, 24 and 48 hours postnatally. In conclusion, the higher leukocyte counts for several days after delivery were correlated with neutrophilic increment which may be influenced by stressful events during delivery. The more higher CFU-GM counts and CD34+ cell counts in CB than those in NB might be correlated with increased expression of cytokine receptors and cell adhesion molecules on the CD34+ cells in CB.