Phenotype and function of lymphocytes from the neonatal umbilical cord compared to paired maternal peripheral blood cells isolated during delivery.

In the present study, we analyzed the immunological characteristics of mononuclear cells (MNC) isolated from both neonatal umbilical cord blood (UCB) and maternal peripheral blood (MPB) during the delivery. The in vitro proliferative response of UCB T lymphocytes was significantly reduced compared to the maternal response to phytohemagglutinin A, pokeweed mitogen, and alloantigen stimulation, in correlation with the lower percentage of UCB than MPB lymphocytes, but not with that of B cells. The mean cytotoxic activity level of interleukin-2 (IL-2)-activated natural killer (NK) was higher in UCB than in MBP, whereas the percentage of CD56(+) NK cell count was similar. Our results show differences in the immune reactivity of T and B lymphocytes from neonate and adult isolated under similar physiological conditions.