Foetal lymphocytes are more sensitive to freezing than adult lymphocytes within a mononuclear cell environment

Previous studies have reported reduced natural killer (NK) cell activity in cord blood (CB) compared to adult blood mononuclear cell populations. We suggest that foetal NK cells have the capacity to kill, but this is suppressed in vitro. This hypothesis is strengthened by our observation that CB mononuclear cell populations had their NK activity restored by freeze/thawing, whereas adult PBMC had a reduced killing ability on freeze/thawing. Thus, either NK cells are activated to kill by the freeze/thawing or there is an NK cell suppressor factor in CB which is lost through freeze/thawing. This report shows clear differences between NK cells within the adult periphery and CB, and may help toward a better understanding of events occurring in vitro.