CD56brightCD16- NATURAL KILLER CELLS ARE IN HIGHER COUNTS IN THE UMBILICAL CORD BLOOD THAN IN THE PERIPHERAL BLOOD

ABSTRACT Umbilical cord blood (UCB) is an alternative source for hematopoietic stem cells allogeneic hematopoietic stem cell transplantation in the absence of compatible donor. UCB transplantation has a lower incidence of chronic graft versus host disease (GvHD) but is associated with slower engraftment and slower immune reconstitution as compared to other sources. Dendritic cells (DC) and Natural Killer cells (NK) play a central role in the development of GVHD, the graft versus leukemia (GvL) effect, and in the control of infectious complications. We quantified by multiparametric flow cytometry monocytes, lymphocytes, NK cells, and DC, including their subsets, in UCB samples from 54 healthy newborns and peripheral blood (PB) from 25 healthy adult volunteers. In the UCB samples, there were higher counts of CD56brightCD16-NK cells (median 0.024×109/L), as compared to the PB samples (0.012×109/L, P<0.0001), CD56dimCD16bright NK cells (median 0.446×109/L vs. 0.259×109/L for PB samples, P= 0.001), and plasmacytoid dendritic cells (pDC, median 0.008×109/L for UCB samples vs. 0.006×109/L for PB samples, P= 0.03). Moreover, non-classical monocytes counts were lower in UCB than in PB (median 0.024×109/L vs. 0.051 x109/L, respectively, P< 0.0001). In conclusion, there were higher counts of NK cells and pDC, and lower counts of non-classical monocytes in UCB than in PB from healthy individuals. These findings might explain the lower incidence and severity of chronic GVHD although maintaining the GVL effect in UCB transplants recipients as compared to other stem cell sources. Highlights CD56brightCD16- NK cells are more frequent in UCB than in PB. Plasmacytoid dendritic cells are more frequent in UCB than in PB. Non-classical monocytes are more frequent in PB than in UCB.