Functional analyses of cord blood natural killer cells and T cells: a distinctive interleukin-18 response

Objective. To search for the functional property of cord blood (CB) cells, the effects of interleukin-18 (IL-18) on interferon-gamma (IFN-gamma) produ ction of T cells or natural killer (NK) cells were compared between CB and adult peripheral blood (PB). Materials and Methods. T cells, CD45RA(+) T cells, and NK cells were purifi ed from CB and adult PB mononuclear cells using magnetic beads or a cell so rter. After stimulation with or without IL-18 in the presence of IL-12 for 48 hours (NK cells) or 72 hours (T cells or CD45RA(+) T cells), IFN-gamma c oncentration was measured in each subset. Although IL-18 induced significan t IFN-gamma production from both CB and adult PB T cells in the presence of IL-12, the IFN-gamma levels from CB T cells were lower than those from adu lt PB T cells. However, CD45RA(+) T cells from CB and from adult PB produce d similar levels of IFN-gamma after stimulation with IL-18 + IL-12. On the other hand, CB NK cells exhibited higher IFN-gamma production and CD69 expr ession than adult PB NK cells after stimulation with IL-18 + IL-12. Cytolyt ic activity of CB NK cells increased to a level comparable to that of adult PB NK cells after the same IL-18/IL-12 stimulation. Conclusions. These results suggest that a low response of CB T cells to IL- 18 is due to a higher proportion of naive (CD45RA(+)) T cells in CB, which may be one of the factors responsible for the neonatal immaturity of the im mune system as well as the low incidence of graft-vs-host disease in patien ts receiving CB stem cell transplantation. On the other hand, a high respon se of CB NK cells to IL-18 may contribute to the host defense during the ne onatal period and antitumor effects in CB stem cell transplantation. (C) 20 01 Society for Experimental Hematology. Published by Elsevier Science Inc.