Phenotypic changes of T-lymphocyte subsets induced by interleukin-12 and interleukin-15 in umbilical cord vs. adult peripheral blood mononuclear cells

The decreased incidence of graft-vs.-host disease found following umbilical cord blood (CB) transplantation, and the increased susceptibility of newbo rns to infections, have been attributed, in part, to functional and phenoty pic immaturity of neonatal T cells. We investigated the phenotypic changes of CB T cells induced by two immunoregulary cytokines, interleukin (IL)-12 and IL-15, alone or in combination. Adult peripheral blood (APB) mononuclea r cells (MNCs) were also tested for comparison. Prior to culture, the perce ntages of CD3(+) CD8(+), CD3(+) CD25(+), and CD3(+) CD56(+) cells were sign ificantly lower in CB MNCs than in APE MNCs. IL-15, but not IL-12, signific antly increased CD3(+) CD8(+) expression among the CB MNCs after 1 week of culture. Combining IL-12 and IL-15, however, resulted in decreased CB CD3() CD8(+) expression compared with IL-15 alone. The percentage of CD3(+) CD2 5(+) cells in CB MNCs spontaneously increased in the absence of cytokines, while that of CD3(+) CD56(+) cells in CB MNCs could not be enhanced with cy tokines. In contrast, the percentages of CD3(+) CD25(+) and CD3(+) CD56(+) cells among the APE MNCs could be increased with IL-12, IL-15, and further with IL-12 and IL-15 combined. Thus, different patterns of T-cell subset ch anges were demonstrated between CB MNCs and APE MNCs in response to IL-12 a nd/or IL-15. These data may serve as a foundation for using cytokine therap y in newborns and children receiving CB transplants.