Summary With an increase in the importance of umbilical cord blood (CB) as an alternative source of haematopoietic progenitors for allogenic transplantation, donor lymphocyte infusion (DLI) with donor CB-derived activated CD4+ T cells in the unrelated CB transplantation setting is expected to be of increased usefulness as a direct approach for improving post-transplant immune function. To clarify the characteristics of activated CD4+ T cells derived from CB, we investigated their mRNA expression profiles and compared them with those of peripheral blood (PB)-derived activated CD4+ T cells. Based on the results of a DNA microarray analysis and quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR), a relatively high level of forkhead box protein 3 (Foxp3) gene expression and a relatively low level of interleukin (IL)-17 gene expression were revealed to be significant features of the gene expression profile of CB-derived activated CD4+ T cells. Flow cytometric analysis further revealed protein expression of Foxp3 in a portion of CB-derived activated CD4+ T cells. The low level of retinoic acid receptor-related orphan receptor γ isoform t (RORγt) gene expression in CB-derived activated CD4+ T cells was speculated to be responsible for the low level of IL-17 gene expression. Our data indicate a difference in gene expression between CD4 + T cells from CB and those from PB. The findings of Foxp3 expression, a characteristic of regulatory T cells, and a low level of IL-17 gene expression suggest that CB-derived CD4+ T cells may be a more appropriate source for DLI.
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