Detection of a CD4+CD8-CD3- cell subpopulation during the differentiation of cord blood CD34+ cells into T cells in vitro

Introduction: Umbilical cord blood contains relatively abundant primitive CD34(+) hematopoietic progenitor cells which can differentiate into T lymphocytes ex vivo. Materials and Methods: In this study, thymic stromal cells (TSCs) were isolated from aborted fetuses and a monolayer culture system was established. Highly-purified CD34(+) cells from umbilical cord blood were cultured on the TSCs after limiting-dilution. The cells were then harvested and evaluated for CD4, CD8, and CD3 expression at different time points. CD4(+)CD8(-)CD3(-) lymphoid progenitor cells that could differentiate into mature T lymphocytes were observed after 15 days when a cocktail of cytokines, including Flt-3 ligand, stem cell factor, interleukin (IL)-12, and IL-2, was added. Results: These results thus show that CD4(+)CD8(-)CD3(-) cells can be derived from CD34(+) cells in vitro when cultured on TSCs. Conclusions: We showed that CD4(+)CD8(-)CD3(-) cells can be derived from highly purified CD34(+) cells on TSCs during T-cell lymphopoiesis in vitro.