Development of gamma delta T-cell subsets from fetal hematopoietic stem cells.

Hematopoietic stem cells (HSC) were isolated from mouse fetus, and their developmental potential was compared with adult HSC. Donor-derived V gamma 3+T cells were detected in fetal thymic lobes, repopulated in vitro with fetal liver HSC, but not in those with adult bone marrow HSC. Single clonogenic fetal HSC gave rise to thymic progeny that include V gamma 3+, other gamma delta+, and alpha beta+ T cells. No V gamma 3+ T cells were detected in adult thymus injected intrathymically with either fetal or adult HSC. These results support a hypothesis that only fetal HSC have the capacity to differentiate into V gamma 3+ T cells in the fetal thymic microenvironment, and that the developmental potential of HSC may change during ontogeny.