Murine fetal thymus lobes isolated from both normal and scid/scid mice can be colonized by donor cells from either human bone marrow or human umbilical cord blood in vitro. Subsequent organ culture results in a transient production of a few CD4+ CD8+ (double-positive) cells and then the accumulation of CD4+ or CD8+ (single-positive) T cells. A significant number of immature T-cell intermediates (e.g., CD8low, CD3-/low cells) were present in early organ cultures, suggesting that these were progenitors of the mature CD3+/high single-positive T cells that dominated late cultures. Depletion of mature T cells from the donor-cell populations did not affect their ability to colonize thymus lobes. However, colonization depended on the presence of CD7+ progenitor T cells. Limiting dilution experiments using mature T-cell populations (human peripheral blood leukocytes, human bone marrow cells, and human umbilical cord blood cells) suggested that thymic organ culture supports the growth of progenitor T cells but does not support the growth of mature human T cells. Each of these donor populations produced single-positive populations with different CD4/CD8 ratios, suggesting that precursor cells from different sources differ qualitatively in their capacity to differentiate into T cells.
|Original language||English (US)|
|Number of pages||5|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Nov 15 1993|
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