Origin of T lymphocyte colony-forming cells in cell populations depleted of XXXX erythrocyte rosette forming cells.

@entity1 @entity18729 @entity28024 @entity742
Cell populations depleted of @entity742 erythrocytes (E) rosette-forming T cells (E-cells) contain cells capable of giving rise to T cell colonies. We have characterized the T cell colony-forming cell from @entity1 bone marrow, blood and tonsil E- cells using a T-cell colony assay. Depletion of @entity28024 +, CD3+ or @entity18729 + cells from E- cells reduced colony formation by 70-100%. Removal of CD8+ cells did not reduce, but rather enhanced colony formation by 50% or more. The most effective reduction (100%) in colony formation was obtained with anti- @entity18729 , indicating that @entity18729 is a marker of all colony-forming T cells. The @entity18729 + lymphocytes generated two types of colonies, types I and II, in the presence or absence, respectively, of CD8+ lymphocytes. Type I were small and compact, reached a peak on days 5-7, and contained @entity18729 + and CD8+ cells. Type II were large and diffuse, reached a peak on days 9-10 and contained @entity18729 + cells. In continuous culture of single type II colony cells, we observed a consistent increase of CD8+ cells. In one colony the combined percentage of @entity18729 + and CD8+ cells exceeded 100% (averaging 83% @entity18729 + and 72% CD8+), indicating the presence of dual markers on some cells. We suggest that colony forming T cells are @entity28024 + CD3+ @entity18729 +, the @entity18729 + antigen being the most consistent marker of such precursor cells.
