Reconstitution of hematopoiesis after bone marrow purging with ricin A chain immunotoxin.

Bone marrow cells from healthy individuals were treated with an antihuman T cell immunotoxin (IT101). The treated marrow cells were cultured for multilineage hematopoietic colonies (CFU-GEMMT) containing various myeloid cell lineages and T lymphocytes, erythroid colonies (BFU-E), and granulocytic colonies (CFU-C). Optimal conditions were defined for the elimination of clonogenic human T leukemic cells artificially admixed with bone marrow cells. Marrow purging with IT101 led to the restoration of hematopoietic colony formation which was abolished in the presence of T leukemic cells. Mixed colonies grown from bone marrow treated with IT101 contained cells that reacted with monoclonal anti-T-cell antibodies. This suggests that pluripotent stem cells are not affected by marrow IT101 purging and may be able to regenerate lymphoid as well as myeloid lineages.