CBA/HT6T6 bone marrow cells (1 x 107) or CBA/H bone marrow cells (1 x 107) plus CBA/HT6T6 thymus cells (5 x 107) were injected intravenously into lethally (800 R) irradiated CBA/H mice. Chromosome analyses of dividing cells in the host lymphoid and myeloid organs were performed at intervals after irradiation.
Donor marrow cells settled and proliferated in the host bone marrow, spleen, and lymph nodes soon after injection, but donor marrow cells did not proliferate in the host thymus until day 10; then host-type cells were quickly replaced by donor-type cells in the thymus by day 20. On the other hand, donor thymus cells settled and proliferated in the host thymus and lymph nodes soon after injection but they gradually disappeared from these organs. On day 20, a few donor-type dividing cells (of thymus origin) were found in the host lymphoid and myeloid organs.