Proliferation of Donor Spleen and Bone-Marrow Cells in the Spleens and Bone Marrows of Unirradiated and Irradiated Adult Mice 1

Abstract

Summary

CBA/HT₆T₆ spleen or bone-marrow cells were injected into unirradiated or irradiated CBA/H mice, and the percentages of donor-type cells in the spleen and the bone marrow were scored at various intervals after irradiation.

When CBA/HT₆T₆ spleen or bone-marrow cells were injected into unirradiated CBA/H hosts, a few donor cells were found in the bone marrows and spleens of the hosts. When CBA/HT₆T₆ bone-marrow cells were injected into CBA/H mice irradiated with 400 R, more than 90% of the dividing cells in the bone marrow were of donor origin at day 10, and more than 70% were still of donor origin at day 15. Increasing the radiation dose to 600 or 800 R resulted in exclusive proliferation of donor cells in the bone marrow at days 10 and 15. When CBA/HT₆ T₆ spleen cells were injected into CBA/H mice irradiated with 400 or 600 R, more than 90% of the dividing cells in the host spleens were of donor origin at day 10, but most of the donor cells were replaced with host cells by day 15. Increasing the radiation dose to 800 R resulted in a higher percentage of donor-type cells in the spleens at day 15, but some of the mice died by day 18. When CBA/HT₆T₆ spleen cells were injected into CBA/H irradiated with 400 or 600 R, less than 10% of the dividing cells in the bone marrow were of donor origin at days 10 and 15. Increasing the radiation dose resulted in dividing cells mainly of donor origin in the bone marrow at days 10 and 15, but some mice died by day 18.

These results suggest that stem cells compete with one another in mitosis, and that division of stem cells is largely regulated by that of other dividing cells.