26. Different Cellular Basis for the Resistance of C3H and STS Strain Mice to the Development of Thymic Lymphomas Following Fractionated Whole-body lrradiation: Analysis Using Radiation Bone Marrow Chimeras

Hitoko Kamisaku, Shiro Aizawa, Kaoru Tanaka, Keiko Watanabe and Toshihiko Sado

Keywords: thymic lymphomas, strain difference, bone marrow transplantation

B10 strain mice are susceptible to the induction of thymic lymphomas by fractionated whole-body X irradiation (FI) , whereas C3H and STS mice are resistant. The nature of the factors responsible for the strain difference in the susceptibility to thymic lymphomagenesis was investigated by using radiation bone marrow chimeras. Radiation bone marrow chimeras were constructed in the reciprocal donorhost combinations of susceptible and resistant mice using Thy 1 markers that allow the genetic origins of thymocytes and thymic lymphomas to be determined. B10.Thy 1.1C3H, B10. Thy 1.1STS as well as B10.Thy 1.1B10 bone marrow chimeras manifested a high incidence of thymic lymphomas after FI-treatment, whereas Call. Thy 1.1B10 and STSB10.Thy 1.1 as well as C3H. Thy 1.1C3H and STSSTS chimeras manifested a low incidence of thymic lymphomas. Furthermore, FI-treatment of [B10.Thy 1.1-l-C3H]B10.Thy 1.1 mixed chimeras resulted in the generation of similar numbers of thymic lymphomas of B10 and C3H origins, whereas FI-treatment of [B1O.Thy 1.1fSTS]B10. Thy 1.1 mixed chimeras preferentially induced thymic lym phomas of B10 origin. These results indicated that (1) genetic factors responsible for the straindependent susceptibility and/or resistance to FI induced lymphomagenesis exert their effects entirely on bone-marrow derived cells, (2) host environ ments of C3H and STS resistant mice are not inhibi tory for the development of thymic lymphomas and (3) the resistance of STS mice to FI-induced thymic lymphomagenesis is an intrinsic property of thymocytes, whereas C3H and B10 thymocytes themselves are similarly susceptible for FI-induced thymic lymphomagenests.

Publications:
1)Kamisaku, H., Aizawa, S., Kitagawa, M. Ikarashi, Y. and Sado, T.: Int. J. Radiat. Biol., 72, 191 199, 1997.
2)Kubota, Y., Takahashi, S., Sun, H-Z., Sato, H. Aizawa, S. and Yoshida, K.: Int. J. Radiat. Biol. 76, 649-659, 2000.
3)Kamisaku, H., Aizawa, S., Tanaka, K., Watanabe, K. and Sado T.: Int. J. Radiat. Biol., 76, 11051111 2000.