I got the answer from the other site. In summary I did not filter soft x-ray and most of energy hit just skin of animals rather than whole body. That was why the animals got radiation burn while their bone marrow cells survived.
8-week-old C57BL/6 mice were irradiated from 700 to 1000Gy with a new X-ray irradiator in an attempt to decide optimal X-ray dose for bone marrow chimera experiment.
The goal was to find the dose of X-ray that completely eradicate recipient BM cells and achieve >99% donor cells.
It has been 4 weeks since mice were irradiated and BM cells from CD45.1 B6 were transferred.
Now irradiated mice show lesions on their dorsal skin and it seems mice with higher dose are severer.
700 and 800Gy mice show just hair loss on small area but 1000Gy mice have scabs all around their back.
I collected and analyzed blood from mice with concern that I might have over-dosed it, but CD45.1+ donor cells were only found less than 20%.
It does not make sense because I heard that BM-derived cells are the least resistant to irradiation, and I think if X-ray dose was strong enough that there is skin damage, then recipient BM cells should be long gone.
900-1000Gy is also routine dose in other publications.
What do you think went wrong? I would appreciate inputs from experienced colleagues.