Fig. 4.

PrP-null HSCs are more sensitive than normal to myelotoxic injury. (A) A total of 5 × 10⁵ CD45.2 PrP-null or wild-type BM cells, pooled from three littermates, were transplanted into lethally irradiated CD45.1 recipients. One month after transplant, 11 recipient mice from each group were treated with 150 mg/kg 5-FU i.p. weekly for 2 weeks. The survival of these two groups was analyzed by using a log-rank nonparametric test (P = 0.0307, n = 11 in each group) and expressed as Kaplan–Meier survival plot. (B) 5-FU (150 mg/kg) was administered i.p. to three wild-type CD45.2 mice. After 3 days, the BM of these treated mice was pooled and fractionated according to PrP expression. A total of 1 × 10⁵ PrP⁺ or 1 × 10⁶ PrP^× BM cells were transplanted, together with 2 × 10⁵ competitor CD45.1 wild-type BM cells, into lethally irradiated CD45.1 recipients. The level of chimerism in the peripheral blood of the recipients was analyzed 4 months later (n = 5).