Engraftment of Ly5.1 cells into nonmyeloablated c-Mpl and Kit^Wv mice. Levels of Ly5.1⁺ cells in the peripheral blood of nonmyeloablated mice injected 4 weeks prior with 10⁶ B6-Ly5.1 bone marrow cells in individual mice (circles) and group means (horizontal bars). Engraftment level escalates with increasing numbers of loss-of-function c-Mpl or Kit alleles. tx indicates transplantation.