OPG levels in plasma from hosts repopulated with WT or

opg^−/− TPO virus–infected BM cells. OPG levels were measured in PPP by ELISA. Each bar represents the mean ± SD of 7 to 10 animals per experimental group as indicated under the x-axis. The mice receiving transplants were analyzed at 1, 2, and 3 months, except for the WT/opg^−/− group where samples were lost accidentally. The level of circulating OPG in WT controls (n = 8) is shown by black bars. One month after transplantation (open bars), OPG levels were 6-fold increased in WT hosts engrafted with TPO virus–infected BM cells from WT or opg^−/−donors. Levels remained about 3-fold elevated at 2 months (hatched bars) and 3 months (dotted bars) with no significant difference (P < .5) between the 2 groups. OPG was undetectable in plasma from control and engrafted opg^−/−hosts.