Look out heme, Mac is back in town.

In this issue of Blood, Kovtunovych et al report the curative effect of a nonmyeloablative bone marrow transplant for anemia and organ dysfunction in heme oxygenase 1 (HO-1)-deficient mice by restoring the ability to detoxify heme through the repopulation of the tissues with wild-type macrophages. These findings provide the basis for new therapies for this lethal disorder in children lacking the HO-1 gene (Hmox1).