Identification of the c-kit ligand: end of the road for understanding aplastic anemia in steel mutant mice?

We here report the initiation of hematopoietic recovery in congenitally hypoplastic S1/S1d mice by the cytotoxic ablation of cells bearing the natural killer (NK) phenotype (NK 1.1+). The most striking finding was the early several-fold increase in the cycling fraction of stem and progenitor cells (with the exception of progenitors committed to megakaryocytopoiesis) in the anti-NK 1.1+ antibody-treated group. This increase resulted in an early, complete restoration of total marrow cellularity to the normal (+/+) littermate level. Our data suggest that NK 1.1+ cells exert functions critical to the negative control of hematopoietic cell proliferation in S1/S1d mice.