Inhibition of hematopoietic recovery from radiation-induced myelosuppression by natural killer cells.

We have examined the role of natural killer (NK) cells in situ in the recovery of marrow hematopoiesis in B6D2F1 mice receiving various doses of total-body irradiation (TBI) as a well-characterized model for treatment-induced myelosuppression. Applying an in situ cytotoxic approach for ablating NK 1.1 cells, we have demonstrated that NK 1.1 cells differentially inhibit the recovery of hematopoietic stem cells (CFU-S) and their progenitor cells committed to granulocyte-macrophage differentiation from a sublethal dose of TBI (9 Gy) while not affecting the recovery of progenitor cells committed to either erythroid or megakaryocyte differentiation from TBI. However, recoveries of CFU-S and progenitor cells were unaffected by the ablation of NK cells prior to a moderate dose of TBI (2 Gy). These findings provide in situ evidence that NK cells are potential inhibitors of hematopoietic recovery from treatment-induced myelosuppression.