Recognition of marrow elements by natural killer cells: are NK cells involved in haemopoietic regulation?

NK cells from young normal mice are cytolytic in vitro for a virus-induced tumour cell line, YAC-1. Cytotoxicity is inhibited by the addition of unlabelled homologous YAC-1 cells and by regenerating bone marrow cells from the spleens of lethally irradiated, bone-marrow-grafted mice. Quiescent marrow from syngeneic and allogeneic mice produces little or no competition. This suggests that NK cells recognize, and may regulate, marrow progenitor cells.