Loss of immunoreactivity in long-term bone marrow culture

WE have developed a long-term bone marrow culture system in which proliferation and differentiation of apparently functionally normal haemopoietic stem cells (CFU-S) can be sustained in vitro for several months1–8. We now find that genetic resistance9,10 or host-versus-graft (H-v-G) reaction, the (possibly) related natural killer (NK) cell activity11 and the ability of cultured cells to reconstitute irradiated allogeneic (non-compatible) recipients (with the subsequent development of G-v-H disease12) are all absent from such cultured cells.