Leukemogenesis by methylnitrosourea in BDF1 mice. The origin of transplantable cells and the activity of the natural killer cells during the preleukemic period.

BDF1 mice injected with methylnitrosourea (MNU, 50 mg/kg) developed T cell leukemias within 9-35 weeks (median induction time 18 weeks). Leukemic cells, determined by transplantation, were found 2-5 weeks before the death of the animals. Natural killer (NK) cell activity in the spleen and peritoneal exudate cells was studied using YAC-1 cells as targets. MNU-treated mice showed reduced lytic activity with or without stimulation by Corynebacterium parvum. NK activity was essentially the same in mice with and without transplantable leukemic cells. No correlation could be demonstrated between the degree of NK cell depression, as studied in the spleen after splenectomy, and the survival time of individual mice.