Haemopoiesis and immune status during BNU-induced leukaemogenesis in mice.

Female BDF1 mice were exposed to 0.04% BNU in the drinking water for 15 weeks. All animals except one observed for more than 3 weeks died of leukaemia. After 1, 2, 3, 5, 7, 10, and 15 weeks of exposure marrow smears, pluripotent (CFU-S) and ganuloid committed (CFU-C) stem cells from bone marrow and spleen, and the lymphocyte response to different T- and B-cell mitogens and to alloantigens were determined. There was a progressive fall of the CFU-S and CFU-C content of the femur and even more in the spleen, and a progressive decrease in the number of normal marrow lymphocytes. After 10 and 15 weeks new "lymphoid" cells, presumably leukaemic cells, were seen in marrow. The lymphocyte stimulation assays showed a depressed reactivity, rather uniform in the thymus after more than 1 week and also, with a partial recovery after 3 weeks, in the spleen. The implications of these results for the chemically induced leukaemogenesis are discussed.