The seeding of a transplanted murine leukemia and its influence on hemopoietic stem cells and immune function of the host.

A butylnitrosourea-induced murine T-cell leukemia, L40, was transplanted in BDF1 mice; 1 X 10(3) cells killed all recipients after conditioning with 400 rad, whereas 1 X 10(5) were needed with normal recipients. No leukemic cells could be detected by transplantation or cytogenetic analysis in the femur or the spleen at day 6 after L40 inoculation and, at day 11, leukemic cells were found in one out of two experiments, more if the host had been irradiated. Up to day 17, when leukemic cells were present, the CFU-S and CFU-C content of the femur was normal, but later a loss was observed with an increase in the enlarging spleen. Lymphocyte-stimulation assays with spleen cells gave normal results up to day 17, but later the 3H-thymidine uptake of stimulated T and B cells was reduced. The NK-cell activity with and without stimulation by Corynebacterium parvum in the spleen began to fall at day 17 and was absent later; this loss was also observed with peritoneal exudate cells. In vitro mixing experiments of L40 cells with normal spleen cells showed "cold target inhibition" by L40 cells in the NK-cell assay as well as interference with the lymphocyte stimulation.