A follow-up study of the progression or spontaneous regression of leukemia in mouse strains.

C3H/He-mg and AKR mice were injected intraperitoneally with lymphocytes prepared from the spleen of (C3H/He-mg x AKR)F1 hybrid mice bearing Gross-virus leukemia. Lymphocyte suspensions were prepared from the spleen, mesenteric lymph node and thymus of mice at different days after the injection and analyzed for the ratio of leukemic to normal lymphocytes with a flow cytometer. The size and the fluorescein content of the cells incubated with fluorescein diacetate served for the distinction between normal and leukemic lymphocytes. After injection with leukemic lymphocytes, lethal leukemia developed in the AKR strain, whereas the C3H/He-mg strain was characterized by a spontaneous regression after a transient development of leukemia. The percentage of leukemic lymphocytes was the highest in the spleen and it was the lowest in the thymus regardless of the stage of the disease. In the thymus of C3H/he-mg mice the leukemic lymphocytes could be detected only during the crisis period.