T-cell subsets in the murine thymus during chemically induced leukemogenesis.

T cell leukemias were induced in BDF 1 mice by methylnitrosourea (MNU). The phenotype of the leukemic cells is Thy1.2 +, PNA-, TdT+, TL+ and heterogeneous with respect to Lyt-1 and Lyt-2. About 70% of the leukemias have elevated amounts of gp70. During latency period of at least 9 + 12 weeks an early reduction in the various thymic cells and the CFU-S is observed, with almost complete recovery. Later PNA+ cells are reduced. Hydrocortisone treatment delays or enhances leukemogenesis, dependent on the time interval between hydrocortisone and MNU. Some mice show elevated amounts of gp70 in their bone marrow 2--3 weeks after MNU. The problem of target cells in the bone marrow and the thymus is discussed.