INVITRO SENSITIVITY OF TRANSPLANTABLE LEUKEMIAS TO ENDOGENOUS GRANULOID (GCE, GI-2) AND LYMPHOID (T4, T4-1) INHIBITORS OF PROLIFERATION

The effect on cell proliferation of crude granulocyte and thymocyte extracts (GCE. T») and of their target-specific fractions (Gl-2, T4-1) was studied in cultures with transplantable subacute myeloid and lymphoid leukemia (ML. LL). In the dose rage studied (1-500 μg/ml) each factor reduced-3H-TdR incorporation into acid-insoluble DNA of bone marrow, thymus and spleen cells with ML or LL as a function of the dose, approximately linearly. Normal bone marrow proved to be less sensitive to GCE than the ML one: According to parallel line bioassay by a factor of μ = 0.56. The reactivity of LL spleen and thymus is also higher to medium T4-1 concentrations (50-200 μg/ml) than that of normal lymphoid populations. T4-1 inhibits-3H-TdR incorporation into the DNA of LL spleen cells sub-maximally in 90’: This effect lasts for > 7 hours. Because of its more homogeneous cell composition and higher sensitivity, subacute myeloid leukemia is more suitable for screening endogenous granuloid inhibitors than are homologous normal cell cultures. © 1978 S. Karger AG, Basel.