Characterization of a suppressor-cell leukemia. Evidence for the requirement of an interaction of two T cells in the development of human suppressor effector cells.

To characterize the suppressor activity of neoplastic T cells from a child with acute lymphoblastic leukemia and hypogammaglobulinemia, we applied an in vitro assay that determines the capacity of pokeweed-mitogen-stimulated lymphocytes to mature into immunoglobulin-secreting cells. The geometric mean synthesis by peripheral blood lymphocytes from 12 normal persons was 3200 ng for IgM, 2447 ng for IgG and 1825 for IgA (2 X 10(6) cells per 12 days in culture). The patient's leukemic cells produced no detectable immunoglobulin and depressed the immunoglobulin production of normal lymphocytes by 85 to 100 per cent in co-culture experiments. However, suppression was observed only when co-operating normal T cells were present. Prior irradiation of either the leukemic T cells or the co-operating normal T cells nullified the suppressor effect. Therefore, an interaction between at least two different T-cell subsets may be required for the generation of suppressor effector T cells in man.