In vitro induction of IgM secretion and switching to IgG production in human B leukemic cells with the help of T cells.

In vitro stimulation of the B leukemic cells (B-CLL cells) with normal allogeneic T cells plus PWM induced IgM secretion and a switching from IgM to IgG production. Induction of IgM and IgG production in B-CLL cells with T cells was demonstrated by the presence of the same idiotype in induced Ig as that present in the monoclonal IgM protein in the patient's serum. Both T cells and PWM were required for Ig induction in B-CLL cells, and x-irradiated T cells showed the comparable helper effect. T cells and PWM induced not only Ig secretion but proliferation of B-CLL cells. Cell division was essential for the differentiation of the leukemic cells to Ig-producing cells. PWM-induced, antigen-nonspecific helper factor(s) were also effective in the induction of differentiation of the leukemic cells. Variations existed among T cell donors in the capabilities to induce differentiation of the same leukemic cells, suggesting the requirement of matching of acceptors on B-CLL cells and T effector molecules for the induction of Ig production in B-CLL cells.