Chronic lymphocytic leukemia cells induce non-T cells to produce IgE in the presence of interleukin-4

Mononuclear cells from peripheral blood and bone marrow from patients with chronic lymphocytic leukemia (CLL) were cultured with interleukin-4 (IL-4) alone or with IL-4 and hydrocortisone (HC) in order to induce IgE synthesis. From a total of 29 experiments with the cells of 17 different donors an IgE secretion was observed only twice. Even in those two cases the IgE was found to be not monoclonal. The additional stimulation of CLL cells by polyclonal B cell activators induced IgM but not IgE production. When CLL cells were cocultured with monocyte-enriched cell preparations (M phi) in the presence of IL-4 and HC, a substantial IgE secretion could be obtained, which again consisted of both IgE kappa and IgE lambda. Since the irradiation of the M phi but not of the CLL cells abolished the formation of IgE, it is likely that the IgE production resided in the contaminating B cell population of the M phi. When the M phi were replaced by T cell-depleted peripheral blood mononuclear cells (non-T cells), irradiated as well as formaldehyde fixed CLL cells were able to stimulate non-T cells to secrete IgE in the presence of IL-4 or to potentiate IL-4- and HC-induced IgE formation. Furthermore, the coculture of irradiated pure CLL cells and purified B cells induced not only IgE but also IgG and IgM production and B cell proliferation in the presence of lymphokines. Our findings suggest that CLL cells, contrary to current opinion, cannot be induced to produce IgE.