Suppression of polyclonal immunoglobulin production by a soluble factor produced by a human thymus hybridoma

A human thymus cell hybridoma was established using thymus cells obtained from a patient with common variable hypogammaglobulinemia and associated thymoma. This hybridoma secreted a suppressor factor for polyclonal antibody synthesis. Supernatants of this hybrid showed 40-80% suppression of both IgM and IgG synthesis by pokeweed mitogen-stimulated human peripheral blood lymphocytes. Hybridoma supernatants were suppressive for immunoglobulin production only if added within the initial 48 h of the seven-day culture period. Suppression of antibody production by the hybridoma supernatant was prevented by preabsorption with T lymphocytes. Further, the suppressor factor was shown to inhibit antibody production in reconstructed cultures containing T4+ cells and B cells, yet the suppression could be abrogated by increasing the number of T4+ cells. The hybrid supernatant had no affect on the proliferation of human mononuclear cells in response to pokeweed mitogen, lipopolysaccharide, concanavalin A or alloantigen but inhibited phytohemagglutinin-induced proliferation. The target cell population for the inhibition of phytohemagglutinin responsiveness was shown to be a T4+ lymphocyte (helper inducer T cell). These results suggest that thymus hybridoma cells can produce immunoregulatory products that act through the modulation of T4+ lymphocyte function. To our knowledge this is the first human thymus cell hybridoma to be reported. Studies on such cell lines may provide important information on immunoregulatory thymic factors.