title: In vitro synthesis of IgE by human lymphocytes. IV. Suppression of the spontaneous IgE synthesis by IgE-binding factors secreted by tunicamycin-treated RPMI 8866 cells.
abstract: It was previously shown that RPMI 8866 cells released IgE-binding factors (IgE-BFs) capable of enhancing the spontaneous in vitro synthesis of IgE by purified B lymphocytes isolated from allergic individuals. In the present study, the influence of tunicamycin, an inhibitor of protein glycosylation, on RPMI 8866 cells was investigated with regard to: (i) the expression of surface receptors for IgE; (ii) the release of IgE-BFs into the culture supernatants, and (iii) the biological activity of IgE-BFs. After preincubation for 60 min with tunicamycin (1 microgram/ml), RPMI 8866 cells were cultured for 48 hr in HB 101 serum-free medium; the culture supernatant was then filtered, concentrated, and its biological activity was compared to that of a parallel culture supernatant from untreated RPMI 8866 cells. The results of these experiments indicate that exposure of RPMI 8866 cells to tunicamycin resulted in: (i) a reduction of surface Fc epsilon R; (ii) no effect on the release of IgE-BFs into the culture supernatant, and (iii) the conversion of IgE-potentiating factors into IgE-suppressing factors. The latter factors suppressed the IgE secretion by U266 myeloma cells and completely inhibited the activity of IgE-potentiating factors on B lymphocytes from allergic individuals. IgE-BFs secreted by tunicamycin-treated cells had no effect on the production of IgG, IgA or IgM by normal or EBV-transformed B cells.
mesh_terms: D000912:Antibodies, Neoplasm / Q000096:biosynthesis; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D002460:Cell Line; D002474:Cell-Free System; D005944:Glucosamine / Q000031:analogs & derivatives*; D006801:Humans; D006969:Hypersensitivity, Immediate / Q000276:immunology; D007073:Immunoglobulin E / Q000096:biosynthesis* / Q000378:metabolism; D008222:Lymphokines / Q000096:biosynthesis / Q000276:immunology*; D009101:Multiple Myeloma / Q000276:immunology; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc / Q000032:analysis; D017455:Receptors, IgE; D014415:Tunicamycin / Q000494:pharmacology*
chemical_list: D000912:Antibodies, Neoplasm; D008222:Lymphokines; D029584:Prostatic Secretory Proteins; D011961:Receptors, Fc; D017455:Receptors, IgE; C043076:beta-microseminoprotein; C013059:immunoglobulin-binding factors; D014415:Tunicamycin; D007073:Immunoglobulin E; D005944:Glucosamine