title: The role of T cells and the effect of hydrocortisone on interleukin-4-induced IgE synthesis by non-T cells.
abstract: The role of T cells for IL-4-induced IgE synthesis by peripheral blood mononuclear cells (PBMC) was investigated. The removal of monocytes from PBMC abolished IL-4-induced IgE synthesis. When PBMC were separated into T and non-T cells, non-T cells alone were not able to secrete significant amounts of IgE in the presence of IL-4. Depending on the separation procedure, the reconstitution of non-T cells with T cells prepared by rosetting did not restore IgE secretion, whereas T cells obtained by the use of anti-CD3 antibodies could co-induce IgE formation. However, when the T cells were first irradiated, large amounts of IgE were produced, which strongly exceeded those found in unseparated PBMC cultures. IL-4-induced IgE synthesis was also obtained in co-cultures of formaldehyde-fixed T cells with non-T cells. Furthermore, not only autologous but also allogeneic T cells, which have been irradiated or fixed, could provide the costimulatory effect on IgE formation by non-T cells in the presence of IL-4. Mitogenically pre-activated T cells, however, were not able to support IgE synthesis. Hydrocortisone (HC) potentiated the IL-4-induced IgE synthesis by PBMC and enabled non-T cells to secrete IgE in the presence of IL-4. Adding both HC and T cells led to a marked synergistic effect on IL-4-induced IgE production. We conclude that monocytes are required for the induction of IgE synthesis in PBMC in addition to T cells and IL-4. Our results support the view that the T cell signal is delivered via cognate and non-cognate T/B cell membrane interaction. Furthermore, active and proliferating T cells rather suppress IgE synthesis. Finally, HC appears to be a potent alternative stimulus, which bypasses the necessity for T cells in IL-4-induced IgE formation.
authors.affiliation: Department of Internal Medicine III, University of Erlangen-Nürnberg, Germany.
authors.forename: H G
authors.initials: HG
authors.lastname: Nüsslein
authors.forename: T
authors.initials: T
authors.lastname: Träg
authors.forename: M
authors.initials: M
authors.lastname: Winter
authors.forename: A
authors.initials: A
authors.lastname: Dietz
authors.forename: J R
authors.initials: JR
authors.lastname: Kalden
mesh_terms: D001402:B-Lymphocytes / Q000276:immunology*; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D007073:Immunoglobulin E / Q000096:biosynthesis*; D066298:In Vitro Techniques; D015847:Interleukin-4 / Q000494:pharmacology*; D008213:Lymphocyte Activation; D008211:Lymphocyte Cooperation; D009000:Monocytes / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D015847:Interleukin-4; D007073:Immunoglobulin E; D006854:Hydrocortisone