title: Hydrocortisone and IL-4 induce IgE isotype switching in human B cells.
abstract: Induction of IgE synthesis in human B cells requires two signals. The first signal is delivered by the cytokine IL-4. The second signal activates B cells and is delivered by T cells, EBV infection, or engagement of the B cell-specific Ag CD40. Hydrocortisone (HC) has recently been shown to synergize with IL-4 to induce IgE synthesis in CD5+ chronic lymphocytic leukemia B cells. We show herein that a combination of HC and rIL-4 induces IgE synthesis in highly purified normal peripheral blood B cells. HC and IL-4 acted directly on B cells, because T cells and monocytes were not required for IgE synthesis. IgE induction was shown to occur in surface IgE- B cells isolated by cell sorting. These results suggest that IgE synthesis results from isotype switching, rather than from expansion of a precommitted B cell population. Furthermore, IgE synthesis was induced in sorted CD5- B cells, indicating that the ability to produce IgE in response to HC and IL-4 is not constrained by CD5 expression. Endogenous IL-6 was critical for induction of IgE synthesis by HC and IL-4, because an anti-IL-6 antibody strongly inhibited IgE production. These data suggest that hormones may play an important role in the regulation of IgE synthesis.
authors.affiliation: Children's Hospital/Department of Pediatrics, Harvard Medical School, Boston, MA 02115.
authors.forename: H H
authors.initials: HH
authors.lastname: Jabara
authors.forename: D J
authors.initials: DJ
authors.lastname: Ahern
authors.forename: D
authors.initials: D
authors.lastname: Vercelli
authors.forename: R S
authors.initials: RS
authors.lastname: Geha
mesh_terms: D015703:Antigens, CD / Q000032:analysis; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte / Q000032:analysis; D001402:B-Lymphocytes / Q000187:drug effects* / Q000276:immunology; D018956:CD5 Antigens; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D007073:Immunoglobulin E / Q000032:analysis / Q000096:biosynthesis*; D007132:Immunoglobulin Isotypes / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000494:pharmacology*; D015850:Interleukin-6 / Q000096:biosynthesis; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D015703:Antigens, CD; D018941:Antigens, CD19; D000944:Antigens, Differentiation, B-Lymphocyte; D018956:CD5 Antigens; D007132:Immunoglobulin Isotypes; D015850:Interleukin-6; D011994:Recombinant Proteins; D015847:Interleukin-4; D007073:Immunoglobulin E; D006854:Hydrocortisone