title: Role of protein tyrosine kinases in CD40/interleukin-4-mediated isotype switching to IgE.
abstract: The B-cell antigen CD40 transduces signals, which synergize with interleukin (IL)-4 to induce IgE synthesis in human B cells. IL-4 induces epsilon germline transcription but not mature epsilon transcripts or IgE protein synthesis in B cells. Addition of anti-CD40 monoclonal antibody to IL-4-treated B cells results in deletional S mu--> S epsilon switch recombination, expression of mature epsilon transcripts, and IgE synthesis and secretion. Because both IL-4 and anti-CD40 induce protein tyrosine phosphorylation in B cells, we investigated the role of protein tyrosine kinase in IL-4/CD40-mediated IgE synthesis. The protein tyrosine kinase inhibitors genistein and herbimycin A, but not the protein kinase C inhibitor 1-(5-isoquinolinesulfonyl)-2-methylpiperazine (H7) or the protein kinase A inhibitor N-2-guanidinoethyl-5-isoquinolinesulfonamide, inhibited IgE synthesis in B cells stimulated with IL-4 and CD40. Genestein and herbimycin, but not H7, inhibited IL-4-driven epsilon germline transcription in B cells. Both genestein and herbimycin, but not H7, inhibited CD40-mediated IgE synthesis in B cells pretreated for 4 days with IL-4 to allow optimal expression of epsilon germline transcripts. Inhibition of IgE synthesis in these cultures was accompanied by inhibition of S mu--> S epsilon deletional switch recombination as assayed by nested polymerase chain reactions. These results suggest that activation of protein tyrosine kinase plays an important role in both the IL-4 and the CD40 signalling pathways that lead to IgE isotype switching in B cells.
authors.affiliation: Division of Immunology, Children's Hospital, Boston, MA 02115.
authors.forename: R K
authors.initials: RK
authors.lastname: Loh
authors.forename: H H
authors.initials: HH
authors.lastname: Jabara
authors.forename: C L
authors.initials: CL
authors.lastname: Ren
authors.forename: S M
authors.initials: SM
authors.lastname: Fu
authors.forename: R S
authors.initials: RS
authors.lastname: Geha
mesh_terms: D015703:Antigens, CD / Q000502:physiology*; D000944:Antigens, Differentiation, B-Lymphocyte / Q000502:physiology*; D001402:B-Lymphocytes / Q000187:drug effects; D001483:Base Sequence; D019013:CD40 Antigens; D017353:Gene Deletion; D006801:Humans; D017578:Immunoglobulin Class Switching; D007073:Immunoglobulin E / Q000096:biosynthesis*; D007132:Immunoglobulin Isotypes; D015847:Interleukin-4 / Q000494:pharmacology / Q000502:physiology*; D015335:Molecular Probes / Q000235:genetics; D008969:Molecular Sequence Data; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*; D014158:Transcription, Genetic
chemical_list: D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D007132:Immunoglobulin Isotypes; D015335:Molecular Probes; D015847:Interleukin-4; D007073:Immunoglobulin E; D011505:Protein-Tyrosine Kinases