title: Sequential switching from mu to epsilon via gamma 4 in human B cells stimulated with IL-4 and hydrocortisone.
abstract: The molecular events leading to IgE synthesis in human B cells stimulated with IL-4 and hydrocortisone were analyzed. IL-4, but not hydrocortisone, induced C epsilon germ line transcription. However, hydrocortisone increased the levels of IL-4-induced germ line C epsilon transcripts by twofold and delivered the signal required for transcription of mature C epsilon mRNA. Nested primer polymerase chain reaction of high m.w. DNA revealed deletional switch recombination occurring in B cells sorted for lack of expression of surface IgE and stimulated with both IL-4 and hydrocortisone, but not in B cells stimulated with IL-4 alone or hydrocortisone alone. DNA sequence analysis of 10 switch fragments revealed direct joining of S mu to S epsilon in eight fragments, one of which exhibited an 876-bp deletion in S mu. The ninth fragment contained a 50-bp insertion at the S mu/S epsilon junction, which was likely to be derived from S gamma 4. The sequence of the 10th fragment was consistent with either a 17-bp insertion at the S mu/S epsilon junction derived from S gamma 4 or with a complex 38-bp deletion within S epsilon. Mapping of the switch junction sites showed "hot spots" for recombination within S mu but not within S epsilon. These findings indicate that hydrocortisone induces S mu-S epsilon deletional switch recombination in IL-4-treated B cells, and support a model of sequential isotype switching from IgM to IgE via IgG4.
authors.affiliation: Division of Immunology, Children's Hospital, Boston, MA 02115.
authors.forename: H H
authors.initials: HH
authors.lastname: Jabara
authors.forename: R
authors.initials: R
authors.lastname: Loh
authors.forename: N
authors.initials: N
authors.lastname: Ramesh
authors.forename: D
authors.initials: D
authors.lastname: Vercelli
authors.forename: R S
authors.initials: RS
authors.lastname: Geha
mesh_terms: D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology*; D001483:Base Sequence; D002478:Cells, Cultured; D006801:Humans; D006854:Hydrocortisone / Q000494:pharmacology*; D017578:Immunoglobulin Class Switching / Q000187:drug effects*; D007073:Immunoglobulin E / Q000096:biosynthesis* / Q000235:genetics; D007074:Immunoglobulin G / Q000096:biosynthesis; D007075:Immunoglobulin M / Q000096:biosynthesis; D015847:Interleukin-4 / Q000494:pharmacology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D011995:Recombination, Genetic; D014158:Transcription, Genetic
chemical_list: D007074:Immunoglobulin G; D007075:Immunoglobulin M; D015847:Interleukin-4; D007073:Immunoglobulin E; D006854:Hydrocortisone