title: IL-4 plus CD40 monoclonal antibody induces human B cells gamma subclass-specific isotype switch: switching to gamma 1, gamma 3, and gamma 4, but not gamma 2.
abstract: Stimulation with IL-4 plus CD40 mAb is known to induce production of IgE and IgG4. In this study, we determined the IgG subclass specificity of IL-4 plus CD40 mAb stimulation for human purified B cells. We determined true in vitro switching by the generation of switch circular DNA (S gamma/S mu) representing primary S mu/S gamma events and production of gamma subclass-specific germ-line transcripts by a combination of reverse transcription-PCR and restriction endonuclease digestion. We simultaneously measured changes in the levels of IgG subclass proteins produced. Forty-two clones of circular switch DNA were identified and sequenced. The IgG subclass of S gamma fragment in the S gamma/S mu chimeric PCR products was determined by analyzing key S gamma nucleotides. The switch-deleted clones were found to consist of S gamma 1/S mu, S gamma 3/S mu, and S gamma 4/S mu chimeric switch sequences, showing that such switching had occurred. No S gamma 2/S mu chimeric switch sequences were found. While a consensus sequence was not identified at the S gamma/S mu breakpoints, four contiguous guanines (GGGG) were noticeably present in the S gamma region near the breakpoint. The induction of gamma 1, gamma 3, and gamma 4 switch circles in human purified B cells was accompanied by enhanced production of IgG1, IgG3, and IgG4 but not IgG2. Similarly, stimulation with IL-4 alone induced gamma 1, gamma 3, and gamma 4 but not gamma 2 germ-line transcripts. These results demonstrate that IL-4 plus CD40 mAb induces Ig isotype switch from mu to gamma 1, gamma 3, and gamma 4 but not to gamma 2.
authors.affiliation: Hart and Louise Lyon Laboratory, Department of Medicine, UCLA School of Medicine 90024-1680; USA.
authors.forename: S
authors.initials: S
authors.lastname: Fujieda
authors.forename: K
authors.initials: K
authors.lastname: Zhang
authors.forename: A
authors.initials: A
authors.lastname: Saxon
mesh_terms: D000911:Antibodies, Monoclonal / Q000276:immunology / Q000502:physiology*; D015703:Antigens, CD / Q000276:immunology; D000944:Antigens, Differentiation, B-Lymphocyte / Q000276:immunology; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D019013:CD40 Antigens; D002460:Cell Line; D006801:Humans; D017578:Immunoglobulin Class Switching / Q000502:physiology*; D007074:Immunoglobulin G / Q000096:biosynthesis* / Q000235:genetics; D007075:Immunoglobulin M / Q000235:genetics / Q000378:metabolism; D015847:Interleukin-4 / Q000502:physiology*; D008969:Molecular Sequence Data; D016133:Polymerase Chain Reaction; D012333:RNA, Messenger / Q000032:analysis; D014158:Transcription, Genetic / Q000502:physiology
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000944:Antigens, Differentiation, B-Lymphocyte; D019013:CD40 Antigens; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D012333:RNA, Messenger; D015847:Interleukin-4