Induction of germ-line and mature C epsilon transcripts in human B cells stimulated with rIL-4 and EBV.
EBV and rIL-4 induce T cell-independent IgE production by normal human B cells. We demonstrate here that EBV and IL-4 induced the synthesis of IgE by surface IgE-negative B cell precursors isolated by cell sorting. This result suggests that the induction of IgE by EBV and IL-4 results not merely from the expansion of a precommitted surface IgE-positive B cell population but more likely from IL-4-directed switching to IgE. At the molecular level, IL-4 and EBV induced the appearance of 2.0- and of 1.8-kilobase (kb) RNA bands, both of which hybridized with an 0.88-kb HinfI fragment spanning part of the C epsilon 1 exon and the entire C epsilon 2 exon. The 1.8-kb band but not the 2.0-kb band also hybridized with a cloned genomic 0.7-kb SmaI fragment located approximately 2 kb upstream of C epsilon. Thus, EBV and IL-4 induced germline (1.8-kb) as well as mature (2.0-kb) C epsilon transcripts. IL-4 by itself induced germ-line C epsilon transcripts but not mature C epsilon transcripts in purified normal B cells. IL-4 failed to induce IgE synthesis in established EBV B cell lines and failed to induce 2.0-kb mature C epsilon transcripts but induced 1.8-kb germ-line C epsilon transcripts. These data show that IL-4 is sufficient for the induction of C epsilon germ-line transcription. In contrast, the transcription of mature epsilon mRNA requires an additional activating signal, provided by infection with EBV. Established EBV transformation results in a dissociation between germ-line C epsilon transcription and the ability to undergo IgE switching in response to IL-4.
Jabara
H H
HH
Division of Immunology, Children's Hospital, Boston, MA 02115.
Schneider
L C
LC
Shapira
S K
SK
Alfieri
C
C
Moody
C T
CT
Kieff
E
E
Geha
R S
RS
Vercelli
D
D
D000956:Antigens, Viral / Q000032:analysis; D001402:B-Lymphocytes / Q000276:immunology* / Q000502:physiology; D019309:Epstein-Barr Virus Nuclear Antigens; D005091:Exons; D006412:Hematopoietic Stem Cells / Q000276:immunology; D004854:Herpesvirus 4, Human / Q000276:immunology*; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis* / Q000235:genetics; D015847:Interleukin-4 / Q000494:pharmacology*; D011994:Recombinant Proteins / Q000494:pharmacology; D014158:Transcription, Genetic
D000956:Antigens, Viral; D019309:Epstein-Barr Virus Nuclear Antigens; D011994:Recombinant Proteins; D015847:Interleukin-4; D007073:Immunoglobulin E