Regulation of germ-line epsilon transcription and induction of epsilon switching in cloned EBV-transformed and malignant human B cell lines by cytokines and CD4+ T cells.
IL-4 induces germ-line epsilon transcript synthesis in normal human B cells, but a second signal provided by CD4+ T cells is required for subsequent production of productive epsilon mRNA and IgE synthesis. In the present study we demonstrate that IL-4 specifically induces germ-line epsilon transcripts in most EBV lymphoblastoid (LCL) and EBV+ and EBV- Burkitt's lymphoma (BL) cells without inducing IgE synthesis. However, cocultivation of cloned sIgM+, sIgE- EBV-LCL or BL cells with activated CD4+ T cell clones in the presence of IL-4 resulted in IgE production in 13 to 24% of the wells. Analysis of rearranged DNA in IgE-producing cloned BL cells indicated that epsilon switching occurred through a recombination deletion event. IgE production is a stable feature of the cloned switched EBV-LCL and BL cells because these cells continued to produce relatively high levels of IgE in the absence of IL-4 and CD4+ T cells. Induction of IgE synthesis was blocked by IFN-gamma, IFN-alpha, and transforming growth factor beta (TGF-beta), but only TGF-beta inhibited IL-4-induced germ-line epsilon mRNA expression. These results suggest that the inhibitory effects of TGF-beta are mediated via inhibition of germ-line epsilon expression, whereas IFN-alpha and IFN-gamma block other steps in the regulatory processes resulting in induction of IgE synthesis by established human B cell line cells. Our results indicate that the same set of signals that induce normal B cells to switch to IgE synthesis also induce high frequency epsilon switching in cloned established EBV transformed and malignant B cell lines including classical cell lines such as JY and BL-2.
Gauchat
J F
JF
Human Immunology Department, DNAX Research Institute, Palo Alto, CA 94304-1104.
Gascan
H
H
de Waal Malefyt
R
R
de Vries
J E
JE
D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D002051:Burkitt Lymphoma / Q000276:immunology*; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology*; D002460:Cell Line; D002472:Cell Transformation, Viral; D016207:Cytokines / Q000494:pharmacology*; D015321:Gene Rearrangement; D005803:Genes, Immunoglobulin; D004854:Herpesvirus 4, Human / Q000235:genetics*; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000494:pharmacology; D008969:Molecular Sequence Data; D012333:RNA, Messenger / Q000096:biosynthesis; D014158:Transcription, Genetic; D016212:Transforming Growth Factor beta / Q000494:pharmacology
D016207:Cytokines; D012333:RNA, Messenger; D016212:Transforming Growth Factor beta; D015847:Interleukin-4; D007073:Immunoglobulin E