Functional significance of IL-4 receptor on B cells in IL-4-induced human IgE production.
IL-4 with the IgE-inducing activity is shown to upregulate the expression of IL-4 receptor (IL-4R) on lymphocytes. Antisense strategy was used that aimed at investigating the significance of IL-4-induced upregulation of IL-4R on B cells in human IgE production. When an antisense phosphorothioate oligodeoxynucleotide to IL-4R (S-oligo 1) was added to B cells together with IL-4, the agent selectively abrogated the upregulation of IL-4R without affecting its constitutive level expression. Moreover, S-oligo 1 had a suppressive effect on the T-cell-independent synthesis of IgE by B cells costimulated with IL-4 and anti-CD40 antibody. This suppression was accompanied by inhibition of mature but not germline C epsilon transcription. These findings indicate that constitutively expressed IL-4R provides a signal or signals responsible for the induction of germline C epsilon transcription and suggest that IL-4R upregulation may be required for the subsequent class switch recombination that leads to mature C epsilon transcription and IgE synthesis. The IL-4R signal transduction mechanism underlying germline C epsilon transcription was also analyzed in a human Burkitt lymphoma B-cell line, DND39. Induction of germline C epsilon transcripts in DND39 cells by IL-4 required at least two distinct signaling cascades. One was mediated by enhancement of tyrosine phosphorylation of a 57 kd protein associated with phospholipase C-gamma 1 (PLC-gamma 1) that resulted in PLC-gamma 1 activation, inositol lipid hydrolysis, and protein kinase C delta translocation. The other was dependent on phosphatidylinositol 3-kinase, whose activation induced protein kinase C zeta translocation. In fact, kinase inhibitors such as herbimycin A, K-252a, and wortmannin were effective in inhibiting IL-4-induced germline C epsilon transcription. Therefore, in addition to activation of protein tyrosine kinases, coordinated actions of PLC-gamma 1 and phosphatidylinositol 3-kinase may be involved in IL-4-driven germline C epsilon transcription in DND39 cells.
Yanagihara
Y
Y
Clinical Research Center for Allergy, National Sagamihara Hospital, Kanagawa, Japan.
Ikizawa
K
K
Kajiwara
K
K
Koshio
T
T
Basaki
Y
Y
Akiyama
K
K
D015703:Antigens, CD / Q000502:physiology*; D001402:B-Lymphocytes / Q000378:metabolism / Q000502:physiology* / Q000648:ultrastructure; D006801:Humans; D007073:Immunoglobulin E / Q000096:biosynthesis*; D015847:Interleukin-4 / Q000494:pharmacology / Q000502:physiology*; D018123:Receptors, Interleukin / Q000502:physiology*; D019948:Receptors, Interleukin-4; D015398:Signal Transduction / Q000502:physiology; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
D015703:Antigens, CD; D018123:Receptors, Interleukin; D019948:Receptors, Interleukin-4; D015847:Interleukin-4; D007073:Immunoglobulin E