title: CD40-mediated regulation of interleukin-4 signaling pathways in B lymphocytes.
abstract: The importance of cytokines in controlling immunoglobulin isotype switching is well known. Given the defect in switching to IgG, IgA and IgE isotypes in mice and humans that carry mutations in the CD40 and CD40 ligand genes, we have investigated the role of CD40 ligation in controlling B cell responses to interleukin (IL)-4. We have found that CD40-mediated signals cause a fivefold upregulation of IL-4 receptor (IL-4R) on the B cell surface and that this is associated with a 100-1000-fold increase in the cells' responsiveness to the cytokine. While we found no evidence of increased affinity or structural change of the receptor, we do find that prestimulation of B cells with anti-CD40 antibodies brings about several changes in the IL-4 signaling pathways. Subsequent delivery of IL-4 to CD40-prestimulated cells provokes intracellular signals distinct from those induced in resting B cells in response to IL-4. While resting B cells phosphorylate Jak3 kinase shortly after IL-4 activation, cells pre-incubated with anti-CD40 exhibit active dephosphorylation of this molecule and phosphorylation of proteins of around 45 kDa upon addition of IL-4. The common gamma chain, Jak3 and Jak1 can all be immunoprecipitated in normal amounts with the IL-4R chain after CD40 prestimulation. We show that the observed dephosphorylation of Jak3 may be due to a stable association with the src-homology protein tyrosine phosphatase SH-PTP2. In contrast, the enzyme appears to be inactive and to dissociate very quickly from the signaling complex in cells that are stimulated with IL-4 alone.
authors.affiliation: Department of Immunology, Royal Postgraduate Medical School, Hammersmith Hospital, London, GB.
authors.forename: K
authors.initials: K
authors.lastname: Siepmann
authors.forename: G
authors.initials: G
authors.lastname: Wohlleben
authors.forename: D
authors.initials: D
authors.lastname: Gray
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000096:biosynthesis / Q000187:drug effects; D001402:B-Lymphocytes / Q000187:drug effects / Q000276:immunology* / Q000378:metabolism; D019013:CD40 Antigens / Q000494:pharmacology*; D005260:Female; D015847:Interleukin-4 / Q000276:immunology / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D053616:Janus Kinase 3; D008213:Lymphocyte Activation / Q000187:drug effects; D008565:Membrane Proteins / Q000378:metabolism; D051379:Mice; D008811:Mice, Inbred DBA; D010766:Phosphorylation / Q000187:drug effects; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D018123:Receptors, Interleukin / Q000096:biosynthesis / Q000187:drug effects; D019948:Receptors, Interleukin-4; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases; D015398:Signal Transduction / Q000276:immunology*; D015854:Up-Regulation / Q000187:drug effects / Q000276:immunology*; D018909:src Homology Domains
chemical_list: D015703:Antigens, CD; D019013:CD40 Antigens; D047908:Intracellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D018123:Receptors, Interleukin; D019948:Receptors, Interleukin-4; D015847:Interleukin-4; D011505:Protein-Tyrosine Kinases; C507935:Jak3 protein, mouse; D053616:Janus Kinase 3; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse; D054593:SH2 Domain-Containing Protein Tyrosine Phosphatases