title: Genetic evidence for Lyn as a negative regulator of IL-4 signaling.
abstract: IL-4 has multiple effects on B lymphocytes, many of which are concentration dependent. This is particularly so for Ig isotype switching, where different thresholds of IL-4 stimulation are needed to induce switching from IgM to either IgG1 or IgE. In this report we describe a critical role for the tyrosine kinase Lyn in setting IL-4 signaling thresholds in mouse B lymphocytes. Upon CD40 ligand stimulation of lyn-/- B cells, 10-fold less IL-4 was required to induce switching from IgM to IgG1 and IgE and an increased proportion of B cells isotype switched at each IL-4 concentration. These in vitro results correlate with the in vivo findings that in lyn-/- mice, IgG1 Ab-forming cells develop prematurely in ontogeny and that adult lyn-/- mice have an abnormally high proportion of IgG1-expressing B cells in their spleens. Adult lyn-/- mice also have significantly higher levels of IgE in their serum. These results identify Lyn as a molecule involved in modulating the IL-4 signal in B cells and provide insights into its regulation and how a B cell signaling imbalance may contribute to atopy.
authors.affiliation: The Walter and Eliza Hall Institute of Medical Research, Royal Melbourne Hospital, Victoria, Australia.
authors.forename: M L
authors.initials: ML
authors.lastname: Janas
authors.forename: P
authors.initials: P
authors.lastname: Hodgkin
authors.forename: M
authors.initials: M
authors.lastname: Hibbs
authors.forename: D
authors.initials: D
authors.lastname: Tarlinton
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000201:enzymology / Q000276:immunology; D002454:Cell Differentiation / Q000235:genetics / Q000276:immunology; D002455:Cell Division / Q000235:genetics / Q000276:immunology; D002478:Cells, Cultured; D015536:Down-Regulation / Q000235:genetics / Q000276:immunology*; D017578:Immunoglobulin Class Switching / Q000235:genetics; D015847:Interleukin-4 / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000502:physiology*; D047908:Intracellular Signaling Peptides and Proteins; D008213:Lymphocyte Activation / Q000235:genetics / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000378:metabolism; D019948:Receptors, Interleukin-4 / Q000378:metabolism; D015398:Signal Transduction / Q000235:genetics / Q000276:immunology*; D019061:src-Family Kinases / Q000172:deficiency / Q000235:genetics* / Q000502:physiology
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D019948:Receptors, Interleukin-4; D015847:Interleukin-4; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; 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