title: Impaired proliferation of peripheral B cells and indication of autoimmune disease in lyn-deficient mice.
abstract: The Src family protein-tyrosine kinase Lyn associates physically with the BCR and has been suggested to play an important role in BCR-mediated signaling. Studies with lyn-/- mice showed that the number of B cells decreased by half in their peripheral tissues. In addition, these B cells do not respond normally to a number of stimuli, including BCR cross-linking and CD40 ligand. Induction of tyrosine phosphorylation on a variety of cellular proteins, such as Vav, Cbl, and HS1, upon BCR cross-linking was also abolished in these B cells. Despite the impaired BCR-mediated signaling, concentrations of IgM and IgA in sera were remarkably elevated, and production of autoantibodies was detected in lyn-/- mice. Histological study showed splenomegaly and enlargement of lymph nodes that became evident with age in the mutant mice. The spleen contained significant number of plasma cells as well as unusual lymphoblast-like cells carrying Mac1 antigen and cytoplasmic IgM. These cells spontaneously secreted a large amount of IgM in vitro. Finally, significant number of lyn-/- mice show glomerulonephritis, an indication of autoimmune disease. From these data, we conclude that Lyn plays a role in signal transduction for not only clonal expansion and terminal differentiation of peripheral B cells but also elimination of autoreactive B cells.
authors.affiliation: Department of Oncology, Institute of Medical Science, University of Tokyo, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Nishizumi
authors.forename: I
authors.initials: I
authors.lastname: Taniuchi
authors.forename: Y
authors.initials: Y
authors.lastname: Yamanashi
authors.forename: D
authors.initials: D
authors.lastname: Kitamura
authors.forename: D
authors.initials: D
authors.lastname: Ilic
authors.forename: S
authors.initials: S
authors.lastname: Mori
authors.forename: T
authors.initials: T
authors.lastname: Watanabe
authors.forename: T
authors.initials: T
authors.lastname: Yamamoto
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D000917:Antibody Formation / Q000235:genetics; D017209:Apoptosis / Q000502:physiology; D001323:Autoantibodies / Q000096:biosynthesis*; D001327:Autoimmune Diseases / Q000276:immunology*; D001402:B-Lymphocytes / Q000276:immunology*; D001483:Base Sequence; D001798:Blood Proteins / Q000378:metabolism; D008213:Lymphocyte Activation / Q000276:immunology*; D016177:Macrophage-1 Antigen / Q000096:biosynthesis; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D011947:Receptors, Antigen, B-Cell / Q000276:immunology; D015398:Signal Transduction / Q000276:immunology; D019061:src-Family Kinases / Q000172:deficiency* / Q000235:genetics*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D001323:Autoantibodies; D001798:Blood Proteins; C061909:HCLS1 protein, human; D016177:Macrophage-1 Antigen; D011947:Receptors, Antigen, B-Cell; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases