Bruton's Tyrosine Kinase Synergizes with Notch2 To Govern Marginal Zone B Cells in Nonobese Diabetic Mice

J Immunol. 2015 Jul 1;195(1):61-70. doi: 10.4049/jimmunol.1400803. Epub 2015 Jun 1.

Abstract

Expansion of autoimmune-prone marginal zone (MZ) B cells has been implicated in type 1 diabetes. To test disease contributions of MZ B cells in NOD mice, Notch2 haploinsufficiency (Notch2(+/-)) was introduced but failed to eliminate the MZ, as it does in C57BL/6 mice. Notch2(+/-)/NOD have MZ B cell numbers similar to those of wild-type C57BL/6, yet still develop diabetes. To test whether BCR signaling supports Notch2(+/-)/NOD MZ B cells, Bruton's tyrosine kinase (Btk) deficiency was introduced. Surprisingly, MZ B cells failed to develop in Btk-deficient Notch2(+/-)/NOD mice. Expression of Notch2 and its transcriptional target, Hes5, was increased in NOD MZ B cells compared with C57BL/6 MZ B cells. Btk deficiency reduced Notch2(+/-) signaling exclusively in NOD B cells, suggesting that BCR signaling enhances Notch2 signaling in this autoimmune model. The role of BCR signaling was further investigated using an anti-insulin transgenic (Tg) BCR (125Tg). Anti-insulin B cells in 125Tg/Notch2(+/-)/NOD mice populate an enlarged MZ, suggesting that low-level BCR signaling overcomes reliance on Notch2. Tracking clonotypes of anti-insulin B cells in H chain-only VH125Tg/NOD mice showed that BTK-dependent selection into the MZ depends on strength of antigenic binding, whereas Notch2-mediated selection does not. Importantly, anti-insulin B cell numbers were reduced by Btk deficiency, but not Notch2 haploinsufficiency. These studies show that 1) Notch2 haploinsufficiency limits NOD MZ B cell expansion without preventing type 1 diabetes, 2) BTK supports the Notch2 pathway in NOD MZ B cells, and 3) autoreactive NOD B cell survival relies on BTK more than Notch2, regardless of MZ location, which may have important implications for disease-intervention strategies.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Agammaglobulinaemia Tyrosine Kinase
  • Animals
  • Autoantibodies / biosynthesis
  • Autoimmunity*
  • B-Lymphocyte Subsets / immunology*
  • B-Lymphocyte Subsets / pathology
  • Cell Differentiation
  • Cell Survival / immunology
  • Diabetes Mellitus, Experimental / genetics
  • Diabetes Mellitus, Experimental / immunology*
  • Diabetes Mellitus, Experimental / pathology
  • Female
  • Gene Expression Regulation
  • Immunoglobulin Heavy Chains / biosynthesis
  • Insulin / immunology
  • Male
  • Mice
  • Mice, Inbred C57BL
  • Mice, Inbred NOD
  • Protein-Tyrosine Kinases / deficiency
  • Protein-Tyrosine Kinases / genetics
  • Protein-Tyrosine Kinases / immunology*
  • Receptor, Notch2 / deficiency
  • Receptor, Notch2 / genetics
  • Receptor, Notch2 / immunology*
  • Receptors, Antigen, B-Cell / genetics
  • Receptors, Antigen, B-Cell / immunology
  • Signal Transduction

Substances

  • Autoantibodies
  • Immunoglobulin Heavy Chains
  • Insulin
  • Notch2 protein, mouse
  • Receptor, Notch2
  • Receptors, Antigen, B-Cell
  • Protein-Tyrosine Kinases
  • Agammaglobulinaemia Tyrosine Kinase
  • Btk protein, mouse