Prof. Dr. Thomas Winkler
Nikolaus-Fiebiger-Zentrum für Molekulare Medizin
Evolution of Anti-DNA autoantibodies by somatic hypermutation
The formation of antibodies against double-stranded (ds) DNA is considered to be the serologic hallmark of systemic lupus erythematosus (SLE) and anti-dsDNA antibodies play an important role in the pathogenesis of the disease. We and others have shown that autoantibodies against DNA arise de novo by somatic mutation from non-autoreactive precursors. Therefore, self-tolerance checkpoints at the post-mutational stage of B cell differentiation have to exist that normally prevent the induction of pathogenic anti-dsDNA specificities. In the first funding period, we further characterized our newly generated model for postmutational B cell tolerance. By backcrossing the mice to the Rag-/- background and characterisation of the B cell development in the BCR-knockin mice we could further substantiate our finding that anti-DNA autoantibodies are derived from non-autoreactive precursors. In addition, we proposed that defective clearance of apoptotic cells is crucially involved in the development of autoantibodies against DNA. With the generation and analysis of a mouse deficient for Dnase1l3 we could show that a single genetic defect is sufficient to generate high affinity IgG anti-dsDNA autoantibodies in the C57Bl/6 background. Furthermore, we showed that a viral trigger can induce systemic autoimmunity by excessive Type I interferon signalling.
In the new funding period, we intend to extend our analysis of the germinal center tolerance checkpoint towards susceptibility genes for autoantibody generation, in particular to loss of Dnase1l3. By using our transgenic mouse model in the context of excessive Type I interferon signalling triggered by persistent virus infection, we will dissect the mechanisms that operate to break germinal center tolerance.
B-lymphocytes engaged in a germinal center reaction against foreign antigens gain anti-dsDNA reactivity de novo by somatic hypermutation in the dark zone (A). A phagocytosis defect in the tingible body macrophages (TBM) leads to accumulation of apoptotic and secondary necrotic material that is bound to FDCs within immune complexes (B). Anti-DNA B-cells (red) that accidentally gained anti-dsDNA reactivity are positively selected by chromatin and nucleoprotein-complexes presented on the FDC network. Under certain conditions, TFH cells might provide help for the GC B cells (C) and anti-dsDNA plasma cells as well as memory cells are exiting the germinal center (modified from Schroeder et al., Autoimmunity, 2013).
Schmitt, H., Sell, S., Koch, J., Seefried, M., Sonnewald, S., Daniel, C., Winkler, T.H.*, and Nitschke, L.* (2016). Siglec-H protects from virus-triggered severe systemic autoimmunity. The Journal of experimental medicine 213, 1627-1644. * authors contributed equally
Krzyzak, L., Seitz, C., Urbat, A., Hutzler, S., Ostalecki, C., Glasner, J., Hiergeist, A., Gessner, A., Winkler, T.H., Steinkasserer, A., and Nitschke, L. (2016). CD83 Modulates B Cell Activation and Germinal Center Responses. Journal of immunology 196, 3581-3594.
Lutz, J., Dittmann, K., Bosl, M.R., Winkler, T.H., Wienands, J., and Engels, N. (2015). Reactivation of IgG-switched memory B cells by BCR-intrinsic signal amplification promotes IgG antibody production. Nature communications 6, 8575.
Brachs, S., Turqueti-Neves, A., Stein, M., Reimer, D., Brachvogel, B., Bosl, M., Winkler, T., Voehringer, D., Jack, H.M., and Mielenz, D. (2014). Swiprosin-1/EFhd2 limits germinal center responses and humoral type 2 immunity. European journal of immunology 44, 3206-3219.
Engels, N., Konig, L.M., Schulze, W., Radtke, D., Vanshylla, K., Lutz, J., Winkler, T.H., Nitschke, L., and Wienands, J. (2014). The immunoglobulin tail tyrosine motif upgrades memory-type BCRs by incorporating a Grb2-Btk signalling module. Nature communications 5, 5456.
Hutzler, S., Ozgor, L., Naito-Matsui, Y., Klasener, K., Winkler, T.H., Reth, M., and Nitschke, L. (2014). The ligand-binding domain of Siglec-G is crucial for its selective inhibitory function on B1 cells. Journal of immunology 192, 5406-5414.
Song, J., Lokmic, Z., Lammermann, T., Rolf, J., Wu, C., Zhang, X., Hallmann, R., Hannocks, M.J., Horn, N., Ruegg, M.A., Sonnenberg, A., Georges-Labouesse, E., Winkler, T. H., Kearney, J. F., Cardell, S., Sorokin, L. (2013). Extracellular matrix of secondary lymphoid organs impacts on B-cell fate and survival. Proceedings of the National Academy of Sciences of the United States of America 110, 2915-2924.
Schroeder, K., Herrmann, M., and Winkler, T.H. (2013). The role of somatic hypermutation in the generation of pathogenic antibodies in SLE. Autoimmunity 46, 121-127.
Wellmann, U., Letz, M., Herrmann, M., Angermüller, S., Kalden, J.R., and Winkler, T.H. (2005). The evolution of human anti-double-stranded DNA autoantibodies. Proc Natl Acad Sci USA 102, 9258-9263.