B cell-orchestrated tolerization of T cell-dependent B cell-mediated autoimmune diseases

Failure of thymic tolerance may result in severe autoimmune diseases that target the central nervous system (CNS), including Multiple Sclerosis (MS), Myelin Oligodendrocyte Glycoprotein (MOG)-associated Disease (MOGAD), and Neuromyelitis Optica Spectrum Disorders (NMOSD). Recently, we discovered a new layer of thymic tolerance in that thymic B cells get licensed to present activation-induced autoantigens, among them AQP4 (the target antigen in NMOSD). Thymic B cells are necessary and sufficient to purge the T cell repertoire of AQP4-specific clones.In BREAKING BAD, we will investigate in depth how thymic B cells shape the AQP4-specific T cell repertoire by either deleting AQP4-specific conventional T cells or agonist-selecting Foxp3+ Treg cells. To understand B cell-intrinsic and extrinsic checkpoints of this process, we will use genetic means to disrupt thymic tolerance to AQP4. Since we have cloned a variety of AQP4-specific TCRs, we are now in the position to track fate decisions and functional phenotypes of naïve T cells that react against AQP4, which is – in contrast to MOG – not only expressed in the CNS but also in peripheral organs. Finally, our data indicate that amyloid precursor protein (APP), associated with cerebral amyloid angiopathy and Alzheimer's disease, is an autoantigen that is – very similar to AQP4 – induced in B cells upon CD40 stimulation and expressed in thymic B cells. Therefore, we will investigate the APP-specific T cell repertoire and its ability to provide T cell help for the generation of anti-amyloid Abeta antibodies upon disruption of B cell-mediated tolerance to Abeta peptides by conditional genetic ablation of APP in B cells.In summary, BREAKING BAD will explore the significance of B cell-mediated tolerance for CNS autoantigens. We anticipate that our experiments will revolutionize the understanding and perhaps potential treatment options of CNS autoimmunity but also of major degenerative disorders like Alzheimer's disease.