Thymic B cells in aging and autoimmune disease

Thymic B cells comprise a heterogenous population of cells localized primarily within the thymic medulla, a region populated by professional antigen-presenting cells (APCs) including dendritic cells, medullary thymic epithelial cells (mTECs), and macrophages. Through expression and presentation of self-antigens, these APCs are responsible for shaping the normal T cell repertoire by negatively selecting thymocytes recognizing self-antigens. It is now clear that thymic B cells have the capacity to participate in negative selection and present cognate antigens distinct from other medullary APCs, thus serving a non-redundant role in mediating T cell central tolerance. Recent work has linked thymic B cells with the development of multiple autoimmune diseases, many of which are increased in prevalence with aging. Here, we will provide a brief overview of the role of thymic B cell subsets in promoting negative selection and immune homeostasis, with a primary focus on the impact of aging on their tolerizing capacity and involvement in autoimmune diseases, highlighting thymic B cells as a potential novel therapeutic target to improve clinical outcomes in patients with autoimmune diseases.