Tolerance Lost: Pathways Linking Immune Regulation to Autoimmune Disorders

Abstract Immune tolerance is a fundamental immunological mechanism that enables discrimination between self and non-self antigens, thereby preventing autoimmunity. It is governed by central tolerance—operating in the thymus and bone marrow—and peripheral tolerance— mediated in secondary lymphoid organs and tissues. Central mechanisms eliminate or edit autoreactive lymphocytes during development, while peripheral tolerance relies on regulatory T cells (Tregs), anergy, clonal deletion, and immune privilege to suppress escaped autoreactive cells. Breakdown of these regulatory systems due to genetic predispositions, environmental triggers, or immune dysregulation leads to autoimmune disease. Understanding the interplay between tolerance and autoimmunity has advanced targeted therapies aimed at restoring immune homeostasis. Innovations such as Treg-based interventions and antigen-specific immunotherapies offer promising avenues for re-establishing tolerance and managing autoimmune conditions more precisely and effectively.