Immunopathology refers to the study of diseases that result from dysfunction or dysregulation of the immune system, as well as to the tissue damage caused by immune responses themselves.
Scope and Mechanisms
The immune system protects organisms from infection and maintains tolerance to self. When its functions become inappropriate, however, it can contribute to pathology. Immunopathology encompasses hypersensitivity reactions, in which an exaggerated response to harmless antigens causes tissue injury; autoimmunity, where loss of self‑tolerance leads to immune attacks on host tissues; and immunodeficiency, where insufficient immune responses permit opportunistic infections and malignancies. Classic hypersensitivity reactions are classified into four types: immediate reactions mediated by IgE and mast cells (e.g., anaphylaxis), antibody‑mediated cytotoxicity, immune complex–mediated inflammation, and delayed type reactions driven by T cells. Autoimmune diseases such as systemic lupus erythematosus involve autoantibodies and immune complexes, whereas multiple sclerosis and type 1 diabetes involve autoreactive T cells. Immunopathology also arises during infection, as in viral hepatitis, dengue haemorrhagic fever and severe acute respiratory syndrome, where host inflammatory responses contribute to tissue damage. Laboratory assessment involves immunohistochemistry, flow cytometry, autoantibody assays and cytokine profiling to characterize immune cell infiltration and mediators.
Examples and Clinical Significance
Examples of immunopathological conditions include allergic asthma, urticaria and food allergies; autoimmune disorders like rheumatoid arthritis, Hashimoto’s thyroiditis and myasthenia gravis; graft‑versus‑host disease following bone marrow transplantation; and immune complex–mediated glomerulonephritis. Infections can trigger immunopathology, such as cytokine storms and vascular leakage in dengue and severe influenza or COVID‑19. Sepsis results from dysregulated host responses to infection leading to organ dysfunction. Understanding the mechanisms of immunopathology informs the development of therapies ranging from antihistamines and corticosteroids to biologics targeting tumour necrosis factor or interleukin‑17, and immune‑checkpoint inhibitors that modulate T‑cell activation. It also guides the design of vaccines that induce protective immunity without excessive inflammation. Immunopathology sits at the interface of immunology and pathology, highlighting how the same responses that defend against pathogens can contribute to disease when dysregulated. Studying these processes enables targeted interventions to restore balance and prevent tissue damage. Related Terms: Autoimmunity, Hypersensitivity, Cytokine storm, Immunodeficiency, Immunopathogenesis