Immunopathology

Immunopathology is the study of diseases in which the immune system contributes to tissue injury and dysfunction. It encompasses autoimmune and hypersensitivity disorders, alloimmune reactions such as transplant rejection, and immunodeficiencies that predispose to infection and cancer. By examining the mechanisms of immune attack, immune regulation, and immune repair, immunopathology seeks to explain how protective responses become pathogenic and how these processes can be targeted therapeutically.

Key mechanisms include autoimmunity, where tolerance to self antigens fails and autoreactive B and T cells attack tissues; hypersensitivity reactions, classified into four types (I-IV) based on mediators and timing; and alloimmunity, in which immune responses directed at non-self antigens from another individual cause graft rejection or GVHD. Immune injury can also follow infections via molecular mimicry and immune complex formation, or result from immunodeficiency with recurrent infections.

Common diseases associated with immunopathology include autoimmune conditions such as rheumatoid arthritis, systemic lupus erythematosus, type 1 diabetes, and multiple sclerosis; allergic diseases like asthma and allergic rhinitis; immune complex–mediated glomerulonephritis; Goodpasture and rheumatic fever; and transplant-related disorders such as GVHD and rejection. The specific manifestations depend on the affected organ and the dominant pathogenic mechanism.

Diagnosis relies on clinical presentation, serology for autoantibodies and immune markers, complement levels, and tissue biopsy when indicated. Treatment aims to reduce immune-mediated damage and may include corticosteroids, disease-modifying antirheumatic drugs, biologic agents targeting specific immune pathways, and plasmapheresis in selected antibody-mediated diseases. Prevention and management also involve avoidance of triggers and allergen immunotherapy where appropriate.