Chapter 7: Immunopathology

Immunopathology on immunopathology provides an extensive review of immune system dysfunctions, serving as a critical resource for medical students studying pathology and preparing for board exams. It offers a detailed classification of hypersensitivity reactions, distinguishing between Type I anaphylactic responses mediated by IgE and mast cells, Type II antibody-dependent cytotoxicity, Type III immune complex disorders such as systemic lupus erythematosus (SLE) and serum sickness, and Type IV delayed cell-mediated responses observed in tuberculosis testing and graft rejection. The text deeply explores autoimmune diseases, outlining the pathophysiology and serological markers of SLE, such as antinuclear antibodies (ANA) and anti-dsDNA, alongside the glandular destruction in Sjögren syndrome and the collagen deposition characteristic of Scleroderma, including the CREST syndrome variant. Significant attention is given to primary immune deficiency syndromes, including X-linked agammaglobulinemia of Bruton caused by BTK mutations, the thymic aplasia of DiGeorge syndrome, and the severe manifestations of Severe Combined Immunodeficiency (SCID) and Wiskott-Aldrich syndrome. The chapter also examines complement system disorders like hereditary angioedema. Furthermore, it provides a thorough analysis of Acquired Immunodeficiency Syndrome (AIDS), detailing the retroviral life cycle of HIV, its attachment to CD4 and chemokine co-receptors, and the clinical progression from acute viremia to an AIDS definition when CD4 counts drop (lesser than) 200 cells/mL. This section lists common opportunistic infections, such as Pneumocystis jirovecii and Kaposi sarcoma, that define the syndrome. Finally, the chapter summarizes the immunology of transplant rejection, categorizing the mechanisms into hyperacute, acute, and chronic rejection based on the involvement of preformed antibodies, T-cells, and vascular fibrosis.