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Type II HS

Mediated by antibodies (IgG / IgM) directed towards antigens present on surface of cells or other tissue components.
  1. Opsonization and Complement and Fc Receptor Mediated Phagocytosis
  1. Complement and Fc Receptor Mediated Inflammation:
Eg Glomerulonephritis, vascular rejection in grafts,
  • When antibodies deposit in extracellular tissues such as basement membrane, the resultant injury is by inflammation and not because of phagocytosis or lysis of cells
  • Antibodies deposited on basement membrane → activate complement → C3a. C5a produced →
    Recruit neutrophils & macrophages → Release of lysosomal enzymes & free radicals → Tissue damage. 
  1. Antibody Mediated Cellular Dysfunction,
  • Myasthenia Gravis - antibodies react with Ach receptor in the motor - end plates of smooth muscle and impair neuromuscular transmission
  • Pemphigus vulgaris - antibodies against desmosomes disrupt inter cellular junctions leading to skin vesicles.
Disease Target Antigen Mechanisms of Disease Clinicopathologic Manifestations
Autoimmune hemolytic anemia
Autoimmune thrombocytopenic purpura
Erythrocyte membrane proteins (Rh blood group antigens, I antigen)
Platelet membrane proteins (gpllb:Illa integrin)
Opsonization and phagocytosis of erythrocytes
Opsonization and phagocytosis of platelets
Hemolysis, anemia
Pemphigus vulgaris Proteins in intercellular junctions of epidermal cells (epidermal cadherin) Antibody-mediated activation of proteases, disruption of intercellular adhesions Skin vesicles (bullae)
Vasculitis caused by ANCA Neutrophil granule proteins, presumably released from activated neutrophils Neutrophil degranulation and inflammation Vasculitis
Goodpasture syndrome Noncollagenous protein in basement membranes of kidney glomeruli and lung alveoli Complement- and Fc receptor-mediated inflammation Nephritis, lung hemorrhage
Acute rheumatic fever Streptococcal cell wall antigen; antibody cross-reacts with myocardial antigen Inflammation, macrophage activation Myocarditis, arthritis
Myasthenia gravis Acetylcholine receptor Antibody inhibits acetylcholine binding, down-modulates receptors Muscle weakness, paralysis
Graves disease (hyperthyroidism) TSH receptor Antibody-mediated stimulation of TSH receptors Hyperthyroidism
Insulin-resistant diabetes Insulin receptor Antibody inhibits binding of insulin Hyperglycemia, ketoacidosis
Pernicious anemia Intrinsic factor of gastric parietal cells Neutralization of intrinsic factor, decreased absorption of vitamin B12 Abnormal erythropoiesis, anemia

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