Type II

• Type II hypersensitivity reactions, or “cytotoxic reactions,” are antibody-mediated and responsible for a number of autoimmune disorders.

• Clinical features, diagnostics, and treatment depend on the underlying etiology (see “Hypersensitivity classification” above).

• Distribution of disease: often limited to a particular tissue type

• Diagnosis may involve autoantibody testing (see “Antibody diagnosis of autoimmune diseases”) and the Coombs test.

IgM and IgG mistakenly bind to surface antigens of the cells in the body, which results in:

• Cellular destruction

  • Antibody-dependent cell-mediated cytotoxicity (NK cells or macrophages)

  • Target cell opsonization → phagocytosis and/or complement activation

• Inflammation

  • Fc-receptor mediated immune cell activation

  • Antibodies bind to cellular surfaces → activation of the complement system

• Impaired cellular function

  • Antibodies bind to cell surface receptors → inhibition or activation of downstream signaling pathways → impaired cellular function

• Hemolysis

  • Acute hemolytic transfusion reaction

  • Autoimmune hemolytic anemia

  • Hemolytic disease of the newborn

• Systemic disorders

  • Goodpasture syndrome

  • Rheumatic fever

  • Myasthenia gravis

  • Graves disease

• Skin disorders

  • Bullous pemphigoid

  • Pemphigus vulgaris