Give an overview.
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.
Describe the pathophysiology.
IgM and IgG mistakenly bind to surface antigens of the cells in the body, which results in:
Antibody-dependent cell-mediated cytotoxicity (NK cells or macrophages)
Target cell opsonization → phagocytosis and/or complement activation
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