Type II Autoimmune reactions
Type II hypersensitivity reactions are caused by antibodies against altered self proteins, such as penicilline-protein conjugates. In the case of autoimmunity, antibodies generated against cell surface antigens/extracellular matrix proteins may be cytotoxic (type IIA) or they may have agonistic/antagonistic properties (type IIB). Autoantibodies to cell surface antigens may initiate cell destruction by complement-mediated lysis (cell destruction), phagocytosis, or antibody-dependent cell-mediated cytotoxicity (ADCC). Examples include autoimmune hemolytic anemia (AIHA), and autoimmune thrombocytopenia. Some autoantibodies bind to surface receptors, either activating (eg anti-TSH receptor autoantibodies in Grave’s disease) or inhibiting (eg anti-acetylcholine antibodies in myasthenia gravis) their function.