Type II hypersensitivity, in the Gell and Coombs classification of allergic reactions, is an antibody-mediated process in which IgG and IgM antibodies are directed against antigens on cells or extracellular material. This subsequently leads to cell lysis, tissue damage or loss of function through mechanisms such ascomplement activation via the classical complement pathway Antibody-dependent cellular cytotoxicity or anti-receptor activity.