Type II hypersensitivity

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 (such as circulating red blood cells) or extracellular material (such as basement membrane). This subsequently leads to cell lysis, tissue damage or loss of function through mechanisms such as

1. complement activation via the classical complement pathway
2. Antibody-dependent cellular cytotoxicity or
3. anti-receptor activity.^[1]

The activation of the complement system results in opsonization, the agglutination of red blood cells, cell lysis, and cell death.^[2]

These reactions usually take between 2 and 24 hours to develop.^[2]