Editing Hypersensitivity (section)

== Type II hypersensitivity ==

{{Main|Type II hypersensitivity}}

Type II hypersensitivity reaction refers to an antibody-mediated immune reaction in which antibodies (IgG or IgM) are directed against cellular or extracellular matrix antigens with the resultant cellular destruction, functional loss, or damage to tissues.<ref name=":4" /> The antigens may be for example glycoproteins on the cell membrane of erythrocytes that are key molecules that determine blood types. Depending on the chemical nature of the antigens, blood types have different levels of hypersensitivity; for instance, A and B are more antigenic than other antigens.<ref name=":4" />
[[File:Type II hypersensitivity.webm|thumb|Type II hypersensitivity]]
Damage can be accomplished via three different mechanisms:<ref name=":4" />
* Antibody binding to cell surface receptors and altering its activity
* Activation of the complement pathway.
* Antibody-dependent cellular cytotoxicity.

The pathophysiology of type II hypersensitivity reactions can be broadly classified into three types:<ref name=":4" />
* Cell depletion or destruction without inflammation
* Inflammation mediated by complement or Fc receptor
* Cellular dysfunction by antibodies

The process involves a series of immune-mediated events that might take different forms.<ref>{{Citation|last1=Bajwa|first1=Shammas F.|title=Type II Hypersensitivity Reaction|date=2021|url=http://www.ncbi.nlm.nih.gov/books/NBK563264/|work=StatPearls|place=Treasure Island (FL)|publisher=StatPearls Publishing|pmid=33085411|access-date=2021-07-05|last2=Mohammed|first2=Reem Hamdy A.}} {{CC-notice|cc=by4}}</ref>