type II hypersensitivity
{{Short description|Type of allergic reaction}}
{{distinguish|type 2 inflammation}}
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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
- complement activation via the classical complement pathway
- Antibody-dependent cellular cytotoxicity or
- anti-receptor activity.{{Cite web | url=https://library.med.utah.edu/WebPath/IMMHTML/IMM102.html |title = Immunopathology}}
The activation of the complement system results in opsonization, the agglutination of red blood cells, cell lysis, and cell death.{{Cite journal|last1=Warrington|first1=Richard|last2=Watson|first2=Wade|last3=Kim|first3=Harold L.|last4=Antonetti|first4=Francesca Romana|date=2011-11-10|title=An introduction to immunology and immunopathology|journal=Allergy, Asthma, and Clinical Immunology|volume=7|issue=1|pages=S1|doi=10.1186/1710-1492-7-S1-S1|issn=1710-1492|pmc=3245432|pmid=22165815 |doi-access=free }}
These reactions usually take between 2 and 24 hours to develop.
Examples
| class="wikitable" | |
| Disease | Autoantibody target |
|---|---|
| Autoimmune hemolytic anemia | Red blood cells |
| Goodpasture syndrome | Glomerular basement membrane |
| Graves disease | Thyroid stimulating hormone receptor |
| Immune thrombocytopenia | Platelets |
| Myasthenia gravis | Muscle acetylcholine receptor |
An example of complement dependent type II hypersensitivity is an acute hemolytic transfusion reaction following transfusion of ABO incompatible blood.{{cite journal |last1=Tinegate |first1=Hazel |last2=Birchall |first2=Janet |last3=Gray |first3=Alexandra |last4=Haggas |first4=Richard |last5=Massey |first5=Edwin |last6=Norfolk |first6=Derek |last7=Pinchon |first7=Deborah |last8=Sewell |first8=Carrock |last9=Wells |first9=Angus |last10=Allard |first10=Shubha |title=Guideline on the investigation and management of acute transfusion reactions Prepared by the BCSH Blood Transfusion Task Force |journal=British Journal of Haematology |date=October 2012 |volume=159 |issue=2 |pages=143–153 |doi=10.1111/bjh.12017 |pmid=22928769 |s2cid=9150295 |doi-access=free }} Preformed antibody (predominantly IgM) against donor red cell antigens not found in an individual of a particular blood group (e.g. anti-A IgM in an individual with blood group B), bind to the donor red cell surface and lead to rapid complement mediated haemolysis and potentially life-threatening clinical consequences. Complement-dependent type II hypersensitivity can also occur during the transmission of incompatible maternal antibodies to fetal red blood cells causing hemolytic anemia in the fetus, known as erythroblastosis fetalis.{{cite book |last1=Betts, J. Gordon |last2=Young, Kelly A. |last3=Wise, James A. |display-authors=etal |title=Anatomy and Physiology |url=https://openstax.org/details/books/anatomy-and-physiology |via=Openstax.org}}{{cite web |title=Hemolytic Anemia |url=https://www.hopkinsmedicine.org/health/conditions-and-diseases/hemolytic-anemia#:~:text=Hemolytic%20anemia%20is%20a%20disorder,blood%20cells%2C%20you%20have%20anemia |website=Johns Hopkins Medicine| date=8 August 2021 }}
Another example of a complement dependent type II hypersensitivity reaction is Goodpasture's syndrome, where the basement membrane (containing collagen type IV) in the lung and kidney is attacked by one's own antibodies in a complement mediated fashion.{{EMedicine|article|240556|Goodpasture Syndrome}}
An example of anti-receptor type II hypersensitivity (also classified as type V hypersensitivity) is observed in Graves disease, in which anti-thyroid stimulating hormone receptor antibodies lead to increased production of thyroxine.{{EMedicine|article|120619|Graves Disease}}
However, there are questions as to the relevance of the Gell and Coombs classification of allergic reactions in modern-day understanding of allergy and it has limited utility in clinical practice.{{cite journal |last1=Descotes |first1=Jacques |last2=Choquet-Kastylevsky |first2=Geneviève |title=Gell and Coombs's classification: is it still valid? |journal=Toxicology |date=February 2001 |volume=158 |issue=1–2 |pages=43–49 |doi=10.1016/S0300-483X(00)00400-5 |pmid=11164991 }}
See also
References
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External links
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{{Hypersensitivity and autoimmune diseases}}
{{Use dmy dates|date=May 2019}}