Precipitin
Encyclopedia
A precipitin is an antibody
which can precipitate out of a solution upon antigen binding.
for antibody, which has since been rendered obsolete by current diagnostic techniques such as ELISA
(enzyme linked immunosorbant assay) and RIA
(Radioimmunoassay). The precipitin reaction is based upon the interaction of antigen
with antibody leading to the production of antigen:antibody complexes.
In the precipitin reaction, varying amounts of soluble antigen are added to a fixed amount of serum containing antibody. As the amount of antigen added in
NB: the small, soluble immune complexes formed in the zone of antigen excess are the cause of many pathological syndromes in vivo.
Antibody can only precipitate antigenic substrates that are multivalent—that is, only antigens that have multiple antibody-binding sites epitopes. This allows for the formation of large antigen:antibody complexes.
Antibody
An antibody, also known as an immunoglobulin, is a large Y-shaped protein used by the immune system to identify and neutralize foreign objects such as bacteria and viruses. The antibody recognizes a unique part of the foreign target, termed an antigen...
which can precipitate out of a solution upon antigen binding.
Precipitin reaction
The precipitin reaction provided the first quantitative assayAssay
An assay is a procedure in molecular biology for testing or measuring the activity of a drug or biochemical in an organism or organic sample. A quantitative assay may also measure the amount of a substance in a sample. Bioassays and immunoassays are among the many varieties of specialized...
for antibody, which has since been rendered obsolete by current diagnostic techniques such as ELISA
ELISA
Enzyme-linked immunosorbent assay , is a popular format of a "wet-lab" type analytic biochemistry assay that uses one sub-type of heterogeneous, solid-phase enzyme immunoassay to detect the presence of a substance in a liquid sample."Wet lab" analytic biochemistry assays involves detection of an...
(enzyme linked immunosorbant assay) and RIA
RIA
RIA can stand for:* Russian Information Agency "RIA Novosti"* Royal Irish Academy* Rich Internet Application* Research into Ageing* Radioimmunoassay* National Rail code for Rhoose Cardiff International Airport railway station, Wales...
(Radioimmunoassay). The precipitin reaction is based upon the interaction of antigen
Antigen
An antigen is a foreign molecule that, when introduced into the body, triggers the production of an antibody by the immune system. The immune system will then kill or neutralize the antigen that is recognized as a foreign and potentially harmful invader. These invaders can be molecules such as...
with antibody leading to the production of antigen:antibody complexes.
In the precipitin reaction, varying amounts of soluble antigen are added to a fixed amount of serum containing antibody. As the amount of antigen added in
- In the zone of antibody excess, each molecule of antigen is bound extensively by antibody and crosslinked to other molecules of antigen. The average size of antibody-antigen complex is small; cross-linking between antigen molecules by antibody is rare.
- In the zone of equivalence, the formation of precipitin complexes is optimal. Extensive lattices of antigen and antibody are formed by cross-linking.
- At high concentrations of antigen, the average size of antibody-antigen complexes is once again small because few antibody molecules are available to cross-link antigen molecules together.
NB: the small, soluble immune complexes formed in the zone of antigen excess are the cause of many pathological syndromes in vivo.
Antibody can only precipitate antigenic substrates that are multivalent—that is, only antigens that have multiple antibody-binding sites epitopes. This allows for the formation of large antigen:antibody complexes.