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immunoassay of a substance that has been radioactively labeled

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/22 05:08:50」(JST)

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Radioimmunoassay (RIA) is a very sensitive in vitro assay technique used to measure concentrations of antigens (for example, hormone levels in blood) by use of antibodies. As such, it can be seen as the inverse of a radiobinding assay, which quantifies an antibody by use of corresponding antigens.

Although the RIA technique is extremely sensitive and extremely specific, requiring specialized equipment, it remains among the least expensive methods to perform such measurements. It requires special precautions and licensing, since radioactive substances are used.

The RAST test (radioallergosorbent test) is an example of radioimmunoassay. It is used to detect the causative allergen for an allergy.

Method

Classically, to perform a radioimmunoassay, a known quantity of an antigen is made radioactive, frequently by labeling it with gamma-radioactive isotopes of iodine, such as 125-I, attached to tyrosine. This radiolabeled antigen is then mixed with a known amount of antibody for that antigen, and as a result, the two specifically bind to one another. Then, a sample of serum from a patient containing an unknown quantity of that same antigen is added. This causes the unlabeled (or "cold") antigen from the serum to compete with the radiolabeled antigen ("hot") for antibody binding sites. As the concentration of "cold" antigen is increased, more of it binds to the antibody, displacing the radiolabeled variant, and reducing the ratio of antibody-bound radiolabeled antigen to free radiolabeled antigen. The bound antigens are then separated from the unbound ones, and the radioactivity of the bound antigen remaining in the supernatant is measured using a gamma counter.

This method can be used for any biological molecule in principle and is not restricted to serum antigens, nor is it required to use the indirect method of measuring the free antigen instead of directly measuring the captured antigen. For example, if it is undesirable or not possible to radiolabel the antigen or target molecule of interest, an RIA can done if two different antibodies that recognize the target are available and the target is large enough (e.g., a protein) to present multiple epitopes to the antibodies. One antibody would be radiolabeled as above while the other would remain unmodified. The RIA would begin with the "cold" unlabeled antibody being allowed to interact and bind to the target molecule in solution. Preferably, this unlabeled antibody is immobilized in some way, such as coupled to an agarose bead, coated to a surface, etc. Next, the "hot" radiolabeled antibody is allowed to interact with the first antibody-target molecule complex. After extensive washing, the direct amount of radioactive antibody bound is measured and the amount of target molecule quantified by comparing it to a reference amount assayed at the same time. This method is similar in principle to the non-radioactive sandwich ELISA method.

References

External links

Radioimmunoassay at the US National Library of Medicine Medical Subject Headings (MeSH)
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/R/Radioimmunoassay.html

UpToDate Contents

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1. 副甲状腺ホルモン測定およびその臨床応用parathyroid hormone assays and their clinical use [show details]
…be reviewed here. PTH physiology, receptor binding, and actions are reviewed separately. Radioimmunoassays for the detection of parathyroid hormone (PTH) are referred to as "first" generation assays; …
2. フルオロキノロン類に対する過敏反応hypersensitivity reactions to fluoroquinolones [show details]
…most convincing study, fluoroquinolone-specific IgE was detected in 30 of 55 patients by radioimmunoassay (RIA), although at very low levels . Inhibition studies were performed to demonstrate that the …
3. 血清および唾液中のコルチゾールの測定measurement of cortisol in serum and saliva [show details]
…reconstituted in assay buffer and assayed by competitive protein-binding assay , radioimmunoassay , or enzyme immunoassay . Radioimmunoassay of unextracted saliva has also been described . With the development of …
4. ランバートイートン筋無力症候群：臨床的特徴および診断lambert eaton myasthenic syndrome clinical features and diagnosis [show details]
…the P/Q-type VGCC are present in approximately 85 to 95 percent of patients with LEMS , and radioimmunoassay for these antibodies is the preferred serologic test. While the anti-P/Q-type VGCC antibody…
5. 重症筋無力症の診断diagnosis of myasthenia gravis [show details]
…percent of those with ocular myasthenia. Binding AChR antibodies are measured by standard radioimmunoassay and are highly specific for myasthenia gravis. There are virtually no false-positive results…

English Journal

Simple and sensitive progesterone detection in human serum using a CdSe/ZnS quantum dot-based direct binding assay.

Oh SD1, Duong HD1, Rhee JI2.
Analytical biochemistry.Anal Biochem.2015 Aug 15;483:54-61. doi: 10.1016/j.ab.2015.05.001. Epub 2015 May 8.
In this study, we developed a CdSe/ZnS quantum dot (QD)-based immunoassay for use in determining the presence of progesterone (P4) in human serum. Hydrophilic QDs were conjugated to anti-progesterone antibody (P4Ab) via ethyl-3-(dimethylaminopropyl)carbodiimide (EDC) and N-hydroxysuccinimide (NHS) a
PMID 25963894

MuSK autoantibodies in myasthenia gravis detected by cell based assay - A multinational study.

Tsonis AI1, Zisimopoulou P2, Lazaridis K3, Tzartos J3, Matsigkou E3, Zouvelou V4, Mantegazza R5, Antozzi C5, Andreetta F5, Evoli A6, Deymeer F7, Saruhan-Direskeneli G7, Durmus H7, Brenner T8, Vaknin A8, Berrih-Aknin S9, Behin A9, Sharshar T10, De Baets M11, Losen M11, Martinez-Martinez P11, Kleopa KA12, Zamba-Papanicolaou E12, Kyriakides T12, Kostera-Pruszczyk A13, Szczudlik P13, Szyluk B13, Lavrnic D14, Basta I14, Peric S14, Tallaksen C15, Maniaol A16, Casasnovas Pons C17, Pitha J18, Jakubíkova M18, Hanisch F19, Tzartos SJ20.
Journal of neuroimmunology.J Neuroimmunol.2015 Jul 15;284:10-7. doi: 10.1016/j.jneuroim.2015.04.015. Epub 2015 Apr 27.
Seronegative myasthenia gravis (MG) presents a serious gap in MG diagnosis and understanding. We applied a cell based assay (CBA) for the detection of muscle specific kinase (MuSK) antibodies undetectable by radioimmunoassay. We tested 633 triple-seronegative MG patients' sera from 13 countries, det
PMID 26025053

Effects of the anti-androgen cyproterone acetate (CPA) on oocyte meiotic maturation in rainbow trout (Oncorhynchus mykiss).

Rime H1, Nguyen T2, Ombredane K2, Fostier A2, Bobe J2.
Aquatic toxicology (Amsterdam, Netherlands).Aquat Toxicol.2015 Jul;164:34-42. doi: 10.1016/j.aquatox.2015.04.009. Epub 2015 Apr 9.
In the present study, we aimed at characterizing the effect of cyproterone acetate (CPA), an anti-androgenic compound, on oocyte meiotic maturation in a freshwater teleost fish species, the rainbow trout (Oncorhynchus mykiss). Fully-grown post-vitellogenic ovarian follicles were incubated in vitro w
PMID 25911576

Japanese Journal

The Reproductive Effects in Rats after Chronic Oral Exposure to Low-dose Depleted Uranium

HAO Yuhui,LI Rong,LENG Yanbine [他]
Journal of radiation research : an official journal of the Japan Radiation Research Society and Japanese Society for Therapeutic Radiology and Oncology 53(3), 377-384, 2012-05
NAID 40019293208

パントテン酸測定法の現状と課題(<特集>ビタミン測定法の現状と課題[IV])

福渡努
ビタミン 85(9), 479-484, 2011-09-25
… Although several methods are available including radioimmunoassay, ELISA, HPLC, GC/MS, LC/MS and optical biosensor-based immunoassay, these methods are restricted to use. … The radioimmunoassay and ELISA lack sensitivity, and need noncommercially available antisera. …
NAID 110008723138

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