Radioiodination antibody

Boerman, O. C., Sharkey, R. M., Wong, G. Y., Blumenthal, R. D., Aninipot, R. L., and Goldenberg, D. M. (1992) Influence of antibody protein dose on therapeutic efficacy of radioiodinated antibodies in nude mice bearing GW-39 human tumor. Cancer Immunol. Immunother. 35,127-134. 

Zalutsky M R, Xu F J, Yu Y, et al. (1999). Radioiodinated antibody targeting of the HER-2/neu oncoprotein Effects of labeling method on cellular processing and tissue distribution. Nucl. Med. Biol. 26 781-790. 

When stored for an appreciable length of time radioiodinated antibodies imdergo radiolysis leading to a loss in purity and immimoreactivity. The rate of radiolysis can be reduced by the addition of carrier proteins or antioxidants such as ascorbic add which scavenge the free radicals responsible (9). A concentration of 0.1-1% albumin or 0.5% ascorbic add is commonly used and... 

Although radioiodinated antibodies have acceptable stability for in vitro applications, their in vivo stability is less ideal These tracers can act as substrates for the iodotransferase enzymes which are normally responsible for metabo lism of the thyroid hormones thyroxine and tri-iodothyronine which bear structural similarities. Although not present in the vascular circulation, these enzymes are widely distributed in many tissues and their action results in the intracellular release of the radionuclide which then either diffuses or is actively transported out of the cell and subsequently excreted in the urine. In order to try and increase the in vivo stability of antibodies labelled with radioiodine, alternative synthetic strategies have been pursued which result in molecules which are not substrates for the iodotransferases (11. 12). AU of these techniques are more complicated than the electrophilic substitution methods described above and require some synthetic chemistry in order to prepare the precursors which are not commercially available. 

Tor many radiotracers the issue of specific activity is important, but this is normally not the case with radioiodinated antibodies as most in vitro applications can be performed with preparations having low specific activities in the range of 40-400 MBq (1-10 mCi)/mg. This is equivalent to a substitution ratio of 0.1-1 atoms of iodine per antibody molecule and, in most instances will have little or no effect on antibody function. Although it may be possible to increase this specific activity by a factor of ten or more, the greater the substitution ratio, the greater the likelihood of a significant loss in immunoreactivity. 

Reagent options and protocols for the radioiodination of antibodies and other molecules may be found in Chapter 12. 

Wilbur, S.D., Pathare, P.M., Hamlin, D.K., Buhler, K.R., and Vessella, R.L. (1998) Biotin reagents for antibody pretargeting. 3. Synthesis, radioiodination, and evaluation of biotinylated starburst dendrim-ers. Bioconjugate Chem. 9, 813-825. 

Burnette WN. 1981. Western blotting electrophoretic transfer of proteins from sodium dodecyl sulfate-poly-acrylamide gels to unmodified nitrocellulose and radio-graphic detection with antibody and radioiodinated protein A. Anal Biochem 112 195-203. 

Hadley, S.W, and D.S. Wilbur, Evaluation of iodovinyl antibody conjugates comparison with a p-iodobenzoyl conjugate and direct radioiodination. Bioconjug Chem, 1990. 1(2) 154-61. 

In most patients with hyperthyroidism, T3, T4, FT4, and FT3 are elevated and TSH is suppressed (Table 38-2). Radioiodine uptake is usually markedly elevated as well. Antithyroglobulin, thyroid peroxidase, and TSH-R Ab [stim] antibodies are usually present. 

Vaidyanathan, G. and Zalutsky, M R. (1990) Radioiodination of antibodies via N-succimmidyl 2,4-dimethoxy-3-(trialkylstannyl)benzoates. Bioconjugate Chem. 1, 387-393... 

The TRH radio-immunoassay was developed as a double antibody assay, with modifications mainly depending on the antiserum used, and on the conditions of incubation. Addition of an enzyme inhibitor to the assay tubes is essential to avoid degradation of TRH in samples and of radioiodinated TRH. 

W. M. Hunter, The Preparation of Radioiodinated Proteins of High Activity, Their Reaction With Antibody in Vitro the Radioimmunoassay, in Handbook ofExperimen -tal Immunology (D. M. Weir, Ed.), F. A. Davis, Philadelphia, 1967. 

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