Paik C H, Phan L N, Hong J J, Sahami M S, Heald S C, Reba R C, Steigman J, Eckelman W C
Int J Nucl Med Biol. 1985;12(1):3-8. doi: 10.1016/0047-0740(85)90004-x.
Labeling of F(ab')2 with 99mTc was investigated. The best labeling procedure for F(ab')2 was then applied to IgG and Fab. Stannous ion was used as the reducing agent for 99mTcO-4 and free DTPA was used as a competing reagent to prevent colloid formation and loosely bound 99mTc. The competition reactions revealed two 99mTc binding sites for F(ab')2 and IgG. One is a high capacity, low affinity site. This accounts for 76 and 84% of total IgG and F(ab')2 binding sites. The labeling of these sites can be prevented if the antibody is labeled in the presence of free DTPA. The second site is a low capacity, high affinity site. The labeling of these sites cannot be prevented by free DTPA. Fab, unlike IgG and F(ab')2, does not have an appreciable percentage of high affinity sites. The determination of sulfhydryl groups using Ellman's reagent indicates the production of 5.5, 4.2 and 0.9 sulfhydryl groups when IgG, F(ab')2 and Fab were exposed to 56 micrograms/mL SnCl2 X 2H2O. These sulfhydryl groups may be the source of the high affinity binding. Biodistribution in mice for 99mTc labeled F(ab')2 and F(ab')2-DTPA, both prepared in the presence of excess free DTPA, was similar to that of F(ab')2-DTPA-111In.
研究了用99mTc标记F(ab')2的方法。然后将最佳的F(ab')2标记程序应用于IgG和Fab。亚锡离子用作99mTcO-4的还原剂，游离二乙三胺五乙酸（DTPA）用作竞争试剂以防止胶体形成和松散结合的99mTc。竞争反应揭示了F(ab')2和IgG有两个99mTc结合位点。一个是高容量、低亲和力位点。这分别占IgG和F(ab')2总结合位点的76%和84%。如果在游离DTPA存在下标记抗体，这些位点的标记可以被阻止。第二个位点是低容量、高亲和力位点。游离DTPA不能阻止这些位点的标记。与IgG和F(ab')2不同，Fab没有明显比例的高亲和力位点。使用埃尔曼试剂测定巯基表明，当IgG、F(ab')2和Fab暴露于56微克/毫升二水合氯化亚锡（SnCl2·2H2O）时，分别产生5.5、4.2和0.9个巯基。这些巯基可能是高亲和力结合的来源。在过量游离DTPA存在下制备的99mTc标记的F(ab')2和F(ab')2-DTPA在小鼠体内的生物分布与F(ab')2-DTPA-111In相似。
