Ichihara K, Yamamoto T, Azukizawa M, Miyai K
Clin Chim Acta. 1979 Oct 15;98(1-2):87-101. doi: 10.1016/0009-8981(79)90169-4.
The kinetics of the antigen-antibody reaction were examined systematically in four kinds of double-antibody radioimmunoassay (RIA). In all the RIAs, the dose-response curves obtained on delayed addition by 24 to 48 h of labeled antigens (curves B), were shifted downwards and to the left of those obtained on simultaneous addition of the reagents (curves A), resulting in improved sensitivity of the assay. On the contrary, the dose-response curves obtained on delayed addition of unlabeled antigens (curves C), were shifted upwards and to the right of curves A, resulting in reduced sensitivity. In human thyrotropin (hTSH) RIA, curves B and C approached curves A very little, even after 168 h of incubation. A similar phenomenon was observed with anti-hTSH antisera from five different sources at two incubation temperatures, and the dilution curves of 125I-labeled hTSH and unlabeled hTSH appeared to be parallel. Therefore, the phenomenon observed with hTSH RIA could not be attributed to the assay conditions or to peculiar properties of the reagents used. In insulin RIA, the reversibilities of the shifts of curves B and C were slight but comparable to those observed in hTSH RIA. In 1-3,5,3'-triiodothyronine RIA, curves B and C gradually approached curves A on prolonged incubation and curves B became nearly identical with curves A after 98 h of incubation. On the other hand, in alpha-fetoprotein (AFP) RIA, curves B and C did not approach curves A, even on prolonged incubation for up to 288 h. The "equilibrium affinity constants" of the antibodies were of the same order of magnitude, thus it is unlikely that differences in the constants can account for the differences in the reversibility of these RIAs. In APF RIA, a significant amount of the antigen-antibody complex was precipitated without second antibody after centrifugation at 3000 X g. These findings suggest that the extent of dissociation of the immune complexes depends on their size, which in turn is related to the molecular weight of the antigen.
在四种双抗体放射免疫分析（RIA）中系统地研究了抗原 - 抗体反应的动力学。在所有的RIA中，标记抗原延迟24至48小时添加时获得的剂量 - 反应曲线（曲线B），相较于试剂同时添加时获得的曲线（曲线A）向下和向左移动，从而提高了分析的灵敏度。相反，未标记抗原延迟添加时获得的剂量 - 反应曲线（曲线C），相较于曲线A向上和向右移动，导致灵敏度降低。在人促甲状腺激素（hTSH）RIA中，即使孵育168小时后，曲线B和曲线C与曲线A的接近程度仍很小。在两个孵育温度下，对来自五个不同来源的抗hTSH抗血清也观察到了类似现象，并且125I标记的hTSH和未标记的hTSH的稀释曲线似乎是平行的。因此，hTSH RIA中观察到的现象不能归因于分析条件或所用试剂的特殊性质。在胰岛素RIA中，曲线B和曲线C的移动可逆性较小，但与hTSH RIA中观察到的相当。在1 - 3,5,3'-三碘甲状腺原氨酸RIA中，孵育时间延长时曲线B和曲线C逐渐接近曲线A，孵育98小时后曲线B与曲线A几乎相同。另一方面，在甲胎蛋白（AFP）RIA中，即使延长孵育至288小时，曲线B和曲线C也未接近曲线A。抗体的“平衡亲和常数”处于相同数量级，因此常数的差异不太可能解释这些RIA可逆性的差异。在AFP RIA中，大量抗原 - 抗体复合物在3000×g离心后无需第二抗体即可沉淀。这些发现表明免疫复合物的解离程度取决于其大小，而这又与抗原的分子量有关。
