Ong G L, Marria V, Mattes M J
Garden State Cancer Center, Center for Molecular Medicine and Immunology, Newark, NJ 07103.
Cancer Immunol Immunother. 1994 Nov;39(5):325-31. doi: 10.1007/BF01519986.
In order to obtain rapid blood clearance of circulating antibodies (Ab) at a desired time, cross-linking reagents such as second Ab are often employed. Such reagents will generally bind to Ab located at the tumor site as well as free Ab, and we therefore investigated whether the cross-linking of Ab bound to the surface of tumor cells affects the processing of those Ab. Cross-linking was induced in various ways: a polyclonal second Ab [rabbit anti-(mouse IgG)], a monoclonal rat anti-(mouse IgG constant region) Ab, and streptavidin used in conjunction with a biotinylated first Ab. Processing was followed for 3 days, to allow nearly all of the bound Ab to reach its ultimate fate. Results depended strongly on the particular first Ab used. Two basic effects were observed. First, the second Ab efficiently prevented the early dissociation of intact Ab from the cell; once the second Ab bound, there was virtually no dissociation of the primary Ab bound to the cells. For most Ab, where only a small proportion of bound Ab dissociated intact, this effect was relatively small. However, for an unusual Ab, where the majority dissociated intact (L6) the effect of a second Ab in prolonging Ab retention by the cell was dramatic. Second, cross-linking sometimes resulted in markedly accelerated internalization and degradation of the bound Ab, coupled with the release of degradation products into the medium. This process resulted in much shorter retention of the radioisotope by the cell. If a "residualizing" radiolabel was used, 125I-dilactitoltyramine, which is probably trapped within lysosomes after Ab catabolism, the effect of the second Ab in accelerating loss from the cell was largely prevented. We also tested anti-idiotype Ab as cross-linking reagents. In addition to testing anti-idiotype Ab known to react with the cell-bound primary Ab, we also tested anti-idiotype Ab not expected to bind to cell-bound Ab, initially as a negative control. Unexpectedly, all anti-idiotype Ab tested induced rapid release of the primary Ab from the cell. This effect was similar to the effect of a large excess of unlabeled Ab, and we attribute it to the blocking of the free binding site of a "wobbling" Ab, which prevents its rebinding to a second antigen molecule. We conclude that the use of selected anti-idiotype Ab to clear circulating Ab, while not reacting with cell-bound Ab, must be done cautiously.(ABSTRACT TRUNCATED AT 400 WORDS)
为了在期望的时间实现循环抗体（Ab）的快速血液清除，常使用诸如第二抗体等交联试剂。此类试剂通常会与位于肿瘤部位的抗体以及游离抗体结合，因此我们研究了与肿瘤细胞表面结合的抗体的交联是否会影响这些抗体的处理过程。通过多种方式诱导交联：多克隆第二抗体[兔抗（小鼠IgG）]、单克隆大鼠抗（小鼠IgG恒定区）抗体，以及与生物素化的第一抗体联合使用的链霉亲和素。跟踪处理过程3天，以使几乎所有结合的抗体达到其最终归宿。结果在很大程度上取决于所使用的特定第一抗体。观察到两种基本效应。首先，第二抗体有效地阻止了完整抗体从细胞的早期解离；一旦第二抗体结合，与细胞结合的第一抗体几乎没有解离。对于大多数抗体，只有一小部分结合的抗体完整解离，这种效应相对较小。然而，对于一种不寻常的抗体，其中大多数完整解离（L6），第二抗体在延长细胞对抗体的保留方面的效果非常显著。其次，交联有时会导致结合抗体的内化和降解明显加速，同时降解产物释放到培养基中。这个过程导致细胞对放射性同位素的保留时间大大缩短。如果使用“残留型”放射性标记物125I - 二乳糖胺，它可能在抗体分解代谢后被困在溶酶体内，那么第二抗体加速从细胞中损失的作用在很大程度上会被阻止。我们还测试了抗独特型抗体作为交联试剂。除了测试已知与细胞结合的第一抗体反应的抗独特型抗体外，我们还测试了预期不会与细胞结合抗体结合的抗独特型抗体，最初作为阴性对照。出乎意料的是，所有测试的抗独特型抗体都诱导了第一抗体从细胞中的快速释放。这种效应类似于大量未标记抗体的效应，我们将其归因于对“摆动”抗体的游离结合位点的阻断，这阻止了它重新结合到第二个抗原分子上。我们得出结论，使用选定的抗独特型抗体清除循环抗体，同时不与细胞结合抗体反应，必须谨慎进行。（摘要截断于400字）
