Ong G L, Shah P B, Mattes M J
Center for Molecular Medicine and Immunology, Newark, NJ 07103, USA.
Immunol Invest. 1996 May;25(3):215-29. doi: 10.3109/08820139609059304.
These experiments were performed to determine why rabbit complement lyses tumor cells very efficiently, while not having particularly strong activity in hemolytic assays or in any other complement assay. The target cells used were human tumor cells coated with three different mouse IgG(2a) monoclonal antibodies, and complement from 5 mammalian species were tested. In antibody titration experiments, rabbit complement was found to lyse target cells at a relatively low antibody concentration, insufficient to allow lysis by complement of other species. Since this result was still observed after absorption of rabbit serum with target cells, the potency of rabbit complement cannot be attributed to the presence of natural antibodies. We then assayed C3 deposition on target cells, using two types of (125)I-labeled anti-C3 Abs to measure C3 deposition: goat antibodies specific for C3 of the human, guinea pig, rabbit, rat or mouse, and chicken antibodies to human C3 which cross-react with C3 of other mammals. Unexpectedly, complement of the human, rat, guinea pig, and BUB mouse deposited large amounts of C3 on the surface of target cells, while rabbit complement deposited 100-1,000 fold less. We discuss the possible reasons that C3 deposition does not correlate with cytotoxicity, and may indeed be inversely related. These data indicate that there is a fundamental difference in the complement cascade between rabbits and the other species tested. The potent lytic activity of rabbit complement is likely to be related to this difference, although the mechanism is not yet understood.
进行这些实验是为了确定为什么兔补体能非常有效地裂解肿瘤细胞，而在溶血试验或任何其他补体试验中却没有特别强的活性。所用的靶细胞是包被有三种不同小鼠IgG(2a)单克隆抗体的人肿瘤细胞，并测试了来自5种哺乳动物的补体。在抗体滴定实验中，发现兔补体在相对较低的抗体浓度下就能裂解靶细胞，而该浓度不足以使其他物种的补体发生裂解。由于在用靶细胞吸收兔血清后仍观察到这一结果，兔补体的效力不能归因于天然抗体的存在。然后，我们使用两种类型的(125)I标记抗C3抗体来测定C3在靶细胞上的沉积：对人、豚鼠、兔、大鼠或小鼠的C3具有特异性的山羊抗体，以及与人C3交叉反应的其他哺乳动物C3的鸡抗人C3抗体。出乎意料的是，人、大鼠、豚鼠和BUB小鼠的补体在靶细胞表面沉积了大量的C3，而兔补体的沉积量则少100 - 1000倍。我们讨论了C3沉积与细胞毒性不相关甚至可能呈负相关的可能原因。这些数据表明，兔与其他受试物种之间的补体级联存在根本差异。兔补体的强大裂解活性可能与此差异有关，尽管其机制尚不清楚。
