Characterization of functional properties of C4-binding protein by monoclonal antibodies.
Characterization of functional properties of C4-binding protein by monoclonal antibodies.
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通过单克隆抗体表征 C4 结合蛋白的功能特性。
DOI：
10.4049/jimmunol.134.5.3320
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发表时间：
1985
影响因子：
4.4
通讯作者：
N. Tamura
中科院分区：
文献类型：
--
作者：
T. Fujita;T. Kamato;N. Tamura
我们通过将纯化的C4-bp免疫小鼠的脾细胞与小鼠骨髓瘤细胞系P3 U1融合，制备了抗人C4-bp的小鼠单克隆抗体。在与完整C4-bp反应的四种单克隆抗体中，两种特异于48 K片段，一种是C4-bp的胰凝乳蛋白酶切割产物，一种特异于另一个片段（160 K）。第四种单克隆抗体不与任一片段反应。与48 K片段反应的单克隆抗体之一阻断了C4-bp与细胞结合的C4 b的结合。该单克隆抗体（TK 3）还抑制C4-bp的另外两种功能，作为C3 b/C4 b灭活剂（I）的必需辅因子，在液相C4 b的裂解中起作用，并加速C2 a从C4 b，2a复合物中的衰变。其他单克隆抗体对C4-bp的这些活性影响很小或没有影响。此外，我们发现48 K片段失去了与C4 b的结合亲和力。然而，它可以作为I的辅因子和作为衰变加速剂，尽管其活性比完整的C4-bp弱约200倍（以摩尔计）。单克隆抗体TK 3完全抑制48 K片段的这些活性。根据这些发现，我们得出结论，C4-bp的功能活性位点位于48 K片段。C4-bp的辅助因子和衰变加速活性可能是C4-bp与C4 b结合的结果。
We prepared mouse monoclonal antibodies to human C4-binding protein (C4-bp) by fusing spleen cells from mice immunized with purified C4-bp to the mouse myeloma line P3U1. Of four monoclonal antibodies that reacted with intact C4-bp, two were specific for a 48K fragment, one of the chymotryptic cleavage products of C4-bp, and one was specific for another fragment (160K). The fourth monoclonal antibody did not react with either fragment. One of the monoclonals that reacted with the 48K fragment blocked the binding of C4-bp to cell-bound C4b. This monoclonal antibody (TK3) also inhibited two other functions of C4-bp, serving as an essential cofactor for C3b/C4b inactivator (I) in the cleavage of fluid-phase C4b and accelerating the decay of C2a from the C4b,2a complex. The other monoclonals had little or no effect on these activities of C4-bp. In addition, we found that the 48K fragment lost the binding affinity for C4b. However, it can function as a cofactor for I and as a decay-accelerator, although its activities were about 200 times weaker than intact C4-bp on a molar basis. The monoclonal antibody TK3 completely inhibited these activities of the 48K fragment. On the basis of these findings, we conclude that the functionally active site of C4-bp is located on the 48K fragment. Probably, the cofactor and decay-accelerating activities of C4-bp result from the binding of C4-bp to C4b.