Milne R W, Blanchette L, Théolis R, Weech P K, Marcel Y L
Clinical Research Institute of Montreal, Quebec, Canada.
Mol Immunol. 1987 May;24(5):435-47. doi: 10.1016/0161-5890(87)90017-4.
Monoclonal antibodies (MAbs) have been prepared against apolipoprotein (apo) B which had been delipidated and resolubilized (apo Bsol). The MAbs were classified into nine groups according to their behavior in competitive binding assays and, following SDS electrophoresis and immunoblots, their corresponding epitopes were assigned to apo B48, apo B74, apo B26 and to fragments of LDL apo B (apo BLDL) generated by limited tryptic proteolysis. In addition to their reactivity with soluble apo B all antibodies also reacted with LDL which had been adsorbed to polystyrene. Competitive binding of MAbs to insolubilized antigen also indicated conformational similarities between apo Bsol and apoBLDL. These similarities were, however, less apparent when the respective antigens were in solution. In competitive radioimmunoassays the majority of anti-apo Bsol MAbs reacted better with apo Bsol than with LDL although the opposite was true for one group of MAbs. In immunoprecipitation studies the MAbs which preferentially recognize apo BLDL could precipitate 95% of 125I-LDL whereas the immunoprecipitation with those MAbs which preferentially recognize soluble apo B varied between 0 and 95%. Between 65 and 82% of 125I-apo Bsol was immunoprecipitated under the same conditions. Thus, epitopes defined by MAbs prepared against apo Bsol may be expressed on apo BLDL when it is adsorbed to plastic but not necessarily when it is in solution. For those epitopes preferentially expressed on apo BLDL, reincorporation of soluble apo B into phospholipid-cholesteryl ester microemulsions or phospholipid-cholesterol liposomes increased their immunoreactivity, whereas, the reincorporation of apo B into lipid vesicles resulted in a decreased reactivity with those MAbs which recognized better apo Bsol than apo BLDL. Thus, while the respective conformations of apo Bsol and apo BLDL are only partially similar, they can be reversibly interchanged by delipidation and relipidation.
已制备出针对脱脂并重新溶解的载脂蛋白（apo）B（apo Bsol）的单克隆抗体（MAb）。根据其在竞争性结合试验中的表现，这些单克隆抗体被分为九组，并且在十二烷基硫酸钠电泳和免疫印迹之后，它们相应的表位被定位到apo B48、apo B74、apo B26以及经胰蛋白酶有限水解产生的低密度脂蛋白apo B（apo BLDL）片段上。除了与可溶性apo B发生反应外，所有抗体还与吸附在聚苯乙烯上的低密度脂蛋白发生反应。单克隆抗体与不溶性抗原的竞争性结合也表明apo Bsol和apo BLDL之间存在构象相似性。然而，当各自的抗原处于溶液中时，这些相似性就不那么明显了。在竞争性放射免疫测定中，大多数抗apo Bsol单克隆抗体与apo Bsol的反应比与低密度脂蛋白的反应更好，尽管有一组单克隆抗体的情况相反。在免疫沉淀研究中，优先识别apo BLDL的单克隆抗体能够沉淀95%的125I-低密度脂蛋白，而用那些优先识别可溶性apo B的单克隆抗体进行免疫沉淀的比例在0%至95%之间变化。在相同条件下，65%至82%的125I-apo Bsol被免疫沉淀。因此，针对apo Bsol制备的单克隆抗体所定义的表位在apo BLDL吸附到塑料上时可能会表达，但在其处于溶液中时不一定会表达。对于那些优先在apo BLDL上表达的表位，将可溶性apo B重新掺入磷脂 - 胆固醇酯微乳液或磷脂 - 胆固醇脂质体中会增加它们的免疫反应性，而将apo B重新掺入脂质囊泡中则会导致与那些识别apo Bsol比识别apo BLDL更好的单克隆抗体的反应性降低。因此，虽然apo Bsol和apo BLDL各自的构象只是部分相似，但它们可以通过脱脂和再脂化而可逆地相互转换。
