Camato R, Marcel Y L, Milne R W, Lussier-Cacan S, Weech P K
Laboratory of Lipoprotein Metabolism, Institut de Recherches Cliniques de Montréal, Québec, Canada.
J Lipid Res. 1989 Jun;30(6):865-75.
Based on our previous observation that monoclonal antibody anti-apoD-4E11 reacted with several HDL proteins we studied them further with three questions in mind: i) is there common protein polymorphism in healthy individuals? ii) how many proteins are present and what are their characteristics? iii) are they all apolipoproteins and do they have the same lipoprotein distribution as apoD? Isolated, delipidated apoD was used as a standard for radioimmunometric assay of plasma with antibody 4E11. The antigen varied from 3 to 11 mumol-equivalents of apoD per liter of plasma (equivalent to 5-20 mg apoD/dl plasma) with means of 6.1 and 6.8 mumol/l in men and women, respectively. Two-dimensional electrophoresis of plasma found up to eight 4E11-antigenic-proteins of different Mr, each heterogeneous in pI. All plasmas tested contained apoD and an Mr 38,000 antigen, the latter being the most immunoreactive. Six proteins of Mr 70,000-94,000 were found, but the number varied between subjects. Eighty nine percent of the plasma antigen was associated with lipoproteins: 83% with HDL and VHDL, 5% with LDL and VLDL. Lipoproteins of all sizes, separated by polyacrylamide gradient gel electrophoresis, contained the antigen. ApoD was almost the only 4E11-antigen in LDL, and was in two states: the one free, the other an apoD-apoB mixed disulfide complex. The apparent proportions of higher Mr antigens increased with increasing lipoprotein density, and the proportion of apoD decreased reciprocally. None of these 4E11-antigenic-proteins cross-reacted with antiserum to retinol-binding protein.
基于我们之前的观察，即单克隆抗体抗载脂蛋白D-4E11可与多种高密度脂蛋白（HDL）蛋白发生反应，我们带着以下三个问题对它们进行了进一步研究：i）健康个体中是否存在常见的蛋白质多态性？ii）存在多少种蛋白质，它们的特征是什么？iii）它们都是载脂蛋白吗，它们与载脂蛋白D具有相同的脂蛋白分布吗？分离的、脱脂的载脂蛋白D用作使用抗体4E11对血浆进行放射免疫测定的标准品。每升血浆中抗原的量相当于3至11微摩尔当量的载脂蛋白D（相当于5 - 20毫克载脂蛋白D/分升血浆），男性和女性的平均值分别为6.1和6.8微摩尔/升。血浆的二维电泳发现多达八种不同相对分子质量（Mr）的4E11抗原性蛋白，每种蛋白的等电点（pI）都不均一。所有检测的血浆都含有载脂蛋白D和一种相对分子质量为38,000的抗原，后者是免疫反应性最强的。发现了六种相对分子质量为70,000 - 94,000的蛋白质，但不同个体之间数量有所不同。89%的血浆抗原与脂蛋白相关：83%与HDL和极高密度脂蛋白（VHDL）相关，5%与低密度脂蛋白（LDL）和极低密度脂蛋白（VLDL）相关。通过聚丙烯酰胺梯度凝胶电泳分离的各种大小的脂蛋白都含有该抗原。载脂蛋白D几乎是LDL中唯一的4E11抗原，并且存在两种状态：一种是游离的，另一种是载脂蛋白D - 载脂蛋白B混合二硫键复合物。较高相对分子质量抗原的表观比例随着脂蛋白密度的增加而增加，而载脂蛋白D的比例则呈反比下降。这些4E11抗原性蛋白中没有一种与抗视黄醇结合蛋白抗血清发生交叉反应。
