Maciejko J J, Mao S J
Clin Chem. 1982 Jan;28(1):199-204.
We describe two techniques for radioimmunoassay of apolipoprotein A-I (apoA-I) in human plasma, each involving use of a non-ionic detergent, Tween-20, to expose antigenic sites, and one involving "IgG SORB" (a suspension of killed staphylococci) as a solid-phase separator. Tween-20 (3.75 g/L) decreased nonspecific binding and unmasked the antigenic sites on the apoA-I molecule in plasma to the same extent as did a tedious delipidation procedure, without altering the binding affinity between apoA-I and apoA-I antibodies as determined by Scatchard analysis (Ka congruent to 2.83 X 10(8) L/mol). The widely accepted double-antibody immunoprecipitation technique for separating bound and unbound 125I-labeled apoA-I is time-consuming, owing to extended periods of incubation and centrifugation IgG SORB effectively separates bound from unbound 125I-labeled apoA-I and the reaction is complete within 10 min. On comparing concentrations of apoA-I in human plasma by the conventional second-antibody (y) and solid-phase IgG SORB methods (x), we found results by the two techniques to be reasonably identical (r = 0.98, y = 1.2x -- 0.17). The mean concentrations of apoA-I in plasma from 65 normal and five hyperlipidemic patients were 1.33 (SD 0.32) and 0.78 (SD 0.35) g/L, respectively, and apoA-I and high-density lipoprotein cholesterol were significantly correlated (r = 0.72, p less than 0.001).
我们描述了两种检测人血浆中载脂蛋白A-I（apoA-I）的放射免疫分析技术，每种技术都使用非离子去污剂吐温-20来暴露抗原位点，其中一种技术使用“IgG SORB”（一种灭活葡萄球菌悬液）作为固相分离剂。吐温-20（3.75 g/L）可降低非特异性结合，并使血浆中apoA-I分子上的抗原位点暴露程度与繁琐的脱脂程序相同，同时不改变通过Scatchard分析测定的apoA-I与apoA-I抗体之间的结合亲和力（Ka约为2.83×10⁸ L/mol）。广泛接受的用于分离结合和未结合的¹²⁵I标记apoA-I的双抗体免疫沉淀技术耗时较长，这是由于孵育和离心时间较长。IgG SORB能有效分离结合和未结合的¹²⁵I标记apoA-I，反应在10分钟内即可完成。通过传统的第二抗体法（y）和固相IgG SORB法（x）比较人血浆中apoA-I的浓度时，我们发现两种技术的结果相当一致（r = 0.98，y = 1.2x - 0.17）。65名正常人和5名高脂血症患者血浆中apoA-I的平均浓度分别为1.33（标准差0.32）和0.78（标准差0.35）g/L，且apoA-I与高密度脂蛋白胆固醇显著相关（r = 0.72，p＜0.001）。
