Pardridge W M, Vinters H V, Miller B L, Tourtellotte W W, Eisenberg J B, Yang J
Biochem Biophys Res Commun. 1987 May 29;145(1):241-8. doi: 10.1016/0006-291x(87)91312-x.
A radioimmunoassay (RIA) was developed to detect the 4200 Dalton amyloid (A4) peptide or it's precursor (A4P) in human serum or cerebrospinal fluid (CSF). A synthetic peptide containing the first 28 amino acids of the 43 amino acid A4 peptide was covalently coupled to bovine thyroglobulin and a polyclonal antiserum in rabbits was prepared. This antiserum was specific for vascular amyloid and neuritic plaques in Alzheimer's disease brain as detected by immunoperoxidase. The synthetic peptide, which has a tyrosine at residue 10, was iodinated with chloramine T and [125I]iodine and was purified to homogeneity by C4 reverse phase high performance liquid chromatography (HPLC). Extraction of human serum over a C18 Sep Pak cartridge indicated immunoreactive A4 peptide was not detectable in human serum. Conversely, high molecular weight A4 peptide immunoreactivity was detectable in human serum, at a concentration of 8.9 +/- 1.2 pmol-eq./ml, and in human CSF, at a concentration of 0.25 +/- 0.01 pmol-eq./ml, giving a CSF/serum ratio of 3.2%. The immunoreactivity in human serum was nearly completely removed by affinity deletion of serum immunoglobulin G (IgG), but not by affinity removal of IgA or IgM. Serum immunoreactivity was decreased 90% in hypogammaglobulinemia, and was increased 83% in human cord serum. There was no statistical difference in serum A4 immunoreactivity in Alzheimer's serum or CSF. Serum immunoreactivity in Down's syndrome was increased 50%. These studies indicate the high molecular weight A4P immunoreactivity in human serum or CSF is an IgG. Whether the A4 precursor in Alzheimer's disease is, in fact, an IgG, or whether there is an antibody in human serum and CSF that cross reacts with the A4 precursor cannot be determined until the serum immunoreactivity is purified and structurally characterized.
已开发出一种放射免疫分析法（RIA），用于检测人血清或脑脊液（CSF）中的4200道尔顿淀粉样蛋白（A4）肽或其前体（A4P）。将包含43个氨基酸的A4肽前28个氨基酸的合成肽与牛甲状腺球蛋白共价偶联，并在兔中制备多克隆抗血清。通过免疫过氧化物酶检测，该抗血清对阿尔茨海默病脑中的血管淀粉样蛋白和神经炎性斑块具有特异性。将在第10位残基处含有酪氨酸的合成肽用氯胺T和[125I]碘进行碘化，并通过C4反相高效液相色谱（HPLC）纯化至同质。在C18 Sep Pak柱上对人血清进行提取表明，在人血清中未检测到免疫反应性A4肽。相反，在人血清中可检测到高分子量A4肽免疫反应性，浓度为8.9±1.2 pmol-eq./ml，在人脑脊液中浓度为0.25±0.01 pmol-eq./ml，脑脊液/血清比值为3.2%。人血清中的免疫反应性几乎可通过血清免疫球蛋白G（IgG）的亲和去除而完全消除，但不能通过IgA或IgM的亲和去除而消除。在低丙种球蛋白血症中，血清免疫反应性降低90%，而在人脐带血清中升高83%。阿尔茨海默病患者的血清或脑脊液中A4免疫反应性无统计学差异。唐氏综合征患者的血清免疫反应性升高50%。这些研究表明，人血清或脑脊液中的高分子量A4P免疫反应性是一种IgG。在血清免疫反应性被纯化并进行结构表征之前，无法确定阿尔茨海默病中的A4前体实际上是否为IgG，或者人血清和脑脊液中是否存在与A4前体发生交叉反应的抗体。
