Xu Yuanyuan, Yamada Toshiyuki, Satoh Takahiko, Okuda Yasuaki
Department of Clinical Pathology, Juntendo University School of Medicine, Tokyo, Japan.
Clin Chem Lab Med. 2006;44(1):59-63. doi: 10.1515/CCLM.2006.012.
Serum amyloid A (SAA), a plasma precursor of reactive amyloid deposits, is a multigene product. SAA1 and SAA2, with primary structures that are 93% identical (98 of 104 amino acids), behave as acute phase proteins, as demonstrated by their increasing levels in plasma. Heretofore, it has been understood that SAA1 predominates and functions as an isotype in plasma. However, accurate measurements differentiating the two isotypes have not been reported. In this study, using monoclonal antibodies specific for SAA1, we developed an enzyme-linked immunosorbent assay (ELISA) for SAA1. The levels and ratios of SAA1 in total SAA (TSAA) were investigated in healthy subjects and patients with rheumatoid arthritis (RA). The SAA1/TSAA ratio was 74 +/- 12% and 77 +/- 12% in healthy subjects and RA patients, respectively. In RA patients, the ratios were not influenced by SAA1 genotype, which has been proposed to affect plasma SAA values. The kinetics of SAA1 in inflamed patients undergoing hemodialysis was found to be parallel with total SAA and C-reactive protein. Finally, this study confirmed that SAA1 is a major isotype of acute phase SAA and may determine total SAA values. This specific assay could be used in the evaluation of SAA behavior in several clinical conditions.
血清淀粉样蛋白A（SAA）是反应性淀粉样沉积物的血浆前体，是一种多基因产物。SAA1和SAA2的一级结构有93%相同（104个氨基酸中有98个相同），表现为急性期蛋白，血浆中其水平升高即证明了这一点。在此之前，人们认为SAA1在血浆中占主导并作为一种同种型发挥作用。然而，尚未有区分这两种同种型的准确测量方法的报道。在本研究中，我们使用针对SAA1的单克隆抗体，开发了一种用于检测SAA1的酶联免疫吸附测定（ELISA）法。我们研究了健康受试者和类风湿性关节炎（RA）患者中SAA1在总SAA（TSAA）中的水平及比例。健康受试者和RA患者的SAA1/TSAA比例分别为74±12%和77±12%。在RA患者中，该比例不受已提出会影响血浆SAA值的SAA1基因型的影响。我们发现，正在接受血液透析的炎症患者体内SAA1的动力学与总SAA和C反应蛋白的动力学平行。最后，本研究证实SAA1是急性期SAA的主要同种型，可能决定总SAA值。这种特异性检测方法可用于评估多种临床情况下SAA的行为。
