Das S, Das B R
J Immunol. 1976 Mar;116(3):761-5.
Double antibody radioimmunoassay (RIA) of carcinoembryonic antigen (CEA) on a series of freshly drawn out concurrent plasma and serum samples of normal human blood donors showed that the serum CEA values were invariably higher than the corresponding plasma CEA values. Extraneous addition of fibrinogen brought down the serum-CEA level to a value comparable to or less than the corresponding plasma value. The effect of certain factors associated with blood clotting, particularly Ca++, fibrinogen, and the fibrinolytic enzyme plasmin, was investigated. Ca++ was shown to play no role whereas the effect of fibrinogen was shown to be indirect in that it served as a specific substrate for plasmin, thereby preventing the plasmin degradation of the primary antibody used in the RIA. The finding stresses the role of enzymes like plasmin in double antibody RIA in general and may explain some of the anomalous results obtained when testing biologic material containing plasmin-like substances.
对一系列从正常献血者新鲜采集的同步血浆和血清样本进行癌胚抗原（CEA）的双抗体放射免疫测定（RIA），结果显示血清CEA值始终高于相应的血浆CEA值。外源添加纤维蛋白原可使血清CEA水平降至与相应血浆值相当或更低的值。研究了与血液凝固相关的某些因素的作用，特别是钙离子（Ca++）、纤维蛋白原和纤维蛋白溶解酶纤溶酶。结果表明Ca++不起作用，而纤维蛋白原的作用是间接的，因为它作为纤溶酶的特异性底物，从而防止了RIA中所用一抗的纤溶酶降解。这一发现强调了纤溶酶等酶在一般双抗体RIA中的作用，并可能解释在检测含有类纤溶酶物质的生物材料时获得的一些异常结果。
