Niewiarowski S, Kornecki E, Hershock D, Tuszynski G P, Bennett J S, Soria C, Soria J, Dunn F, Pidard D, Kieffer N
J Lab Clin Med. 1985 Dec;106(6):651-60.
Previous experiments demonstrated that chymotrypsin, but not adenosine diphosphate (ADP), exposed fibrinogen binding sites on platelets from patients with Glanzmann's thrombasthenia. Three of these patients have been reexamined, and previous observations were confirmed. The quantity of iodine 125-labeled glycoprotein IIb (GPIIb) and glycoprotein IIIa (GPIIIa) on the platelets of these patients was considerably less than normal but was detectable by immunoprecipitation, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, and autoradiography. The amount of residual GPIIb and GPIIIa as measured by binding studies with radiolabeled monoclonal antibodies was between 3% and 12% of the normal value. Platelet suspensions from these patients did not aggregate with fibrinogen and did not bind 125I-fibrinogen on stimulation with ADP. However, incubation of these platelets with chymotrypsin or pronase resulted in fibrinogen binding and platelet aggregation. Monoclonal antibodies specific for the GPIIb-GPIIIa complex blocked both the fibrinogen binding and the aggregation of enzyme-treated platelets. The treatment of washed platelets of a fourth thrombasthenic patient with ADP or with chymotrypsin failed to result in fibrinogen binding and aggregation. However, the level of GPIIb and GPIIIa on these platelets as measured by a Western blot technique and by monoclonal antibody binding amounted to less than 0.35% to 0.5% of normal values. In conclusion, fibrinogen binding sites exposed on thrombasthenic platelets by chymotrypsin are derived from GPIIb-GPIIIa molecules. Aggregation of chymotrypsin-treated thrombasthenic platelets by fibrinogen appears to represent a sensitive test for detection of functionally active GPIIb-GPIIIa complex on the platelet surface.
先前的实验表明，胰凝乳蛋白酶可使血小板上的纤维蛋白原结合位点暴露，而二磷酸腺苷（ADP）则不能，这一现象在患有Glanzmann血小板无力症的患者中得到证实。对其中3名患者进行了复查，先前的观察结果得到了确认。这些患者血小板上125碘标记的糖蛋白IIb（GPIIb）和糖蛋白IIIa（GPIIIa）的量明显低于正常水平，但可通过免疫沉淀、十二烷基硫酸钠-聚丙烯酰胺凝胶电泳和放射自显影检测到。通过与放射性标记的单克隆抗体结合研究测得的残余GPIIb和GPIIIa的量为正常值的3%至12%。这些患者的血小板悬液在ADP刺激下不与纤维蛋白原聚集，也不结合125I-纤维蛋白原。然而，将这些血小板与胰凝乳蛋白酶或链霉蛋白酶一起孵育会导致纤维蛋白原结合和血小板聚集。对GPIIb-GPIIIa复合物具有特异性的单克隆抗体可阻断酶处理后血小板的纤维蛋白原结合和聚集。用ADP或胰凝乳蛋白酶处理第四名血小板无力症患者的洗涤血小板未能导致纤维蛋白原结合和聚集。然而，通过蛋白质印迹技术和单克隆抗体结合测定，这些血小板上的GPIIb和GPIIIa水平低于正常值的0.35%至0.5%。总之，胰凝乳蛋白酶使血小板无力症患者血小板上暴露的纤维蛋白原结合位点源自GPIIb-GPIIIa分子。纤维蛋白原使经胰凝乳蛋白酶处理的血小板无力症患者血小板聚集似乎是检测血小板表面功能性活性GPIIb-GPIIIa复合物的灵敏试验。
