Lian E C, Mui P T, Siddiqui F A, Chiu A Y, Chiu L L
J Clin Invest. 1984 Feb;73(2):548-55. doi: 10.1172/JCI111242.
Plasma from patients with thrombotic thrombocytopenic purpura (TTP) caused the aggregation of autologous and homologous platelets, and effect which was inhibited by normal plasma. IgG purified from seven normal adults at a concentration of 0.7 mg/ml completely inhibited the platelet aggregation induced by plasma obtained from two TTP patients with active disease. The inhibition of platelet aggregation by human adult IgG was concentration dependent, and the inhibitory activity of human IgG was neutralized by rabbit antihuman IgG. Fab fragments inhibited the TTP plasma-induced platelet aggregation as well as intact IgG, whereas Fc fragments had no effect. Platelet aggregation caused by ADP, collagen, epinephrine, or thrombin was not affected by purified human IgG. The prior incubation of IgG with TTP plasma caused a significantly greater reduction of platelet aggregation by TTP plasma than that of IgG and platelet suspension, suggesting that the IgG inhibits TTP plasma-induced platelet aggregation through direct interaction with platelet aggregating factor in TTP plasma. IgG obtained initially from five infants and young children under the age of 4 yr did not possess any inhibitory activity. When one of the children reached 3 yr of age, his IgG inhibited the aggregation induced by one TTP plasma, but not that caused by another plasma. The IgG procured from the same boy at 4 yr of age inhibited the aggregation induced by both TTP plasmas. The IgG purified from the TTP plasma during active disease failed to inhibit the aggregation caused by the same plasma. After recovery, however, the IgG effectively inhibited aggregation. These observations suggest that platelet-aggregating factors present in the TTP plasma are heterogeneous in nature and that the IgG present in the normal adult plasma, which inhibits the TTP plasma-induced platelet aggregation, may be partially responsible for the success of plasma infusion therapy in TTP.
血栓性血小板减少性紫癜（TTP）患者的血浆可导致自体和同源血小板聚集，而这种效应可被正常血浆抑制。从7名正常成年人中纯化得到的浓度为0.7mg/ml的IgG可完全抑制两名处于疾病活动期的TTP患者血浆诱导的血小板聚集。成人IgG对血小板聚集的抑制作用呈浓度依赖性，且人IgG的抑制活性可被兔抗人IgG中和。Fab片段与完整的IgG一样能抑制TTP血浆诱导的血小板聚集，而Fc片段则无此作用。纯化的人IgG对ADP、胶原、肾上腺素或凝血酶诱导的血小板聚集无影响。IgG与TTP血浆预先孵育后，TTP血浆诱导的血小板聚集的减少程度明显大于IgG与血小板悬液预先孵育的情况，这表明IgG通过与TTP血浆中的血小板聚集因子直接相互作用来抑制TTP血浆诱导的血小板聚集。最初从5名4岁以下婴幼儿获得的IgG不具有任何抑制活性。当其中一名儿童3岁时，其IgG可抑制一种TTP血浆诱导的聚集，但不能抑制另一种血浆诱导的聚集。该男孩4岁时获得的IgG可抑制两种TTP血浆诱导的聚集。在疾病活动期从TTP血浆中纯化得到的IgG不能抑制同一血浆诱导的聚集。然而，恢复后，该IgG可有效抑制聚集。这些观察结果表明，TTP血浆中存在的血小板聚集因子本质上是异质性的，正常成人血浆中存在的可抑制TTP血浆诱导的血小板聚集的IgG可能是TTP血浆输注治疗成功的部分原因。
