Purification and characterization of burst-promoting activity

红细胞生成需要两种不同的生长因子。促红细胞生成素(EP)既能促进晚期红系前体细胞(CFU-E)的生长，又能促进其向原红细胞的成熟，在原红细胞中血红蛋白(Hb)的合成被启动。另一种因子是猝发促进活性(BPA)，作用于早期前体细胞(BFU-E)，负责将这些细胞分化为对EP具有高反应性的CFU-E。本项目的目的是从人的来源中纯化BPA，并探讨BPA和EP两种因素对人外周血单个核细胞在甲基纤维素培养中红系祖细胞集落形成的影响。从再生障碍性贫血患者的尿液中分离到EP，去除EP后的残留物中发现了BPA。BPA的大量纯化得到了完全不含EP的BPA制剂。单独加入EP可形成微红色的突起。BPA的加入不仅增加了猝发次数，而且减少了形成猝发所需的EP量。BPA单独存在于培养物中不允许形成爆发，但确实允许不含Hb的小菌落的生长。将EP添加到这些小集落中会导致红系爆裂的形成。如果在BPA存在的情况下启动培养，则给药可延迟6天而不会减少爆发数；在没有BPA的情况下，如果在培养开始时不提供EP，则BFU-E会迅速丢失。BPA产生的爆发比仅有EP时产生的爆发更大。对爆发物中Hb的微量分析表明，BPA增加了每个爆发物中的Hb量。这一增加不能完全用每个突发细胞数的增加来解释，但部分归因于Hb量的增加。每个细胞。

Two distinct growth factors are needed for erythropoiesis. Erythropoietin (Ep) promotes both the growth of late erythroid precursor cells (CFU-E) and their maturation into proerythroblasts in which hemoglobin (Hb) synthesis is initiated. The other factor, burst-promoting activity (BPA) acts on the early precursor cells (BFU-E) and is responsible for differentiation of these cells into CFU-E with high responsiveness to Ep. This project was aimed at purifying BPA from a human source and exploring the effects of the two factors, BPA and Ep, on erythroid burst-colony formation of human peripheral blood mononuclear cells in methlycellulose cultures. Ep was isolated from the urine of patients with aplastic anemia and BPA was found in the resiue obtained after removal of Ep. Extensive purification of BPA yielded a preparation of BPA completely free from Ep. Reddish bursts were formed with the addition of Ep alone. Addition of BPA not only elevated the number of bursts but also grealty reduced the amount of Ep reqiured for burst formation. The presence of BPA alone in cultures did not permit bursts to form but did permit the growth of small colonies that did not contain Hb. Addition of Ep to these small colonies led to the formation of erythroid bursts. Administration of Ep to the culture could be delayed for 6 days without decreasing the number of bursts if the cultures were initiated in the presence of BPA; in the absence of BPA, BFU-E were repidly lost if Ep was not provided at the start of the culture. BPA produced larger bursts than those formed in the presence of Ep alone. Microassays of Hb in the bursts indicated that BPA increased the amount of Hb per burst. This increase could not be entirely explained by the augumentation in cell number per burst but was partly ascribable to the increased amount of Hb. per cell.