Knutson F, Lööf H, Högman C F
Department of Clinical Immunology and Transfusion Medicine, University Hospital, Uppsala, Sweden.
Transfus Sci. 1999 Dec;21(3):185-91. doi: 10.1016/s0955-3886(99)00091-0.
The bottom-and-top (BAT) procedure separates the buffy coat (BC) from plasma and red blood cells (RBC). The contents of mononuclear cells (MNC) remaining in the RBC are about 1 x 10(6) cells/unit, whereas the granulocytes are removed less effectively, 500-800 x 10(6) or more remaining in the RBC unit. The aim was to improve the separation efficacy by collecting the blood in an hyperosmolar anticoagulant, followed by BAT separation. It was expected that the red cells would shrink, thereby increasing their density, while the granulocytes would not change volume and density.
18 donors were included in the study, 12 in the test group and 6 in the control group. CPD-SAGM bags were used, with a modification of the anticoagulant by removal of 20-ml CPD from all units and addition of 20-ml mannitol (test group) or 20 ml of isotonic saline (control group). The collected blood units were cooled on butanediol plates for 2-4 h, then centrifuged and separated into components. The levels of leukocytes in the whole blood, the BC and the RBC were determined by flow cytometry gated for intact CD45+ cells. A number of other tests were performed during 42-day storage.
The plasma yield was slightly higher in the test group than in the control group (ns). The contents of leukocytes (CD 45+ intact cells) in the RBC units were 32 +/- 20 x 10(6) in the test group and 573 +/- 241 x 10(6) in the control group. The numbers of MNC were 1.2 +/- 0.6 x 10(6) and 2.6 +/- 1.8 x 10(6), respectively. The RBC 2,3-DPG concentration was slightly better maintained in the test group at day 7 of refrigerated storage (p = 0.0027), but most other tested parameters showed no difference during 42-day storage. It was possible to prepare platelet concentrates with good yield using the pooled-BC method.
This study indicates that considerable improvement in the BAT procedure can be obtained if the anticoagulant is made hypertonic by the addition of mannitol. This is achieved without altering the already low levels of MNC and keeping the same quality.
底-顶（BAT）程序可将血沉棕黄层（BC）与血浆及红细胞（RBC）分离。红细胞中残留的单核细胞（MNC）含量约为1×10⁶个细胞/单位，而粒细胞的去除效果较差，红细胞单位中仍残留500 - 800×10⁶个或更多。目的是通过在高渗抗凝剂中采集血液，随后进行BAT分离来提高分离效果。预计红细胞会收缩，从而增加其密度，而粒细胞的体积和密度不会改变。
18名供者纳入研究，试验组12名，对照组6名。使用CPD-SAGM袋，对抗凝剂进行改良，从所有单位中去除20 ml CPD并添加20 ml甘露醇（试验组）或20 ml等渗盐水（对照组）。采集的血液单位在丁二醇板上冷却2 - 4小时，然后离心并分离成各成分。通过针对完整CD45⁺细胞的流式细胞术测定全血、BC和RBC中的白细胞水平。在42天储存期间进行了多项其他检测。
试验组的血浆产量略高于对照组（无显著性差异）。试验组红细胞单位中的白细胞（CD45⁺完整细胞）含量为32±20×10⁶个，对照组为573±241×10⁶个。MNC数量分别为1.2±0.6×10⁶个和2.6±1.8×10⁶个。在冷藏储存第7天时，试验组中红细胞2,3 - DPG浓度的维持情况略好（p = 0.0027），但在42天储存期间，大多数其他检测参数无差异。使用汇集BC法可以制备出产量良好的血小板浓缩物。
本研究表明，如果通过添加甘露醇使抗凝剂变为高渗，则BAT程序可得到显著改善。这在不改变已经很低的MNC水平并保持相同质量的情况下得以实现。
