Stone P C, Stuart J, Nash G B
Department of Physiology, Medical School, University of Birmingham, United Kingdom.
Am J Hematol. 1996 Jul;52(3):135-43. doi: 10.1002/(SICI)1096-8652(199607)52:3<135::AID-AJH2>3.0.CO;2-U.
Abnormal adhesion of sickle cells to vascular endothelium may be a factor in the initiation of painful vaso-occlusive crisis. The sickle cell population contains an unusually large number of less dense reticulocytes that are known to be more adhesive than mature red cells, but there is contradictory evidence regarding the adhesiveness of dense sickle cells. We used a flow-based assay of adhesion to cultured human umbilical vein endothelial cells to test the properties of density fractions of sickle cells, prepared either by density gradient or by centrifugation of packed cells. We also examined the effects of incubating sickle cells with or without cyclical deoxygenation on their adhesion. After fractionation on a Percoll-isopaque gradient, the less dense 10% (reticulocyte-rich) cells and the most dense 10% cells adhered in greater number than the remainder (by about twofold). However, after centrifugation of packed cells, the less dense 10% were again more adhesive than the "middle" cells, but the most dense were not. Exposing sickle cells to constituents of the gradient had no consistent effect on adhesion, while centrifugal packing induced a degree of hemolysis, and tended to reduce adhesiveness of the dense fraction previously obtained from a gradient. Incubation in air at 37 degrees C for 15 hr reduced the number of reticulocytes and the adhesiveness of less dense sickle cells compared to those held at 4 degrees C. On the other hand, incubation at 37 degrees C for 15 hr with cyclical deoxygenation caused formation of dense cells and increased adhesiveness compared to incubation without cyclical deoxygenation. We conclude that young, less dense sickle cells are unusually adhesive, but that this adhesiveness is reduced during maturation. However, repeated sickling in vivo causes formation of an abnormally dense subpopulation of cells which either redevelop an increased tendency to adhere to endothelial cells or preserve their initial adhesiveness. Both adhesive cell populations may be implicated in promoting vascular obstruction.
镰状细胞与血管内皮的异常黏附可能是引发疼痛性血管闭塞危象的一个因素。镰状细胞群体中含有异常大量密度较低的网织红细胞，已知这些网织红细胞比成熟红细胞更具黏附性，但关于高密度镰状细胞的黏附性存在相互矛盾的证据。我们使用一种基于流动的方法来检测镰状细胞与培养的人脐静脉内皮细胞的黏附特性，这些镰状细胞的密度组分是通过密度梯度法或对压实细胞进行离心制备的。我们还研究了镰状细胞在有或无周期性脱氧情况下孵育对其黏附性的影响。在Percoll - 不透射线梯度上进行分级分离后，密度较低的10%（富含网织红细胞）细胞和密度最高的10%细胞比其余细胞黏附的数量更多（约为两倍）。然而，对压实细胞进行离心后，密度较低的10%细胞再次比“中间”细胞更具黏附性，但密度最高的细胞并非如此。将镰状细胞暴露于梯度成分中对黏附性没有一致的影响，而离心压实会导致一定程度的溶血，并倾向于降低先前从梯度中获得的高密度组分的黏附性。与在4℃保存的细胞相比，在37℃空气中孵育15小时会减少网织红细胞的数量以及密度较低的镰状细胞的黏附性。另一方面，与无周期性脱氧的孵育相比，在37℃进行15小时的周期性脱氧孵育会导致高密度细胞的形成并增加黏附性。我们得出结论，年轻的、密度较低的镰状细胞具有异常的黏附性，但这种黏附性在成熟过程中会降低。然而，体内反复的镰变会导致形成异常高密度的细胞亚群，这些细胞要么重新发展出增加的黏附于内皮细胞的倾向，要么保持其初始黏附性。这两种具有黏附性的细胞群体都可能与促进血管阻塞有关。
