Sperandio Markus, Smith Michael L, Forlow S Bradley, Olson Timothy S, Xia Lijun, McEver Rodger P, Ley Klaus
University of Virginia Health System, Cardiovascular Research Center, MR5 Bldg, Rm. 1013, P.O. Box 801 394, Charlottesville, VA 22908-1394, USA.
J Exp Med. 2003 May 19;197(10):1355-63. doi: 10.1084/jem.20021854.
Leukocyte rolling in postcapillary venules of inflamed tissues is reduced in L-selectin-deficient mice and mice treated with L-selectin blocking antibodies, but the glycoprotein ligand for L-selectin in inflamed venules is unknown. Here, we show that L-selectin-dependent rolling after P-selectin blockade is completely absent in P-selectin glycoprotein ligand-1 (PSGL-1)-/- mice or wild-type mice treated with a PSGL-1 blocking monoclonal antibody. Immunohistochemistry and flow cytometry failed to show PSGL-1 expression on resting or inflamed endothelium or on platelets. To investigate whether leukocyte-expressed PSGL-1 is mediating L-selectin-dependent rolling, we reconstituted lethally irradiated wild-type mice with PSGL-1-/- bone marrow cells. These chimeric mice showed no L-selectin-dependent rolling, suggesting that leukocyte-expressed PSGL-1 mediates L-selectin-dependent rolling. Frame-to-frame video analysis of L-selectin-dependent rolling in wild-type mice showed that the majority of observed L-selectin-dependent leukocyte rolling was between free flowing leukocytes and already adherent leukocytes or possibly leukocyte fragments, followed by E-selectin-dependent leukocyte rolling along the endothelium. Leukocyte rolling was significantly slower for leukocyte-endothelial than leukocyte-leukocyte interactions. We conclude that leukocyte-expressed PSGL-1 serves as the main L-selectin ligand in inflamed postcapillary venules. L-selectin binding to PSGL-1 initiates tethering events that enable L-selectin-independent leukocyte-endothelial interactions. These findings provide a molecular mechanism for the inflammatory defects seen in L-selectin-deficient mice.
在L-选择素缺陷小鼠和用L-选择素阻断抗体处理的小鼠中，炎症组织毛细血管后微静脉中的白细胞滚动减少，但炎症微静脉中L-选择素的糖蛋白配体尚不清楚。在此，我们表明，在P-选择素糖蛋白配体-1（PSGL-1）基因敲除小鼠或用PSGL-1阻断单克隆抗体处理的野生型小鼠中，P-选择素阻断后L-选择素依赖性滚动完全缺失。免疫组织化学和流式细胞术未能显示静息或炎症内皮细胞或血小板上有PSGL-1表达。为了研究白细胞表达的PSGL-1是否介导L-选择素依赖性滚动，我们用PSGL-1基因敲除小鼠的骨髓细胞重建了经致死性照射的野生型小鼠。这些嵌合小鼠未显示L-选择素依赖性滚动，表明白细胞表达的PSGL-1介导L-选择素依赖性滚动。对野生型小鼠中L-选择素依赖性滚动的逐帧视频分析显示，观察到的大多数L-选择素依赖性白细胞滚动发生在自由流动的白细胞与已经黏附的白细胞或可能的白细胞碎片之间，随后是E-选择素依赖性白细胞沿内皮滚动。白细胞与内皮细胞之间的滚动明显慢于白细胞与白细胞之间的相互作用。我们得出结论，白细胞表达的PSGL-1是炎症毛细血管后微静脉中主要的L-选择素配体。L-选择素与PSGL-1的结合引发拴系事件，从而实现不依赖L-选择素的白细胞与内皮细胞相互作用。这些发现为L-选择素缺陷小鼠中所见的炎症缺陷提供了分子机制。
