Neeson Paul J, Thurlow Peter J, Jamieson Gary P, Bradley Chris
Immunology Unit, Division of Laboratory Medicine, Austin and Repatriation Medical Centre, Melbourne, Victoria, Australia.
Pathology. 2003 Feb;35(1):50-5.
Lymphocytes transiently express an active form of the beta_2 integrin LFA-1 (LFA-1Af) which has conformational changes in extracellular domains enabling higher affinity binding to the ligand ICAM-1. In this study, we investigated the role of lymphocytes bearing LFA-1Af as potential mediators of binding of ICAM-1-positive tumour cells to endothelium.
LFA-1 expression on 51Cr-PBLs was modulated in order to express high affinity LFA-1Af and conjugates were formed with 35S-labelled COLO526. The binding of the conjugates to resting or IL-1beta-stimulated human umbilical vein endothelial cells (HUVECs) was then assessed via a modified radioactive HUVEC binding assay. In addition, the binding of PBL-COLO526 conjugates to HUVECs was demonstrated by confocal microscopy.
The binding of COLO526 to endothelial cells did not change significantly between unstimulated and stimulated HUVECs. In addition, pre-incubating the COLO526 with fresh PBLs did not significantly alter the binding of COLO526 to resting or activated HUVECs; whereas, in the presence of PBLs with LFA-1Af, the COLO526 conjugate binding dramatically increased from basal levels to 41% on resting HUVECs and 81% on stimulated HUVECs. COLO526-PBL(LFA-1Af) conjugate adhesion to stimulated HUVECs was inhibited by blocking antibody to LFA-1 (50%), VLA-4 (32%) or L-selectin (40%). Antibodies to the HUVEC adhesion molecules ICAM-1, VCAM-1 and E-selectin also inhibited COLO526-PBL(LFA-1Af) conjugate binding to activated HUVECs by 79, 60 and 73%, respectively.
PBLs bearing LFA-1Af can enhance COLO526 adhesion to both resting and activated HUVECs. Furthermore, blocking studies demonstrate that a range of pathways are involved in this phenomenon (LFA-1/ICAM-1, VLA4/VCAM-1, L-selectin/E-selectin). These studies have identified a novel alternative pathway for lymphocyte-facilitated tumour cell adhesion to endothelial cells.
淋巴细胞短暂表达β₂整合素LFA-1的活性形式（LFA-1Af），其细胞外结构域发生构象变化，使其与配体ICAM-1的结合亲和力更高。在本研究中，我们调查了携带LFA-1Af的淋巴细胞作为ICAM-1阳性肿瘤细胞与内皮细胞结合的潜在介质的作用。
调节⁵¹Cr-PBLs上LFA-1的表达，以表达高亲和力的LFA-1Af，并与³⁵S标记的COLO526形成缀合物。然后通过改良的放射性人脐静脉内皮细胞（HUVEC）结合试验评估缀合物与静息或IL-1β刺激的HUVEC的结合。此外，通过共聚焦显微镜证实了PBL-COLO526缀合物与HUVEC的结合。
在未刺激和刺激的HUVEC之间，COLO526与内皮细胞的结合没有显著变化。此外，将COLO526与新鲜PBL预孵育不会显著改变COLO526与静息或活化HUVEC的结合；然而，在存在LFA-1Af的PBL的情况下，COLO526缀合物的结合从基础水平显著增加，在静息HUVEC上增加到41%，在刺激的HUVEC上增加到81%。COLO526-PBL（LFA-1Af）缀合物对刺激的HUVEC的粘附被LFA-1阻断抗体（50%）、VLA-4阻断抗体（(32%）或L-选择素阻断抗体（40%）抑制。针对HUVEC粘附分子ICAM-1、VCAM-1和E-选择素的抗体也分别抑制COLO526-PBL（LFA-1Af）缀合物与活化HUVEC的结合79%、60%和73%。
携带LFA-1Af的PBL可以增强COLO526对静息和活化HUVEC的粘附。此外，阻断研究表明，一系列途径参与了这一现象（LFA-1/ICAM-1、VLA4/VCAM-1、L-选择素/E-选择素）。这些研究确定了一种新的淋巴细胞促进肿瘤细胞与内皮细胞粘附的替代途径。
