Lynam E B, Rogelj S, Edwards B S, Sklar L A
Department of Pathology, University of New Mexico School of Medicine, Albuquerque 87131, USA.
J Leukoc Biol. 1996 Sep;60(3):356-64. doi: 10.1002/jlb.60.3.356.
MnCl2 and dithiothreitol (DTT) enhance the adhesive functions of beta 2 -integrins. We have used these agents and flow cytometry to distinguish the contributions of beta 2-integrins and L-selectin to neutrophil aggregation. Although neither compound induced aggregation, they prolonged N-formyl-methionyl-leucyl-phenylalanine-induced aggregation and produced larger aggregates. Because activated polymorphonuclear granulocytes (PMN) shed L-selectin in the presence of MnCl2, but not DTT, we could evaluate the role of L-selectin in the early and late stages of aggregation. Blocking L-selectin sites with DREG200 Fab and/or beta 2-integrin sites with IB4 Fab indicated that aggregation under all conditions remained beta 2-integrin- and L-selectin-dependent. Disaggregation was integrin-dependent whether L-selectin was present or shed. The disaggregation kinetics suggested that integrin bonds turned over at a slower rate in MnCl2-treated cells. Enhanced aggregation due to DTT and MnCl2 required sustained energy output, suggesting intracellular rather than strictly conformational control. These results provide evidence that PMN aggregation, like leukocyte-endothelial cell adhesion, utilizes L-selectin to form intercellular contacts that are maintained through activated integrins.
氯化锰（MnCl₂）和二硫苏糖醇（DTT）可增强β₂整合素的黏附功能。我们使用这些试剂和流式细胞术来区分β₂整合素和L-选择素对中性粒细胞聚集的作用。尽管这两种化合物都不会诱导聚集，但它们会延长N-甲酰甲硫氨酰亮氨酰苯丙氨酸诱导的聚集，并产生更大的聚集体。由于活化的多形核粒细胞（PMN）在MnCl₂存在下会脱落L-选择素，但在DTT存在下不会，因此我们可以评估L-选择素在聚集早期和晚期的作用。用DREG200 Fab封闭L-选择素位点和/或用IB4 Fab封闭β₂整合素位点表明，在所有条件下的聚集仍然依赖于β₂整合素和L-选择素。无论L-选择素是否存在或脱落，解聚都依赖于整合素。解聚动力学表明，在MnCl₂处理的细胞中，整合素键的转换速率较慢。DTT和MnCl₂导致的聚集增强需要持续的能量输出，这表明是细胞内控制而非严格的构象控制。这些结果提供了证据，表明PMN聚集与白细胞-内皮细胞黏附一样，利用L-选择素形成通过活化整合素维持的细胞间接触。
