Burns A R, Doerschuk C M
Pulmonary Research Laboratory, University of British Columbia, St. Paul's Hospital, Vancouver, Canada.
J Immunol. 1994 Oct 1;153(7):3177-88.
In the systemic circulation, the leukocyte adhesion molecule, L-selectin facilitates the initial adhesion of the neutrophil to the inflamed endothelium, whereas CD11/CD18 is essential to transendothelial migration. Previous work from our laboratory showed that neutrophil emigration in the lung occurs through either a CD18-independent or CD18-dependent mechanism, depending on the inflammatory stimulus. This study quantitated and compared the surface expression of L-selectin and CD18 on neutrophils in the lungs of rabbits during emigration toward Streptococcus pneumoniae (a CD18-independent stimulus) and Escherichia coli endotoxin (a CD18-dependent stimulus). Ultrathin frozen lung tissue sections were immunogold labeled for 1-selectin and CD18, and gold particles were quantitated on intravascular, interstitial, and airspace neutrophils by transmission electron microscopy. The results show that CD18-independent neutrophil emigration was associated with L-selectin down-modulation (78%) and CD18 up-modulation (260%) on intravascular neutrophils, before emigration. A similar alteration in the expression of L-selectin and CD18 was observed during CD18-dependent neutrophil emigration, but only on neutrophils that emigrated into the interstitium and airspace. In emigration induced by either stimulus, alterations in L-selectin and CD18 expression were restricted to the inflammatory focus and emigrated airspace neutrophils consistently expressed greater levels of CD18 than intravascular and interstitial neutrophils. We conclude that before emigration, L-selectin and CD18 expression on intravascular neutrophils is altered only during CD18-independent emigration and only on those neutrophils within the inflammatory focus. The increased CD18 expression on airspace neutrophils may facilitate bacterial phagocytosis.
在体循环中，白细胞粘附分子L-选择素促进中性粒细胞与炎症内皮细胞的初始粘附，而CD11/CD18对于跨内皮迁移至关重要。我们实验室之前的研究表明，肺内中性粒细胞的渗出通过CD18非依赖性或CD18依赖性机制发生，具体取决于炎症刺激因素。本研究定量并比较了兔肺内中性粒细胞在向肺炎链球菌（一种CD18非依赖性刺激物）和大肠杆菌内毒素（一种CD18依赖性刺激物）迁移过程中L-选择素和CD18的表面表达。超薄冷冻肺组织切片用免疫金标记L-选择素和CD18，通过透射电子显微镜对血管内、间质和肺泡腔中性粒细胞上的金颗粒进行定量。结果显示，在渗出前，CD18非依赖性中性粒细胞渗出与血管内中性粒细胞上L-选择素下调（78%）和CD18上调（260%）相关。在CD18依赖性中性粒细胞渗出过程中也观察到L-选择素和CD18表达的类似变化，但仅发生在迁移到间质和肺泡腔的中性粒细胞上。在任何一种刺激诱导的渗出过程中，L-选择素和CD18表达的变化都局限于炎症灶，并且迁移到肺泡腔的中性粒细胞始终比血管内和间质中性粒细胞表达更高水平的CD18。我们得出结论，在渗出前，血管内中性粒细胞上L-选择素和CD18的表达仅在CD18非依赖性渗出过程中且仅在炎症灶内的那些中性粒细胞上发生改变。肺泡腔中性粒细胞上CD18表达的增加可能有助于细菌吞噬作用。
