Shi J, Fujieda H, Kokubo Y, Wake K
Department of Anatomy, School of Medicine, Tokyo Medical and Dental University, Japan.
Hepatology. 1996 Nov;24(5):1256-63. doi: 10.1053/jhep.1996.v24.pm0008903407.
The fate of neutrophils in the peripheral circulation is poorly understood. In this study, the role of Kupffer cells in eliminating aged and apoptotic neutrophils was investigated. Liver, spleen, lung, and blood samples from Wistar rats were examined by light and electron microscopy, the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick end labeling (TUNEL) method, and immunohistochemistry after the intravenous injection of OK-432, a streptococcal preparation. Neutrophils were trapped predominantly in the periportal and midzonal regions of hepatic lobules and were in contact with endothelial cells and Kupffer cells, or were surrounded by Kupffer cells. The trapping of neutrophils peaked after 6 hours. Apoptotic neutrophils, with or without buds, were found in the lumen of hepatic sinusoids as early as 6 hours, reached maximal levels after 12 hours, and represented greater than 60% of the total number of neutrophils in the liver. The presence of apoptotic neutrophils was correlated with the degree of neutrophil phagocytosis. Double-staining showed that TUNEL-positive neutrophils were phagocytosed or encircled by ED1- or ED2-positive Kupffer cells. In contrast, apoptosis and phagocytosis of neutrophils were rare in the spleen, lung, and peripheral blood. These results suggested that the appearance of apoptotic neutrophils in the hepatic sinusoids and their rapid clearance by Kupffer cells occurs after the invasion of bacteria (i.e., bacteremia or bacteriotoxemia) or the release of inflammatory mediators into the blood stream. These findings have important implications for the regulation of neutrophil homeostasis, the limitation of inflammation and tissue injury, and provide insight into the physiological removal of circulating, senescent neutrophils.
外周循环中中性粒细胞的命运目前了解甚少。在本研究中，探讨了库普弗细胞在清除衰老和凋亡中性粒细胞中的作用。通过光镜和电镜、末端脱氧核苷酸转移酶介导的脱氧尿苷三磷酸生物素缺口末端标记（TUNEL）法以及免疫组化，对静脉注射链球菌制剂OK-432后的Wistar大鼠的肝脏、脾脏、肺和血液样本进行了检查。中性粒细胞主要被困在肝小叶的门静脉周围和中区区域，与内皮细胞和库普弗细胞接触，或被库普弗细胞包围。中性粒细胞的捕获在6小时后达到峰值。早在6小时就可在肝血窦腔内发现有或无芽的凋亡中性粒细胞，12小时后达到最高水平，占肝脏中中性粒细胞总数的60%以上。凋亡中性粒细胞的存在与中性粒细胞吞噬程度相关。双重染色显示，TUNEL阳性的中性粒细胞被ED1或ED2阳性的库普弗细胞吞噬或包围。相比之下，中性粒细胞的凋亡和吞噬在脾脏、肺和外周血中很少见。这些结果表明，肝血窦中凋亡中性粒细胞的出现及其被库普弗细胞的快速清除发生在细菌入侵（即菌血症或细菌毒素血症）或炎症介质释放到血流之后。这些发现对于中性粒细胞稳态的调节、炎症和组织损伤的限制具有重要意义，并为循环衰老中性粒细胞的生理性清除提供了见解。
