Yong K L, Rowles P M, Patterson K G, Linch D C
Department of Haematology, University College and Middlesex School of Medicine, London, UK.
Blood. 1992 Sep 15;80(6):1565-75.
Granulocyte-macrophage colony-stimulating factor (GM-CSF) causes upregulation of neutrophil surface CD11b/CD18 expression, and enhances the adhesion of neutrophils to cultured human endothelial cells in vitro. Systemic administration of GM-CSF results in a rapid, transient decrease in circulating phagocyte numbers. Using a nonhuman primate model (Cynomolgus), we provide histologic evidence that this transient leukopenia is associated with the margination of neutrophils in the pulmonary microcirculation. In four animals receiving 2 to 15 micrograms/kg recombinant human GM-CSF (rhGM-CSF), light microscopic sections of lung contained 36 +/- 8, 17 +/- 7, 21 +/- 6, and 15 +/- 8 (mean +/- SD, n = 20) neutrophils within a graticule grid, as compared with two control animals receiving saline injections whose lung sections contained 2.1 +/- 1.6 and 3.1 +/- 2.1 (mean +/- SD, n = 20) neutrophils within the same grid. Scanning electron microscopy shows activated leukocytes adherent to pulmonary vascular endothelium, but no morphologic evidence of endothelial damage, and no migration of cells into the extravascular space. Margination is associated with an increase in surface expression of CD11b/CD18 on circulating phagocytes, which could contribute to the adhesion to capillary endothelial cells, but CD11b/CD18 levels remain elevated even when demargination is complete. In vitro, monoclonal antibodies (MoAbs) to CD18 and CD11b were able to inhibit neutrophil aggregation and adhesion to endothelium. FMLP-induced neutrophil aggregation was inhibited by 39.8% +/- 11.5% and 44.8% +/- 12.3%, respectively, by MoAbs to CD18 and CD11b (P less than .0005, n = 4 for both); a similar effect was demonstrated on TPA-induced aggregation. MoAb CD18 reduced the adhesion of unstimulated neutrophils to endothelium by 44% (P less than .01, n = 7), and inhibited the amount of GM-CSF-stimulated adhesion by 74% (P less than .001, n = 7), while MoAb to CD11b produced a reduction of unstimulated neutrophil adhesion by 30%, and of GM-CSF-stimulated adhesion by 40% (P less than .01, n = 5, for both). However, when administered in vivo, MoAb CD18 produced only a small, albeit significant, amelioration of GM-CSF-induced margination in vivo, while MoAb CD11b was without effect. These results show that GM-CSF-induced transient leukopenia is associated with enhanced neutrophil adherence to pulmonary vascular endothelium, but suggest that the beta 2 leukocyte integrins CD11/CD18 play only a minor role in this process.
粒细胞-巨噬细胞集落刺激因子（GM-CSF）可使中性粒细胞表面CD11b/CD18表达上调，并增强中性粒细胞在体外与培养的人内皮细胞的黏附。全身性给予GM-CSF会导致循环吞噬细胞数量迅速、短暂减少。使用非人类灵长类动物模型（食蟹猴），我们提供了组织学证据，表明这种短暂性白细胞减少与肺微循环中中性粒细胞的边缘化有关。在4只接受2至15微克/千克重组人GM-CSF（rhGM-CSF）的动物中，肺组织光镜切片在一个网格内含有36±8、17±7、21±6和15±8（平均值±标准差，n = 20）个中性粒细胞，而2只接受盐水注射的对照动物的肺组织切片在同一网格内含有2.1±1.6和3.1±2.1（平均值±标准差，n = 20）个中性粒细胞。扫描电子显微镜显示活化的白细胞黏附于肺血管内皮，但没有内皮损伤的形态学证据，也没有细胞迁移到血管外间隙。边缘化与循环吞噬细胞表面CD11b/CD18表达增加有关，这可能有助于与毛细血管内皮细胞的黏附，但即使边缘化完成后，CD11b/CD18水平仍保持升高。在体外，针对CD18和CD11b的单克隆抗体（MoAbs）能够抑制中性粒细胞聚集和与内皮的黏附。针对CD18和CD11b的MoAbs分别使FMLP诱导的中性粒细胞聚集受到39.8%±11.5%和44.8%±12.3%的抑制（P均小于0.0005，n = 4）；对TPA诱导的聚集也显示出类似效果。MoAb CD18使未刺激的中性粒细胞与内皮的黏附减少44%（P小于0.01，n = 7），并使GM-CSF刺激的黏附量减少74%（P小于0.001，n = 7），而针对CD11b的MoAb使未刺激的中性粒细胞黏附减少30%，使GM-CSF刺激的黏附减少40%（P均小于0.01，n = 5）。然而，在体内给药时，MoAb CD18仅使GM-CSF诱导的体内边缘化有轻微但显著的改善，而MoAb CD11b则无作用。这些结果表明，GM-CSF诱导的短暂性白细胞减少与中性粒细胞对肺血管内皮的黏附增强有关，但提示β2白细胞整合素CD11/CD18在此过程中仅起次要作用。
