Contribution of neutrophils in lung defense for infection and in the pathogenesis of lung tissue injury.

我们研究了中性粒细胞在气管内滴注铜绿假单胞菌(P.A.)后对细菌感染的保护作用和对肺损伤的影响。在豚鼠身上。中性粒细胞减少组经环磷酰胺处理后，从支气管肺泡灌洗液(BALF)中回收活菌。对照组和中性粒细胞集落刺激因子(G-CSF)组动物肺内中性粒细胞聚集。中性粒细胞集落形成单位(CFU)为108pA时，死亡率明显高于对照组和中性粒细胞减少组，反映肺重量增加，提示肺损伤严重。我们得出结论，中性粒细胞在低水平细菌挑战时对肺损伤具有保护作用，但在高水平细菌挑战时却加剧了肺损伤并导致死亡。然后，我们研究了G-CSF对单核细胞释放肿瘤坏死因子(TNF)的体外影响。外周血单核细胞和中性粒细胞均取自健康献血者(n=8)。中性粒细胞单独、单核细胞、中性粒细胞加单核细胞与G-CSF共同孵育，研究肿瘤坏死因子的释放。中性粒细胞单独在脂多糖(LPS)刺激后不产生肿瘤坏死因子，与G-CSF治疗无关。加入中性粒细胞后，G-CSF可抑制单核细胞释放肿瘤坏死因子(P&lt；0.01)。单核细胞未观察到内毒素对肿瘤坏死因子释放的抑制作用。单核细胞与G-CSF激活的中性粒细胞培养上清液孵育后，单核细胞释放的肿瘤坏死因子不受抑制。用流式细胞仪检测，G-CSF也能抑制脂多糖刺激的单核细胞内肿瘤坏死因子的产生(p&lt；0.05)。提示G-CSF激活的中性粒细胞可直接抑制脂多糖刺激的单核细胞释放肿瘤坏死因子。

We investigated the roles of neutrophils in mediating both the protective effect against bacterial infection and the effect of lung injury induced after intratracheal instillation of Pseudomonas aeruginosa (P.a.) in guinea pigs. Viable bacteria were recovered from bronchoalveolar lavage fluid (BALF) in the neutropenic group pretreated with cyclophosphamide. Neutrophil recruitment was observed in the lungs of animals in the control group and neutrophilic group preteated with granulocyte colony-stimulating factor (G-CSF). With 10^8 colony forming unit (CFU) P.a., the mortality rate was increased in the neutrophilic group as compared with the control and the neutropenic groups, which was reflected an increased lung weight indicating severe lung injury. We conclude that neutrophils protect against lung injury during low-level bacterial challege, but enhance lung injury and contribute to mortality during high-level bacterial challenge.We then investigated the in vitro effects of G-CSF on tumor necrosis factor (TNF) release from monocytes. Peripheral blood monocytes and neutrophils were obtained from healthy donors (n=8). Neutrophils alone, monocytes alone, and neutrophils plus monocytes were incubated with and without G-CSF and were studies for TNF release. Neutrophils alone did not produce TNF after lipopolysaccharide (LPS) stimulation irrespective of G-CSF treatment. TNF release after LPS from monocytes was suppressed by pretreatment with G-CSF in the presence of Neutrophils (P<0.01). The suppression of TNF release after LPS was not observed in the monocytes alone. TNF release from monocytes after LPS was not inhibited when monocytes were incubated with the supernatant from G-CSF-activated neutrophils. Preteatment with G-CSF also inhibited intracellular TNF production, as measured by flow cytometry, of monocytes stimulated by LPS (p<0.05). These data suggest that neutrophils activated by G-CSF directly suppress TNF release from monocytes stimulated by LPS.