Marra M N, Wilde C G, Griffith J E, Snable J L, Scott R W
Invitron Corporation, Redwood City, CA 94063.
J Immunol. 1990 Jan 15;144(2):662-6.
Neutrophil granules contain proteins important in host defense against bacterial pathogens. Granule proteins released from activated neutrophils facilitate opsonization, phagocytosis, tissue digestion, and antimicrobial activity. Three similar, if not identical, neutrophil proteins, bactericidal/permeability-increasing protein (BPI), 57,000 m.w. cationic antimicrobial protein, and bactericidal protein have been described that specifically kill gram negative bacteria. Since LPS is a structure common to all gram-negative bacteria, we investigated whether the microbicidal protein BPI affects biologic activity of LPS in vitro. Human neutrophils can be activated both in vitro and in vivo by LPS. Upon stimulation, surface expression of CR1 and CR3 increases markedly. Using flow microfluorimetry, we analyzed surface expression of CR1 and CR3 as a measure of neutrophil stimulation in response to LPS. CR up-regulation on neutrophils was TNF independent, suggesting direct LPS stimulation of neutrophils in this system. Purified BPI completely inhibited CR up-regulation on neutrophils stimulated with both rough and smooth LPS chemotypes at 1.8 to 3.6 nM (100 to 200 ng/ml). By comparison, the polypeptide antibiotic polymyxin B completely inhibited the same dose of LPS at 0.4 nM. The inhibitory activity of BPI appeared to be specific for LPS because neutrophil stimulation by formylated peptide or TNF was unaffected. The specificity of BPI for LPS was further demonstrated by inhibition of LPS activity in the limulus amebocyte lysate assay. Therefore, the role of BPI in infection may not be limited to its microbicidal activity, but it may also regulate the neutrophil response to LPS.
中性粒细胞颗粒含有对宿主抵御细菌病原体至关重要的蛋白质。活化的中性粒细胞释放的颗粒蛋白有助于调理作用、吞噬作用、组织消化和抗菌活性。已描述了三种相似（即便不完全相同）的中性粒细胞蛋白，即杀菌/通透性增加蛋白（BPI）、57,000分子量的阳离子抗菌蛋白和杀菌蛋白，它们能特异性杀死革兰氏阴性菌。由于脂多糖（LPS）是所有革兰氏阴性菌共有的结构，我们研究了杀菌蛋白BPI在体外是否会影响LPS的生物活性。人中性粒细胞在体外和体内均可被LPS激活。受到刺激后，补体受体1（CR1）和补体受体3（CR3）的表面表达会显著增加。我们使用流式微荧光测定法分析CR1和CR3的表面表达，以此作为中性粒细胞对LPS刺激反应的指标。中性粒细胞上CR的上调不依赖肿瘤坏死因子（TNF），表明在该系统中LPS可直接刺激中性粒细胞。纯化的BPI在1.8至3.6 nM（100至200 ng/ml）时完全抑制了粗糙型和平滑型LPS化学型刺激的中性粒细胞上CR的上调。相比之下，多肽抗生素多粘菌素B在0.4 nM时完全抑制相同剂量的LPS。BPI的抑制活性似乎对LPS具有特异性，因为甲酰化肽或TNF对中性粒细胞的刺激未受影响。在鲎试剂检测中LPS活性受到抑制进一步证明了BPI对LPS的特异性。因此，BPI在感染中的作用可能不仅限于其杀菌活性，还可能调节中性粒细胞对LPS的反应。
