Schnur R A, Newman S L
Department of Internal Medicine, University of Cincinnati College of Medicine, OH 45267.
J Immunol. 1990 Jun 15;144(12):4765-72.
Human neutrophils (PMN) have received little attention as to the role they play in host defense against Histoplasma capsulatum (Hc). We have characterized the binding and phagocytosis of Hc yeasts by human PMN and quantified the PMN respiratory burst in response to this organism. mAb specific for CD11a, CD11b, and CD11c all partially blocked the attachment of unopsonized yeasts to PMN; a mAb to CD18 inhibited attachment by greater than 90%. Thus, human PMN recognize and bind Hc yeasts via CD18 adhesion receptors as has been found for human cultured macrophages and alveolar macrophages. Unopsonized yeasts were phagocytosed by PMN, but phagocytosis was increased markedly by heat-labile and heat-stable serum opsonins. These opsonins promoted enhanced phagocytosis of yeasts by increasing the attachment of Hc yeasts to the PMN membrane. Phagocytosis of viable or heat-killed Hc yeasts by PMN did not induce the secretion of superoxide anion (O2-) as quantified by the reduction of cytochrome c. O2- was not detected when yeasts were opsonized in normal serum or immune serum, or at a ratio of yeasts to PMN of up to a 100:1. However, phagocytosis of opsonized yeasts by PMN did not prevent them from subsequently releasing O2- after further incubation with opsonized zymosan or PMA. Opsonized Hc yeasts clearly stimulated the PMN respiratory burst as quantified by intracellular reduction of nitroblue tetrazolium, reduction of cytochrome c in the presence of cytochalasin D, oxygen consumption, luminol-enhanced and nonenhanced chemiluminescence, and H2O2 production. These data suggest that phagocytosis of Hc yeasts by PMN is associated with intracellular entrapment of O2- that is not detectable by reduction of extracellular cytochrome c.
人类中性粒细胞（PMN）在宿主抵御荚膜组织胞浆菌（Hc）的防御机制中所起的作用鲜受关注。我们已对人类PMN与Hc酵母的结合及吞噬作用进行了表征，并对PMN针对该病原体的呼吸爆发进行了定量分析。针对CD11a、CD11b和CD11c的单克隆抗体（mAb）均部分阻断了未调理酵母与PMN的附着；一种针对CD18的mAb抑制附着的效果超过90%。因此，人类PMN通过CD18黏附受体识别并结合Hc酵母，这与人类培养巨噬细胞和肺泡巨噬细胞的情况相同。未调理的酵母被PMN吞噬，但热不稳定和热稳定的血清调理素可显著增强吞噬作用。这些调理素通过增加Hc酵母与PMN膜的附着，促进了酵母的吞噬作用增强。PMN对活的或热杀死的Hc酵母的吞噬作用，并未如通过细胞色素c还原所定量的那样诱导超氧阴离子（O2-）的分泌。当酵母在正常血清或免疫血清中被调理，或酵母与PMN的比例高达100:1时，未检测到O2-。然而，PMN对调理酵母的吞噬作用并不妨碍它们在随后与调理酵母聚糖或佛波酯进一步孵育后释放O2-。如通过硝基蓝四氮唑的细胞内还原、在细胞松弛素D存在下细胞色素c的还原、氧气消耗、鲁米诺增强和非增强化学发光以及H2O2产生所定量的那样，调理的Hc酵母明显刺激了PMN呼吸爆发。这些数据表明，PMN对Hc酵母的吞噬作用与细胞内截留O2-有关，而通过细胞外细胞色素c的还原无法检测到这种截留。
