Department of Pathology and Laboratory Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
Shock. 2012 Jan;37(1):56-62. doi: 10.1097/SHK.0b013e3182356f3e.
Sepsis is one of the leading causes of death in hospitals worldwide. Even with optimal therapy, severe sepsis results in 50% mortality, indicating variability in the response of individuals towards treatment. We hypothesize that the presence of preexisting antibodies present in the blood before the onset of sepsis induced by cecal ligation and puncture (CLP) in mice accounts for the differences in their survival. A plasma-enhanced killing (PEK) assay was performed to calculate the PEK capacity of plasma, that is, the ability of plasma to augment polymorphonuclear neutrophil killing of bacteria. Plasma-enhanced killing was calculated as PEK = [1 / log (N)] × 100, where N = number of surviving bacteria; a higher PEK indicated better bacterial killing. A range of PEK in plasma collected from mice before CLP was observed, documenting individual differences in bacterial killing capacity. Mortality was predicted based on plasma IL-6 levels at 24 h after CLP. Mice predicted to die (Die-P) had a lower PEK (<14) and higher peritoneal bacterial counts at 24 h after sepsis compared with those predicted to live (Live-P) with a PEK of greater than 16. Mice with PEK of less than 14 were 3.1 times more likely to die compared with the group with PEK of greater than 16. To understand the mechanism of defense conferred by the preexisting antibodies, binding of IgM or IgG to enteric bacteria was documented by flow cytometry. To determine the relative contribution of IgM or IgG, the immunoglobulins were specifically immunodepleted from the naive plasma samples and the PEK of the depleted plasma measured. Compared with naive plasma, depletion of IgM had no effect on the PEK. However, depletion of IgG increased PEK, suggesting that an inhibitory IgG binds to antigenic sites on bacteria preventing optimal opsonization of the bacteria. These data demonstrate that, before CLP, circulating inhibitory IgG antibodies exist that prevent bacterial killing by polymorphonuclear neutrophils in a CLP model of sepsis.
脓毒症是全球医院死亡的主要原因之一。即使采用最佳治疗方法，严重脓毒症的死亡率仍高达 50%，这表明个体对治疗的反应存在差异。我们假设，在盲肠结扎和穿刺（CLP）诱导的脓毒症发作之前存在于血液中的预先存在的抗体是导致它们存活差异的原因。进行了血浆增强杀伤（PEK）测定，以计算血浆的 PEK 能力，即血浆增强多形核中性粒细胞杀伤细菌的能力。PEK 计算为 PEK = [1 / log (N)] × 100，其中 N =存活细菌的数量；较高的 PEK 表示更好的细菌杀伤。在 CLP 之前从小鼠收集的血浆中观察到 PEK 的范围，记录了细菌杀伤能力的个体差异。根据 CLP 后 24 小时的血浆 IL-6 水平预测死亡率。与预测存活（Live-P）的小鼠相比，预测死亡（Die-P）的小鼠在 CLP 后 24 小时的 PEK 较低（<14），腹腔内细菌计数较高。PEK 小于 14 的小鼠死亡的可能性是 PEK 大于 16 的小鼠的 3.1 倍。为了了解预先存在的抗体赋予的防御机制，通过流式细胞术记录了 IgM 或 IgG 与肠细菌的结合。为了确定 IgM 或 IgG 的相对贡献，从幼稚血浆样品中特异性耗尽免疫球蛋白，并测量耗尽的血浆的 PEK。与幼稚血浆相比，IgM 的耗尽对 PEK 没有影响。然而，IgG 的耗尽增加了 PEK，表明抑制性 IgG 结合到细菌的抗原性位点上，从而阻止了细菌的最佳调理作用。这些数据表明，在 CLP 之前，循环抑制性 IgG 抗体存在于 CLP 脓毒症模型中，可阻止多形核中性粒细胞对细菌的杀伤。
