Food and Drug Administration, Division of Biotechnology Review and Research III, Silver Spring, MD 20993, United States.
Duke University Medical Center, Division of Hematology, Durham, NC 27710, United States.
Thromb Res. 2017 Nov;159:39-47. doi: 10.1016/j.thromres.2017.09.018. Epub 2017 Sep 21.
Heparin-induced thrombocytopenia (HIT) is an immune-mediated complication of heparin anticoagulation therapy resulting in thrombocytopenia frequently accompanied by thrombosis. Current evidence suggests that HIT is associated with antibodies developed in response to multi-molecular complexes formed by platelet factor 4 (PF4) bound to heparin or cell surface glycosaminoglycans. These antibody complexes activate platelets and monocytes typically through FcγRIIA receptors increasing the production of PF4, inflammatory mediators, tissue factor and thrombin. The influence of underlying events in HIT including complex-induced pro-inflammatory cell activation and structural determinants leading to local inflammatory responses are not fully understood.
The stoichiometry and complex component requirements were determined by incubating fresh peripheral blood mononuclear cells (PBMC) with different concentrations of unfractionated heparin (H), low molecular weight heparin (LMWH), PF4- and anti-PF4-H complex antibodies (KKO). Cytokine mRNA or protein were measured by qRT-PCR or Meso Scale Discovery technology, respectively. Gene expression profile analysis for 594 genes was performed using Nanostring technology and analyzed using Ingenuity Pathway Analysis software.
The data show that antibodies magnify immune responses induced in PBMCs by PF4 alone or in complex with heparin or LMWH. We propose that following induction of HIT antibodies by heparin-PF4 complexes, binding of the antibodies to PF4 is sufficient to induce a local pro-inflammatory response which may play a role in the progression of HIT. In vitro assays using PBMCs may be useful in characterizing local inflammatory and innate immune responses induced by HIT antibodies in the presence of PF4 and different sources of heparins.
The findings and conclusions in this article are solely the responsibility of the authors and are not being formally disseminated by the Food and Drug Administration. Thus, they should not be construed to represent any Agency determination or policy.
肝素诱导的血小板减少症（HIT）是肝素抗凝治疗的一种免疫介导的并发症，常导致血小板减少症，常伴有血栓形成。目前的证据表明，HIT 与针对与肝素或细胞表面糖胺聚糖结合的血小板因子 4（PF4）形成的多分子复合物产生的抗体有关。这些抗体复合物通过 FcγRIIA 受体激活血小板和单核细胞，通常会增加 PF4、炎症介质、组织因子和凝血酶的产生。HIT 中潜在事件的影响，包括复合物诱导的促炎细胞激活和导致局部炎症反应的结构决定因素，尚未完全了解。
通过将不同浓度的未分级肝素（H）、低分子量肝素（LMWH）、PF4-和抗 PF4-H 复合物抗体（KKO）与新鲜外周血单核细胞（PBMC）孵育，确定化学计量和复合物成分要求。通过 qRT-PCR 或 Meso Scale Discovery 技术分别测量细胞因子 mRNA 或蛋白质。使用 Nanostring 技术对 594 个基因的基因表达谱进行分析，并使用 Ingenuity Pathway Analysis 软件进行分析。
数据表明，抗体放大了由 PF4 单独或与肝素或 LMWH 形成复合物诱导的 PBMC 中的免疫反应。我们提出，在肝素-PF4 复合物诱导 HIT 抗体后，抗体与 PF4 的结合足以诱导局部促炎反应，这可能在 HIT 的进展中发挥作用。使用 PBMC 的体外测定可能有助于在存在 PF4 和不同来源的肝素的情况下，表征 HIT 抗体诱导的局部炎症和先天免疫反应。
本文中的发现和结论完全是作者的责任，食品和药物管理局并未正式传播。因此，它们不应被解释为代表任何机构的决定或政策。
