Heparin enhances uptake of platelet factor 4/heparin complexes by monocytes and macrophages.
Heparin enhances uptake of platelet factor 4/heparin complexes by monocytes and macrophages.
复制标题
肝素可通过单核细胞和巨噬细胞增强血小板因子4/肝素复合物的摄取。
DOI：
10.1111/jth.13003
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发表时间：
2015-08
期刊：
影响因子：
--
通讯作者：
Arepally GM
中科院分区：
文献类型：
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作者：
Joglekar M;Khandelwal S;Cines DB;Poncz M;Rauova L;Arepally GM
肝素诱导的血小板减少症(HIT)是肝素治疗的医源性并发症，由自身抗原抗体、血小板因子(4)和肝素引起。为什么抗体是针对PF4/肝素，而不是针对与其他细胞糖胺多聚糖结合的PF4，其原因还知之甚少。为了研究细胞结合的PF4和PF4/肝素复合体的细胞反应的差异，我们研究了外周血单核细胞、树突状细胞和中性粒细胞对它们的内化。使用未标记的荧光标记抗原和/或标记的抗PF4/肝素复合体(KKO)的单抗，我们发现PF4/肝素复合体可被单核细胞以肝素依赖的方式摄取，并被人单核细胞和树突状细胞内化，但不被中性粒细胞所摄取。PF4/低分子肝素复合体和肝素与小鼠PF4、鱼精蛋白或溶菌酶组成的复合体也被类似地内化，提示存在共同的内吞途径。复合体的摄取是由巨噬细胞吞噬作用介导的，如细胞松弛素D和阿米洛利的抑制所显示的那样。内化的复合体被完整地运输到晚期内吞体内，如小泡与KKO和溶酶体相关膜蛋白-2(LAMP-2)的共同染色所示。最后，我们发现细胞摄取伴随着MHCII和CD83共刺激分子的表达。综上所述，这些研究确立了肝素在增强抗原摄取和激活细胞免疫反应中对含有PF4的复合体的初始步骤中的独特作用。
Heparin-induced thrombocytopenia (HIT) is an iatrogenic complication of heparin therapy caused by antibodies to a self-antigen, platelet factor (4) and heparin. The reasons why antibodies form to PF4/heparin, but not to PF4 bound to other cellular glycosaminoglycans are poorly understood. To investigate differences in cellular responses to cell-bound PF4 and PF4/heparin complexes, we studied the internalization of each by peripheral blood-derived monocytes, dendritic cells and neutrophils. Using unlabeled, fluorescently-labeled antigen and/or labeled monoclonal antibody to PF4/heparin complexes (KKO), we show that PF4/heparin complexes are taken up by monocytes in a heparin-dependent manner and are internalized by human monocytes and dendritic cells, but not by neutrophils. Complexes of PF4/low-molecular weight heparin and complexes composed of heparin and murine PF4, protamine, or lysozyme are internalized similarly, suggesting a common endocytic pathway. Uptake of complexes is mediated by macropinocytosis, as shown by inhibition using cytochalasin D and amiloride. Internalized complexes are transported intact to late endosomes, as indicated by co-staining of vesicles with KKO and lysosomal associated membrane protein-2 (LAMP-2). Lastly, we show cellular uptake is accompanied by expression of MHCII and CD83 co-stimulatory molecules. Taken together, these studies establish a distinct role for heparin in enhancing antigen uptake and activation of the initial steps in the cellular immune response to PF4-containing complexes.