Determinants of PF4/heparin immunogenicity
Determinants of PF4/heparin immunogenicity
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DOI：
10.1182/blood-2007-08-105098
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发表时间：
2007-12-15
期刊：
影响因子：
20.3
通讯作者：
Arepally, Gowthami M.
中科院分区：
文献类型：
--
作者：
Suvarna, Shayela;Espinasse, Benjamin;Arepally, Gowthami M.
肝素诱导的血小板减少症（HIT）是一种抗体介导的疾病，在暴露于肝素的患者中发生频率不同。HIT抗体优先识别PF 4和肝素之间形成的大分子复合物，但启动抗体产生的复合物的生物物理性质是未知的。为了确定PF 4/肝素免疫原性的结构决定因素，我们表征了鼠PF 4（mPF 4）和肝素在光吸收、大小和表面电荷（zeta电位）方面的体外相互作用。我们发现，PF 4/肝素大分子组装发生通过胶体相互作用，其中肝素通过电荷中和促进复合物的生长。PF 4/肝素大分子的大小取决于反应物的摩尔比。最大复合物尺寸发生在PF 4/肝素的摩尔比，在该摩尔比下表面电荷是中性的。当用大小和/或ζ电位不同的复合物免疫小鼠时，抗体形成与肝素浓度成反比，并且在用显示净正ζ电位的复合物免疫的动物中最稳健。这些研究表明，HIT免疫应答的临床异质性可能部分是由于在强烈血小板活化和PF 4释放的环境中发生的PF 4/肝素复合物的特定生物物理参数的要求。
Heparin-induced thrombocytopenia (HIT) is an antibody-mediated disorder that occurs with variable frequency in patients exposed to heparin. HIT antibodies preferentially recognize large macromolecular complexes formed between PF4 and heparin over a narrow range of molar ratios, but the biophysical properties of complexes that initiate antibody production are unknown. To identify structural determinants underlying PF4/heparin immunogenicity, we characterized the in vitro interactions of murine PF4 (mPF4) and heparin with respect to light absorption, size, and surface charge (zeta potential). We show that PF4/heparin macromolecular assembly occurs through colloidal interactions, wherein heparin facilitates the growth of complexes through charge neutralization. The size of PF4/heparin macromolecules is governed by the molar ratios of the reactants. Maximal complex size occurs at molar ratios of PF4/ heparin at which surface charge is neutral. When mice are immunized with complexes that differ in size and/or zeta potential, antibody formation varies inversely with heparin concentration and is most robust in animals immunized with complexes displaying a net positive zeta-potential. These studies suggest that the clinical heterogeneity in the HIT immune response may be due in part to requirements for specific biophysical parameters of the PF4/heparin complexes that occur in settings of intense platelet activation and PF4 release.